HomeMy WebLinkAboutLake Cornelia Use Attainability Analysis_2010Lake Cornelia
Use Attainability Analysis
REVISED DRAFT
Prepared by
Barr Engineering Co.
Prepared for
Nine Mile Creek Watershed District
January 2010
Lake Cornelia
Use Attainability Analysis
Updated Draft
Prepared for
Nine Mile Creek Watershed District
January 2010
4700 West 77th Street
Minneapolis, MN 55435-4803
Phone: (952) 832-2600
Fax: (952) 832-2601
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Executive Summary
Overview
This report describes the results of the Use Attainability Analysis (UAA) for Lake Cornelia in Edina,
MN. The UAA provides the scientific foundation for a lake-specific best management plan that will
permit maintenance of, or attainment of, the intended beneficial uses of Lake Cornelia. The UAA is
a scientific assessment of a water body’s physical, chemical, and biological condition. This study
includes both a water quality assessment and prescription of protective and/or remedial measures for
Lake Cornelia and the tributary watershed. The conclusions and recommendations are based on
historical water quality data, the results of an intensive lake water quality monitoring in 2004 &
2008, and computer simulations of land use impacts on water quality in Lake Cornelia using
watershed and lake models calibrated to the water quality data sets. In addition, best management
practices (BMPs) were evaluated to compare their relative effect on total phosphorus concentrations
and Secchi disc transparencies (i.e., water clarity). Management options were then assessed to
determine attainment or non-attainment with the lake’s beneficial uses.
Nine Mile Creek Watershed District Water Quality Goals
The Nine Mile Creek District Water Management Plan (Barr, 2007) lists the NMCWD goals for both
the North and South basins of Lake Cornelia as Level III, with the desired use listed as fishing and
aesthetic viewing.
The NMCWD goal was quantified using the standardized lake rating system termed the Carlson’s
Trophic State Index (TSI). This index considers the lake’s total phosphorus, chlorophyll a, and
Secchi disc transparencies to assign a water quality index number reflecting the lake’s general
fertility level. The rating system results in index values between 0 and 100, with the index value
increasing with increased lake fertility. Total phosphorus, chlorophyll a, and Secchi disc
transparency are key water quality indicators for the following reasons.
• Phosphorus generally controls the growth of algae in lake systems. Of all the substances
needed for biological growth, phosphorus is typically the limiting nutrient.
• Chlorophyll a is the main photosynthetic pigment in algae. Therefore, the amount of
chlorophyll a in the water indicates the abundance of algae present in the lake.
• Secchi disc transparency is a measure of water clarity, and is inversely related to the
abundance of algae. Water clarity typically determines recreational-use impairment.
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All three of the parameters can be used to determine a TSI. However, water transparency is typically
used to develop the TSISD (trophic state index based on Secchi disc transparency) because people’s
perceptions of water clarity are often directly related to recreational-use impairment. The TSI rating
system results in the placement of a lake with medium fertility in the mesotrophic trophic status
category. Water quality trophic status categories include oligotrophic (i.e., excellent water quality),
mesotrophic (i.e., good water quality), eutrophic (i.e., poor water quality), and hypereutrophic (i.e.,
very poor water quality). Water quality characteristics of lakes in the various trophic status categories
are listed below with their respective TSI ranges:
1. Oligotrophic – [20 < TSISD < 38] clear, low productive lakes, with total phosphorus
concentrations less than or equal to 10 μg/L, chlorophyll a concentrations of less than or equal to
2 μg/L, and Secchi disc transparencies greater than or equal to 4.6 meters (15 feet).
2. Mesotrophic – [38 < TSISD < 50] intermediately productive lakes, with total phosphorus
concentrations between 10 and 25 μg/L, chlorophyll a concentrations between 2 and 8 μg/L, and
Secchi disc transparencies between 2 and 4.6 meters (6 to 15 feet).
3. Eutrophic – [50 < TSISD < 62] high productive lakes relative to a neutral level, with 25 to
57 μg/L total phosphorus, chlorophyll a concentrations between 8 and 26 μg/L, and Secchi disc
measurements between 0.85 and 2 meters (2.7 to 6 feet).
4. Hypereutrophic – [62 < TSISD < 80] extremely productive lakes which are highly eutrophic and
unstable (i.e., their water quality can fluctuate on daily and seasonal basis, experience periodic
anoxia and fish kills, possibly produce toxic substances, etc.) with total phosphorus
concentrations greater than 57 μg/L, chlorophyll a concentrations of greater than 26 μg/L, and
Secchi disc transparencies less than 0.85 meters (2.7 feet).
The NMCWD’s management strategy typically is to “protect” lakes similar to Lake Cornelia.
According to the NMCWD Water Management Plan, “protect” means “to avoid significant
degradation from point and nonpoint pollution sources and from wetland alterations, in order to
maintain existing beneficial uses, aquatic and wetland habitats, and the level of water quality
necessary to protect these uses in receiving waters.” The five specific goals are outlined below.
The Water Quantity Goal for Lake Cornelia is to provide sufficient water storage of surface runoff
during a regional flood, the critical 100-year frequency storm event. This goal is attainable with no
action.
The Water Quality Goal for Lake Cornelia currently is a Level III classification level, which is
generally intended for fishing and aesthetic viewing. The Minnesota Department of Natural
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Resources (MDNR) stocks the lake annually with approximately 300 - 400 bluegill for the Fishing in
the Neighborhood Program. The specific NMCWD goal for Level III classification is to achieve and
maintain a TSISD between 60 and 70.
The Aquatic Communities Goal for Lake Cornelia is to achieve a water quality that will result in a
diverse and balanced native ecosystem. The MDNR did not include Lake Cornelia’s fisheries-use
classification in the 1992 report, An Ecological Classification of Minnesota Lakes with Associated
Fish Communities (Schupp, 1992). Since the MDNR did not specify the ecological classification for
Lake Cornelia there is no specific fisheries related TSI goal. However, the MDNR stocks the lake
with bluegills as part of the Fishing in the Neighborhood program, and it is the goal of the NMCWD
to achieve water quality that will result in a diverse and balanced native ecosystem.
The Recreational-Use Goal for Lake Cornelia is to achieve water quality that supports the functions
of the lake and maintain a balanced ecosystem. Lake Cornelia is a wildlife lake generally intended
for wildlife habitat, aesthetic viewing and runoff management. Since the MDNR stocks the lake with
bluegill for the Fishing in the Neighborhood Program, a reasonable recreational use goal would be to
achieve Level III water quality.
The Wildlife Goal for Lake Cornelia is to protect existing beneficial wildlife uses. The wildlife goal
can be achieved with no action, especially if the wetlands and natural land surrounding the lake
remain intact.
In additional to the goals set by the NMCWD, the MPCA has developed assessment methodologies,
conducted extensive sampling of lakes, and ultimately derived ecoregion-based lake eutrophication
standards for deep and shallow lakes for total phosphorus, chlorophyll-a, and Secchi depths (MPCA,
2008). For shallow lakes in the North Central Hardwood Forests (NCHF) ecoregion (where Lake
Cornelia is located), the total phosphorus standard established by the MPCA is 60 μg/L, which serves
as the upper threshold for lake water quality. The chlorophyll-a and Secchi disc standards are listed
as less than 20 µg/L greater than 1.0 meters, respectively. Because the water quality in Lake
Cornelia does not meet these standards, it is currently listed on the 2020 (draft) 303(d) impaired
waters list with an expected total maximum daily load (TMDL) study start date of 2013.
Table EX-1 summarizes the 2004 and 2008 water quality in Lake Cornelia as well as the NMCWD
and MPCA goals for the lake.
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v
Lake Characteristics
Lake Cornelia is located in the north central portion of Edina. The lake is part of a natural marsh
area. Lake Cornelia is comprised of a north (North Cornelia) and south (South Cornelia) basin,
connected by a 12-inch culvert under 66th Street (with an invert elevation of 859 feet MSL) on the
south side of the North Cornelia, and a secondary 12-inch pipe located on the southeast side of the
North Cornelia (with an invert elevation of 860.22 feet MSL). The elevation in North Cornelia is
ultimately controlled by the outlet structure on South Cornelia. The outflow from South Cornelia
discharges over a weir structure at 859.1 feet MSL and flows through an extensive storm sewer
system to Lake Edina.
North Cornelia
North Cornelia has a water surface of approximately 19 acres, a maximum depth of 5 feet, and a
mean depth of approximately 3 feet at a normal water surface elevation of 859.1. At this elevation
the lake volume is approximately 61 acre-feet. The water level in the lake is controlled mainly by
weather conditions (snowmelt, rainfall, and evaporation), by the outlet capacity of the pipe on North
Cornelia, and by the elevation of the outlet structure located on South Cornelia.
South Cornelia
South Cornelia has a water surface of approximately 31 acres, a maximum depth of 7 feet, and a
mean depth of 4.2 feet at a normal surface elevation of 859.1. At this elevation the lake volume is
approximately 130 acre-feet. The water level in the lake is controlled by the elevation of the weir
structure at the south side of the lake.
Water Quality Problem Assessment
Baseline Lake Water Quality Status
The Minnesota Lake Eutrophication Analysis Procedure (MnLEAP) is intended to be used as a
screening tool for estimating lake conditions and for identifying “problem” lakes. MnLEAP is
particularly useful for identifying lakes requiring “protection” versus those requiring “restoration”
(Heiskary and Wilson, 1990). In addition, MnLEAP modeling has been done in the past to identify
Minnesota lakes which may be in better or worse condition than they “should be” based on their
location, watershed area and lake basin morphometry (Heiskary and Wilson, 1990). Results of
MnLEAP modeling done for Lake Cornelia suggest that the lake could achieve “better” water quality
than is currently observed (Heiskary and Lindbloom, 1993). For the MnLEAP analysis, Lake
Cornelia was treated as a single basin, rather than two separate basins. The results of the various
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
vi
models used to estimate the baseline total phosphorus (TP) concentration are summarized in Table
EX-2.
Vighi and Chiaudani (1985) developed another method to determine the phosphorus concentration in
lakes that are not affected by anthropogenic (human) inputs. As a result, the phosphorus
concentration in a lake resulting from natural, background phosphorus loadings can be calculated
from information about the lake’s mean depth and alkalinity or conductivity. Alkalinity is
considered more useful for this analysis because it is less influenced by development of the
watershed. Alkalinity data from 2008 was used as well as epilimnetic specific conductivity data
collected throughout the summer of 2004 and 2008 to predict the total phosphorus concentration
range from natural, background loadings.
Finally, the Wisconsin Lake Modeling Suite (WiLMS) model (WI-DNR, 2004) was also used to
estimate Lake Cornelia’s water quality under natural (predevelopment) watershed conditions. The
WiLMS model (Lake Total Phosphorus Prediction Module) uses an annual time step and predicts
spring overturn, growing season mean, and annual average TP concentrations in lakes. The model
uses information about the lake and watershed characteristics in conjunction with 13 different
published phosphorus prediction regressions to predicted the expected in-lake TP. The historic
watershed information for Lake Cornelia was used to estimate the model input parameters and the
expected water quality in Lake Cornelia.
Table EX-2 Summary of Lake Cornelia Baseline Water Quality Modeling Results
Model Lake Expected Water Quality
(Total Phosphorus)
MnLEAP Lake Cornelia
(North & South)
55 – 97 ug/L
Vighi and Chiaudani
(1985) – Alkalinity
North Cornelia 34 – 40 ug/L
South Cornelia 34 – 40 ug/L
Vighi and Chiaudani
(1985) – Specific
Conductivity
North Cornelia 27 – 61 ug/L
South Cornelia 27 – 66 ug/L
WiLMS (Canfield and
Bachman (1981))
Lake Cornelia
(North & South)
53 – 133 ug/L
Comparison of the predicted baseline TP concentrations to observed annual average phosphorus
concentrations indicates that the water quality in Lake Cornelia is worse than it likely was
historically, based on its location, watershed area and lake basin morphometry. The predicted ranges
of TP concentrations indicates that the NMCWD Level III classification goal should be attainable,
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vii
given the appropriate phosphorus loadings to the lake. When compared to the MPCA shallow lakes
standard (60 μg/L), the upper end of the Vighi and Chiaudani predicted natural background TP
concentration range falls right around the standard, indicating that it may be possible to attain the
MPCA shallow lake standard for phosphorus. However, when considering the TP ranges predicted
by the MnLEAP and WiLMS models, the MPCA shallow lake standard may be attainable only on the
very low end of the expected range of TP concentrations, and is likely not attainable for most
conditions.
Lake Cornelia Current Water Quality
Because recreational use is greatest during the summer (June, July, and August) months, and because
it is during these times that algal blooms and diminished transparency are most common, attention is
usually focused on summer water quality in the upper (epilimnetic) portions of the lake.
The NMCWD conducted intensive water quality monitoring in North and South Cornelia in 2004 and
again in 2008. The Metropolitan Council Citizen Assisted Monitoring Program (CAMP) also
collected water quality data in North Cornelia in 2003, 2005, 2006, 2007, and 2008. Figure EX-1
shows the historic summer average TP and Chl-a concentrations, and transparency data from 2003
through 2008 for Lake Cornelia.
When comparing the three key water quality parameters, North Cornelia has slightly better water
quality than in South Cornelia. However, the 2008 summer average TP, Chl a, and transparency
place both North and South Cornelia in the hypereutrophic category throughout the summer, meaning
that Lake Cornelia is rich in algal nutrients, susceptible to dense algal blooms, and exhibits poor
water clarity. Figure EX-2a and Figure EX-2b show the most recent (2008) water quality throughout
the monitoring season in North and South Cornelia, respectively. The summer averages of the
various water quality parameters for 2004 and 2008 are also summarized in Table EX-1.
253
164 160
169
211
153
190
150
50
100
150
200
250
300
TP
(
u
g
/
L
)
(a) Total Phosphorus Concentration (ug/L)
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2008
Total Phosphorus Concentrations
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 153 ug/L
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2008
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 51 ug/L
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Figure EX-2a
North Cornelia Lake 2008 Seasonal Changes
in Concentration of Total Phosphorus,
Chlorophyll-a and Secchi Disc
Transparencies
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2008
Total Phosphorus Concentrations
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 153 ug/L
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2008
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 51 ug/L
0
1
2
3
4
5
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(m
e
t
e
r
s
)
Date
Cornelia (North Basin)--2008
Secchi Disc Transparency
Summer Average = 0.4 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
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0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2008
Total Phosphorus Concentrations
Summer Average = 150 ug/L
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2008
Chlorophyll-a
Summer Average = 61 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
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Figure EX-2b
South Cornelia Lake 2008 Seasonal
Changes in Concentration of Total
Phosphorus, Chlorophyll-a and Secchi
Disc Transparencies
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2008
Total Phosphorus Concentrations
Summer Average = 150 ug/L
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2008
Chlorophyll-a
Summer Average = 61 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
0
1
2
3
4
5
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(
m
e
t
e
r
s
)
Date
Cornelia (South Basin)--2008
Secchi Disc Transparency
Summer Average = 0.3 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
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xi
Trend Analysis
A trend analysis was performed on the water quality data for North Cornelia, as there was a sufficient
amount of data to perform the analyses. The trend analyses were performed to determine if the
changes in water quality over time indicate a significant improvement or degradation in water
quality. Over the entire period of record (2003-2008), results for TP, Chl a, and SD trend analyses
all indicated that there was no significant improvement or degradation in water quality over the past
5 years in North Cornelia.
Watershed Runoff Pollution
Historically, the Lake Cornelia watershed was primarily comprised of basswood, sugar maple, and
oak forests. There were also numerous wetlands located throughout the watershed. The terrain varies
from relatively flat to rolling.
Lake Cornelia’s 975 acre watershed, including the surface area of the lake (50.1 acres) is within the
City of Edina. Runoff from the watershed enters both North and South Cornelia through overland
flow and at storm sewer outfalls at various points along the lakeshore. Existing land use patterns
(see Figure EX-3) within the watershed were identified for the purpose of predicting changes in
runoff volumes and annual phosphorus loads before and after development. Based on existing land
use data from the city of Edina and analysis of aerial photographs, the entire contributing watershed
is developed, with the majority of the land use being low-density residential (44 percent). The
watershed also includes commercial (22 percent), highway (10 percent), open water (9 percent), high
density residential (7 percent), developed park (4 percent), high impervious institutional (2 percent),
park/open space (2 percent), wetland (1 percent), and less than 1 percent of industrial/office uses.
(see Figure EX-4).
Future land use is not expected to vary significantly from present use. As a result the watershed is
considered fully-developed and neither the quality nor the quantity of the stormwater runoff from the
watershed is expected to change due to alterations in land use.
NC_62
NC_4
NC_3
NC_5
SC_1
NC_88
NC_30
NC_72
NC_2
SC_2
NC_78
SC_3
NC_6
NC_130
NC_135
Ba
r
r
F
o
o
t
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r
:
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:
1
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7
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P
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Lake Cornelia SubwatershedsLand Use
Developed Parkland
Wetland
Natural/Park/Open
High Density Residential
Medium Density Residential
Low Density Residential
Institutional
XXXXXXXXXXXXXXXGolf Course
Highway
Commercial
Mixed Use Industrial
Industrial/Office
Open Water
0 1,000 2,000
Feet
Figure EX-3
Subwatersheds and Land Use
Lake Cornelia UAA
Nine Mile Creek Watershed District
Ü
Commercial
22%
Golf Course
0%
Highway
9%
High Density
Residential
6%
Medium Density
Residential
2%
Low Density
Residential
43%Institutional
2%
High Impervious
Institutional
0.1%
Industrial/ Office
0%
Natural\Park\Open
8%
Open Water
8%
Lake Cornelia Watershed Use Attainability
Existing Land Uses
975 Acres Including Lake Surface Area
Institutional
1%
High Impervious
Institutional
0.1%Industrial/ Office
Lake Cornelia Watershed Use Attainability
Future (2020) Land Uses
975 Acres Including Lake Surface Area
P:\23\27\634\NORMANDALEUAA\Excel Files\LUsummary_tablescharts.xls
Figure EX-4
Lake Cornelia Watershed
Land Uses - Contributing Area Only
Commercial
22%
Golf Course
0%
Highway
9%
High Density
Residential
6%
Medium Density
Residential
2%
Low Density
Residential
43%Institutional
2%
High Impervious
Institutional
0.1%
Industrial/ Office
0%
Natural\Park\Open
8%
Open Water
8%
Lake Cornelia Watershed Use Attainability
Existing Land Uses
975 Acres Including Lake Surface Area
Commercial
22%
Golf Course
0%
Highway
8%
High Density
Residential
6%
Medium Density
Residential
2%
Low Density
Residential
44%
Institutional
1%
High Impervious
Institutional
0.1%Industrial/ Office
2%
Natural\Park\Open
7%
Open Water
8%
Lake Cornelia Watershed Use Attainability
Future (2020) Land Uses
975 Acres Including Lake Surface Area
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xiv
Lake Cornelia receives phosphorus loads from external sources, contained in the runoff from the
lakes’ immediate and tributary watersheds, through atmospheric deposition, and from external
discharges, such as the Southdale cooling water system. In addition, the data suggest that the lake
also receives phosphorus loads from internal sources—such as release from the lake sediments,
activity of benthivorous fish, and from the die-back of Curlyleaf pondweed. Figures EX-5a, EX-5b,
and EX-5c summarize the annual water and phosphorus budgets for North and South Cornelia for
average, wet, and dry climatic conditions, respectively.
Watershed analysis suggests that under existing conditions and all climatic scenarios, watershed
loading is the largest external phosphorus loading source to both North and South Cornelia. The
watershed contributes approximately 71 to 82 percent of the annual phosphorus load and 78 to 83
percent of the annual water load to North Cornelia. The majority of the water and phosphorus loads
to South Cornelia come from North Cornelia. The South Cornelia watershed, including the discharge
from North Cornelia, contributing approximately 87 to 93 percent of the annual phosphorus load and
91 to 92 percent of the water load to South Cornelia.
For existing conditions in the Lake Cornelia watershed, modeling simulations for average climatic
conditions indicate an annual (2004 water year) total phosphorus load to North Cornelia from the
watershed of 296 lbs and a watershed stormwater runoff volume of 569 acre-feet. For wet climatic
conditions, the annual (2002 water year) total phosphorus load from the North Cornelia watershed
was 400 lbs and the stormwater runoff volume was 855 acre-feet. For dry climatic conditions, the
annual (2008 water year) total phosphorus load from the North Cornelia watershed was 247 lbs and
the stormwater runoff volume was 515 acre-feet.
For existing conditions in the Lake Cornelia watershed, modeling simulations for average climatic
conditions indicate an annual (2004 water year) total phosphorus load to South Cornelia from the
watershed of 28 lbs and a watershed stormwater runoff volume of 32 acre-feet. These results include
the watersheds draining directly to South Cornelia but exclude the loading from North Cornelia. For
wet climatic conditions, the annual (2002 water year) total phosphorus load from the South Cornelia
watershed was 40 lbs and the stormwater runoff volume was 56 acre-feet. For dry climatic
conditions, the annual (2008 water year) total phosphorus load from the South Cornelia watershed
was 22 lbs and the stormwater runoff volume was 28 acre-feet.
Although the runoff from the watershed is the major source of water and phosphorus loads to North
Cornelia, the lake also receives discharge from the Southdale Center (via the Point of France Pond).
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xv
Southdale Center operates a heating/cooling system that pumps water from the groundwater. This
water passes once-through the Southdale heating/cooling system and is continuously discharged. As
it is part of the cooling system, more water is discharged during the summer than in the winter.
Based on pumping records submitted to the MDNR and the water quality samples collected in 2009,
it was estimated that North Cornelia receives approximately 103 to 114 acre-feet of water annually
from this system (11 to 16 percent of its annual water load). This discharge also contributes 31 to 34
lbs of phosphorus annually to Lake Cornelia (7 to 9 percent of its annual phosphorus load).
In addition to the water and phosphorus loads from the watershed and from the Southdale Center
cooling system discharge, atmospheric deposition and direct precipitation also contribute water and
phosphorus to Lake Cornelia. In North Cornelia, atmospheric deposition and direct precipitation
account for about 6 percent of the annual water load and about 1 percent of the annual phosphorus
load. In South Cornelia, atmospheric deposition and direct precipitation account for about 8 to 9
percent of the annual water load and about 2 percent of the annual phosphorus load.
The remainder of the phosphorus loading in North and South Cornelia comes from internal sources of
phosphorus. The sediment core analysis performed in 2008 indicates that release from anoxic
sediments is a likely source of the internal phosphorus load. Another potential source of phosphorus
to Lake Cornelia is the presence of benthivorous fish, such as carp, in the lake which can resuspend
sediments and phosphorus into the water column and can be a significant source of phosphorus to a
lake system. Finally, the nonnative aquatic plant, Curlyleaf pondweed (Potamogeton crispus), was
also present in small patches in both North and South Cornelia in 2008. Although it is currently not a
significant source of phosphorus in Lake Cornelia, this macrophyte grows through the winter and then
dies back in early to mid-summer, releasing phosphorus into the water column which can impact algal
growth and water clarity.
The internal phosphorus loading in North Cornelia for average climatic conditions was estimated to
be approximately 55 lbs. For wet climatic conditions, the internal phosphorus loading in North
Cornelia was calculated to be roughly 50 lbs, and for dry climatic conditions, the internal load was
estimated to be 66 lbs. Internal loading accounts for 10 to 19 percent of the annual phosphorus load
to North Cornelia.
The annual internal phosphorus loading in South Cornelia for average climatic conditions was
calculated to be approximately 23 lbs. For wet climatic conditions, the internal phosphorus loading in
South Cornelia was calculated to be approximately 36 lbs, and for dry climatic conditions, the
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xvi
internal load was calculated to be approximately 48 lbs. Internal loading accounts for 5 to 11 percent
of the annual phosphorus load to South Cornelia.
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%South Cornelia
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
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n
d
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t
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s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
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t
i
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n
s
An
n
u
a
l
W
a
t
e
r
B
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d
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t
(
7
2
9
a
c
r
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-
f
t
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
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n
d
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t
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n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%North Cornelia
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
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t
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n
s
An
n
u
a
l
P
h
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s
p
h
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r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
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n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
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r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
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m
a
t
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c
C
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n
d
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t
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s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%NC_3 32%NC_72
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
In
t
e
r
n
a
l
L
o
a
d
14%North Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)4%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%NC_3 32%NC_72 2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
38
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
In
t
e
r
n
a
l
L
o
a
d
14%North Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)4%North Cornelia 87%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
38
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Figure EX-5a Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Average Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
NC
_
2
In
t
e
r
n
a
l
L
o
a
d
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(
2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric DepositionSC_2 1%
In
t
e
r
n
a
l
L
o
a
d
South Cornelia
We
t
(
2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
6%
NC
_
3
37
%
NC
_
6
2
(
D
i
r
e
c
t
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
10
%
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
8%
South Cornelia
We
t
(2002) Climatic Conditions
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
6%
NC
_
3
37
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
37
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
10
%
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)7%North Cornelia 81%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
8%
South Cornelia
We
t
(2002) Climatic Conditions
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Figure EX-5b Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Wet Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
NC
_
2
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3
In
t
e
r
n
a
l
L
o
a
d
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
19
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 0%SC_1 (Direct Watershed)4%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
11
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
33
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
19
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 0%SC_1 (Direct Watershed)4%North Cornelia 82%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
11
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Figure EX-5c Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Dry Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
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xx
Sediment Core Analysis
To better understand the internal loading component from the lake sediments, five sediment cores
were collected from Lake Cornelia in October 2008 and were analyzed for mobile phosphorus (which
contributes directly to internal phosphorus loading) and organic bound phosphorus. The internal
sediment loading rates calculated for North Cornelia ranged 5.3 mg/m2/day to 7.6 mg/m2/day. In
South Cornelia, the measured sediment internal loading rates were significantly less, ranging from
1.0 mg/m2/day to 1.3 mg/m2/day. It is important to note that these rates represent the maximum
potential internal loading rate that the lakes could experience, given the ideal dissolved oxygen
concentrations and mixing conditions.
Aquatic Weeds
Macrophyte (i.e., lake weed) surveys were conducted during June and August of 2004 and again in
June and August of 2008.
The June 2004 macrophyte survey for North Cornelia showed that most vegetation in the lake is
located in the shallow waters along the shoreline. No aquatic vegetation was found in waters deeper
than 3.0 feet. The dominant vegetation in the lake is cattail (Typha sp.) which is found in low
densities along the entire shoreline. Additionally, other emergent plants such as bullrush and the
invasive purple loosestrife (Scirpus sp. and Lythrum salicaria) are found in the shallow waters along
the north shore of North Cornelia. A small patch of coontail (Ceratophyllum demersum) is found
along the north shore as well. The August 2004 survey shows a similar distribution of plants within
the lake. Sporadic, low-density patches of narrowleaf pondweed and sago pondweed (Potamogeton
sp. and Potamogeton pectinatus) were also present along the north shoreline. In 2008, the
macrophyte surveys indicated that similar species and distribution within the lake. However, in the
June 2008 survey, a small area of the nonnative species, Curlyleaf pondweed (Pomatogeton crispus)
was observed. Because of its unique lifecycle, this species can overtake and replace native plants.
Additionally, when it dies back in early to mid-summer, it can be a significant source of phosphorus
to the water column.
In the June 2004 macrophyte survey of South Cornelia, there were no macrophytes found in water
deeper than 2.0 feet. Emergent vegetation such as cattail, bullrush, purple loosestrife, and blue flag
iris (Typha sp., Scirpus sp., Lythrum salicaria, and Iris vericolor) were all present in sporadic, low
densities along the shoreline of the lake, although the purple loosestrife was found mainly along the
north shore. Both narrowleaf pondweed and sago pondweed (Potamogeton sp. and Potamogeton
pectinatus) were found in low densities along the north and south shores of South Cornelia. Like
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xxi
North Cornelia, the August distribution of macrophytes was similar to that of the June survey.
However, in addition to the sago and narrowleaf pondweed, a small patch of floating leaf pondweed
(Potamogeton natans) was present on the southwest shore of the lake. Similar to the surveys of
North Cornelia, the 2008 macrophyte survey of South Cornelia showed a similar distribution of
species within the lake. Also, like North Cornelia, a small patch of Curlyleaf pondweed
(Pomatogeton crispus) was found along the south shore of South Cornelia that was not present in
2004.
Ecosystem and Fisheries
The phytoplankton (algae) communities in Lake Cornelia form the base of the lake’s food web and
affect recreational-use of the lake. Phytoplankton surveys were completed in both North and South
Cornelia in 2004 and 2008. In 2004, green algae were the dominant types of phytoplankton present
in Lake Cornelia although both basins experienced blue-green algal blooms in mid to late summer.
The blue green algae species that were present in Lake Cornelia in 2004 are known to produce a
hepatotoxin (liver toxin), indicating the need to manage lake water quality to help control the growth
of these potentially hazardous species. In 2008, blue-green algae were present in North Cornelia
throughout the summer, in concentrations almost equal to that of green algae and diatoms, while
blue-green algae dominated the phytoplankton groups present in South Cornelia throughout the
summer of 2008. Again, the blue-green algae species present were those known to produce
hepatotoxins.
Zooplankton—microscopic crustaceans—are vital to the health of a lake ecosystem because they feed
upon the phytoplankton and are food themselves for many fish species. If present in abundance,
larger bodied zooplankton can decrease the number of algae and improve water transparency within a
lake. Zooplankton were surveyed in 2004 and again in 2008. Throughout the 2004 season, there was
a very unbalanced distribution of zooplankton in North Cornelia with small-bodied zooplankton
dominating much of the sampling season. In 2004, South Cornelia had a more balanced distribution
of zooplankton than North Cornelia with the large-bodied zooplankton being the dominant group at
the end of the sampling season. In general, the summer of 2008 had a more-balanced zooplankton
population in both North and South Cornelia than in 2004, with a mixture of both small and large
bodied zooplankton present throughout much of the sampling season.
The MDNR completed a fishery survey in June 2005 for Lake Cornelia. Bluegills and black crappies
were the primary species sampled in Lake Cornelia. Common carp were also abundant in Lake
Cornelia. Other species present included black bullheads, yellow perch, green sunfish, hybrid
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xxii
sunfish, pumpkinseeds, and gold fish. Dissolved oxygen readings during the survey indicate that
winter fish kills are probable in Lake Cornelia. Benthivorous fish, such as carp and bullhead, can
have a direct influence on the phosphorus concentration in a lake (LaMarra, 1975). In the 2005
fishery survey, small carp were present in high numbers, indicating that carp, and other benthivorous
fish in Lake Cornelia, may have a significant impact on the current water quality in the lake. The
MDNR will complete a new fishery survey in 2010.
Additionally, Lake Cornelia is part of the Fishing in the Neighborhood Program and has been stocked
by the MDNR with bluegill from 2000 through 2009. Typically 300-400 adult bluegills are
introduced each year as part of an annual Fishing in the Neighborhood Program.
Recommended Lake and Watershed Management Practices
In -lake improvement scenarios and site-specific structural BMPs were evaluated for feasibility and
cost-effectiveness. It is important that all BMPs currently required by the NMCWD continue to be
implemented as development or redevelopment occurs, in addition to those recommended below.
The following BMP recommendations were developed in the course of this study. While the
implementation of structural and in-lake BMPs are usually given priority, it is important to note that
source control through the implementation of nonstructural BMPs is crucial to protecting the lakes’
water quality. The cumulative water quality benefits several BMP alternatives are presented in Table
EX-3. Figure EX-6 illustrates the location of the various BMP alternatives. Figures EX-7a and EX-
7b illustrate the cost and resulting Trophic State Index (TSI) related to Secchi depth of each BMP
Scenario analyzed for this UAA.
The following sections summarize the recommended aquatic plant, in-lake, and watershed
management techniques scenarios.
North Lake Cornelia
TP CHLa SD TSISD TP CHLa SD TSISD TP CHLa SD TSISD
(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)
1 Existing (2008) Watershed Conditions1
with Southdale System Operating 153 55.4 0.39 74 164 60.5 0.37 74 127 44.0 0.45 71
2 Existing (2008) Watershed Conditions1
with Southdale System Not Operating 160 58.6 0.38 74 182 68.4 0.34 76 166 61.7 0.36 75
3 Infiltration (NMCWD Rules) in
Redevelopment Areas2 162 59.7 0.37 74 199 76.2 0.32 77 129 45.1 0.45 72
4 42" RCP outlet from Swimming Pool
Pond to North Cornelia2 151 54.8 0.39 73 177 66.2 0.35 75 126 43.6 0.46 71
5
42" RCP outlet from Swimming Pool
Pond to North Cornelia & Infiltration of
1" of Runoff From All Impervious
Surfaces in the Watershed2
135 47.7 0.43 72 244 96.5 0.27 79 132 46.1 0.44 72
6
Future Conditions: Infiltration
(NMCWD Rules) in Redevelopment
Areas & 42" RCP outlet from
Swimming Pool Pond to North
Cornelia2
159 58.1 0.38 74 201 76.9 0.31 77 128 44.4 0.45 71
7 Future Conditions & NURP Pond in NC-
62a 142 50.8 0.41 73 197 75.3 0.32 77 124 42.6 0.46 71
8
Future Conditions & Alum Treatment
Plant at the outlet of Swimming Pool
Pond3
135 47.6 0.43 72 174 65.1 0.35 75 114 38.1 0.50 70
9
Future Conditions & Iron-Enhanced
Sand Filter at the outlet of Swimming
Pool Pond4
142 50.6 0.41 73 182 68.5 0.34 76 118 40.2 0.48 71
10 Future Conditions & In-Lake Alum
Treatment of North Cornelia 139 49.4 0.42 72 136 48.2 0.43 72 115 38.7 0.49 70
11
Future Conditions, NURP Pond in NC-
62a, Alum Treatment Plant at outlet of
Swimming Pool Pond3, & Alum
Treatment of North Cornelia
99 31.5 0.55 68 106 34.7 0.52 69 97 30.7 0.56 68
1 - Reflects the 2004 dredging of Point of France Pond and Swim Pool Pond
2 - Assumes the Southdale System in NOT Operating
3 - Assumes treatment of 5 cfs of discharge
4 - Assumes treatment of 3.5 cfs
South Lake Cornelia
TP CHLa SD TSISD TP CHLa SD TSISD TP CHLa SD TSISD
(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)
1 Existing (2008) Watershed Conditions1
with Southdale System Operating 150 67.2 0.24 81 176 79.8 0.21 83 133 58.7 0.26 79
2 Existing (2008) Watershed Conditions1
with Southdale System Not Operating 154 69.0 0.23 81 188 85.8 0.19 84 147 65.8 0.24 81
3 Infiltration (NMCWD Rules) in
Redevelopment Areas2 151 67.9 0.23 81 190 86.4 0.19 84 133 58.7 0.26 79
4 42" RCP outlet from Swimming Pool
Pond to North Cornelia2 149 67.0 0.24 81 183 83.3 0.20 83 133 59.1 0.26 79
5
42" RCP outlet from Swimming Pool
Pond to North Cornelia & Infiltration of
1" of Runoff From All Impervious
Surfaces in the Watershed2
149 66.5 0.24 81 117 51.3 0.29 78 129 56.9 0.27 79
6
Future Conditions: Infiltration
(NMCWD Rules) in Redevelopment
Areas & 42" RCP outlet from
Swimming Pool Pond to North
Cornelia2
152 68.0 0.23 81 185 84.2 0.20 83 133 59.2 0.26 79
7 Future Conditions & NURP Pond in NC-
62a 139 61.6 0.25 80 185 84.5 0.20 83 135 59.7 0.26 79
8
Future Conditions & Alum Treatment
Plant at the outlet of Swimming Pool
Pond3
131 58.0 0.26 79 146 65.2 0.24 80 125 54.9 0.28 79
9
Future Conditions & Iron-Enhanced
Sand Filter at the outlet of Swimming
Pool Pond4
138 61.2 0.25 80 158 70.9 0.23 81 128 56.7 0.27 79
10 Future Conditions & In-Lake Alum
Treatment of North Cornelia 149 66.7 0.24 81 154 69.0 0.23 81 115 50.1 0.30 78
11
Future Conditions, NURP Pond in NC-
62a, Alum Treatment Plant at outlet of
Swimming Pool Pond3, & Alum
Treatment of North Cornelia
115 50.4 0.30 78 115 50.3 0.30 78 107 46.4 0.32 77
1 - Reflects the 2004 dredging of Point of France Pond and Swim Pool Pond
2 - Assumes the Southdale System in NOT Operating
3 - Assumes treatment of 5 cfs of discharge
4 - Assumes treatment of 3.5 cfs
Scenario
Number
Best Management Practice (BMP)
Strategy
Scenario
Number
Best Management Practice (BMP)
Strategy
Dry Climatic Conditions (2007-2008) Average Climatic Conditions (2003-2004)
Table EX-3 Lake Cornelia Predicted Total Phosphorus and Chlorophyll a Concentration,
Secchi Disc Transparency, and TSISD for All Management Alternatives Analyzed
Dry Climatic Conditions (2007-2008) Average Climatic Conditions (2003-2004) Wet Climatic Conditions (2001-2002)
Summer Average Summer Average Summer Average
Wet Climatic Conditions (2001-2002)
Summer Average Summer Average Summer Average
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\InLakeModels\LakeCorneliaSummary.xls
"/!.
NC_4
NC_3NC_62a
NC_5
SC_1
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NC_88
NC_30
NC_72
NC_2
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NC_130
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Figure EX-6
Location of BMP Alternatives
Lake Cornelia UAA
Nine Mile Creek Watershed District
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xxvii
Aquatic Weed Management
Macrophyte surveys should continue on this lake to monitor the development and growth of
undesirable non-native species. A decline in native aquatic plant species reduces available habitat
for wildlife, invertebrates, and other food organisms for small fish. Species of special concern in
Lake Cornelia are purple loosestrife (Lythrum salicaria) and Curlyleaf pondweed (Pomatogeton
crispus).
Curlyleaf pondweed was not observed in Lake Cornelia during the 2004 macrophyte survey;
however, it small areas were present in both North and South Cornelia in 2008. The appearance of
the small patches of the nonnative Curlyleaf pondweed should continue to be monitored in both
North and South Cornelia. Once a lake becomes infested with Curlyleaf pondweed, the plant
typically replaces native vegetation, increasing its coverage and density. Curlyleaf pondweed begins
growing in late-August and grows throughout the winter at a slow rate, grows rapidly in the spring,
and dies early in the summer (Madsen et al. 2002). Native plants that grow from seed in the spring
are unable to grow in the areas already occupied by the Curlyleaf pondweed, and are displaced by
this plant. Curlyleaf pondweed dies off in early to mid summer, releasing phosphorus into the water
column, and often resulting in increased algal growth for the remainder of the summer.
Macrophyte surveys should be conducted regularly to evaluate the change and distribution of these
notnative species. A general macrophyte survey costs approximately $3,000 per lake.
Both the 2004 and 2008 macrophyte surveys also indicated that the dominant emergent vegetation in
the North Cornelia is the cattail (Typha sp.) which is found in low densities along the entire
shoreline. Cattail is also found in patches along the shoreline of South Cornelia. In some locations,
recreational access to Lake Cornelia is affected by the presence of the cattails along the shoreline. In
order to harvest any emergent vegetation (including cattails) to create a recreational access to Lake
Cornelia, an aquatic plant management control permit from the MDNR is required. Currently, the
MDNR only permits the removal of these plants only in a small area to provide boat access to deeper
lake water. It is important to note that the MDNR does not grant aquatic plant management control
permits automatically, and site inspections are required for first time permits. For more information
related to aquatic plant management, see the following website:
http://www.dnr.state.mn.us/shorelandmgmt/apg/permits.html
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In-Lake Management
Water quality simulations using the P8 model and an in-lake model indicated that the internal release
of phosphorus accounts for approximately 10 to 19 percent of existing phosphorus loading to North
Cornelia and roughly 5 to 11 percent of phosphorus loading to South Cornelia during the various
climatic conditions. The sources of these internal phosphorus loads are likely attributed to two key
sources: the release of phosphorus from anoxic sediments and the resuspension of the bottom
sediments (and associated phosphorus) into the water column by the activities of benrhivorous fish
and other mixing events (e.g., wind) in the lake.
Internal Sediment Release
The 2008 sediment core analysis indicated that phosphorus release from anoxic sediment in Lake
Corneria is possible, given the right conditions. In-lake application of alum (aluminum sulfate) to
prevent sediment phosphorus release in the lake during the summer and fall months was scenario
analyzed. This BMP Scenario (Scenario 10) assumed alum application only to North Cornelia and
t he alum dosing was based on the results of the sediment core analysis. The estimated to cost for
alum treatment of North Cornelia is $90,000 (which includes the cost of the alum as well as the
buffer, sodium aluminate). Scenario 10 (North Cornelia in-lake alum treatment) is the most cost
effective alternative and does improve the water quality in both North and South Cornelia. However,
even with this improvement both lakes still remain in NMCWD’s Level IV and above the MPCA’s
shallow lake criteria.
Because benthivorous fish (e.g. carp) populations are abundant in Lake Cornelia, the alum treatment
of North Cornelia should follow any fisheries management activities as the longevity of an alum
treatment may be reduced as the result of the resuspension of sediments by these fish species.
Management of Benthivorous Fish Populations
Carp, along with other benthivorous (bottom-feeding) fish, can have a direct influence on the
phosphorus concentration in a lake or water body (LaMarra, 1975). They can also cause
resuspension of sediments in shallow ponds and lakes, causing reduced water clarity and poor aquatic
plant growth, as well as high phosphorus concentrations (Cooke et al., 1993). Because of the
abundance of carp in Lake Cornelia, along with other rough fish species, their feeding and spawning
activities may have a significant impact on the water quality in the lake. Additionally, information
from the MDNR indicates that winter fish kills are very likely in Lake Cornelia.
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Lake Cornelia is part of the Fishing in the Neighborhood Program and has been stocked by the
MDNR with bluegill from 2000 through 2009. The 2005 MDNR fisheries survey indicates that
bluegills and black crappies were the primary species sampled in Lake Cornelia. Common carp were
also abundant in Lake Cornelia. Other species present included black bullheads, yellow perch, green
sunfish, hybrid sunfish, pumpkinseeds, and gold fish. The MDNR will complete a new fishery
survey in 2010.
To better understand the carp activity in the system and the potential contribution of carp to the
phosphorus loads to Lake Cornelia, an evaluation of the fishery, focusing mainly on carp and other
benthivorous fish should be conducted. This includes understanding where the carp in Lake Cornelia
spawn, and if there are carp located in any of the water bodies located upstream of North Cornelia.
Potential items to be considered when evaluating the impact of carp on water quality should include:
• Quantifying carp population in North and South Cornelia as well as upstream water bodies
• Tracking carp movement between the water bodies in the system, throughout the course of a
year (Dr. Peter Sorenson from the University of Minnesota has done similar tracking of carp
in several west metro area lakes)
• Identification of the key carp spawning locations within the system
• Understanding of how other fish populations may use the Lake Cornelia (spawning, feeding,
etc.)
Potential partnerships with the University of Minnesota and the MDNR may be possible as there is
significant interest in carp management in Lake Cornelia, and there is currently research being
conducted to better understand this invasive fish.
If the review of the fishery indicates that carp management may be an option, a typical management
strategy would include the combination of the following key steps: elimination of reinfestation,
suppressment of recruitment, and removal of adult carp (Sorenson, 2009). Removal and management
of carp would require permitting and guidance from the MDNR.
Watershed Management
Several watershed management BMPs were considered for this UAA. However, model simulations
indicated that even with the implementation of several combined BMPs (Scenario 11), it may not be
possible to meet the Level III Classification goal based on TSI or the MPCA shallow lake standards
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xxx
in neither North nor South Cornelia. While it was predicted that water quality will improve with the
implementation of the various BMPs, model simulations indicate the water quality will typically
remain in the Level IV classification.
Public Participation
Finally, it should be mentioned that it is a general NMCWD goal to encourage public participation in
all NMCWD activities and decisions that may affect the public. In accordance with this goal, the
NMCWD seeks to involve the public in the discussion of this UAA. This goal is expected to be
achieved through a public meeting to obtain comments on the Lake Cornelia UAA.
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Lake Cornelia
Use Attainability Analyses
Table of Contents
Executive Summary ....................................................................................................................................... i
Overview ................................................................................................................................................ i
Nine Mile Creek Watershed District Water Quality Goals .................................................................... i
Lake Characteristics .............................................................................................................................. v
North Cornelia ............................................................................................................................ v
South Cornelia ............................................................................................................................ v
Water Quality Problem Assessment ...................................................................................................... v
Baseline Lake Water Quality Status ........................................................................................... v
Lake Cornelia Current Water Quality ....................................................................................... vii
Trend Analysis ........................................................................................................................... xi
Watershed Runoff Pollution ...................................................................................................... xi
Sediment Core Analysis ...................................................................................................................... xx
Aquatic Weeds .................................................................................................................................... xx
Ecosystem and Fisheries .................................................................................................................... xxi
Recommended Lake and Watershed Management Practices ............................................................ xxii
Aquatic Weed Management ................................................................................................. xxvii
In -Lake Management ........................................................................................................... xxviii
Internal Sediment Release ...................................................................................... xxviii
Management of Benthivorous Fish Populations ..................................................... xxviii
Watershed Management ........................................................................................................ xxix
Public Participation ................................................................................................................. xxx
1.0 Introduction ............................................................................................................................................ 1
1.1 Purpose and Process of the UAA ................................................................................................ 1
1.2 Watershed and Lake Water Quality Modeling Tools ................................................................. 2
1.3 Scope ........................................................................................................................................... 3
1.4 General Framework of the UAA ................................................................................................. 3
1.4.1 Identification of Goals and Expectations ....................................................................... 3
1.4.1.1 NMCWD Goals and Desired Uses ................................................................. 3
1.4.1.2 Lake Cornelia and the Impaired Waters List .................................................. 3
1.4.1.3 Baseline Water Quality Prediction Methods .................................................. 4
1.4.1.3 Water Quality Trend Analyses ....................................................................... 5
1.4.2 Assessment of Current Conditions ................................................................................. 5
1.4.3 Assessment of Future Conditions .................................................................................. 6
1.4.4 Evaluation of Management Strategies ........................................................................... 7
2.0 General Concepts in Lake Water Quality .............................................................................................. 8
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2.1 Eutrophication ............................................................................................................................. 8
2.2 Trophic States ............................................................................................................................. 8
2.3 Limiting Nutrients ....................................................................................................................... 9
2.4 Stratification .............................................................................................................................. 10
2.5 Nutrient Recycling and Internal Loading .................................................................................. 11
3.0 Identification of Goals and Expectations ............................................................................................. 14
3.1 NMCWD Goals for Lake Cornelia ........................................................................................... 14
3.1.1 Water Quantity Goal .................................................................................................... 14
3.1.2 Water Quality Goal ...................................................................................................... 14
3.1.3 Aquatic Communities Goal .......................................................................................... 16
3.1.4 Recreational-Use Goal ................................................................................................. 16
3.1.5 Wildlife Goal ............................................................................................................... 16
3.2 Expected Benefits of Water Quality Improvements ................................................................. 16
3.2.1 Enhancement of Recreational Use ............................................................................... 16
3.2.2 Improvements in Aquatic Habitat ................................................................................ 17
4.0 Lake Basin and Watershed Characteristics .......................................................................................... 18
4.1 Lake Basin Characteristics ........................................................................................................ 18
4.1.1 North Cornelia ............................................................................................................. 18
4.1.2 South Cornelia ............................................................................................................. 18
4.2 Watershed Characteristics ......................................................................................................... 21
4.2.1 Present Land Use ......................................................................................................... 21
4.2.2 Future Land Use .......................................................................................................... 22
4.3 Lake Inflows and Drainage Areas ............................................................................................. 22
4.3.1 Natural Conveyance Systems....................................................................................... 22
4.3.2 Stormwater Conveyance Systems ................................................................................ 22
4.3.3 Southdale Center Cooling System Discharge .............................................................. 23
5.0 Existing Water Quality ........................................................................................................................ 28
5.1 Water Quality ............................................................................................................................ 28
5.1.1 Data Collection ............................................................................................................ 28
5.1.2 Baseline/Current Water Quality ................................................................................... 37
5.1.2.1 Baseline Lake Water Quality Status ............................................................. 37
5.1.2.2 Lake Cornelia Current (2008) Water Quality ............................................... 39
5.1.2.3 Lake Cornelia Water Quality Trend Analysis .............................................. 40
5.2 Nutrient Loading ....................................................................................................................... 40
5.2.1 External Loads ............................................................................................................. 40
5.2.1.1 Watershed Runoff ........................................................................................ 40
5.2.1.2 Southdale Cooling Water System Discharge ............................................... 42
5.2.1.3 Direct Precipitation & Atmospheric Deposition .......................................... 43
5.2.2 Internal Loads .............................................................................................................. 48
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5.2.2.1 Internal Phosphorus Loading Based on the Mass Balance Modeling .......... 48
5.2.2.2 Sediment Core Analysis ............................................................................... 49
5.3 Aquatic Communities ............................................................................................................... 52
5.3.1 Phytoplankton .............................................................................................................. 52
5.3.2 Zooplankton ................................................................................................................. 58
5.3.3 Macrophytes ................................................................................................................. 64
5.3.4 Fish and Wildlife.......................................................................................................... 66
6.0 Water Quality Modeling for the UAA ................................................................................................. 67
6.1 Use of the P8 Model ................................................................................................................. 67
6.2 Water Quality Model (P8) Calibration ...................................................................................... 68
6.2.1 Climatic Conditions ..................................................................................................... 68
6.2.2 Stormwater Volume Calibration .................................................................................. 68
6.2.3 Phosphorus Loading Calibration .................................................................................. 69
6.2.4 Atmospheric Deposition .............................................................................................. 69
6.3 In -Lake Modeling ..................................................................................................................... 72
6.3.1 Balance Modeling to Existing Water Quality .............................................................. 72
6.3.2 Accounting for Internal Loading.................................................................................. 73
6.3.3 In-Lake Water Quality Model Calibration ................................................................... 74
6.4 Use of the P8/In-Lake Models .................................................................................................. 77
6.5 Modeling Chlorophyll a and Secchi Disc Transparency .......................................................... 77
7.0 Analysis of Future Conditions ............................................................................................................. 80
7.1 Future Conditions Modeling Assumptions ............................................................................... 80
7.2 Modeling Results ...................................................................................................................... 83
7.2.1 Water Quality Model Results under Existing Conditions ............................................ 83
7.2.2 Water Quality Model Results under Future Conditions ............................................... 83
7.2.3 Expected Water Levels Under Future Conditions ....................................................... 93
8.0 Evaluation of Possible Management Initiatives ...................................................................................... 95
8.1 General Discussion of Improvement Scenarios ........................................................................ 95
8.1.1 Structural BMPs ........................................................................................................... 95
8.1.1.1 Wet Detention Ponds .................................................................................... 96
8.1.1.2 Infiltration .................................................................................................... 97
8.1.1.3 Vegetated Buffer Strips ................................................................................ 99
8.1.1.4 Oil and Grit Separators ................................................................................. 99
8.1.1.5 Alum Treatment Plants ............................................................................... 100
8.1.1.6 Iron-Enhanced Sand Filtration ................................................................... 100
8.1.2 Nonstructural BMPs ................................................................................................... 101
8.1.2.1 Public Education ........................................................................................ 101
8.1.2.2 Ordinances .................................................................................................. 101
8.1.2.3 Street Sweeping .......................................................................................... 102
8.1.2.4 Deterrence of Waterfowl ............................................................................ 102
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8.1.3 In-Lake BMPs ............................................................................................................ 102
8.1.3.1 Removal of Benthivorous (Bottom-Feeding) Fish ..................................... 103
8.1.3.2 Application of Alum (Aluminum Sulfate) ................................................. 103
8.2 Feasibility Analysis ................................................................................................................. 104
8.2.1 Statement of Problem ................................................................................................. 104
8.2.2 Selection and Effectiveness of Alternatives ............................................................... 106
8.2.2.1 Site-Specific Structural BMPs ................................................................... 106
8.2.2.1.1 Add Pond NC_62A designed to meet MPCA/NURP criteria . 106
8.2.2.1.2 Add Alum Treatment Plant to treat inflows from NC_3
(Swimming Pool Pond) ............................................................................... 110
8.2.2.1.3 Add Iron-Enhanced Sand Filter to treat inflows from NC_3
(Swimming Pool Pond) ............................................................................... 111
8.2.2.1.4 Infiltration of 1-inch of Runoff from ALL Impervious Surfaces
Watershed-Wide .......................................................................................... 113
8.2.2.2 In -Lake Treatments .................................................................................... 122
8.2.2.2.1 Treat - Application of Alum to the Entire Lake Surface Area of
North Cornelia ............................................................................................. 122
8.3 Combination of BMP Scenarios ............................................................................................. 124
9.0 Discussion and Recommendations..................................................................................................... 126
9.1 Attainment of Stated Goals ..................................................................................................... 126
9.1.1 Water Quantity Goal .................................................................................................. 126
9.1.2 Water Quality Goal .................................................................................................... 126
9.1.3 Aquatic Communities Goal ........................................................................................ 129
9.1.4 Recreational-Use Goal ............................................................................................... 130
9.1.5 Wildlife Goal ............................................................................................................. 130
9.2 Recommendations ................................................................................................................... 133
9.2.1 Aquatic Weed Management ....................................................................................... 133
9.2.2 In-Lake Management ................................................................................................. 134
9.2.2.1 Internal Sediment Release .......................................................................... 134
9.2.2.2 Management of Benthivorous Fish Populations ........................................ 134
9.2.3 Watershed Management ............................................................................................. 136
9.2.4 Public Participation .................................................................................................... 137
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List of Tables
Table EX-1 Lake Cornelia Management Table. Water quality, recreational-use and ecological
classifications of, and management philosophies for Lake Cornelia, referencing
Carlson’s Trophic State index (TSI) values (Secchi disc transparency basis) .............iv
Table EX-2 Summary of Lake Cornelia Baseline Water Quality Modeling Results ..........................vi
Table EX-3 Lake Cornelia Predicted Total Phosphorus and Chlorophyll a Concentration, Secchi
Disc Transparency, and TSISD for All Management Alternatives Analyzed .......... xxiii
Table 3-1 Lake Cornelia Management Table. Water quality, recreational-use and ecological
classifications of, and management philosophies for Lake Cornelia, referencing
Carlson’s Trophic State index (TSI) values (Secchi disc transparency basis) ............ 15
Table 4-1 Stage-Storage-Discharge Relationship for Lake Cornelia ......................................... 20
Table 4-2 Land Use in the Lake Cornelia Watershed ............................................................... 26
Table 5-1a Lake Cornelia Water Quality Data (2004) ................................................................ 30
Table 5-1b Lake Cornelia Water Quality Data (2008) ................................................................ 31
Table 5-2 Summary of Lake Cornelia Depths of Runoff and Areal TP Loading Rates .............. 41
Table 5-3 Summary of Lake Cornelia Water and Phosphorus Budgets ..................................... 44
Table 5-4 Comparison Lake Cornelia Internal Phosphorus Loading Rates to Those of Other
Metro Area Lakes .................................................................................................... 50
Table 6-1 Precipitation Amounts for Various Climatic Conditions ........................................... 68
Table 7-1 Summary of Lake Cornelia Water and Phosphorus Budgets for Future Conditions ... 85
Table 7-2 Total Phosphorus Loading Impact of Future Conditions on Lake Cornelia ............... 86
Table 7-2 Lake Cornelia Average Annual Water Level Summary ............................................ 93
Table 7-3 Point of France Pond Average Annual Water Level Summary ................................. 94
Table 8-1 General Effectiveness of Stormwater BMPs at Removing Common Pollutants from
Runoff ..................................................................................................................... 96
Table 8-2 Lake Cornelia Predicted Total Phosphorus and Chlorophyll a Concentration, Secchi
Disc Transparency, and TSISD for All Management Alternatives Analyzed ............ 105
Table 8-3 Lake Cornelia UAA MPCA/NURP Wet Detention Volumes (Required per
MPCA/NURP) ...................................................................................................... 108
Table 8-4 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of NURP Pond NC_62a .................................................................... 110
Table 8-5 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of Alum Treatment Plant treating inflow from NC_3 (Swimming Pool
Pond) .................................................................................................................... 111
Table 8-6 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of an Iron-Enhanced Sand Filter treating inflow from NC_3 (Swimming
Pool Pond) ............................................................................................................ 113
Table 8-7 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Infiltration of 1-inch of Runoff from ALL Impervious Surfaces Watershed-Wide .. 114
Table 8-8 Lake Cornelia Average Annual Water Level Summary – 1-inch of Infiltration from
ALL Impervious Surfaces Watershed-Wide ........................................................... 114
Table 8-9 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with In-
Lake Alum Treatment in North Cornelia ................................................................ 124
Table 8-10 Lake Cornelia Total Phosphorus Loading Reduction for BMP Scenario 11 ............ 125
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Table 9-1 Lake Cornelia Management Table. Water quality, recreational-use and ecological
classifications of, and management philosophies for Lake Cornelia, referencing
Carlson’s Trophic State index (TSI) values (Secchi disc transparency basis) .......... 128
Table 9-2 NMCWD Water Quality Management Goals ......................................................... 129
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List of Figures
Figure EX-1 Lake Cornelia Historic Summer Average Water Quality (a) Total Phosphorus
Concentration (b) Chlorophyll-a Concentration and (c) Secchi Disc Transparency . viii
Figure EX-2a North Cornelia 2008 Seasonal Changes in Concentration of Total Phosphorus and
Chlorophyll a and Secchi Disc Transparencies .........................................................ix
Figure EX-2b South Cornelia 2008 Seasonal Changes in Concentration of Total Phosphorus and
Chlorophyll a and Secchi Disc Transparencies .......................................................... x
Figure EX-3 Lake Cornelia UAA Subwatersheds and Existing Land Use .................................... xii
Figure EX-4 Lake Cornelia Watershed Land Uses ..................................................................... xiii
Figure EX-5a Lake Cornelia Watershed Phosphorus and Water Budgets – Average Climatic
Conditions ............................................................................................................. xvii
Figure EX-5b Lake Cornelia Watershed Phosphorus and Water Budgets – Wet Climatic Conditionsxviii
Figure EX-5c Lake Cornelia Watershed Phosphorus and Water Budgets – Dry Climatic Conditionsxix
Figure EX-6 Location of BMP Alternatives .............................................................................. xxiv
Figure EX-7a North Cornelia: Estimated TSISD Following BMP Implementation and BMP Cost xxv
Figure EX-7b South Cornelia: Estimated TSISD Following BMP Implementation and BMP Costxxvi
Figure 4-1 Lake Cornelia Approximate Bathymetry .................................................................. 19
Figure 4-2 Lake Cornelia UAA Watersheds and Existing Land Use .......................................... 24
Figure 4-3 Lake Cornelia Watershed Land Uses ....................................................................... 25
Figure 4-4 Lake Cornelia UAA Watersheds and Existing Storm Sewer System ......................... 27
Figure 5-1a North Cornelia 2004 Seasonal Changes in Concentration of Total Phosphorus,
Chlorophyll a and Secchi Disc Transparencies ........................................................ 32
Figure 5-1b South Cornelia 2004 Seasonal Changes in Concentration of Total Phosphorus,
Chlorophyll a and Secchi Disc Transparencies ........................................................ 33
Figure 5-1c North Cornelia 2008 Seasonal Changes in Concentration of Total Phosphorus,
Chlorophyll a and Secchi Disc Transparencies ........................................................ 34
Figure 5-1d South Cornelia 2008 Seasonal Changes in Concentration of Total Phosphorus,
Chlorophyll a and Secchi Disc Transparencies ........................................................ 35
Figure 5-2 Lake Cornelia Historic Summer Average Water Quality (a) Total Phosphorus
Concentration (b) Chlorophyll-a Concentration and (c) Secchi Disc Transparency ... 36
Figure 5-3a Lake Cornelia Water and Phosphorus Budgets – Average Climatic Conditions ........ 45
Figure 5-3b Lake Cornelia Water and Phosphorus Budgets – Wet Climatic Conditions ............... 46
Figure 5-3c Lake Cornelia Water and Phosphorus Budgets – Dry Climatic Conditions ............... 47
Figure 5-4 Lake Cornelia 2008 Sediment Mobile Phosphorus Estimates ................................... 51
Figure 5-5a North Lake Cornelia 2004 Phytoplankton Surveys, Data Summary by Division ....... 54
Figure 5-5b South Lake Cornelia 2004 Phytoplankton Surveys, Data Summary by Division ....... 55
Figure 5-5c North Lake Cornelia 2008 Phytoplankton Surveys, Data Summary by Division ....... 56
Figure 5-5d South Lake Cornelia 2008 Phytoplankton Surveys, Data Summary by Division ....... 57
Figure 5-6a North Lake Cornelia 2004 Zooplankton Surveys, Data Summary by Division .......... 60
Figure 5-6b South Lake Cornelia 2004 Zooplankton Surveys, Data Summary by Division .......... 61
Figure 5-6c North Lake Cornelia 2008 Zooplankton Surveys, Data Summary by Division .......... 62
Figure 5-6d South Lake Cornelia 2008 Zooplankton Surveys, Data Summary by Division .......... 63
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Figure 6-1a North Cornelia Calibrated Water Balance Model 2007-2008 .................................... 70
Figure 6-1b South Cornelia Calibrated Water Balance Model 2007-2008 .................................... 71
Figure 6-2a North & South Cornelia In-Lake Model Calibration Results for Average Climatic
Conditions with Watershed and Spring Decay ......................................................... 75
Figure 6-2b North & South Cornelia In-Lake Model Calibration Results for Dry Climatic
Conditions with Watershed and Spring Decay ......................................................... 76
Figure 6-3 North Cornelia Relationship between Total Phosphorus Concentration, Chlorophyll a
Concentration, and Secchi Disc Transparency .......................................................... 79
Figure 7-1 Lake Cornelia Future Conditions Assumptions ........................................................ 82
Figure 7-2a North Cornelia Estimated Average Summer Total Phosphorus Concentration under
Varying Climatic Conditions ................................................................................... 87
Figure 7-2b South Cornelia Estimated Average Summer Total Phosphorus Concentration under
Varying Climatic Conditions ................................................................................... 88
Figure 7-3a North Cornelia Estimated Average Summer Chlorophyll a Concentrations under
Varying Climatic Conditions ................................................................................... 89
Figure 7-3b South Cornelia Estimated Average Summer Chlorophyll a Concentrations under
Varying Climatic Conditions ................................................................................... 90
Figure 7-4a North Cornelia Estimated Average Summer Secchi Disc Transparency under Varying
Climatic Conditions ................................................................................................. 91
Figure 7-4b South Cornelia Estimated Average Summer Secchi Disc Transparency under Varying
Climatic Conditions ................................................................................................. 92
Figure 8-1 Lake Cornelia Location of BMP Alternatives ........................................................ 107
Figure 8-2a North Cornelia: Estimated Average Summer Total Phosphorus Concentration
Following BMP Implementation ............................................................................ 116
Figure 8-2b South Cornelia: Estimated Average Summer Total Phosphorus Concentration
Following BMP Implementation ............................................................................ 117
Figure 8-3a North Cornelia: Estimated Average Summer Chlorophyll a Concentration Following
BMP Implementation ............................................................................................ 118
Figure 8-3b South Cornelia: Estimated Average Summer Chlorophyll a Concentration Following
BMP Implementation ............................................................................................ 119
Figure 8-4a North Cornelia: Estimated Average Summer Secchi Disc Transparency Following
BMP Implementation ............................................................................................ 120
Figure 8-4b South Cornelia: Estimated Average Summer Secchi Disc Transparency Following
BMP Implementation ............................................................................................ 121
Figure 9-1a North Cornelia: Estimated Summer Average Total Phosphorus Concentration
Following BMP Implementation and BMP Cost .................................................... 131
Figure 9-1b South Cornelia: Estimated Summer Average Total Phosphorus Concentration
Following BMP Implementation and BMP Cost .................................................... 132
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List of Appendices
Appendix A Data Collection Methods
Appendix B P8 Model Parameter Selection
Appendix C Pond Data
Appendix D Southdale Center Inflows
Appendix E Lake Cornelia 2004 & 2008 Water Quality Data
Appendix F Lake Cornelia Biological and Fisheries Data
Appendix G BMP Cost Estimates
Appendix H Lake Cornelia 2004 & 2008 Macrophyte Surveys
Appendix I Lake Cornelia Sediment Core Analysis
Appendix J Lake Cornelia Trend Analyses
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1.0 Introduction
This report describes the results of the Use Attainability Analysis (UAA) for Lake Cornelia in Edina,
MN. The UAA provides the scientific foundation for a lake-specific best management plan that will
permit maintenance of, or attainment of, the intended beneficial uses of Lake Cornelia. The UAA is
a scientific assessment of a water body’s physical, chemical, and biological condition. This study
includes both a water quality assessment and prescription of protective and/or remedial measures for
Lake Cornelia and the tributary watershed. The conclusions and recommendations are based on
historical water quality data, the results of an intensive lake water quality monitoring in 2004 amd
again in 2008, and computer simulations of land use impacts on water quality in Lake Cornelia using
watershed and lake models calibrated to the 2008 data set. Water quality goals for the lake were
identified based on the lake’s designated beneficial uses (e.g., runoff management). In addition, best
management practices (BMPs) were evaluated to compare their relative effect on total phosphorus
concentrations and Secchi disc transparencies (i.e., water clarity). Management scenarios were then
assessed to determine attainment or non-attainment with the lake’s beneficial uses.
1.1 Purpose and Process of the UAA
The intent of the UAA is to provide a means by which the effects of various watershed and lake
management strategies can be evaluated. To evaluate management strategies, it is first necessary to
identify the intended uses of the lake in question. With these uses in mind, appropriate water quality
goals for the lake can be established and reviewed. Once the intended uses and corresponding goals
for the lake have been identified, it becomes possible to evaluate lake and watershed management
strategies.
The UAA employs a watershed runoff model and a lake water quality model; the lake water quality
model predicts changes in lake water quality based on the results of the watershed runoff model.
Using these models, various watershed and lake management strategies can be evaluated to determine
their likely effects on the lake. The resulting lake water quality can then be compared with the water
quality goals for the lake to see if the management strategies are able to produce the desired changes
in the lake. Using the tools of the UAA, the cost-effectiveness of the management strategies can also
be evaluated.
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1.2 Watershed and Lake Water Quality Modeling Tools
Central to the water quality analysis is the use of a water quality model that predicts the amount of
pollutants that reach a lake via stormwater runoff. During development of the Nine Mile Creek
Watershed District’s Water Management Plan (Barr, 1996), a simplified model using literature-based
export rate coefficients was used to estimate the annual water and phosphorus loads to the lake. The
1996 Plan recommended using the water quality model XP-SWMM (the EPA’s Stormwater and
Wastewater Management Model with a graphical interface by XP Software) in the UAA to provide a
more precise estimate of water and phosphorus loads. Since the P8 model (Program for Predicting
Polluting Particle Passage through Pits, Puddles and Ponds; IEP, Inc., 1990) is less data intense and
provides similar predictions of phosphorus loads to a lake as XP-SWMM, this UAA uses the P8
model instead.
The P8 model requires hourly precipitation and daily temperature data; long-term climatic data can
be used so that watersheds and BMPs can be evaluated for varying hydrologic conditions. To
properly develop and calibrate the model also requires an accurate assessment of land use and
impervious percentages, pond system morphology, flow routing, and lake water quality. After
supplying the required input data, the P8 model was used to estimate both the water and phosphorus
loads introduced from the entire watershed of Lake Cornelia.
The phosphorus and water loads estimated with P8 for 2007-08 were entered into a separate in-lake
mass balance model so that the phosphorus concentration in Lake Cornelia could be estimated.
These modeled 2008 phosphorus concentrations were compared to 2008 sampling data to calibrate
the in-lake model and ensure that it was producing reasonable results. The calibrated model was then
used to estimate phosphorus loads and concentrations with varying climatic regimes and BMP
scenarios. Details of the modeling results and a discussion of management opportunities are
presented later in this report.
When evaluating the results of the modeling, it is important to consider that the results provided can
be assumed to be more accurate in terms of relative differences than in absolute results. The model
will predict the percent difference in phosphorus reduction between various BMP scenarios in the
watershed fairly accurately. It also provides a realistic estimate of the relative differences in
phosphorus and water loadings from the various subwatersheds and major inflow points to the lake.
However, since runoff quality is highly variable with time and location, the phosphorus loadings
estimated by the model for a specific watershed may not necessarily reflect the actual loadings, in
absolute terms. Various site-specific factors, such as lawn care practices, illicit point source
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discharges and erosion due to construction are not accounted for in the model. The model provides
values that are considered to be typical of the region, given the land uses identified for the watershed
in question.
1.3 Scope
This UAA evaluates current and future conditions for Lake Cornelia. As a result, the watershed
analysis intrinsic to the UAA focuses on the local watershed of the lake.
1.4 General Framework of the UAA
Several steps were necessary for the evaluation of the watershed, lake, and management initiatives
conducted for this UAA. Those steps are outlined in the sections that follow.
1.4.1 Identification of Goals and Expectations
To evaluate lake management strategies, it is first necessary to establish the criteria against which
outcomes can be measured.
1.4.1.1 NMCWD Goals and Desired Uses
To identify those criteria, past NMCWD documents were consulted, as well as the city of Edina
Comprehensive Water Resource Management Plan (Barr Engineering Co., 2009 (draft)). In addition,
present and future uses of the lake were considered. The Nine Mile Creek District Water
Management Plan (Barr, 2007) lists the NMCWD goals for both the North and South basins of Lake
Cornelia as Level III, with the desired use listed as fishing and aesthetic viewing.
1.4.1.2 Lake Cornelia and the Impaired Waters List
The federal Clean Water Act requires states to define water quality standards, varying on the
designated use of the water body. The MPCA has developed assessment methodologies, conducted
extensive sampling of lakes, and ultimately derived ecoregion-based lake eutrophication standards
for deep and shallow lakes for total phosphorus, chlorophyll-a, and Secchi depths (MPCA, 2008).
These standards are outlined in Minnesota Rules, Chapter 7050 (Standards for the Protection of
Waters of the State).
For shallow lakes in the North Central Hardwood Forests (NCHF) ecoregion (where Lake Cornelia is
located), the total phosphorus standard established by the MPCA is 60 μg/L, which serves as the
upper threshold for lake water quality. The chlorophyll-a and Secchi disc standards are listed as less
than 20 µg/L greater than 1.0 meters, respectively. For lakes not meeting these standards, greater
frequencies of nuisance algal blooms and reduced recreational uses are expected.
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The federal Clean Water Act require not only requires states to establish water quality standards, it
also requires states to identify the waters that are impaired (or not meeting the established standards)
and to develop plans to improve the water quality in the impaired waters so that the standards are
met. As a result of the requirements of the federal Clean Water Act, the MPCA created 303(d)
Impaired Waters list. Every 2 years, the MPCA is required to publish an updated list of impaired
waters that do not meet the state’s water quality standards.
For all water bodes listed on the 303(d) Impaired Waters list, the MPCA requires that a strategy is
developed to improve the quality of impaired waters by conducting a Total Maximum Daily Load
(TMDL) study for each pollutant that causes the water body to not meet the state water quality
standards. Lake Cornelia was first listed on the 303(d) Impaired Waters list in 2008 for impaired
aquatic recreational use as the result of Nutrients/Eutrophication/Biological Indicators. According to
the MPCA 2010 (draft) 303(d) Impaired Waters list, the expected TMDL study start date is 2013
with completion in 2018.
1.4.1.3 Baseline Water Quality Prediction Methods
The Minnesota Lake Eutrophication Analysis Procedure (MnLEAP) is intended to be used as a
screening tool for estimating lake conditions and for identifying “problem” lakes. MnLEAP is
particularly useful for identifying lakes requiring “protection” versus those requiring “restoration”
(Heiskary and Wilson, 1990). In addition, MnLEAP modeling has been done in the past to identify
Minnesota lakes which may be in better or worse condition than they “should be” based on their
location, watershed area and lake basin morphometry (Heiskary and Wilson, 1990).
The MPCA has also reconstructed water quality from analysis of fossil diatoms contained in
sediment cores obtained from some Minnesota lakes (Heiskary and Swain, 2004). As part of this
study, the MPCA found that there was good agreement between the phosphorus contained in diatom
fossils and the Vighi and Chiaudani (MEI) model (1985) for lakes with background phosphorus
concentrations of 30 μg/L or less. The Vighi and Chiaudani MEI model provides reasonable accurate
estimates of pre-European settlement total phosphorus concentrations for lakes, based on current
alkalinity or conductivity water quality measurements. Vighi and Chiaudani (1985) recommend
using current measurements of alkalinity over conductivity measurements from lakes that are
affected by anthropogenic (human) sources of phosphorus.
Additionally, the Wisconsin Lake Modeling Suite (WiLMS) model (WI-DNR, 2004) was also used to
estimate Lake Cornelia’s water quality under natural watershed conditions. The WiLMS model
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(Lake Total Phosphorus Prediction Module) uses an annual time step and predicts spring overturn,
growing season mean, and annual average total phosphorus concentrations in lakes. The model uses
information about the lake and watershed characteristics and phosphorus loadings in conjunction
with 13 different published phosphorus prediction regressions to predicted the expected in-lake total
phosphorus concentration.
1.4.1.3 Water Quality Trend Analyses
Trend analyses of lake water quality data are completed to determine if a lake has experienced
significant degradation or improvement during all (or a portion) of the years for which water quality
data are available. Water quality data from the “summer” growing season (June-September) are
compiled from previous investigations for each analysis. The summer averages of the water quality
data are used to determine water quality trends. Long term trends are typically determined using
standard statistical methods (i.e., linear regression and analysis of variance).
For this report, the District used the Mann-Kendall/Sen’s Slope Trend Test to determine water
quality trends and their significance. To complete the trend test, the calculated summer average must
be based on at least four measured values during the sampling season, and at least five years of data
are required. The NMCWD considers a lake’s water quality to have significantly improved or
declined if the Mann-Kendall/Sen’s Slope Trend Test is statistically significant at the 95 percent
confidence interval. Also, to conclude an improvement requires concurrent decreases in total
phosphorus and chlorophyll a concentrations, and increases in Secchi disc transparencies; a
conclusion of degradation requires the inverse relationship.
1.4.2 Assessment of Current Conditions
The condition of the lake’s watershed, biological communities, and water quality within Lake
Cornelia was evaluated for this study.
The watershed analysis involved assessment of soil type, land use and residential density, and the
impervious fraction of the land in the watershed. Land use assumptions were made based on the
Metropolitan Council land use coverage GIS database. Subwatersheds were delineated using two-
foot topographic data from the city of Edina and field verified where necessary. The storm sewer
routing was determined using storm sewer information provided by the city of Edina. The pond
storage data was taken from bathymetry data from the city of Edina to allow correct evaluation of the
ponds’ current water treatment performance. Based on the wetland inventories for the surrounding
area, pond characteristics were estimated for the ponds that did not have survey information.
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Biological communities were evaluated through consideration of past sampling of the lakes’
phytoplankton, zooplankton, and macrophyte communities. Current lake water quality was assessed
through examination of recent and historical water sampling data. In particular, the evaluation of
current in-lake water quality was based on the results of intensive monitoring completed in 2003-04
and again in 2007-08. These data were also used in calibration of the current water quality model
used in the UAA.
1.4.3 Assessment of Future Conditions
The Lake Cornelia watershed is fully-developed and as a result, changes in the overall type of land
use within the watershed are unlikely. The future condition of Lake Cornelia will depend primarily
on increased storage area in ponds, changes in water routing within the watershed, and
redevelopment within the watershed. Using this information, the P8 model was used to predict
watershed loading of the lake under various climatic conditions. The watershed loadings (water and
nutrient loadings) were then used as inputs to the in-lake model to provide predictions of future water
quality.
In the fall of 2004 Swimming Pool Pond and Point of France Pond were dredged to increase dead
storage volume. The updated pond volumes are included in the watershed modeling.
To assist in heating and cooling processes Southdale Center routes approximately 30 to 40 million
gallons per year to Lake Cornelia. Originally taken from the groundwater, this water passes once-
through the Southdale heating/cooling system and is continuously discharged to Point of France Pond
which ultimately flows into North Cornelia. The amount of water varies, but ranges from 1.0 million
gallons per month to 6.8 million gallons per month, with highest volumes during warm summer
months. The discharge is currently permitted by the MDNR and monthly readings of the volume
pumped from the groundwater are submitted. See Appendix D for water usage in this system for
2005 through 2008. According to the MDNR, the system is not permanent and must be abandoned
by 2010. The watershed was modeled under various conditions both including and removing the
Southdale Center inflows.
In a previous study performed for the City of Edina, a 42-inch RCP arch pipe was recommended to
convey the water discharged from Swimming Pool Pond (SPP) to North Cornelia. This proposal was
made to lower flood levels for SPP and surrounding areas. Currently low flows outlet from SPP to
North Cornelia through a 3-3/4” pipe and SPP water levels equalize with Garrison Pond. The outlet
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from Garrison Pond to Lake Pamela was modeled using survey data collected in 2009. Both the
current outlet configuration and proposed pipe configuration were modeled.
1.4.4 Evaluation of Management Strategies
Having modeled the watershed loading and lake response under assumed future conditions, it is
possible to evaluate the potential impacts of various watershed and lake management strategies.
Several likely approaches to watershed and lake management were selected and evaluated under
various climatic conditions. Costs of the strategies were estimated so that those costs could be
compared to the in-lake benefits that the management initiatives are expected to provide.
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2.0 General Concepts in Lake Water Quality
There are a number of concepts and terminology that are necessary to describe and evaluate a lake’s
water quality. This section is a brief discussion of those concepts, divided into the following topics:
• Eutrophication
• Trophic states
• Limiting nutrients
• Stratification
• Nutrient recycling and internal loading
To learn more about these five topics, one can refer to any text on limnology (the science of lakes
and streams).
2.1 Eutrophication
Eutrophication, or lake degradation, is the accumulation of sediments and nutrients in lakes. As a
lake naturally becomes more fertile, algae and weed growth increases. The increasing biological
production and sediment inflow from a lake’s watershed eventually fill the lake’s basin. Over a
period of many years, the lake successively becomes a pond, a marsh and, ultimately, a terrestrial
site. This process of eutrophication is natural and results from the normal environmental forces that
influence a lake. Cultural eutrophication, however, is an acceleration of the natural process caused by
human activities. Nutrient and sediment inputs (i.e., loadings) from wastewater treatment plants,
septic tanks, and stormwater runoff can far exceed the natural inputs to the lake. The accelerated rate
of water quality degradation caused by these pollutants results in unpleasant consequences. These
include profuse and unsightly growths of algae (algal blooms) and/or the proliferation of rooted
aquatic weeds (macrophytes).
2.2 Trophic States
Not all lakes are at the same stage of eutrophication; therefore, criteria have been established to
evaluate the nutrient status of lakes. Trophic state indices (TSIs) are calculated for lakes on the basis
of total phosphorus, chlorophyll a concentrations, and Secchi disc transparencies. TSI values range
upward from 0, describing the condition of the lake in terms of its trophic status (i.e., its degree of
fertility). All three of the parameters can be used to determine a TSI. However, water transparency is
typically used to develop the TSISD (trophic state index based on Secchi disc transparency) because
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9
people’s perceptions of water clarity are often directly related to recreational-use impairment. The
TSI rating system results in the placement of a lake with high fertility in the hypereutrophic status
category. Water quality trophic status categories include oligotrophic (i.e., excellent water quality),
mesotrophic (i.e., good water quality), eutrophic (i.e., poor water quality), and hypereutrophic (i.e.,
very poor water quality). Water quality characteristics of lakes in the various trophic status categories
are listed below with their respective TSI ranges:
1. Oligotrophic – [20 < TSISD < 38] clear, low productive lakes, with total phosphorus
concentrations less than or equal to 10 µg/L, chlorophyll a concentrations of less than or equal to
2 µg/L, and Secchi disc transparencies greater than or equal to 4.6 meters (15 feet).
2. Mesotrophic – [38 < TSISD < 50] intermediately productive lakes, with total phosphorus
concentrations between 10 and 25 µg/L, chlorophyll a concentrations between 2 and 8 µg/L, and
Secchi disc transparencies between 2 and 4.6 meters (6 to 15 feet).
3. Eutrophic – [50 < TSISD < 62] high productive lakes relative to a neutral level, with 25 to
57 µg/L total phosphorus, chlorophyll a concentrations between 8 and 26 µg/L, and Secchi disc
measurements between 0.85 and 2 meters (2.7 to 6 feet).
4. Hypereutrophic – [62 < TSISD < 80] extremely productive lakes which are highly eutrophic and
unstable (i.e., their water quality can fluctuate on daily and seasonal basis, experience periodic
anoxia and fish kills, possibly produce toxic substances, etc.) with total phosphorus
concentrations greater than 57 µg/L, chlorophyll a concentrations of greater than 26 µg/L, and
Secchi disc transparencies less than 0.85 meters (2.7 feet).
Determining the trophic status of a lake is an important step in diagnosing water quality problems.
Trophic status indicates the severity of a lake’s algal growth problems and the degree of change
needed to meet its recreational-use goals. Additional information, however, is needed to determine
the cause of algal growth and a means of reducing it.
2.3 Limiting Nutrients
The quantity or biomass of algae in a lake is usually limited by the water’s concentration of an
essential element or nutrient “the limiting nutrient”. (For rooted aquatic plants, the nutrients are
derived from the sediments.) The limiting nutrient concept is a widely applied principle in ecology
and in the study of eutrophication. It is based on the idea that plants require many nutrients to grow,
but the nutrient with the lowest availability, relative to the amount needed by the plant, will limit
plant growth. It follows then, that identifying the limiting nutrient will point the way to controlling
algal growth.
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Nitrogen (N) and phosphorus (P) are generally the two growth-limiting nutrients for algae in most
natural waters. Analysis of the nutrient content of lake water and algae provides ratios of N:P. By
comparing the ratio in water to the ratio in the algae, one can estimate whether a particular nutrient
may be limiting. Algal growth is generally phosphorus-limited in waters with N:P ratios greater
than 12. Laboratory experiments (bioassays) can demonstrate which nutrient is limiting by growing
the algae in lake water with various concentrations of nutrients added. Bioassays, as well as
fertilization of in-situ enclosures and whole-lake experiments, have repeatedly demonstrated that
phosphorus is usually the nutrient that limits algal growth in freshwaters. Reducing phosphorus in a
lake, therefore, is required to reduce algal abundance and improve water transparency. Failure to
reduce phosphorus concentrations will allow the process of eutrophication to continue at an
accelerated rate.
2.4 Stratification
The process of internal loading is dependent on the amount of organic material in the sediments and
the depth-temperature pattern, or “thermal stratification,” of a lake. Thermal stratification profoundly
influences a lake’s chemistry and biology. When the ice melts and air temperature warms in spring,
lakes generally progress from being completely mixed to stratified with only an upper warm well-
mixed layer of water (epilimnion), and cold temperatures in a bottom layer (hypolimnion). Because
of the density differences between the lighter warm water and the heavier cold water, stratification in
a lake can become very resistant to mixing. When this occurs, generally in mid-summer, oxygen
from the air cannot reach the bottom lake water and, if the lake sediments have sufficient organic
matter, biological activity can deplete the remaining oxygen in the hypolimnion. The epilimnion can
remain well-oxygenated, while the water above the sediments in the hypolimnion becomes
completely devoid of dissolved oxygen (anoxic). Complete loss of oxygen changes the chemical
conditions in the water and allows phosphorus that had remained bound to the sediments to reenter
the lake water.
As the summer progresses, phosphorus concentrations in the hypolimnion can continue to rise until
oxygen is again introduced (recycled). Dissolved oxygen concentration will increase if the lake
sufficiently mixes to disrupt the thermal stratification. Phosphorus in the hypolimnion is generally
not available for plant uptake because there is not sufficient light penetration to the hypolimnion to
allow for growth of algae. The phosphorus, therefore, remains trapped and unavailable to the plants
until the lake is completely mixed. In shallow lakes this can occur throughout the summer, with
sufficient wind energy (polymixis). In deeper lakes, however, only extremely high wind energy is
sufficient to destratify a lake during the summer and complete mixing only occurs in the spring and
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11
fall (dimixis). Cooling air temperature in the fall reduces the epilimnion water temperature, and
consequently increases the density of water in the epilimnion. As the epilimnion water density
approaches the density of the hypolimnion water very little energy is needed to cause complete
mixing of the lake. When this fall mixing occurs, phosphorus that has built up in the hypolimnion is
mixed with the epilimnion water and becomes available for plant and algal growth.
2.5 Nutrient Recycling and Internal Loading
The significance of thermal stratification in lakes is that the density change in the metalimnion (i.e.,
middle transitional water temperature stratum) provides a physical barrier to mixing between the
epilimnion and the hypolimnion. While water above the metalimnion may circulate as a result of
wind action, hypolimnetic waters at the bottom generally remain isolated. Consequently, very little
transfer of oxygen occurs from the atmosphere to the hypolimnion during the summer.
Shallow water bodies may circulate many times during the summer as a result of wind mixing. Lakes
possessing these wind mixing characteristics are referred to as polymictic lakes. In contrast, deeper
lakes generally become well-mixed only twice each year. This usually occurs in the spring and fall.
Lakes possessing these mixing characteristics are referred to as dimictic lakes. During these periods,
the lack of strong temperature/density differences allows wind-driven circulation to mix the water
column throughout. During these mixing events, oxygen may be transported to the deeper portions of
the lake, while dissolved phosphorus is brought up to the surface.
Phosphorus enters a lake from either watershed runoff or direct atmospheric deposition. It would,
therefore, seem reasonable that phosphorus in a lake can decrease by reducing these external loads of
phosphorus to the lake. All lakes, however, accumulate phosphorus (and other nutrients) in the
sediments from the settling of particles and dead organisms. In some lakes this reservoir of
phosphorus can be reintroduced in the lake water and become available again for plant uptake. This
resuspension or dissolution of nutrients from the sediments to the lake water is known as “internal
loading”. As long as the lake’s sediment surface remains sufficiently oxidized (i.e., dissolved oxygen
remains present in the water above the sediment), its phosphorus will remain bound to sediment
particles as ferric hydroxy phosphate. When dissolved oxygen levels become extremely low at the
water-sediment interface (as a result of microbial activity using the oxygen), the chemical reduction
of ferric iron to its ferrous form causes the release of dissolved phosphorus, which is readily
available for algal growth, into the water column. The amount of phosphorus released from internal
loading can be estimated from depth profiles (measurements from surface to bottom) of dissolved
oxygen and phosphorus concentrations. Even if the water samples indicate the water column is well
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12
oxidized, the oxygen consumption by the sediment during decomposition can restrict the thickness of
the oxic sediment layer to only a few millimeters. Therefore, the sediment cannot retain the
phosphorus released from decomposition or deeper sediments, which result in an internal phosphorus
release to the water column. Low-oxygen conditions at the sediments, with resulting phosphorus
release, are to be expected in eutrophic lakes where relatively large quantities of organic material
(decaying algae and macrophytes) are deposited on the lake bottom.
If the low-lying phosphorus-rich waters near the sediments remain isolated from the upper portions
of the lake, algal growth at the lake’s surface will not be stimulated. Shallow lakes and ponds can be
expected to periodically stratify during calm summer periods, so that the upper warmer portion of the
water body is effectively isolated from the cooler, deeper (and potentially phosphorus-rich) portions.
Deep lakes typically retain their stratification until cooler fall air temperatures allow the water layers
to become isothermal and mix again. Deep lakes are, therefore, frequently dimictic, typically mixing
only twice a year. However, relatively shallow lakes are less thermally stable and may mix frequently
during the summer periods.
The pH of the water column can also play a vital role in affecting the phosphorus release rate under
oxic conditions. Photosynthesis by macrophytes and algae during the day tend to raise the pH in the
water column, which can enhance the phosphorus release rate from the oxic sediment. Enhancement
of the phosphorus release at elevated pH (pH > 7.5) is thought to occur through replacement of the
phosphate ion (PO4-3) with the excess hydroxyl ion (OH-) on the oxidized iron compound (James,
et al., 2001).
Another potential source of internal phosphorus loading is the die-off of Curlyleaf pondweed.
Curlyleaf pondweed is an exotic (i.e. non-native) lake weed that is common in many of the lakes in
the Twin Cities metropolitan area. Curlyleaf pondweed grows tenaciously during early spring,
crowding out native species. It releases a small reproductive pod that resembles a small pine cone in
late June, and then begins its die-back in early July. The biomass sinks to the bottom of the lake and
begins to decay, releasing phosphorus into the water column and causing oxygen depletion,
exacerbating the internal sediment release of phosphorus. This cycle typically results in an increase
in phosphorus concentrations in the lake in late-June of early July.
Benthivorous fish, such as carp and bullhead, can have a direct influence on the phosphorus
concentration in a lake (LaMarra, 1975). These fish typically feed on decaying plant and animal
matter and other organic particulates found at the sediment surface. The fish digest the organic
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13
matter, and excrete soluble nutrients, thereby transforming sediment phosphorus into soluble
phosphorus available for uptake by algae at the lake surface. Depending on the number of
benthivorous fish present, this process can occur at rates similar to watershed phosphorus loads.
Benthivorous fish can also cause resuspension of sediments in shallow ponds and lakes, causing
reduced water clarity and poor aquatic plant growth, as well as high phosphorus concentrations
(Cooke et al., 1993). In some cases, the water quality impairment caused by benthivorous fish can
negate the positive effects of BMPs and lake restoration.
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14
3.0 Identification of Goals and Expectations
3.1 NMCWD Goals for Lake Cornelia
The NMCWD Plan (Barr, 2007) currently lists the water quality conditions (and corresponding TSI
indices) for both the North and South basins of Lake Cornelia, and has established the water quality
goals for both basins as a Level III, with desired uses as fishing and aesthetic viewing. The five
specific goals criteria for Lake Cornelia are outlined and discussed here and in Table 3-1. Table 3-1
lists the water quality goals, recreational-use and ecological classifications for Lake Cornelia. The
table lists total phosphorus (TP) and chlorophyll a concentrations, Secchi disc (SD) transparencies,
and Carlson’s Trophic State Index (TSI) based on Secchi disc.
3.1.1 Water Quantity Goal
The water quantity goal for Lake Cornelia is to provide sufficient water storage during a regional
flood.
3.1.2 Water Quality Goal
The NMCWD Water Management Plan (Barr, 2007) lists water quality goals for both the North and
South basins of Lake Cornelia. Current water quality levels place Lake Cornelia at a Level IV
classification, which indicates the lake is generally intended for runoff management and has limited
recreational use value. The specific NMCWD goal for this lake classification is to achieve and
maintain a TSISD greater than 70. However, the Minnesota Department of Natural Resources
(MDNR) stocks the lake annually with approximately 300 to 400 bluegill for the Fishing in the
Neighborhood Program. To account for this level of recreational use, the NMCWD has assigned a
Level III classification which fully supports recreational activities that include fishing and aesthetic
viewing appears to be a reasonable goal. The specific NMCWD goal for Level III classification is to
achieve and maintain a TSISD between 60 and 70.
The MPCA has developed assessment methodologies, conducted extensive sampling of lakes, and
ultimately derived ecoregion-based lake eutrophication standards for deep and shallow lakes for total
phosphorus, chlorophyll-a, and Secchi depths (MPCA, 2008). These standards are outlined in
Minnesota Rules, Chapter 7050 (Standards for the Protection of Waters of the State). For shallow
lakes in the North Central Hardwood Forests (NCHF) ecoregion, the total phosphorus standard
established by the MPCA is 60 μg/L. The chlorophyll-a standard of less than 20 µg/L and for Secchi
disc transparency, the standard is not less than 1.0 meters.
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16
3.1.3 Aquatic Communities Goal
In 1992, the MDNR categorized many Minnesota lakes according to the type of fishery each lake
might reasonably be expected to support (An Ecological Classification of Minnesota Lakes with
Associated Fish Communities; Schupp, 1992). The MDNR’s ecological classification system takes
into account factors such as the lake area, percentage of the lake surface area that is littoral,
maximum depth, degree of shoreline development, Secchi disc transparency, and total alkalinity.
However, the MDNR did not classify Lake Cornelia as part of its 1992 study.
Since the MDNR did not specify the ecological classification for Lake Cornelia there is no specific
fisheries related TSI goal. However, the MDNR stocks the lake with fish, and it is the goal of the
NMCWD to achieve water quality that will result in a diverse and balanced native ecosystem.
3.1.4 Recreational-Use Goal
Lake Cornelia is a wildlife lake, indicating the lake is generally intended for wildlife habitat,
aesthetic viewing, and runoff management (i.e., stormwater detention, providing sufficient
pretreatment of runoff to remove course suspended particles). Therefore, the recreational use goal
for Lake Cornelia is to achieve water quality that supports these functions as well as to maintain a
balanced ecosystem. In accordance with the NMCWD’s non degradation policy, the lake shall be
protected from significant degradation from point and nonpoint sources and shall maintain existing
water uses, aquatic habits, and the necessary water quality to protect these uses. The implementation
of possible BMPs will likely achieve the goal of nondegradation and enhance the lake’s recreational
uses.
3.1.5 Wildlife Goal
The wildlife goal for Lake Cornelia is to protect existing beneficial wildlife uses.
3.2 Expected Benefits of Water Quality Improvements
Lake Cornelia is an important aquatic resource for the region. The management strategy for Lake
Cornelia should be to protect the resource. If Lake Cornelia’s water quality is protected, all
recreational and aquatic habitat uses for the lake should be maintained.
3.2.1 Enhancement of Recreational Use
Lake Cornelia is not used for extensive recreation. A fishing pier exists on the northeast side of
North Cornelia. South Cornelia is only accessible through private land. Lake Cornelia is part of the
MDNR Fishing in the Neighborhood Program and approximately 300 to 400 bluegill are annually
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17
deposited into Lake Cornelia. Potentially the NMCWD Water Management Plan could classify the
lake as a “Fishing Lake.” However, according to the plan, this means the lake “supports natural
populations of gamefish, without intensive management such as aeration to prevent winterkill” which
is likely not the case for Lake Cornelia.
Decreases in phosphorus concentrations and resulting transparency improvements for the lake will
likely improve the lake’s aesthetic appeal, make fish kills less likely, and reduce the frequency of
odor-producing algal blooms that thrive on over-fertilization of the waters. Such improvements will
make the lake more pleasant for the residents surrounding the lake and others who enjoy the lake.
3.2.2 Improvements in Aquatic Habitat
Improving the eutrophic status of Lake Cornelia is expected to benefit the aquatic communities of the
lake. Reduction in the eutrophication process typically results in reduced algal concentrations
(especially blue-green algae) and increased transparency. These changes allow for greater plant and
animal diversity, as species with less tolerance for low light and low oxygen are once again able to
populate the lake and its littoral regions. Higher diversity and improved habitat for the communities
lowest on the food chain (algae, zooplankton, etc.) are reflected in benefits to higher-order species—
from benthic invertebrates through birds and mammals.
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4.0 Lake Basin and Watershed Characteristics
The following sections describe the unique characteristics of the Lake Cornelia basin. General
features of the land use in the lakes’ watersheds—under both present and future conditions—are
discussed. The network of water storage and treatment ponds is also described, as well as the flows in
and out of the lake.
4.1 Lake Basin Characteristics
Lake Cornelia is located in the north central portion of Edina. The lake is a natural marsh area. Lake
Cornelia is comprised of North (North Cornelia) and South (South Cornelia) basins, connected by a
12-inch culvert under 66th Street (with an invert elevation of 859.0 feet MSL) on the south side of the
North Cornelia, and a secondary 12-inch pipe located on the southeast side of North Cornelia (with
an invert elevation of 860.22 feet MSL). Ultimately the water levels in North Cornelia are controlled
by the outlet structure at South Cornelia. The outflow from South Cornelia discharges directly into
over a 14-foot long weir structure with a control elevation of 859.1 feet MSL. Discharges from
South Cornelia are conveyed to Lake Edina through an extensive storm sewer network. Due to
limited stormsewer capacity downstream of Lake Cornelia, stormwater runoff backs-up into the lake
during large storm events which provides temporary storage of the flood volumes.
4.1.1 North Cornelia
North Cornelia has a water surface of approximately 19 acres, a maximum depth of 5 feet, and a
mean depth of approximately 3 feet at a normal water surface elevation of 859.1. At this elevation
the lake volume is approximately 61 acre-feet (see Figure 4-1 for bathymetry information). The
water level in the lake is controlled mainly by weather conditions (snowmelt, rainfall, and
evaporation), by the outlet capacity of the pipe on North Cornelia, and by the elevation of the outlet
structure located on South Cornelia. The stage-storage-discharge relationship that was used in this
study for North Cornelia is shown in Table 4-1.
4.1.2 South Cornelia
South Cornelia has a water surface of approximately 31 acres, a maximum depth of 7 feet, and a
mean depth of 4.2 feet at a normal surface elevation of 859.1. At this elevation the lake volume is
approximately 130 acre-feet (see Figure 4-1 for bathymetry information). The water level in the lake
is controlled by the elevation of the weir structure at the south side of the lake. The stage-storage-
discharge relationship that was used in this study for Lake Cornelia is shown in Table 4-1.
854
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Lake Cornelia
Approximate Bathymetry
from 1975 survey data
0 300 600150
Feet
Barr Footer: Date: 1/4/2006 12:08:47 PM File: I:\Client\Nmcwd\Lakes\UAA\LakeCornelia\GIS\Projects\bathymetry.mxd User: wde
NORMAL WATER ELEVATION 859
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Table 4-1 Stage-Storage-Discharge Relationship for Lake Cornelia
Elevation Area
Cumulative
Storage
(ac-ft)
Discharge
(cfs) Comment
North Cornelia
854.00 2.8 0.0 0.0
855.00 7.2 5.0 0.0
856.00 10.7 14.0 0.0 Wet Detention Storage Volume
857.00 13.7 26.1 0.0
858.00 16.6 41.3 0.0
859.00 18.7 58.9 0.0 Invert of Outlet Pipe
859.1 18.9 60.8 0 NWL*
859.25 19.3 63.7 0.8
859.50 19.8 68.6 1.9
860.00 20.9 78.7 2.2
860.22 31.1 84.5 2.6
860.51 31.1 93.5 4.1 Available Live Storage for Flood
861.00 31.1 108.7 5.5 Control
862.00 32.7 140.6 8.6
863.00 35.0 174.5 11.0
863.30 35.6 185.0 11.7
864.00 37.3 210.6 69.0
South Cornelia
851.00 0.0 0.0 0.0
852.00 0.4 0.2 0.0 Wet Detention Storage Volume
853.00 0.1 0.4 0.0
855.00 8.7 9.3 0.0
857.00 27.7 45.7 0.0
859.10 31.4 107.8 0.0 NWL
859.25 31.6 112.6 2.5
859.50 31.9 120.5 10.9
859.75 32.3 128.5 22.7
860.00 32.6 136.6 24.2 Available Live Storage for Flood
861.00 33.9 169.8 30.4 Control
863.00 37.2 240.9 35.5
864.00 39.3 279.2 35.5
865.80 41.2 351.6 123.0
868.00 44.0 445.4 106.9
*Based on South Cornelia outlet elevation
Since Lake Cornelia is shallow, the lake is expected to be prone to frequent wind-driven mixing of
the lake’s shallow waters during the summer. One would therefore expect Lake Cornelia to be
polymictic (mixing many times per year) as opposed to lakes with deep, steep-sided basins that are
usually dimictic (mixing only twice per year). Daily monitoring of the lake would be necessary to
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21
precisely characterize the mixing dynamics of a lake, but the limited data gathered from Lake
Cornelia strongly suggests that the lake is indeed polymictic.
4.2 Watershed Characteristics
All land use practices within a lake’s watershed impact the lake and influence its water quality. The
impacts result from sediment and nutrient transfer, primarily phosphorus, from the lake’s watershed
to the lake. Each land use contributes a different quantity of phosphorus to the lake, thereby
impacting the lake’s water quality differently. As land use changes over time, changes can be
expected in downstream water bodies as a result.
Historically, the Lake Cornelia watershed was primarily comprised of basswood, sugar maple, and
oak forests. There were also numerous wetlands located throughout the watershed. The terrain
varies from relatively flat to rolling.
Lake Cornelia’s 975 acre watershed, including the surface area of the lake (50.1 acres) is within the
City of Edina. Runoff from the watershed enters both North and South Cornelia through overland
flow and at storm sewer outfalls at various points along the lakeshore, although the majority of the
watershed flows through North Cornelia before entering South Cornelia. Existing land use patterns
within the watershed were identified for the purpose of predicting changes in runoff volumes and
annual phosphorus loads before and after development.
4.2.1 Present Land Use
Based on existing land use data from the City of Edina and analysis of 2004 aerial photographs, the
entire Lake Cornelia watershed is developed, with the majority of the land use being low-density
residential (44 percent). The watershed also includes some commercial (22 percent), highway (10
percent), open water (9 percent), high density residential (7 percent), developed park (4 percent),
high impervious institutional (2 percent), park/open space (2 percent), wetland (1 percent), and less
than 1 percent of industrial/office uses. Figures 4-2 and 4-3 and Table 4-2 detail the primary existing
land uses within the Lake Cornelia watershed.
Analyses of these data indicate that, under existing land use conditions, Lake Cornelia’s 975-acre
contributing watershed consists of:
• Low-Density Residential (1 to 4 housing units per acre): …432 acres
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• Commercial: ........................................................................... 213 acres
• Highways/Transport: .............................................................. 97 acres
• Open Water: ............................................................................ 77 acres
• High-Density Residential (>8 housing units per acre): ......... 66 acres
• Developed Park: ...................................................................... 37 acres
• High Impervious Institutional: ............................................... 17 acres
• Natural/Park/Open: ................................................................. 15 acres
• Wetland: .................................................................................. 10 acres
• Industrial/Office: ...................................................................... .0 acres
4.2.2 Future Land Use
Future land use is not expected to vary significantly from present use. As a result the watershed is
considered fully-developed and neither the quality nor the quantity of the stormwater runoff from the
watershed is expected to change due to alterations in land use.
4.3 Lake Inflows and Drainage Areas
Because the watershed modeling depends on the evaluation of the watershed conditions as they relate
to stormwater runoff, the hydrology of the Lake Cornelia watershed is discussed in the following
sections.
4.3.1 Natural Conveyance Systems
Under existing conditions, Lake Cornelia receives natural surface water inflows only from its direct
watershed.
4.3.2 Stormwater Conveyance Systems
The Lake Cornelia’s stormwater conveyance systems is comprised of a network of storm sewers,
ditches, wet detention ponds, dry detention ponds, lakes and wetlands within the tributary watershed,
which provide water quality treatment of stormwater runoff. Storm sewers and ditches convey
stormwater runoff to and from the wet and dry detention ponds and wetlands, and ultimately convey
the runoff from the watershed to Lake Cornelia. The locations of the major stormwater conveyance
features are shown on Figure 4-4. There are about 15 ponding areas (wet and dry detention ponds,
and wetlands) in the Lake Cornelia watershed. A detailed listing of existing pond information is
located in Appendix C.
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23
4.3.3 Southdale Center Cooling System Discharge
In addition to runoff from its tributary watershed, North Cornelia receives approximately 40 million
gallons per year from Southdale Center (via the Point of France Pond). Originally taken from the
groundwater, this water passes once-through the Southdale heating/cooling system and is
continuously discharged. As it is part of the cooling system, more water is discharged during the
summer than in the winter. The discharge is currently permitted by the MDNR and monthly readings
of the volume pumped from the groundwater are submitted. The system is not permanent and must be
abandoned by 2010. See Appendix D for water usage in this system from 2005 through 2008.
NC_62
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Lake Cornelia SubwatershedsLand Use
Developed Parkland
Wetland
Natural/Park/Open
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Medium Density Residential
Low Density Residential
Institutional
XXXXXXXXXXXXXXXGolf Course
Highway
Commercial
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Industrial/Office
Open Water
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Feet
Figure 4-2
Subwatersheds and Land Use
Lake Cornelia UAA
Nine Mile Creek Watershed District
Ü
Commercial
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Golf Course
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Highway
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High Density
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Medium Density
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Low Density
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43%Institutional
2%
High Impervious
Institutional
0.1%
Industrial/ Office
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Natural\Park\Open
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Open Water
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Lake Cornelia Watershed Use Attainability
Existing Land Uses
975 Acres Including Lake Surface Area
Institutional
1%
High Impervious
Institutional
0.1%Industrial/ Office
Lake Cornelia Watershed Use Attainability
Future (2020) Land Uses
975 Acres Including Lake Surface Area
P:\23\27\634\NORMANDALEUAA\Excel Files\LUsummary_tablescharts.xls
Figure 4-3
Lake Cornelia Watershed
Land Uses - Contributing Area Only
Commercial
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Golf Course
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Highway
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High Density
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Medium Density
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Low Density
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High Impervious
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Industrial/ Office
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Natural\Park\Open
8%
Open Water
8%
Lake Cornelia Watershed Use Attainability
Existing Land Uses
975 Acres Including Lake Surface Area
Commercial
22%
Golf Course
0%
Highway
8%
High Density
Residential
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Medium Density
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Low Density
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Institutional
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High Impervious
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2%
Natural\Park\Open
7%
Open Water
8%
Lake Cornelia Watershed Use Attainability
Future (2020) Land Uses
975 Acres Including Lake Surface Area
P:\23\27\634\NORMANDALEUAA\Excel Files\LUsummary_tablescharts.xls
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Figure 4-4
Subwatersheds and Existing
Storm Sewer System
Lake Cornelia UAA
Nine Mile Creek Watershed District
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P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
28
5.0 Existing Water Quality
5.1 Water Quality
5.1.1 Data Collection
The NMCWD collected water quality data during 2004 and again in 2008, in both North and South
Cornelia. Additionally, the Metropolitan Council Citizen-Assisted Monitoring Program (CAMP) has
also collected water quality data in North Cornelia in 2003, 2005, 2006, 2007, and 2008. The water
quality data was typically collected between late-April and early September. Summer averages were
calculated from the data for June through September to remain consistent with the MPCA’s mean
growing season values used to assess impairments.
The NMCWD monitoring in 2004 and 2008 were intensive water quality sampling efforts to
document conditions within Lake Cornelia and to assist in the calibration of the water quality models
used in the UAA. Several water quality indices were evaluated in the 2004 sampling, including
temperature, turbidity, dissolved oxygen (DO), pH, specific conductivity (conductivity), total
phosphorus (TP), orthophosphate, total Kjeldahl Nitrogen (TKN), Nitrate + Nitrite Nitrogen,
chlorophyll a (Chl a), and Secchi disc transparency (transparency). The 2008 sampling effort
monitored the same parameters as 2004 but instead of measuring orthophosphate, total Kjeldahl
Nitrogen (TKN), and Nitrate + Nitrite Nitrogen, dissolved phosphorus was tested. Temperature, DO,
and conductivity were all measured at the surface and depths of 1 meter and 1.5 meter throughout the
water column to allow characterization of the lakes’ stratification profiles. TP and pH were
measured near the water surface for each sampling event. Additionally, in 2008, a single alkalinity
sample was collected in both North and South Cornelia.
Water quality data collected by the CAMP program typically includes TP and Chl a at the water
surface along with transparency. Additionally, physical observations of the lake are recorded on the
sampling date.
TP, Chl a, and transparency are the key determinants of water quality and eutrophic state for the
lakes (see Section 2.0 for further discussion). The 2004 and 2008 sampling results for TP, Chl a, and
transparency are summarized in Table 5-1a and Table 5-1b. The 2004 and 2008 sampling results for
these three water quality parameters are presented graphically on Figure 5-1a through Figure 5-1d for
both North and South Cornelia.
Because recreational use is greatest during the summer (June, July, and August) months, and because
it is during these times that algal blooms and diminished transparency are most common, attention is
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
29
usually focused on summer water quality in the upper (epilimnetic) portions of the lake. Figure 5-2
shows the historic summer average TP and Chl-a concentrations, and transparency data from 2003
through 2008 for Lake Cornelia.
In 2004, the epilimnetic summer averages for TP, Chl a, and transparency in North Cornelia were
164 μg/L, 70 μg/L, and 0.4 meters, respectively. For South Cornelia, the 6/10/2004 sample for TP
(49 μg/L) was unrealistically low. For calibration, this TP concentration was assumed equal to the
North Cornelia concentration (120 μg/L) since the inflows from North Cornelia comprise the
majority of the inflow to South Cornelia. Also, this TP sample is not included in summer average
calculations discussed in the UAA. For South Cornelia, the 2004 epilimnetic summer averages for
TP, Chl a, and transparency were 190 μg/L, 95 μg/L, and 0.2 meters.
In 2008, the epilimnetic summer averages for TP, Chl a, and transparency in North Cornelia were
153 μg/L, 51 μg/L, and 0.4 meters, respectively. For South Cornelia, the 2008 epilimnetic summer
averages for TP, Chl a, and transparency were 150 μg/L, 61 μg/L, and 0.3 meter.
When comparing the three key water quality parameters, North Cornelia has slightly better water
quality than in South Cornelia. However, the 2004 and 2008 summer average TP, Chl a, and
transparency place both North and South Cornelia in the hypereutrophic category throughout the
summer. This characterization means that by comparison to other lakes, Lake Cornelia is rich in
algal nutrients, susceptible to dense algal blooms, and exhibits poor water clarity.
Table 5-1a Lake Cornelia Water Quality Data (2004)
Sample
Date
Epilimnetic
Total
Phosphorus
Epilimnetic
Chloraphyll
Secchi
Disc
Summer Average
Epilimnetic Total
Phosphorus
Summer Average
Epilimnetic
Chlorophyll
Summer
Average Secchi
Disc
(µg/L)(µg/L)(m)(µg/L)(µg/L)(m)
4/21/2004 78 67 0.5
6/10/2004 120 24 0.6
7/7/2004 200 20 0.6 164 70 0.4
8/11/2004 200 200 0.2
8/24/2004 170 65 0.4
9/10/2004 130 51 0.4
4/21/2004 124 60 0.4
6/10/2004 49*61 0.3
7/7/2004 180 88 0.2 190**95 0.2
8/11/2004 220 150 0.2
8/24/2004 160 87 0.2
9/10/2004 200 91 0.2
** 6/10/2004 Total Phosphorus concentration not included in average calculation
South Cornelia
North Cornelia
*Data point unrealistically low. For calibration purposes on 6/10/2004 South Cornelia Total Phosphorus
concentration was assumed equal to North Cornelia concentration, 120 µg/L.
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Tables\Lake Cornelia UAA tables_updated.xlsx
Table 5-1b Lake Cornelia Water Quality Data (2008)
Sample
Date
Epilimnetic Total
Phosphorus
Epilimnetic
Chlorophyll
Secchi
Disc
Summer Average
Epilimnetic Total
Phosphorus
Summer Average
Epilimnetic
Chlorophyll
Summer
Average Secchi
Disc
(µg/L)(µg/L)(m)(µg/L)(µg/L)(m)
4/27/2008 79 21 0.8
4/30/2008 81 11 0.7
5/9/2008 84 18 0.8
5/23/2008 108 16 0.6
6/5/2008 173 40 0.4
6/16/2008 160 33 0.3
6/19/2008 87 15 0.6
7/5/2008 162 53 0.4
7/7/2008 140 49 0.3
7/15/2008 132 65 0.5 153 51 0.4
7/21/2008 120 28 0.4
8/2/2008 166 92 0.4
8/4/2008 200 64 0.3
8/15/2008 164 100 0.4
8/18/2008 210 49 0.2
8/29/2008 160 87 0.4
9/3/2008 200 49 0.2
9/12/2008 110 29 0.5
9/17/2008 110 32 0.4
9/23/2008 159 47 0.4
9/30/2008 140 32 0.3
10/9/2008 127 34 0.5
4/30/2008 88 16 0.5
6/16/2008 130 97 0.2
7/7/2008 160 72 0.3
7/21/2008 190 79 0.2
8/4/2008 210 56 0.2 150 61 0.3
8/18/2008 130 28 0.3
9/3/2008 220 81 0.2
9/17/2008 60 31 0.4
9/30/2008 100 40 0.3
1 - Data included NMCWD and CAMP data collected in 2008
North Cornelia1
South Cornelia
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Tables\Lake Cornelia UAA tables_updated.xlsx
0
50
100
150
200
250
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2004
Total Phosphorus Concentrations
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 164 ug/L
0
50
100
150
200
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2004
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 70 ug/L
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Figures\Cornelia N. Basin WQ04_08 Data.xls
Figure 5-1a
North Cornelia Lake 2004 Seasonal Changes
in Concentration of Total Phosphorus,
Chlorophyll-a and Secchi Disc
Transparencies
0
50
100
150
200
250
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2004
Total Phosphorus Concentrations
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 164 ug/L
0
50
100
150
200
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2004
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 70 ug/L
0
1
2
3
4
5
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(m
e
t
e
r
s
)
Date
Cornelia (North Basin)--2004
Secchi Disc Transparency
Summer Average = 0.4 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Figures\Cornelia N. Basin WQ04_08 Data.xls
0
50
100
150
200
250
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2004
Total Phosphorus Concentrations
Summer Average = 190 ug/L*
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
*Summer Average does not include unrealistically low TP measurement from 6/10/2004
0
50
100
150
200
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2004
Chlorophyll-a
Summer Average = 95 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Figures\Cornelia S. Basin WQ04_08 Data.xls
Figure 5-1b
South Cornelia Lake 2004 Seasonal
Changes in Concentration of Total
Phosphorus, Chlorophyll-a and Secchi
Disc Transparencies
0
50
100
150
200
250
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2004
Total Phosphorus Concentrations
Summer Average = 190 ug/L*
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
*Summer Average does not include unrealistically low TP measurement from 6/10/2004
0
50
100
150
200
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2004
Chlorophyll-a
Summer Average = 95 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
0
1
2
3
4
5
4/1/2004 5/1/2004 6/1/2004 7/1/2004 8/1/2004 9/1/2004 10/1/2004Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(
m
e
t
e
r
s
)
Date
Cornelia (South Basin)--2004
Secchi Disc Transparency
Summer Average = 0.2 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Figures\Cornelia S. Basin WQ04_08 Data.xls
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2008
Total Phosphorus Concentrations
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 153 ug/L
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2008
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 51 ug/L
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Figures\Cornelia N. Basin WQ04_08 Data.xls
Figure 5-1c
North Cornelia Lake 2008 Seasonal Changes
in Concentration of Total Phosphorus,
Chlorophyll-a and Secchi Disc
Transparencies
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (North Basin)--2008
Total Phosphorus Concentrations
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
Summer Average = 153 ug/L
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (North Basin)--2008
Chlorophyll-a
OligotrophicMesotrophicEutrophic
Hypereutrophic
Summer Average = 51 ug/L
0
1
2
3
4
5
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(m
e
t
e
r
s
)
Date
Cornelia (North Basin)--2008
Secchi Disc Transparency
Summer Average = 0.4 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
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0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2008
Total Phosphorus Concentrations
Summer Average = 150 ug/L
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2008
Chlorophyll-a
Summer Average = 61 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
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Figure 5-1d
South Cornelia Lake 2008 Seasonal
Changes in Concentration of Total
Phosphorus, Chlorophyll-a and Secchi
Disc Transparencies
0
50
100
150
200
250
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
u
g
/
L
)
Date
Cornelia (South Basin)--2008
Total Phosphorus Concentrations
Summer Average = 150 ug/L
Oligotrophic Mesotrophic
Eutrophic
Hypereutrophic
0
50
100
150
200
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008
Ch
l
o
r
o
p
h
y
l
l
-
a
(u
g
/
L
)
Date
Cornelia (South Basin)--2008
Chlorophyll-a
Summer Average = 61 ug/L
OligotrophicMesotrophicEutrophic
Hypereutrophic
0
1
2
3
4
5
4/1/2008 5/1/2008 6/1/2008 7/1/2008 8/1/2008 9/1/2008 10/1/2008 11/1/2008Se
c
c
h
i
D
i
s
c
T
r
a
n
s
p
a
r
e
n
c
y
(
m
e
t
e
r
s
)
Date
Cornelia (South Basin)--2008
Secchi Disc Transparency
Summer Average = 0.3 m
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
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253
164 160
169
211
153
190
150
50
100
150
200
250
300
TP
(
u
g
/
L
)
(a) Total Phosphorus Concentration (ug/L)
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37
5.1.2 Baseline/Current Water Quality
Current Lake Cornelia water quality data were evaluated according to the trophic status categories.
The trophic status categories use the lake’s total phosphorus concentration, chlorophyll a
concentration, and Secchi disc transparency measurements to assign the lake to a water quality
category that best describes its water quality. Water quality categories include oligotrophic (i.e.,
excellent water quality), mesotrophic (i.e., good water quality), eutrophic (i.e., poor water quality),
and hypereutrophic (i.e., very poor water quality). Total phosphorus, chlorophyll a, and Secchi disc
transparency are key water quality indicators for the following reasons:
• Phosphorus generally controls the growth of algae in lake systems. Of all the substances
needed for biological growth, phosphorus is typically the limiting nutrient.
• Chlorophyll a is the main photosynthetic pigment in algae. Therefore, the amount of
chlorophyll a in the water indicates the abundance of algae present in the lake
• Secchi disc transparency is a measure of water clarity, and is inversely related to the
abundance of algae. Water clarity determines recreational-use impairment.
5.1.2.1 Baseline Lake Water Quality Status
The Minnesota Lake Eutrophication Analysis Procedure (MnLEAP) is intended to be used as a
screening tool for estimating lake conditions and for identifying “problem” lakes. MnLEAP is
particularly useful for identifying lakes requiring “protection” versus those requiring “restoration”
(Heiskary and Wilson, 1990). In addition, MnLEAP modeling has been done in the past to identify
Minnesota lakes which may be in better or worse condition than they “should be” based on their
location, watershed area and lake basin morphometry (Heiskary and Wilson, 1990). Results of
MnLEAP modeling done for Lake Cornelia suggest that the lake could achieve “better” water quality
than is currently observed (Heiskary and Lindbloom, 1993). For the MnLEAP analysis, Lake
Cornelia was treated as a single basin, rather than two separate basins. MnLEAP predicts a TP
concentration of approximately 76 μg/L (with a standard error of 21 μg/L), a Chl a concentration of
37.1 μg/L (with a standard error of 20 μg/L), and a Secchi disc transparency of 0.9 meters (with a
standard error of 0.3 meters). Comparison of the predicted MnLEAP values and observed annual
average phosphorus concentrations indicates that the water quality in Lake Cornelia is worse than it
“should be” based on its location, watershed area and lake basin morphometry.
Vighi and Chiaudani (1985) developed another method to determine the phosphorus concentration in
lakes that are not affected by anthropogenic (human) inputs. As a result, the phosphorus
concentration in a lake resulting from natural, background phosphorus loadings can be calculated
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38
from information about the lake’s mean depth and alkalinity or conductivity. Alkalinity is
considered more useful for this analysis because it is less influenced by development of the
watershed. Using the alkalinity measurements collected in the summer of 2008 in North and South
Cornelia (120 mg/L and 130 mg/L, respectively), the predicted phosphorus concentrations from
natural background loadings would range from 33.6 to 39.9 μg/L for both North and South Cornelia.
Using the epilimnetic specific conductivity data collected throughout the summer of 2004 (mean
specific conductivity of 676 µmho/cm for North Cornelia and 695 µmho/cm for South Cornelia) and
the summer of 2008 (mean specific conductivity of 877 µmho/cm for North Cornelia and
1074 µmho/cm for South Cornelia) the predicted total phosphorus concentration range from natural,
background loadings should be between 27 and 61 μg/L for North Cornelia and 27 and 66 μg/L for
South Cornelia.
The Wisconsin Lake Modeling Suite (WiLMS) model (WI-DNR, 2004) was also used to estimate
Lake Cornelia’s water quality under natural watershed conditions. The WiLMS model (Lake Total
Phosphorus Prediction Module) uses an annual time step and predicts spring overturn, growing
season mean, and annual average TP concentrations in lakes. The model uses information about the
lake and watershed characteristics in conjunction with 13 different published phosphorus prediction
regressions to predicted the expected in-lake TP.
For Lake Cornelia, the existing watershed has been significantly altered from its natural
(predevelopment) watershed. The natural conditions watershed was delineated using a topographic
map of the Twin Cities area from 1901 and had an area of approximately 836 acres (including the
surface area of the lake). The presettlement vegetation for the Lake Cornelia watershed was
classified as oak openings and barrens (MDNR, 1994). To estimate the runoff volume from the
watershed, a runoff coefficient of 0.03 (published value typical for forests) was used with average
annual precipitation for the Twin Cities area. TP loading from the natural watershed was based on a
range of typical areal loading rates for forested areas (0.05 – 0.18 kg/ha/year or 0.045 – 0.16
lbs/ac/yr) as programmed in the WiLMS model. Using the Canfield and Bachman (1981) regression
equation, the TP concentration in Lake Cornelia under natural conditions would range from 53 to 133
μg/L.
The range of TP concentration predicted by the Vighi and Chiadani method (27 μg/L to 66 μg/L) is
significantly lower than the NMCWD water quality goal for total phosphorus concentrations in Lake
Cornelia. The NMCWD TP goal falls within the ranges predicted by MnLEAP (55 μg/L to 97 μg/L)
and the WiLMS (53 μg/L to 133 μg/L) models. This indicates that the NMCWD Level III
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39
classification goal should be attainable, given the appropriate phosphorus loadings to the lake. When
compared to the MPCA shallow lakes standard (60 μg/L), the upper end of the Vighi and Chiaudani
predicted natural background TP concentration range falls right around the standard, indicating that it
may be possible to attain the MPCA shallow lake standard for phosphorus. However, when
considering the TP ranges predicted by the MnLEAP and WiLMS models, the MPCA shallow lake
standard may be attainable only on the very low end of the expected range of TP concentrations, and
is likely not attainable for most conditions.
5.1.2.2 Lake Cornelia Current (2008) Water Quality
The NMCWD conducted the first intensive lake water quality monitoring in 2004. Figures 5-1a and
5-1b summarize the 2004 seasonal changes in concentration of TP, Chl a, and Secchi disc
transparencies for both North and South Cornelia.
More recently in 2008, the NMCWD performed a second round of intensive lake water quality
monitoring in both North and South Cornelia. Figure 5-1c and Figure 5-1d summarize the seasonal
changes in concentration of TP, Chl a, and Secchi disc transparencies for both North and South
Cornelia during 2008. The data are shown compared to the trophic status categories. Year round the
total phosphorus data collected were in the hypereutrophic (i.e., very poor water quality) category.
This was likely the result of significant amounts of phosphorus added to the lake water by watershed
runoff and by release of phosphorus from anoxic lake sediments.
As Figure 5-1c illustrates, the epilimnetic (surface water, i.e., 0-2 meter depth) TP concentration in
North Cornelia in 2008 increased throughout the spring to the maximum concentration in August and
September before decreasing in late summer. As Figure 5-1d illustrates, the epilimnetic TP
concentration in South Cornelia in 2008 increased from the lake’s steady-state spring concentration
to its maximum TP concentration in August and September before decreasing in late summer.
Because phosphorus has been shown to most often be the limiting nutrient for algal growth, the
phosphorus-rich waters indicate the lake had the potential for abundant algal growth throughout the
monitoring period. According to previous studies (Heiskary and Wilson, 1990), phosphorus
concentrations of 60 µg/L typically result in the frequency of nuisance algal blooms (greater than
20 µg/L Chl a) to be about 70 percent of the summer. Since the summer average TP concentrations
for both North and South Cornelia in 2008 (153 μg/L and 150 μg/L, respectively) was higher than the
60 µg/L, Lake Cornelia likely experienced nuisance algal blooms for much of the summer.
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Chl a concentrations (0 to 2 meters) for North Cornelia during 2008 ranged from 11 µg/L to 100
µg/L and in South Cornelia ranged from 16 µg/L to 97 µg/L. Similarly, the 2008 summer averages
for North and South Cornelia (51 µg/L to 61 µg/L, respectively) also indicate a hypereutrophic
system. These data indicate algal blooms (greater than 20 µg/L Chl a) were likely prevalent in 2008.
The 2008 Lake Cornelia Secchi disc measurements were primarily in the hypereutrophic (i.e., very
poor water quality) category. In 2008, the summer average Secchi disc transparencies were 0.4
meters for North Cornelia and 0.3 meters for South Cornelia. With average secchi depths less than
0.4 meters, the TSISD for both North Cornelia and South Cornelia exceed the NMCWD’s TSISD goal
of 70 , currently placing the lakes within the Management Category IV: Runoff Management.
5.1.2.3 Lake Cornelia Water Quality Trend Analysis
A trend analysis was performed on the water quality data for North Cornelia, as there was a sufficient
amount of data to perform the analyses. The trend analyses were performed to determine if the
changes in water quality over time indicate a significant improvement or degradation in water
quality. Over the entire period of record (2003-2008), results for TP, Chl a, and SD trend analyses
all indicated that there was no significant improvement or degradation in water quality over the past
5 years in North Cornelia.
5.2 Nutrient Loading
Lake Cornelia receives phosphorus loads from external sources, contained in the runoff from the
lakes’ immediate and tributary watersheds, through atmospheric deposition, and from external
discharges, such as the Southdale cooling water system. In addition, the data suggest that the lake
also receives phosphorus loads from internal sources—from lake sediments via chemical and mixing
processes. These sources of phosphorus are discussed in the following sections.
5.2.1 External Loads
5.2.1.1 Watershed Runoff
Most of the phosphorus that runs off a watershed is particulate (i.e., is associated with soil or debris
particles). However, it is assumed in the P8 model that 30 percent of the phosphorus that
accumulates on a watershed is soluble (i.e., not associated with particles). While BMPs that rely on
particle settlement, such as detention ponds and grit chambers, are effective at removing phosphorus
associated with particles in stormwater runoff, they are ineffective at removing soluble phosphorus.
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Table 5-2 summarizes the annual depth of runoff and areal TP loading rates to North and South
Cornelia from their direct watersheds for all climatic conditions. Table 5-3 summarizes the annual
water and phosphorus loads to North and South Cornelia for all climatic conditions. Figures 5-3a, 5-
3b, and 5-3c summarize the annual water and phosphorus budgets for North and South Cornelia for
average, wet, and dry climatic conditions, respectively.
Table 5-2 Summary of Lake Cornelia Depths of Runoff and Areal TP Loading Rates
Average Climatic
Conditions (2004)
Wet Climatic
Conditions (2002)
Dry Climatic
Conditions (2008)
North Cornelia
Annual Runoff Depth
(in)1,2
8.1 12.1 7.3
Annual TP Areal
Loading Rate
(lbs TP/acre/yr)1,2
0.35 0.47 0.29
South Cornelia
Annual Runoff Depth
(in)1,2
4.7 9.3 4.1
Annual TP Areal
Loading Rate
(lbs TP/acre/yr)1,2
0.34 0.49 0.27
1 – To estimate runoff depths and TP areal loading rates, based on contributing watershed area not including
the surface area of the lake (North Cornelia = 844 acres & South Cornelia = 81 acres)
2 – Annual estimations based on the corresponding water year (October 1 – September 30)
The estimated annual depths of runoff and the TP areal loading rates from the contributing
watersheds were based on the total watershed area not including the surface area of the lake. The
estimated values for these parameters fall within the expected ranges given the land use within the
North and South Cornelia watersheds.
For existing conditions in the Lake Cornelia watershed, modeling simulations for average climatic
conditions indicate an annual (2004 water year) total phosphorus load to North Cornelia from the
watershed of 296 lbs and a watershed stormwater runoff volume of 569 acre-feet. For wet climatic
conditions, the annual (2002 water year) total phosphorus load from the North Cornelia watershed
was 400 lbs and the stormwater runoff volume was 855 acre-feet. For dry climatic conditions, the
annual (2008 water year) total phosphorus load from the North Cornelia watershed was 247 lbs and
the stormwater runoff volume was 515 acre-feet. .
For existing conditions in the Lake Cornelia watershed, modeling simulations for average climatic
conditions indicate an annual (2004 water year) total phosphorus load to South Cornelia from the
watershed of 28 lbs and a watershed stormwater runoff volume of 32 acre-feet. These results include
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42
the watersheds draining directly to South Cornelia but exclude the loading from North Cornelia. For
wet climatic conditions, the annual (2002 water year) total phosphorus load from the South Cornelia
watershed was 40 lbs and the stormwater runoff volume was 56 acre-feet. For dry climatic
conditions, the annual (2008 water year) total phosphorus load from the South Cornelia watershed
was 22 lbs and the stormwater runoff volume was 28 acre-feet.
Watershed analysis suggests that under existing conditions and all climatic scenarios, watershed
loading is the largest external phosphorus loading source to both North and South Cornelia. The
watershed contributes approximately 71 to 82 percent of the annual phosphorus load and 78 to 83
percent of the annual water load to North Cornelia. The majority of the water and phosphorus loads
to South Cornelia come from North Cornelia. The South Cornelia watershed, including the discharge
from North Cornelia, contributing approximately 87 to 93 percent of the annual phosphorus load and
91 to 92 percent of the water load to South Cornelia.
5.2.1.2 Southdale Cooling Water System Discharge
Although the runoff from the watershed is the major source of water and phosphorus loads to North
Cornelia, the lake also receives discharge from the Southdale Center (via the Point of France Pond).
Southdale Center operates a heating/cooling system that pumps water from the groundwater. This
water passes once-through the Southdale heating/cooling system and is continuously discharged. As
it is part of the cooling system, more water is discharged during the summer than in the winter.
Two water quality samples were collected from the discharge of the Southdale cooling system in
August and September of 2009. The first sample was collected and particulates were observed in the
sample. The sample had a TP concentration of 270 µg/L. A second sample was collected due to
concern about the observed particulates in the first sample collected. For the second sample, the
system was allowed to flush for 30-minutes before the sample was collected. This sample had a TP
concentration of 110 µg/L which was the concentration used in this assessment.
Based on pumping records submitted to the MDNR, it was estimated that North Cornelia receives
approximately 103 to 114 acre-feet of water annually from this system (11 to 16 percent of its annual
water load). This discharge also contributes 31 to 34 lbs of phosphorus annually to Lake Cornelia (7
to 9 percent of its annual phosphorus load).
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5.2.1.3 Direct Precipitation & Atmospheric Deposition
In addition to the water and phosphorus loads from the watershed and from the Southdale Center
cooling system discharge, atmospheric deposition and direct precipitation also contribute water and
phosphorus to Lake Cornelia.
In North Cornelia, atmospheric deposition and direct precipitation account for about 6 percent of the
annual water load and about 1 percent of the annual phosphorus load. In South Cornelia,
atmospheric deposition and direct precipitation account for about 8 to 9 percent of the annual water
load and about 2 percent of the annual phosphorus load. The remainder of the phosphorus loading in
North and South Cornelia comes from internal sources, which will be discussed in the following
section.
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0.1 0.1
In
t
e
r
n
a
l
L
o
a
d
36
48 23
To
t
a
l
I
N
T
E
R
N
A
L
L
o
a
d
36
48 23
TO
T
A
L
L
O
A
D
44
2
430 448
In
t
e
r
n
a
l
S
o
u
r
c
e
s
Ex
t
e
r
n
a
l
S
o
u
r
c
e
s
In
t
e
r
n
a
l
S
o
u
r
c
e
s
Ex
t
e
r
n
a
l
S
o
u
r
c
e
s
Ex
t
e
r
n
a
l
S
o
u
r
c
e
s
Ex
t
e
r
n
a
l
S
o
u
r
c
e
s
So
u
t
h
C
o
r
n
e
l
i
a
N o rt
h
C
o
r
n
e
l
i
a
An
n
u
a
l
W
a
t
e
r
L
o
a
d
(
O
c
t
1
-
Se
pt
3
0
)
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
L
o
a
d
(O
c
t
1
-
S
e
p
t
3
0
)
An
n
u
a
l
W
a
t
e
r
L
o
a
d
(O
c
t
1
-
S
e
p
t
3
0
)
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
L
o
a
d
(O
c
t
1
-
S
e
p
t
3
0
)
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%South Cornelia
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%North Cornelia
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e
r
a
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%NC_3 32%NC_72
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
In
t
e
r
n
a
l
L
o
a
d
14%North Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)4%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Direct Precipitation 9%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
8
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 1%NC_2 4%NC_3 32%NC_72 2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
38
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
In
t
e
r
n
a
l
L
o
a
d
14%North Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
X
X
X
l
b
s
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)4%North Cornelia 87%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
5%
South Cornelia
Av
e
ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
8
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
A v e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
2
9
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
38
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
14
%
No
r
t
h
C
o
r
n
e
l
i
a
Av
e ra
g
e
(
2
0
0
4
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
8
9
l
b
s
)
Figure 5-3a Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Average Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
NC
_
2
In
t
e
r
n
a
l
L
o
a
d
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(
2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric DepositionSC_2 1%
In
t
e
r
n
a
l
L
o
a
d
South Cornelia
We
t
(
2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
6%
NC
_
3
37
%
NC
_
6
2
(
D
i
r
e
c
t
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
10
%
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
8%
South Cornelia
We
t
(2002) Climatic Conditions
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
8%NC
_
3
56
%
NC
_
7
2
3%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
16
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
11
%
No
r
t
h
C
o
r
n
e
l
i
a
W e t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
0
3
2
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
6%
NC
_
3
37
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
37
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
7%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
10
%
No
r
t
h
C
o
r
n
e
l
i
a
We
t
(2
0
0
2
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
8
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 1%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
87
%
South Cornelia
W e t (2002) Climatic Conditions
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
1
1
3
5
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 1%SC_1 (Direct Watershed)7%North Cornelia 81%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
8%
South Cornelia
We
t
(2002) Climatic Conditions
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
4
2
l
b
s
)
Figure 5-3b Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Wet Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
I
n
L
a
k
e
M
o
d
e
l
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
u
m
m
a
r
y
.
x
l
s
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
NC
_
2
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3
In
t
e
r
n
a
l
L
o
a
d
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
19
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 0%SC_1 (Direct Watershed)4%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
11
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Di
r
e
c
t
P
r
e
c
i
p
i
t
a
t
i
o
n
6%
NC
_
2
7%
NC
_
3
55
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
14
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
16
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
6
5
7
a
c
r
e
-
f
t
)
At
m
o
s
p
h
e
r
i
c
D
e
p
o
s
i
t
i
o
n
1%
NC
_
2
4%
NC
_
3
32
%
NC
_
7
2
2%
NC
_
6
2
(
D
i
r
e
c
t
Wa
t
e
r
s
h
e
d
)
33
%
So
u
t
h
d
a
l
e
C
o
o
l
i
n
g
W
a
t
e
r
9%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
19
%
No
r
t
h
C
o
r
n
e
l
i
a
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
3
4
9
l
b
s
)
Direct Precipitation 8%SC_2 1%SC_3 0%SC_1 (Direct Watershed)3%
No
r
t
h
C
o
r
n
e
l
i
a
88
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
W
a
t
e
r
B
u
d
g
e
t
(
7
1
4
a
c
r
e
-
f
t
)
Atmospheric Deposition 2%SC_2 1%SC_3 0%SC_1 (Direct Watershed)4%North Cornelia 82%
Cu
r
l
y
l
e
a
f
P
o
n
d
w
e
e
d
0%
In
t
e
r
n
a
l
L
o
a
d
11
%
South Cornelia
Dr
y
(
2
0
0
8
)
C
l
i
m
a
t
i
c
C
o
n
d
i
t
i
o
n
s
An
n
u
a
l
P
h
o
s
p
h
o
r
u
s
B
u
d
g
e
t
(
4
3
0
l
b
s
)
Figure 5-3c Lake Cornelia Water and Phosphorus
B
u
d
g
e
t
s
-
Dry Climatic Conditions
P:
\
M
p
l
s
\
2
3
M
N
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5.2.2 Internal Loads
In addition to being affected by the runoff from the watershed, atmospheric deposition, and the
discharge from the Southdale Center heating and cooling system, the water quality of Lake Cornelia
appears to be influenced by internal phosphorus loading. Computer simulations and observed water
quality data indicate internal phosphorus loading is a component of the lake’s annual phosphorus
budget.
The sediment core analysis (discussed in Section 5.2.2.2 below) indicates that release from anoxic
sediments is a likely source of the internal phosphorus load. And because Lake Cornelia is a
polymictic lake, phosphorus released from the sediment is brought to the surface waters and mixed in
the water column throughout the open water season. Another potential source of phosphorus to Lake
Cornelia is the presence of benthivorous fish, such as carp, in the lake (See Section 5.3.4 for more
details). Because these species feed along the bottom of the lake, they can resuspend sediments and
phosphorus into the water column and can be a significant source of phosphorus to a lake system if
there is a large enough population.
In addition to sediment phosphorus release and the presence of benthivorous fish, the nonnative
aquatic plant, Curlyleaf pondweed (Potamogeton crispus), was also present in small patches in both
North and South Cornelia in 2008. This macrophyte grows through the winter and then dies back in early
to mid-summer, releasing phosphorus into the water column which can impact algal growth and water
clarity (see Section 5.3.3 for more information). Although it is currently not a significant part of the
phosphorus load to Lake Cornelia (less than 1 percent), its presence in the lake should be monitored in the
future, as it may become a significant source of phosphorus to a lake.
5.2.2.1 Internal Phosphorus Loading Based on the Mass Balance Modeling
Using the phosphorus mass balance model, the internal phosphorus loading in North Cornelia for
average climatic conditions was estimated to be approximately 55 lbs. For wet climatic conditions,
the internal phosphorus loading in North Cornelia was calculated to be roughly 50 lbs, and for dry
climatic conditions, the internal load was estimated to be 66 lbs. Internal loading accounts for 10 to
19 percent of the annual phosphorus load to North Cornelia, as shown in Figures 5-3a, 5-3b, and 5-
3c.
The annual internal phosphorus loading in South Cornelia for average climatic conditions was
calculated to be approximately 23 lbs. For wet climatic conditions, the internal phosphorus loading in
South Cornelia was calculated to be approximately 36 lbs, and for dry climatic conditions, the
internal load was calculated to be approximately 48 lbs. Internal loading accounts for 5 to 11 percent
of the annual phosphorus load to South Cornelia, as shown in Figures 5-3a, 5-3b, and 5-3c.
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49
The hypereutrophic condition of North and South Cornelia, along with the relatively shallow depth of
the lakes, would be expected to provide a situation in which frequent mixing and internal phosphorus
loading are likely. Internal loading will delay the lakes’ response to phosphorus loading reduction
efforts in the watershed. Large reductions in phosphorus loading from the watershed would
eventually lead to reduced internal loading of phosphorus, although internal loading can be treated in
the interim to improve water quality.
5.2.2.2 Sediment Core Analysis
To better understand the internal loading component from the lake sediments, five sediment cores
were collected from Lake Cornelia in October 2008 and were analyzed for mobile phosphorus (which
contributes directly to internal phosphorus loading) and organic bound phosphorus. Figure 5-4
shows the Lake Cornelia sediment core locations and the interpolated distribution of mobile
phosphorus loading rates based on the sediment core results. The maximum internal sediment
loading rates calculated for North Cornelia ranged from 5.3 mg/m2/day to 7.6 mg/m2/day. In South
Cornelia, the measured sediment internal loading rates were significantly less, ranging from 1.0
mg/m2/day to 1.3 mg/m2/day. Table 5-4 shows how the maximum internal loading rates in North
and South Cornelia compare to the rates calculated for other Metro Area lakes, using the same
methodology. None of the lakes shown in Table 5-4 had alum treatments at the time of the sediment
core sampling.
The average internal phosphorus loading rate calculated for all of the Metro Area Lakes in Table 5-4
is 6.3 mg/m2/day. It is important to note that these rates represent the maximum potential internal
loading rate that the lakes could experience, given the ideal dissolved oxygen concentrations and
mixing conditions. Therefore, Lake Cornelia likely experiences less internal phosphorus loadings
than these rates would indicate (as they assume perfect internal loading conditions).
Assuming that the internal phosphorus loading estimated from the phosphorus mass balance
modeling (see Section 5.2.2.1) occurs over the entire area of the lake during the 122 days in the
growing season (June through September), the internal areal total phosphorus loading rate for North
Cornelia is estimated to be 2.4 to 3.2 mg/m2/day. In South Cornelia the estimated rate is 0.7 to 1.4
mg/m2/day. For both North and South Cornelia, these values fall within (or below) the range
developed as part of the sediment core analysis, indicating the internal phosphorus loading rates
predicted by the mass balance model are reasonable.
More information about the sediment core analysis for Lake Cornelia can be found in Appendix I.
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Table 5-4 Comparison Lake Cornelia Internal Phosphorus Loading Rates to Those of Other
Metro Area Lakes
Lake Internal P Load (mg/m2/d)
Kohlman1 17.0
Isles (pre-alum, deep hole)2 14.1
Harriett (pre-alum, deep hole) 2 11.1
Calhoun (pre-alum, deep) 2 10.8
Fish E3 10.5
Cedar (pre-alum) 2 9.3
Fish W 3 8.1
Como3 7.6
North Cornelia 7.6
Harriet3 6.9
Como-litoral3 5.7
Calhoun (pre-alum, shallow) 3 5.6
Keller1 3.5
Parkers3 3.5
Phalen3 2.3
McCarrons3 2.0
Bryant3 1.5
South Cornelia 1.3
Nokomis3 1.0
Minnewashta3 0.2
Christmas3 0.0
______________________
Sources:
1Barr (2005)
2Huser et al. (2009)
3Pilgrim et al. (2007)
!?
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!?
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SC3
SC2
SC1
NC2
NC1
0 250 500
Feet
Figure 5-4
Lake Cornelia 2008 Sediment Mobile
Phosphorus Estimates
Lake Cornelia UAA
Nine Mile Creek Watershed District
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52
5.3 Aquatic Communities
In addition to the physical and chemical indices of lake water quality, an evaluation of the plant and
animal species that inhabit the water provides valuable information as to the health of the lake. An
assessment of the current situation with respect to the aquatic communities in the lake is given in the
following sections.
5.3.1 Phytoplankton
The phytoplankton communities in Lake Cornelia form the base of the lake’s food web and affect
recreational-use of the lake. Phytoplankton, also called algae, is small aquatic plants naturally
present in all lakes. They derive energy from sunlight (through photosynthesis) and from dissolved
nutrients found in lake water. They provide food for several types of animals, including
zooplankton, which are in turn eaten by fish. Green algae are considered beneficial in that they are
edible to zooplankton and serve as a valuable food source. Blue-green algae are considered a
nuisance algae because they:
• are generally inedible for fish, waterfowl, and most zooplankton;
• float at the lake surface in expansive algal blooms;
• may be toxic to animals when occurring in large blooms; and
• can interfere with recreational uses of the lake
An inadequate phytoplankton population limits the lake’s zooplankton population and can, thereby,
limit the fish production in a lake. Conversely, excess phytoplankton can alter the structure of the
zooplankton community and interfere with sight-based fish predation, thereby also having an adverse
effect on the lake’s fishery. In addition, excess phytoplankton reduces water clarity; reduced water
clarity can in itself make recreational-usage of a lake less desirable.
Figures 5-5a and 5-5b show the overall phytoplankton levels in 2004 in North and South Cornelia,
respectively. In general, North Cornelia typically has a higher concentration of algae than in South
Cornelia throughout the season. Green algae were the dominant type of phytoplankton in North
Cornelia during the sampling events in April through June. However in July, there was a blue-green
algae bloom that continued through August. This increase in the number of blue-green algae is
typical of lakes receiving excess phosphorus loads and warm growing conditions such as in North
Cornelia. It is also important to note the presence of a small number of Cylindrospermopsis
raciborski and Microcystis aeruginosa during some of the sampling events. This species is known to
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53
produce a hepatotoxin (liver toxin). The presence of this species indicates the need to manage lake
water quality to help control the growth of these potentially hazardous species.
During the early sampling events in South Cornelia in 2004, there was a more even distribution in the
types of phytoplankton present with green algae being only slightly more dominant than the blue-
green algae, the cyrptomonads, and the diatoms. However, in the mid-June, there was a very large
blue-green algae bloom that lasted through the end of August. During this blue-green algal bloom in
South Cornelia, there were Cylindrospermopsis raciborski present as well as Microcystis aeruginosa.
Figures 5-5c and 5-5d show the overall phytoplankton levels in 2008 in North and South Cornelia,
respectively. Similar to 2004, the overall concentration of algae is typically higher in North Cornelia
than in South Cornelia. However, unlike 2004 which had a blue-green algae bloom in mid- to late-
summer, blue-green algae were present in North Cornelia throughout the summer of 2008, in
concentrations almost equal to that of green algae and diatoms. Cylindrospermopsis raciborski and
Microcystis aeruginosa were present in North Cornelia during much of the summer of 2008.
Blue-green algae dominated the phytoplankton groups present in South Cornelia throughout the
summer of 2008, with only small numbers of green algae and diatoms present. The blue-green algae
species Cylindrospermopsis raciborski was present along with Microcystis aeruginosa.
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58
5.3.2 Zooplankton
Zooplankton—microscopic crustaceans—are vital to the health of a lake ecosystem because they feed
upon the phytoplankton and are food themselves for many fish species. Protection of the lake’s
zooplankton community through proper water quality management practices protects the lake’s
fishery. Zooplankton is also important to lake water quality. The zooplankton community is
generally comprised of three groups: cladocera, copepoda, and rotifera. If present in abundance,
large cladocera can decrease the number of algae and improve water transparency within a lake.
There is not a surrogate measurement of zooplankton biomass similar to Chl a concentration for
phytoplankton biomass. Therefore, zooplankton must be identified and counted to get an estimate of
zooplankton biomass. Figure 5-6a through Figure 5-6d show the zooplankton totals (expressed as the
number of organisms per square meter of lake surface) for North and South Cornelia in 2004 and
2008 on each of the sampling dates throughout the summers. The zooplankton data are present in
Appendix F. Each total shown is divided into the three main divisions of zooplankton to give an
indication of their relative abundance.
The rotifers and copepods in lakes graze primarily on extremely small particles of plant matter and,
therefore, do not significantly affect lake water transparency by removing algae. By contrast,
cladocera graze primarily on algae and can increase transparency if they are present in abundance.
Daphnia spp. is among the larger cladocera species and is considered especially desirable in lakes
because of their ability to consume large quantities of algae.
Planktivorous fish (such as sunfish and bluegills) eat zooplankton and will preferentially select the
large Daphnia. Therefore, to thrive, the Daphnia require either a refuge from predators (i.e., deep,
well-oxygenated water) or a smaller predator population. The 2005 MDNR fishery survey (see
Section 5.3.4) indicates that the Lake Cornelia fishery is dominated by plantivorous fish (bluegills,
crappies, and sunfish), likely the result of the annual bluegill stocking by the MDNR as well as the
lack of piscivorous fish in the lake. The introduction or increase in piscivorous fish such as walleye
or northern pike in either lake could potentially lead to an increase in the Daphnia population.
Throughout the 2004 season, there was a very unbalanced distribution of zooplankton in North
Cornelia. During April, the copepods were the dominant group of zooplankton, probably due to new
hatchings and a young fishery unable to feed on the copepods. However, by June the dominance of
copepods was reduced, most likely because of the shallow lake that allows for more grazing. The
small-bodied rotifers were the dominant zooplankton for the rest of the sampling season. Because
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59
the rotifers are so small, they have very little impact on the clarity of the water in Lake Cornelia.
There were very also low numbers of cladocera in North Cornelia, again most likely due to the
shallow lake and grazing by the fishery. The highest numbers of zooplankton occurred at the end of
the sampling season (end of August and September).
South Cornelia had a more balanced distribution of zooplankton than North Cornelia in 2004. The
rotifers were typically the most dominant group of zooplankton present in the lake. However, there
were copepods and cladocera present during nearly all sampling events, and the large-bodied
cladocera were the dominant group at the end of the sampling season. The largest numbers of
zooplankton occurred in the first half of the season, with the highest number occurring in April.
In general, the summer of 2008 had a more-balanced zooplankton population in both North and South
Cornelia than in 2004. In North Cornelia, the rotifers were the dominant zooplankton group
throughout the summer of 2008. However, the copepods and cladocera were present during all
sampling events. The highest numbers of zooplankton occurred in August, with all three
zooplankton groups peaking during that month.
In 2008, South Cornelia was zooplankton population was relatively well-balanced throughout the
summer, with a somewhat equal distribution between the three zooplankton groups during all
sampling events. The zooplankton concentration remained fairly constant during the first half of the
summer and the highest number of zooplankton occurred in late-August and early-September.
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5.3.3 Macrophytes
Aquatic plants—macrophytes—are a natural and integral part of most lake communities, providing
valuable refuge, habitat and forage for many animal species. The lake’s aquatic plants, generally
located in the shallow areas near the shoreline of the lake:
• Provide habitat for fish, insects, and small invertebrates
• Provide food for waterfowl, fish, and wildlife
• Produce oxygen
• Provide spawning areas for fish in early-spring/provide cover for early-life stages of fish
• Help stabilize marshy borders and protect shorelines from wave erosion
• Provide nesting sites for waterfowl and marsh birds
Surveys of the aquatic plant community in Lake Cornelia were completed by the NMCWD during
June and August of 2004 and again in June and August of 2008. Survey results are presented in
Appendix H, and are summarized below.
The June 2004 macrophyte survey for North Cornelia showed that most vegetation in the lake is
located in the shallow waters along the shoreline. No aquatic vegetation was found in waters deeper
than 3.0 feet. The dominant vegetation in the lake is cattail (Typha sp.) which is found in low
densities along the entire shoreline. Additionally, other emergent plants such as bullrush and the
invasive purple loosestrife (Scirpus sp. and Lythrum salicaria) are found in the shallow waters along
the north shore of North Cornelia. A small patch of coontail (Ceratophyllum demersum) is found
along the north shore as well. The August 2004 survey shows a similar distribution of plants within
the lake. Sporadic, low-density patches of narrowleaf pondweed and sago pondweed (Potamogeton
sp. and Potamogeton pectinatus) were also present along the north shoreline.
In the June 2004 macrophyte survey of South Cornelia, there were no macrophytes found in water
deeper than 2.0 feet. Emergent vegetation such as cattail, bullrush, purple loosestrife, and blue flag
iris (Typha sp., Scirpus sp., Lythrum salicaria, and Iris vericolor) were all present in sporadic, low
densities along the shoreline of the lake, although the purple loosestrife was found mainly along the
north shore. Both narrowleaf pondweed and sago pondweed (Potamogeton sp. and Potamogeton
pectinatus) were found in low densities along the north and south shores of South Cornelia. Like
North Cornelia, the August distribution of macrophytes was similar to that of the June survey.
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However, in addition to the sago and narrowleaf pondweed, a small patch of floating leaf pondweed
(Potamogeton natans) was present on the southwest shore of the lake.
Since coontail absorbs its nutrients from the water column, its presence in North Cornelia could have
impacted the TP concentration observed in the lake. Another non-native emergent wetland species,
purple loosestrife (Lythrum salicaria) appeared at various locations along the shores of both North
and South Cornelia during the entire summer 2004. Purple loosestrife out-competes native plants,
such as cattail, and can eventually replace the native species, thereby interfering with the wildlife-u se
of the lake. Animals that rely on native vegetation for food, shelter, and breeding sites cannot use
purple loosestrife. The sporadic area in which purple loosestrife was found suggests the purple
loosestrife growth is a more recent development.
The June 2008 macrophyte survey for North Cornelia showed that most vegetation in the lake is
located in the shallow waters along the shoreline. No aquatic vegetation was found in waters deeper
than 3.0 feet. The dominant vegetation in the lake is cattail (Typha sp.) which is found in low
densities along the entire shoreline. Additionally, other emergent plants such as bullrush and the
invasive purple loosestrife (Scirpus sp. and Lythrum salicaria) are found in the shallow waters along
the north shore of North Cornelia. A small patch of coontail (Ceratophyllum demersum) is found
along the north shore as well as the nonnative Curlyleaf pondweed (Pomatogeton crispus). The
August 2008 survey shows a similar distribution of plants within the lake.
In the June 2008 macrophyte survey of South Cornelia, there were no macrophytes found in water
deeper than 2.0 feet. Emergent vegetation such as cattail, bullrush, purple loosestrife, and blue flag
iris (Typha sp., Scirpus sp., Lythrum salicaria, and Iris vericolor) were all present in sporadic, low
densities along the shoreline of the lake, although the purple loosestrife was found mainly along the
north shore. Sago pondweed (Potamogeton pectinatus) was found in low densities along the north
shore of South Cornelia. A small patch of Curlyleaf pondweed (Pomatogeton crispus) was found
along the south shore of South Cornelia. The August distribution of macrophytes was similar to that
of the June survey. However, in addition to the sago pondweed, a small patch of longleaf pondweed
(Potamogeton nodosus) was present on the southwest shore of the lake.
The appearance of the small patches of the nonnative Curlyleaf pondweed should continue to be
monitored in both North and South Cornelia. Once a lake becomes infested with Curlyleaf
pondweed, the plant typically replaces native vegetation, increasing its coverage and density.
Curlyleaf pondweed begins growing in late-August and grows throughout the winter at a slow rate,
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grows rapidly in the spring, and dies early in the summer (Madsen et al. 2002). Native plants that
grow from seed in the spring are unable to grow in the areas already occupied by the Curlyleaf
pondweed, and are displaced by this plant. Curlyleaf pondweed dies off in early to mid summer,
releasing phosphorus into the water column, and often resulting in increased algal growth for the
remainder of the summer. Therefore, it is extremely important to consider the impacts of improved
water clarity on the potential growth of Curlyleaf pondweed.
5.3.4 Fish and Wildlife
The MDNR completed a fishery survey in June 2005 for Lake Cornelia. Bluegills and black crappies
were the primary species sampled in Lake Cornelia. Common carp were also abundant in Lake
Cornelia. Other species present included black bullheads, yellow perch, green sunfish, hybrid
sunfish, pumpkinseeds, and gold fish. Dissolved oxygen readings during the survey indicate that
winter fish kills are probable in Lake Cornelia. The MDNR fishery report can be found in
Appendix H.
Benthivorous fish, such as carp and bullhead, can have a direct influence on the phosphorus
concentration in a lake (LaMarra, 1975). These fish typically feed on decaying plant and animal
matter and other organic particulates found at the sediment surface. The fish digest the organic
matter, and excrete soluble nutrients, thereby transforming sediment phosphorus into soluble
phosphorus available for uptake by algae at the lake surface. Benthivorous fish can also cause
resuspension of sediments in shallow ponds and lakes, causing reduced water clarity and poor aquatic
plant growth, as well as high phosphorus concentrations (Cooke et al., 1993). In the 2005 fishery
survey, small carp were present in high numbers, indicating that carp, and other benthivorous fish in
Lake Cornelia, may have a significant impact on the current water quality in the lake.
Lake Cornelia is part of the Fishing in the Neighborhood Program and has been stocked by the
MDNR with bluegill from 2000 through 2009. Typically 300-350 adult bluegills are introduced each
year as part of an annual Fishing in the Neighborhood Program. Conversation with the West Metro
contact for the Fishing in the Neighborhood indicated that the lake is stocked only with bluegill in
the spring each year from the fishing pier in North Cornelia (Nemeth, 1/14/2010). He mentioned that
there are indications of severe winter kills in North Cornelia when stocking the lake in the spring.
He also indicated that both North and South Cornelia will have a new fishery survey completed in
2010 and the stocking program for Lake Cornelia will be reviewed once those data are available.
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6.0 Water Quality Modeling for the UAA
Phosphorus levels in Lake Cornelia are high, and will continue to be greatly affected by the amount
of phosphorus loading the lake receives. For this study, a detailed analysis of current and future
discharges was completed to determine phosphorus sources and management opportunities to reduce
the amount of phosphorus added to the lake. Phosphorus typically moves either in water as soluble
phosphorus (dissolved in the water) or attached to sediments carried by water. Therefore, the
determination of the volume of water discharged annually to Lake Cornelia is integral to defining the
amount of phosphorus discharged to the lake.
6.1 Use of the P8 Model
The P8 model was used (see Section 1.2) to estimate both the water and phosphorus loads introduced
from the entire Lake Cornelia watershed. The model requires hourly precipitation and daily
temperature data; long-term climatic data can be used so that watersheds and BMPs can be evaluated
for varying hydrologic conditions. Hourly precipitation data was obtained from the National
Weather Service (NWA) site at the Minneapolis-St. Paul International Airport, approximately 8 miles
away from the lake, as well as from NMCWD monitoring station at Metro Blvd. in Edina,
approximately 2 miles away from the lake. Precipitation for select storm events was adjusted based
on comparison to local gages from the High Density Network. Daily temperature data was obtained
from the Minneapolis-St. Paul International Airport.
When evaluating the results of P8 modeling, it is important to consider that the results provided are
more accurate in terms of relative differences than in terms of absolute results. The model will
predict the percent difference in phosphorus reduction between various BMP scenarios in the
watershed fairly accurately. It also provides a realistic estimate of the relative differences in
phosphorus and water loadings from the various subwatersheds and major inflow points to the lake.
However, since runoff quality is highly variable with time and location, the phosphorus loadings
estimated by the model for a specific watershed may not necessarily reflect the actual loadings, in
absolute terms. Various site-specific factors, such as lawn care practices, illicit point discharges and
erosion due to construction are not accounted for in the model. The model provides values that can
be expected to be typical of the region, given the watershed’s respective land uses.
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6.2 Water Quality Model (P8) Calibration
6.2.1 Climatic Conditions
The annual water and watershed phosphorus loadings for Lake Cornelia under existing land use
conditions were estimated for three different years, each representing a distinct climatic pattern. The
varying climatic conditions affect the lake’s volume and hydrologic residence time, and thereby
affect the phosphorus concentrations in the lake. The precipitation totals during the three years
modeled are summarized in Table 6-1.
Table 6-1 Precipitation Amounts for Various Climatic Conditions
Climatic Condition
Water Year
(Oct 1 through
Sept 30)
Precipitation
(inches)
Growing
Season (May 1
through
September 30)
Precipitation
(inches)
Dry (2007-2008) 22.58 14.00
Average (2003-2004) 26.31 20.98
Wet (2001-02) 35.68 27.93
6.2.2 Stormwater Volume Calibration
The annual runoff volume predicted by the P8 watershed model was calibrated to the observed water
surface elevations of North and South Cornelia during the period of May 2007 through September
2008. To translate the water loadings into water surface elevations, a water balance model was
utilized for both North and South Cornelia. The model uses estimated daily inflows (i.e., predicted by
the P8 model), daily precipitation, daily evaporation, an outlet rating curve, and observed lake levels
to estimate total annual outflow. The North Cornelia water balance model also included the inflows
from the Southdale Center discharge. The South Cornelia water balance model included the
discharge predicted by the North Cornelia water balance model as inflow as well. The stage-storage-
discharge relationship provided in Table 4-1 was developed based on basin bathymetry data and
outlet characteristics.
Figure 6-1a and Figure 6-1b illustrate the results of the water balance modeling for North and South
Cornelia respectively. The water balance modeling assumes no groundwater exchange in Lake
Cornelia. The predicted water levels shown by the blue line on the plot closely matched the observed
water levels (the pink squares). The stormwater runoff volume calibration was then verified using
the water balance model and the P8 predicted runoff and lake level information available during the
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period of the other climatic conditions (May 2003 through September 2004 and May 2001 through
September 2002).
The modeled surface runoff water load from the North Cornelia watershed, assuming existing land
use conditions during October 2007 to September 2008 of 515 acre-feet, is equivalent to 7.3 inches
of runoff over the 844 acre watershed, excluding the surface area of North Cornelia (19 acres).
The modeled surface runoff water load from the South Cornelia watershed, assuming existing land
use conditions during October 2007 to September 2008 of 28 acre-feet, is equivalent to 4.1 inches of
runoff over the 81 acre watershed, excluding the surface area of South Cornelia (31 acres).
6.2.3 Phosphorus Loading Calibration
Because no data had been collected regarding the inflow water quantity or quality for Lake Cornelia,
detailed calibration of the P8 model was not possible. The P8 model output, used as input for the in-
lake model (described below) is thought to be best-suited for considering relative changes in loading
under varying watershed conditions.
6.2.4 Atmospheric Deposition
An atmospheric wet and dry deposition rate of 0.2615 kg/ha/yr (Barr, 2005) was applied to the
surface area of the lake to determine annual phosphorus loading. An annual total phosphorus load
from atmospheric deposition of 4.4 pounds (2.0 kg) was estimated for Lake Cornelia during the dry
climatic year (2007-2008).
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6.3 In-Lake Modeling
While the P8 model is a useful tool for evaluating runoff volumes and pollutant concentrations from
a watershed, a separate means is required for predicting the in-lake phosphorus concentrations that
are likely to result from the phosphorus loads. For evaluating the resultant in-lake concentrations for
North and South Cornelia, a spreadsheet water quality model based on the empirical equation set
forth by Dillion and Rigler (1974) was developed for each basin.
To calibrate the mass balance in-lake water quality model for existing land use conditions,
phosphorus loads for each climatic condition were predicted using the P8 model and then used with
the in-lake water quality data during that same time period to calculate the internal phosphorus load
(described in more detail in Section 6.3.2).
6.3.1 Balance Modeling to Existing Water Quality
Water quality sample data, consisting of total phosphorus data, was used to calibrate and verify the
lake water quality mass balance model for each climatic condition. For dry climatic conditions
(2007-2008), the models were calibrated using the NMCWD and CAMP data collected in North and
South Cornelia during 2008. For average climatic conditions (2003-2004), the models were
calibrated using the NMCWD data collected in both North and South Cornelia. For wet climatic
conditions (2001-2002), the calibrated models were used to predicted expected water quality for the
wet conditions as no water quality data were collected in 2002.
Water quality data were used to determine the empirical model that would best predict the spring
concentration in the lake in all three climatic conditions. For both North and South Cornelia, the
Dillon and Rigler model with the Kirchner and Dillion phosphorus retention term (Kirchner and
Dillion, 1984) was used to predict the spring total phosphorus concentration of the lake. The
following steady-state mass balance equation was used for modeling the springtime total phosphorus
concentration of North and South Cornelia:
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ρz
R)L(
SPRING
−1 = P
where:
PSPRING = spring total phosphorus concentration (μg/L)
L = areal total phosphorus loading rate (mg/m²/yr)
R = retention coefficient = Kirchner and Dillion (1975)
)(574.0)(426.0 *00949.0*271.0 qsqsee−−+=
vs = apparent settling velocity (m/yr)
= qs*td0.5 (Thomann and Mueller, 1987)
qs = annual areal water outflow load (m/yr)
= Q/A
z = lake mean depth (m)
ρ = hydraulic flushing rate (1/yr)
= 1/( td)
td = hydraulic residence time = (V/Q)
Q = annual outflow (m³/yr)
V = lake volume (m³)
A = lake surface area (m²)
While these empirical models adequately predicted the spring steady-state concentration of
phosphorus in lake, early-summer, summer average and fall overturn concentrations were not
accounted for in the above model. Based on the limited data available, the phosphorus
concentrations varied during the summer time. These variations could be the result of additional
watershed runoff and internal loading due to the release of phosphorus from bottom sediments or
from the activity of benthivorous fish (see Section 6.3.3 for the in-lake calibration results).
6.3.2 Accounting for Internal Loading
Most of the empirical phosphorus models (including Kirchner and Dillon) assume that the lake to be
modeled is well-mixed, meaning that the phosphorus concentrations within the lake are uniform.
This assumption is useful in providing a general prediction of lake conditions, but it does not account
for the seasonal changes in phosphorus concentrations that can occur in a lake. As has been
discussed, these changes can also occur seasonally as a result of internal loading. Extensions of the
Vollenweider model are therefore needed to allow the use of the P8-generated TP loads to provide
reasonable predictions of summer average epilimnetic lake phosphorus concentrations.
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Based on observed temperature and dissolved oxygen profiles in Lake Cornelia throughout the
summer months of 2004 and again in 2008, both North and South Cornelia appear to be “polymictic”
(normally well-mixed). During periods of stratification the bottom waters can become anoxic
(devoid of oxygen), even for short periods, and internal phosphorus load from the lake sediments
may occur. The phosphorus released from the sediments can build up in the hypolimnion during
periods of stratification, especially during periods of high temperatures and low wind. This internal
load of phosphorus can be transported to the entire water column as wind increases and causes lake
circulation or as fall approaches and mixing typically begins to occur.
The internal loading of phosphorus to Lake Cornelia was calculated from the following mass balance
equation:
Internal P = Observed P + Outflow P - Runoff P - Atmospheric P
The phosphorus mass balance was calculated for each lake basin based on existing land use
conditions and the measured phosphorus concentrations. The estimated internal loads using the mass
balance equation are summarized in Section 5.2.2.
6.3.3 In-Lake Water Quality Model Calibration
The in-lake phosphorus model simulation of the existing conditions watershed scenario was
essentially used to validate the estimated watershed and internal loads for average and dry climatic
conditions since actual in-lake water quality data were available for those years. Figure 6-2a and 6-
2b compares the simulated and the actual in-lake phosphorus concentrations for spring steady-state,
early-summer peak, summer average and fall overturn for North and South Cornelia for both the
average and dry years. The modeling results are accurately predicting the observed total phosphorus
concentrations for the individual basins for the time periods of interest.
6 13
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55
20
120
200 200
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0.0
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Pr
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North Cornelia
Average Climatic Conditions (2004) Calibration
79 73
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North Cornelia
Average Climatic Conditions (2004) Calibration
Spring Phosphorus Atmospheric Deposition Wateshed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
0.0
0.7 0250
South Cornelia
Average Climatic Condition (2004) Calibration
79 73
28 17 6 5 2
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1
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0 86
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84 86 84
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North Cornelia
Average Climatic Conditions (2004) Calibration
Spring Phosphorus Atmospheric Deposition Wateshed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
57 56
19 13 7 5 4
0
1 2 2 2 2
0
5 6 5 5 6
4 69
142
188
148 15165
26
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124 120
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0.0
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Pr
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In
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(
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South Cornelia
Average Climatic Condition (2004) Calibration
79 73
28 17 6 5 2
0
1
2
2 2 2
0 86
91
84 86 84
1
6 13
18 22 21
4
0
77 91
55
20
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120
200 200
170
130
0.0
10.2
2.3
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0.7
1.8
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6
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10
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50
100
150
200
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Pr
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a
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(
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)
In
-
L
a
k
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[
T
P
]
(
µµµµg/
L
)
North Cornelia
Average Climatic Conditions (2004) Calibration
Spring Phosphorus Atmospheric Deposition Wateshed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
57 56
19 13 7 5 4
0
1 2 2 2 2
0
5 6 5 5 6
4 69
142
188
148 15165
26
17
17
0
37
124 120
180
220
160
200
0.0
10.2
2.3
3.0
0.7
1.8
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4
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10
12
14
0
50
100
150
200
250
4/29/2004 5/1/2004 6/10/2004 7/7/2004 8/11/2004 8/24/2004 9/10/2004
Pr
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c
i
p
i
t
a
t
i
o
n
(
i
n
)
In
-
L
a
k
e
[
T
P
]
(
µµµµg/
L
)
)
South Cornelia
Average Climatic Condition (2004) Calibration
Spring Phosphorus Atmospheric Deposition Watershed Runoff North Cornelia Discharge
Internal Release Observed Precipitation
Figure 6-2a
North & South Cornelia In-Lake Model Calibration
Results for Average Climatic Conditions with
Watershed and Spring Decay
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13
12 16 13
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Pr
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k
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[
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P
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North Cornelia
Dry Climatic Condition (2008) Calibration
84
44
31 22 19 12 7 6 5 3 2 2 2 1 1 1 1 0 0 0 0
0
0
1 2
1 1 2 2 1 1 1 1 2 2 2 2 1 1 2 2
36
36 53
105
105
72 69
108 114
100 97 97
111 99 110 104
83 89 87 81
1
3
9
13
12
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16 13
12 17 19
21
21
21 20
18
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0 13
24
33
30
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69
10 1
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48
81
29
87
26
73
8 2
49
31
81 84
108
173
160
87
162
140
132
120
166
200
164
210
160
200
110 110
159
140
1.7
0.2 0.5
1.5 1.6
0.1 0.2
0.6
2.6
0.4 0.5
0.0
1.1
0.0
2.0
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0
2
4
6
8
10
12
14
0
50
100
150
200
250
Pr
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North Cornelia
Dry Climatic Condition (2008) Calibration
Spring Phosphorus Atmospheric Deposition Watershed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
0.9
0.5
1.1 0.9
0.1
0250
South Cornelia
Dry Climatic Condition (2008) Calibration
84
44
31 22 19 12 7 6 5 3 2 2 2 1 1 1 1 0 0 0 0
0
0
1 2
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36
36 53
105
105
72 69
108 114
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1
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21
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140
1.7
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8
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50
100
150
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Pr
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North Cornelia
Dry Climatic Condition (2008) Calibration
Spring Phosphorus Atmospheric Deposition Watershed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
59 55
32 27 17 14
0
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83
103 118 128
113
146
54
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130
160
190
210
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8
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50
100
150
200
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Pr
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South Cornelia
Dry Climatic Condition (2008) Calibration
84
44
31 22 19 12 7 6 5 3 2 2 2 1 1 1 1 0 0 0 0
0
0
1 2
1 1 2 2 1 1 1 1 2 2 2 2 1 1 2 2
36
36 53
105
105
72 69
108 114
100 97 97
111 99 110 104
83 89 87 81
1
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81
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173
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87
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140
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164
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110 110
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1.7
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8
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50
100
150
200
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Pr
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(
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In
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[
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(
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North Cornelia
Dry Climatic Condition (2008) Calibration
Spring Phosphorus Atmospheric Deposition Watershed Runoff Southdale Cooling Water
Internal Release Observed Precipitation
59 55
32 27 17 14 9 7 2 2
0
2 3
2 3 2 3
1 2
5
6 8
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83
103 118 128
113
146
54
65
22
7
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58
0
56
0
29
88
130
160
190
210
130
220
60
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1.7
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0.9
3.0
0.5
1.1
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0.9
0.1
0
2
4
6
8
10
12
14
0
50
100
150
200
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4/29/2008 5/2/2008 6/16/2008 7/7/2008 7/21/2008 8/4/2008 8/18/2008 9/3/2008 9/17/2008 9/30/2008
Pr
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(
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South Cornelia
Dry Climatic Condition (2008) Calibration
Spring Phosphorus Atmospheric Deposition Watershed Runoff North Cornelia Discharge
Internal Release Observed Preciptitation
Figure 6-2b
North & South Cornelia In-Lake Model Calibration
Results for Dry Climatic Conditions with
Watershed and Spring Decay
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77
6.4 Use of the P8/In-Lake Models
The in-lake models, adjusted to account for internal loading and calibrated to measured in-lake TP
concentrations, were subsequently used to estimate the in-lake total phosphorus concentration under
varying BMP scenarios.
As previously discussed, the internal loading for each lake varies during different climatic
conditions. Therefore, the calibrated in-lake water quality model for each climatic condition was
used to evaluate the lake’s response to the P8-predicted loadings resulting from several BMP
scenarios. Details of the modeling results and a discussion of management opportunities follow.
6.5 Modeling Chlorophyll a and Secchi Disc Transparency
The P8 model used for the analysis predicts phosphorus loads to North and South Cornelia, and the
in-lake model is used to determine water quality in the lake itself only estimates phosphorus
concentrations. To estimate the likely chlorophyll a concentrations and Secchi disc transparencies, it
was necessary to develop additional models (i.e., regression relationships).
Several authors have published equations giving general relationships between TP and Chl a , and
between Chl a and transparency. These published equations are generally best-fit regression
equations developed as general descriptions of the results of water quality analysis for many lakes.
The published regression equations give reasonable indications of the algal growth and transparency
dynamics for lakes of a particular class or region, but they may or may not be well-suited for
application to a specific lake.
However, since there are six years of water quality data available for North Cornelia and two years of
data available for South Cornelia, reliable lake-specific relationships between the water quality data
collected on all sampling dates was successful. For both North and South Cornelia, relationships
between TP and Chl a and between TP and transparency were developed. Figure 6-3 depicts the
numerical water quality models used to estimate chlorophyll a and Secchi disc values for North
Cornelia and South Cornelia.
For North Cornelia, the equations are:
[Chl a] = 0.4436*[TP] – 12.642 R2 = 0.4355
SD = 22.697*[TP] -0.808 R2 = 0.5727
And for South Cornelia, the equations are:
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78
[Chl a] = 0.4863*[TP] – 5.7388 R2 = 0.5117
SD = 18.051*[TP] -0.866 R2 = 0.7137
Where:
[TP] = measured or estimated epilimnetic (mixed surface layer) mean summer
total phosphorus concentration (µg/L)
[Chl a] = estimated epilimnetic mean summer chlorophyll a concentration (µg/L)
Secchi (SD) = estimated mean summer Secchi disc transparency (m)
These equations were subsequently used to give indications of what may be expected with respect to
Chl a and transparency, given the P8/in-lake model results for TP. It should be noted that the
response of Chl a and Secchi depth to TP is highly variable. Due to the high variability, the
regression equations can be expected only to allow a general indication of the lake response to
changing TP concentrations, and the predicted Chl a and Secchi depth values should not be construed
as absolute.
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80
7.0 Analysis of Future Conditions
The response of Lake Cornelia to future watershed changes was evaluated using the P8 model in
conjunction with the calibrated in-lake models. The purpose of this portion of the UAA is to provide
a means of evaluating the likely future lake condition if no management initiatives (apart from those
the NMCWD already requires for new development and redevelopment) are taken. Modeling
assumptions and results are presented in the following sections.
7.1 Future Conditions Modeling Assumptions
The land use used in the modeling for the ultimate watershed conditions was as described in
Section 4.2 of this report. In general, the land use for Lake Cornelia is fully-developed and not
expected to change significantly in future years. There are, however, several areas within the Lake
Cornelia watershed that are expected to redevelop in the future. At that time, the current NMCWD
rules regarding redevelopment will be applied to the redevelopment areas.
In addition to the NMCWD water quality treatment standards that are required for new and
redevelopment (60 percent removal of total phosphorus and 90 percent removal of total suspended
solids), the NMCWD also requires onsite retention of one inch of runoff from all impervious surfaces
(see the NMCWD website for complete details regarding the water management rules for new and
redevelopment). The City of Edina provided general parcels within the watershed that are expected
to redevelop in the future. The land use of these parcels is typically commercial, and the type of land
use is not expected to change during redevelopment. However, to evaluate the impact of the
NMCWD onsite retention standard, it was assumed that the first inch of runoff from the impervious
surfaces in these areas would be infiltrated.
In addition to the redevelopment, North Cornelia receives approximately 40 million gallons per year
from Southdale Center (via the Point of France Pond). The discharge is currently permitted by the
MDNR and monthly readings of the volume pumped from the groundwater are submitted. The
system is not permanent and must be abandoned by 2010 according to the MDNR.
Finally, as part of the hydrologic and hydraulic modeling performed for the City of Edina, to
minimize flooding problems around the Swimming Pool Pond located just upstream of Lake
Cornelia, a new outlet (a 42-inch pipe arch pipe) be installed to replace the existing outlet structure.
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81
Using this information, the P8 model was used to predict watershed loading of the lake under various
climatic conditions. The watershed loadings (water and nutrient loadings) were then used as input to
the in-lake model to provide predictions of the future water quality in Lake Cornelia.
Figure 7-1 shows the assumption used to evaluate the future conditions in the Lake Cornelia
watershed.
NC_62
NC_4
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NC_5
SC_1
NC_88
NC_30
NC_72
NC_2
SC_2
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Figure 7-1
Future Conditions
Lake Cornelia UAA
Nine Mile Creek Watershed District
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Ü
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83
7.2 Modeling Results
As was discussed in Section 6.0, three climatic conditions (wet year, dry year, average year) were
used in evaluating the likely water quality of Lake Cornelia under future land use conditions. The
modeling results for land use projections under the three climate conditions for Lake Cornelia are
presented below. Water quality simulations using the P8 and in-lake water quality models indicate
that the average climatic condition will produce the greatest strain upon water quality in Lake
Cornelia (i.e., result in the worst water quality of the three climatic conditions modeled).
7.2.1 Water Quality Model Results under Existing Conditions
The modeling analysis indicated that the lake currently has very poor water quality under all climatic
conditions. The estimated average summer total phosphorus concentrations for both North and South
Cornelia and for all climatic conditions were in the hypereutrophic category (i.e., very poor water
quality; see Figure 7-2a and 7-2b). The modeled average summer chlorophyll a concentration for
both North and South Cornelia under the wet, dry and average conditions were in the hypereutrophic
category (i.e. very poor water quality; see Figure 7-3a and 7-3b). Under average, dry, and wet
conditions for both lakes the modeled average summer Secchi disc transparencies were also in the
hypereutrophic category (i.e., very poor water quality; see Figures 7-4a and 7-4b).
7.2.2 Water Quality Model Results under Future Conditions
Numerous future conditions models were run to show different situations. As previously mentioned,
land use within the Lake Cornelia watershed is not expected to change significantly in the future.
Therefore, the change reflected in the modeling analysis of future conditions is the result replacing
the outlet from Swimming Pool Pond with a 42” arch pipe, the elimination of the Southdale Center
discharge into North Cornelia, and the implementation of the NMCWD on-site retention rule in all
areas expected to be redeveloped in the future. The first future scenario only considered the
elimination of the Southdale discharge. The second future conditions scenario evaluated considered
all three parameters listed above. This condition reflects the future conditions model used as the
basis for the evaluation of the BMP scenarios (as discussed in Section 8.0). The estimated effect of
the future conditions on water quality in Lake Cornelia is shown in Figures 7-2a, 7-2b, 7-3a, 7-3b, 7-
4a, and 7-4b.
It is most instructive to examine the water quality impacts via the lake’s projected summer average
TP values (Figure 7-2a and 7-2b). The estimated summer average TP concentrations under current
conditions are in the hypereutrophic category (i.e., very poor water quality) for all modeled climatic
conditions. Under future conditions, TP concentrations will increase, with the summer average TP
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
84
concentrations remaining in the hypereutrophic category (i.e., very poor water quality) for all
modeled climatic conditions. The extent of increase in average summer phosphorus concentration
ranged from approximately 0 percent to 22 percent for North Cornelia and approximately 0 percent to
5 percent for South Cornelia for the three climatic conditions (wet, dry, average). The largest
estimated percent increase in average summer phosphorus concentration due to future conditions
occurred under the average climatic conditions for both North Cornelia (22 percent increase) and
South Cornelia (5 percent increase).
Table 7-1 summarizes the water and phosphorus budgets for Lake Cornelia under the future
conditions. Table 7-2 compares the total phosphorus loading for North and South Cornelia under
existing conditions (Scenario 1) and future conditions (Scenario 6). The expected future condition
decreases the water load to North Cornelia significantly (between 19 and 31 percent). Additionally,
the phosphorus load to North Cornelia (between 12 and 17 percent) was also reduced. Because
discharge from North Cornelia is such a large portion of the water and phosphorus load to South
Cornelia, the decrease in water and phosphorus load to North Cornelia will also result in decreases in
the loading to South Cornelia. The future conditions are expected to decrease the water load to South
Cornelia by 17 to 28 percent and reduce the phosphorus load by 27 to 44 percent, on an annual basis.
Despite decreased phosphorus loading to both North and South Cornelia, a simultaneous decrease in
water load (and thus flushing from the system) results in increased phosphorus concentrations for all
climatic conditions. However, as discussed above, the increase in phosphorus concentrations in
expected to more significant in North Cornelia than in South Cornelia.
Ta
b
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e
7
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TP Load (lbs)TP Load (lbs)
Di
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P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
86
Table 7-2 Total Phosphorus Loading Impact of Future Conditions on Lake Cornelia
Climatic Condition
Modeled Annual1
Total Phosphorus
Load for Existing
Conditions
(Scenario 1)
(lbs)
Modeled Annual1 Total
Phosphorus Load for
Future Conditions
(Scenario 6)
(lbs)
Change
in Load
(lbs)
Percent
Reduction
(%)
North Cornelia
Average (2003-2004) 389 330 59 15
Wet (2001-2002) 489 432 57 12
Dry (2007-2008) 349 290 59 17
South Cornelia
Average (2003-2004) 448 260 188 42
Wet (2001-2002) 442 368 74 17
Dry (2007-2008) 430 240 190 44
1 – Based on Water Year (October 1 – September 30)
Figures 7-3a and 7-3b compare the estimated chlorophyll a summer average concentrations for
current and future conditions for the climatic conditions (dry, wet, and average). The average
summer Chl a values, based on the regression equations discussed in Section 6.5, can be expected to
show changes corresponding to those of total phosphorus. Under existing conditions the predicted
summer average Chl a values for North and South Cornelia fall within the hypereutrophic range
(Chla > 26 µg/L). Under future conditions, the Chla concentrations for all climatic conditions in
both North and South Cornelia are expected to still fall within the hypereutrophic classification.
Figures 7-4a and 7-4b compare the estimated Secchi disc summer averages for the current and future
conditions for the climatic conditions evaluated (dry, wet, and average). The average summer Secchi
values, based on the regression equations discussed in Section 6.5, can be expected to show changes
corresponding to those of total phosphorus. Under existing and future conditions the predicted
summer average Secchi disc transparency is in the hypereutrophic range (< 0.8 m) for both North and
South Cornelia.
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7.2.3 Expected Water Levels Under Future Conditions
In addition to evaluating the impact of abandoning the Southdale Center cooling water system on the
water quality in Lake Cornelia, there is also interest in the impact of eliminating this water load from
the water levels in Lake Cornelia and the Point of France Pond.
The water balance model developed for the Lake Cornelia was used to evaluate the expected impact
on water levels in North and South Cornelia with and without the Southdale Center discharge for all
three climatic conditions. Table 7-2 summarizes the average annual lake levels for the existing
conditions as well as without the operation of the Southdale cooling water system. Additionally,
Table 7-2 also includes average annual lake levels for the future conditions including the elimination
of the Southdale Center discharge, the onsite retention of stormwater runoff in the proposed
redevelopment areas, as well as replacing the Swimming Pool Pond outlet with a 42-inch arch pipe.
Table 7-2 Lake Cornelia Average Annual Water Level Summary
Scenario 1 - Existing
Conditions
Scenario 2 – Existing
Conditions: No
Southdale Discharge
Scenario 61 – Future
Conditions
North Cornelia
Average (2003-2004) 859.4 859.4 859.3
Wet (2001-2001) 859.5 859.4 859.4
Dry (2007-2008) 859.4 859.4 859.3
South Cornelia
Average (2003-2004) 859.2 859.2 859.1
Wet (2001-2001) 859.2 859.2 859.2
Dry (2007-2008) 859.2 859.2 859.1
1 - No Southdale Discharge, Implement NMCWD Rules in Redevelopment Areas, and Install 42-inch Outlet from Swimming Pool Pond
The elimination of the Southdale Center cooling water discharge would likely have very little impact
on the overall lake levels in both North and South Cornelia, only reducing average annual water
levels by approximately 0.0 to 0.1 feet.
In addition to evaluating the impact of the elimination of the Southdale Center discharge on Lake
Cornelia’s water levels, a water balance model was also developed to evaluate the relative impact on
the water levels in the Point of France Pond. A water balance was developed using the pond’s stage,
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storage, and discharge information as well as the watershed inflows to the pond as predicted by the
P8 model. It was assumed that there is no groundwater interaction in the Point of France Pond.
Water levels have not been monitored in the Point of France Pond; therefore, the water balance could
not be calibrated to actual data and the interpretation of the results should be based on the relative
difference in the water levels between the various scenarios and not on the absolute differences in the
predicted water elevations. Table 7-3 summarizes the Point of France Pond water levels for existing
conditions, with the elimination of the Southdale Center cooling water discharge, as well as with the
elimination of the Southdale Discharge and replacing the outlet from Swimming Pool Pond with the
42 inch outlet. Modeling suggests that the elimination of the Southdale Cooling water discharge will
have very little impact on the annual average water levels in the Point of France Pond, with the
expected average annual decrease in the water elevation ranging from 0.03 to 0.12 feet.
Table 7-3 Point of France Pond Average Annual Water Level Summary
Climatic Condition Existing
Conditions
No Southdale
Discharge
No Southdale
Discharge &
42-inch Outlet
from
Swimming
Pool Pond
Difference in
Water Elevation
(ft)
Average (2003-2004) 862.96 862.93 862.86 0.03 – 0.1
Wet (2001-2001) 862.99 862.94 862.87 0.05 – 0.12
Dry (2007-2008) 862.96 862.93 862.87 0.03 – 0.09
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8.0 Evaluation of Possible Management Initiatives
Analysis of the modeling done to evaluate the likely future conditions for Lake Cornelia indicated
that improvements could be made within the lake and its watershed. The modifications necessary to
achieve these improvements were evaluated under three climatic conditions to determine what effect
they might have on lake water quality. The modifications, their costs, and benefits are presented in
Section 8.2.
8.1 General Discussion of Improvement Scenarios
This section discusses improvement scenarios and general BMPs to remove phosphorus and/or
reduce sediment and litter entering a lake. Three types of BMPs were considered during the
preparation of this report: structural, nonstructural, and in-lake.
1. Structural BMPs remove a fraction of the pollutants and sediment loads contained in
stormwater runoff prior to discharge into receiving waters.
2. Nonstructural BMPs (source control) eliminate pollutants at the source and prevent pollutants
from entering stormwater flows.
3. In -Lake BMPs reduce phosphorus already present in a lake, and/or prevent the release of
phosphorus from anoxic lake sediments.
8.1.1 Structural BMPs
Structural BMPs temporarily store and treat urban stormwater runoff to reduce flooding, remove
pollutants, and provide other amenities (Schueler, 1987). Water quality BMPs are specifically
designed for pollutant removal. The effectiveness of the various BMPs is summarized in Table 8-1.
Structural BMPs control total suspended solids and total phosphorus loadings by slowing stormwater
and allowing particles to settle in areas before they reach the stream. Settling areas can be ponds,
storm sewer sediment traps, or vegetative buffer strips. Settling can be enhanced by treatment with a
flocculent prior to entering the settling basin (see alum treatment plants below).
When choosing a structural BMP, the ultimate objective must be well understood. The BMP should
accomplish the following (Schueler 1987):
1. Reproduce, as nearly as possible, the stream flow before development.
2. Remove at least a moderate amount of most urban pollutants.
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3. Require reasonable maintenance.
4. Have a neutral impact on the natural and human environments.
5. Be reasonably cost-effective compared with other BMPs.
Table 8-1 General Effectiveness of Stormwater BMPs at Removing Common Pollutants from
Runoff
Best
Management
Practice (BMP)
Suspended
Sediment
Total
Phosphorus
Total
Nitrogen
Oxygen
Demand
Trace
Metals Bacteria
Overall
Removal
Wet Pond 5 3 2 3 4 ? 4
Infiltration
Trench or Basin
5 3 3 4 5 4 4
Porous
Pavement
4 4 4 4 4 5 4
Water Quality
Inlet (Grit
Chamber)
1 ? ? ? ? ? ?
Filter Strip 2 1 1 1 1 ? 1
Percent Removal Score
80 to 100 5
60 to 80 4
40 to 60 3
20 to 40 2
0 to 20 1
Insufficient Knowledge ?
Source: Schueler 1987
Examples of structural BMPs commonly installed to improve water quality include:
• Wet detention ponds
• Vegetative buffer strips
• Oil and grit separators
• Alum treatment plants
Each of the BMPs is described below and their general effectiveness is summarized in Table 8-1.
8.1.1.1 Wet Detention Ponds
Wet detention ponds (sometimes called “NURP” ponds after the Nationwide Urban Runoff Program)
are impoundments that have a permanent pool of water and also have the capacity to hold runoff and
release it at slower rates than incoming flows. Wet detention ponds are one of the most effective
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methods available for treatment of stormwater runoff. Wet detention ponds are used to interrupt the
transport phase of sediment and pollutants associated with it, such as trace metals, hydrocarbons,
nutrients, and pesticides. When designed properly, wet detention ponds can also provide some
removal of dissolved nutrients. Detention ponds have also been credited with reducing the amount of
bacteria and oxygen-demanding substances as runoff flows through the pond.
During a storm, polluted runoff enters the detention basin and displaces “clean” water until the plume
of polluted runoff reaches the basin’s outlet structure. When the polluted runoff does reach the outlet,
it has been diluted by the water previously held in the basin. This dilution further reduces the
pollutant concentration of the outflow. In addition, much of the total suspended solids and total
phosphorus being transported by the polluted runoff and the pollutants associated with these
sediments are trapped in the detention basin. A well-designed wet detention pond could remove
approximately 80 to 95 percent of total suspended solids and 40 to 60 percent of total phosphorus
entering the pond (MPCA, 1989).
As storm flows subside, finer sediments suspended in the pond’s pool will have a relatively longer
period of time to settle out of suspension during the intervals between storm events. These finer
sediments eventually trapped in the pond’s permanent pool will continue to settle until the next storm
flow occurs. In addition to efficient settling, this long detention time allows some removal of
dissolved nutrients through biological activity (Walker, 1987). These dissolved nutrients are mainly
removed by algae and aquatic plants. After the algae die, the dead algae can settle to the bottom of
the pond, carrying with them the dissolved nutrients that were consumed, to become part of the
bottom sediments.
The wet detention process results in good pollutant removal from small storm events. Runoff from
larger storms will experience pollutant removal, but not with the same high efficiency levels as the
runoff from smaller storms. Studies have shown that because of the frequency distribution of storm
events, good control for more frequent small storms (wet detention’s strength) is very important to
long-term pollutant removal.
8.1.1.2 Infiltration
Infiltration is the movement of water into the soil surface. For a given storm event, the infiltration
rate will tend to vary with time. At the beginning of the storm, the initial infiltration rate is the
maximum infiltration that can occur because the soil surface is typically dry and full of air spaces.
The infiltration rate will tend to gradually decrease as the storm event continues because the soil air
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spaces fill with water. For long duration storms the infiltration rate will eventually reach a constant
value, the minimum infiltration rate (the design infiltration rate). The infiltrated runoff helps
recharge the groundwater and mitigate the impacts of development. Stormwater flows in, ponds on
the surface, and gradually infiltrates into the soil bed. Pollutants are removed by adsorption,
filtration, volatilization, ion exchange, and decomposition. Therefore, infiltration is one of a few
BMPs that can reduce the amount of dissolved pollutant in stormwater. Infiltration BMP devices,
such as porous pavements, infiltration trenches and basins, and rainwater gardens, can be utilized to
promote a variety of water management objectives, including:
• Reduced downstream flooding
• Increased groundwater recharge
• Reduced peak stormwater discharges and volumes
• Improved stormwater quality
An infiltration basin collects and stores stormwater until it infiltrates to the surrounding soil and
evaporates to the atmosphere. Infiltration basins remove fine sediment, nutrients (including
dissolved nutrients), trace metals, and organics through filtration by surface vegetation, and through
infiltration through the subsurface soil. Deep-rooted vegetation can increase infiltration capacity by
creating small conduits for water flow. Infiltration basins are designed as a grass-covered depression
underlaid with geotextile fabric and coarse gravel. A layer of topsoil is usually placed between the
gravel layer and the grassed surface. Pretreatment is often required to remove any coarse particulates
(leaves and debris), oil and grease, and soluble organics to reduce the potential of groundwater
contamination and the likelihood of the soil pores being plugged. Infiltration can also be promoted in
existing detention ponds by excavating excess sediments (typically the fines that have seal the
bottom of the pond) and exposing a granular sub-base (assuming one was present prior to the original
construction of the detention pond).
Rainwater gardens (a form of bio-retention) are shallow, landscaped depressions that channel and
collect runoff. To increase infiltration, the soil bed is sometimes amended, such as with mulch.
Vegetation takes up nutrients, and stored runoff is reduced through evapotranspiration. Bio-retention
is commonly located in parking lot islands, or within small pockets in residential areas. Bio-retention
is primarily designed to remove sediment, nutrients, metals, and oil and grease. Secondary benefits
include flow attenuation, volume reduction, and removal of floatables, fecal coliform, and BOD.
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8.1.1.3 Vegetated Buffer Strips
Vegetative buffer strips are low sloping areas that are designed to accommodate stormwater runoff
traveling by overland sheet flow. Vegetated buffer strips perform several pollutant attenuation
functions, mitigating the impact of development. Urban watershed development often involves
disturbing natural vegetated buffers for the construction of homes, parking lots, and lawns. When
natural vegetation is removed, pollutants are given a direct path to the lake -- sediments cannot settle
out; nutrients and other pollutants cannot be removed. Additional problems resulting from removal of
natural vegetation include streambank erosion and loss of valuable wildlife habitat (Rhode Island
Department of Environmental Management, 1990).
The effectiveness of buffer strips is dependent on the width of the buffer, the slope of the site, and
the type of vegetation present. Buffer strips should be 20-feet wide at a minimum, however 50- to 75-
feet is recommended. Many attractive native plant species can be planted in buffer strips to create
aesthetically pleasing landscapes, as well as havens for wildlife and birds. When properly designed,
buffer strips can remove 30 to 50 percent of total suspended solids from lawn runoff. In addition,
well-designed buffer strips will discourage waterfowl from nesting and feeding on shoreland lawns.
Such waterfowl can be a significant source of phosphorus to the pond, by grazing turfed areas
adjacent to the water and defecating in or near the water’s edge where washoff into the pond is
probable.
8.1.1.4 Oil and Grit Separators
Oil-grit separators (e.g., StormCeptors) are concrete chambers designed to remove oil, sediments,
and floatable debris from runoff, and are typically used in areas with heavy traffic or high potential
for petroleum spills such as parking lots, gas stations, roads, and holding areas. A three-chamber
design is common; the first chamber traps sediment, the second chamber separates oil, and a third
chamber holds the overflow pipe. The three-chambered unit is enclosed in reinforced concrete. They
are good at removing coarse particulates, but soluble pollutants probably pass through. In order to
operate properly, they must be cleaned out regularly (at least twice a year). The major benefit of a
water oil-grit separator is as a pre-treatment for an infiltration basin or pond. They can also be
incorporated into existing stormwater system or included in an underground vault detention system
when no available land exists for a surface detention basin. Only moderate removals of total
suspended solids can be expected; however, oil and floatable debris are effectively removed from
properly designed oil and grit separators.
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8.1.1.5 Alum Treatment Plants
In addition to the commonly installed structural BMPs discussed above, alum treatment plants are
becoming an option for efficiently removing phosphorus from tributaries, rather than directly treating
the lake with alum to remove phosphorus. Alum (aluminum sulfate) is commonly used as a
flocculent in water treatment plants and as an in-lake treatment for phosphorus removal. To treat
inflows in streams or storm sewers, part of the flow is diverted (e.g., 5 cfs) from the main flow and
treated with alum. After the alum is injected in the diverted flow it passes to a detention pond to
allow the flocculent to settle out before the water enters the lake. Alum treatment has been shown to
remove up to 90 percent of the soluble and particulate phosphorus from the inflows.
8.1.1.6 Iron-Enhanced Sand Filtration
Sand filtration systems are typically designed to remove particulate matter and phosphorus from
stormwater flows. With the addition of steel fiber, steel wool blankets, or other types of iron
amendments, additional removal of soluble and non-settleable phosphorus is possible. Pretreatment
of the stormwater flow is necessary to ensure that proper hydraulics and that infiltration rates are
maintained for phosphorus removal. When stormwater flow exceeds the capacity of the filter system,
only partial treatment will be possible with higher flows being bypassed around the filter. Because
aerobic conditions are required, flow must be diverted from the filter to allow for drainage and
drying and, thus, a parallel system or a system with a controlled bypass is recommended.
A sand filter facility in Bellevue, WA receiving stormwater with inflow concentrations of total and
soluble phosphorus of 94 and 26 µg/L, reduced loading between 43 and 72 percent (City of Bellevue,
Washington, 1999). This facility uses chopped granular steel wool that increased clogging, creating
anaerobic conditions within the filter, thereby reducing its effectiveness at removing phosphorus. A
column design by Erickson et al. (2006) provided between 40 and 90 percent removal of soluble
phosphorus in a system comprised of C33 sand with granular steel wool or steel wool fabric as an
amendment. An iron enhanced sand filter was installed in the Ramsey Washington Metro Watershed
District (RWMWD) using iron filings with a grain size distribution similar to the sand used in the
filter (Barr, 2009). Using iron filings instead of chopped steel wool provides a number of benefits
including less chance for filter plugging and less pollutants that can be associated with steel wool
(oil). Testing of the design installed at RWMWD was conducted and phosphorus removal was
between 80 and 90% (Erickson et al. 2009). Longevity, based on the testing parameters, was at least
20 years. This will vary between systems however, based on hydraulic loading rate and
concentration of phosphorus of the inflows.
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8.1.2 Nonstructural BMPs
Nonstructural (“Good Housekeeping”) BMPs discussed below include:
1. Public Education
2. City Ordinances
3, Street Sweeping
4. Deterrence of Waterfowl
Good housekeeping practices reduce the pollutant at its source.
8.1.2.1 Public Education
Public education regarding proper lawn care practices, such as fertilizer use and disposal of lawn
debris, would result in reduced organic matter and phosphorus loadings to the lake. A public
information and education program may be implemented to teach residents within the Lake Cornelia
watershed how to protect and improve the quality of the lake. The program would include
distribution of fliers to all residents in the watershed and placement of advertisements and articles in
the city’s newsletters and the local newspapers. Information could also be distributed through
organizations such as local schools, Girl Scouts and Boy Scouts, and other local service clubs.
Initiation of a stenciling program to educate the public would help reduce loadings to the storm sewer
system. Volunteers could place stenciled messages (i.e., “Dump No Waste, Drains to Lake Cornelia”)
on all storm sewer catch basins within the Lake Cornelia watershed.
8.1.2.2 Ordinances
Water quality problems can be addressed through legislative methods, such as a watershed-wide ban
on the use of phosphorus fertilizers or a commercial lawn care ordinance to control content of
mixture and ensure that no phosphorus is present in the case of a complete phosphorus ban. A new
legislated fertilizer phosphorus limitation became effective in 2004, which bans the use of fertilizers
containing phosphorus on lawns in the Twin Cities metro area (Anoka, Carver, Dakota, Hennepin,
Ramsey, Scott and Washington counties). Exceptions to such a ban would be granted in cases where
a resident was able to demonstrate, by means of soil analyses, that phosphorus was required. Other
ordinances pertaining to littering, pet feces, and buffer strips adjacent to lakes and other water bodies
could be strengthened or created.
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8.1.2.3 Street Sweeping
Most often, street sweeping is performed only in the spring, after the snow has melted and in the fall,
after the leaves have fallen, to reduce this potential source of phosphorus from entering the storm
sewer. For most urban areas, street sweeping has relatively low effectiveness from late-spring (after
the streets are cleaned of accumulated loads) until early-fall (prior to the onset of leaf fall)
(Bannerman, 1983). In addition, the use of vacuum sweepers is preferred over the use of mechanical,
brush sweepers. The vacuum sweepers are more efficient at removing small phosphorus-bearing
particles from impervious surfaces within the watershed. Fall street sweeping is particularly
important in the watershed directly tributary to the lake, where treatment of stormwater is not
available.
8.1.2.4 Deterrence of Waterfowl
The role of waterfowl in the transport of phosphorus to lakes is often not considered. However, when
the waterfowl population of a lake is large relative to the lake size, a substantial portion of the total
phosphorus load to the lake may be caused by the waterfowl. Waterfowl tend to feed primarily on
plant material in or near a lake; the digestive processes alters the form of phosphorus in the food
from particulate to dissolved. Waterfowl feces deposited in or near a lake may result in an elevated
load of dissolved phosphorus to the lake. One recent study estimated that one Canada goose might
produce 82 grams of feces per day (dry weight) while a mallard may produce 27 grams of feces per
day (dry weight) (Scherer et al., 1995). Waterfowl prefer to feed and rest on areas of short grass
adjacent to a lake or pond. Therefore, shoreline lawns that extend to the water’s edge will attract
waterfowl. The practice of feeding bread and scraps to waterfowl at the lakeshore not only adds
nutrients to the lake, but attracts more waterfowl to the lake and encourages migratory waterfowl to
remain at the lake longer in the fall.
Two practices often recommended to deter waterfowl are construction of vegetated buffer strips, and
prohibiting the feeding of waterfowl on public shoreline property. As stated above, vegetated strips
along a shoreline will discourage geese and ducks from feeding and nesting on lawns adjacent to the
lake, and may decrease the waterfowl population.
8.1.3 In-Lake BMPs
In -lake BMPs reduce phosphorus already present in a lake or prevent the release of phosphorus from
the lake sediments. Several in-lake BMPs are discussed below.
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8.1.3.1 Removal of Benthivorous (Bottom-Feeding) Fish
Benthivorous fish, such as carp and bullhead, can have a direct influence on the phosphorus
concentration in a lake (LaMarra, 1975). These fish typically feed on decaying plant and animal
matter and other organic particulates found at the sediment surface. The fish digest the organic
matter, and excrete soluble nutrients, thereby transforming sediment phosphorus into soluble
phosphorus available for uptake by algae at the lake surface. Depending on the number of
benthivorous fish present, this process can occur at rates similar to watershed phosphorus loads.
Benthivorous fish can also cause resuspension of sediments in shallow ponds and lakes, causing
reduced water clarity and poor aquatic plant growth, as well as high phosphorus concentrations
(Cooke et al., 1993). In some cases, the water quality impairment caused by benthivorous fish can
negate the positive effects of BMPs and lake restoration. Depending on the numbers of fish present,
the removal of benthivorous fish may cause an immediate improvement in lake water quality. The
predicted water quality improvement following removal of the bottom-feeding fish is difficult to
estimate, and will require permitting and guidance from the Minnesota Department of Natural
Resources (MDNR). Therefore, it is not included as an option in this report. In addition, using fish
barriers to prevent benthivorous fish from spawning may adversely affect the spawning of game fish,
such as northern pike.
8.1.3.2 Application of Alum (Aluminum Sulfate)
As discussed in Section 6.3.2, there is an internal load of phosphorus from the sediments in Lake
Cornelia. Sediment release of phosphorus to the lake basins occurs during the summer months, when
the oxygen in the water overlying the sediments is depleted of oxygen. This internal load of
phosphorus is transported to the entire lake during mixing events (in shallow lakes) or in the late-
summer, when the surface waters cool sufficiently for wind-mixing to mix the entire lake (often
referred to as “fall turnover”) (in deeper, dimictic lakes). Phosphorus released from the sediments is
typically in a dissolved form, which can be quickly utilized by algae, leading to intense algae
blooms. A real application of alum has proven to be a highly effective and long-lasting control of
phosphorus release from the sediments, especially where an adequate dose has been delivered to the
sediments and where watershed sediment and phosphorus loads have been minimized (Moore and
Thorton, 1988). Alum will remove phosphorus from the water column as it settles and then forms a
layer on the lake bottom that covers the sediments and prevents phosphorus from entering the lake as
internal load. An application of alum to the lake sediments will decrease the internal phosphorus load
by 80 percent (Effectiveness and Longevity of Phosphorus Inactivation with Alum, Welch and Cook,
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104
1999) and will likely be effective for approximately 10 years, depending on the control of watershed
nutrient loads.
8.2 Feasibility Analysis
8.2.1 Statement of Problem
Because Lake Cornelia is annually stocked with bluegill for the Fishing in the Neighborhood
Program by the MDNR, the lake use aligns with the NMCWD Level III category for fishing and
aesthetic viewing. Lake Cornelia currently meets requirements for a Level IV Lake, one generally
intended for runoff management with no significant recreational use value. Based on this
classification, water quality modeling simulations show the phosphorus load to Lake Cornelia under
current and future conditions will likely result in total phosphorus and chlorophyll a concentrations
and Secchi disc transparencies that exceed the NMCWD’s Level III goals for the lake (see
Table 8-2). Several lake management scenarios to maintain and/or improve the water quality of Lake
Cornelia were explored. Table 8-2 details the predicted summer average total phosphorus
concentration, chlorophyll a concentration, Secchi disc transparency, and TSISD for existing
conditions and all management alternatives analyzed. Several lake management scenarios are
discussed below.
North Lake Cornelia
TP CHLa SD TSISD TP CHLa SD TSISD TP CHLa SD TSISD
(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)
1 Existing (2008) Watershed Conditions1
with Southdale System Operating 153 55.4 0.39 74 164 60.5 0.37 74 127 44.0 0.45 71
2 Existing (2008) Watershed Conditions1
with Southdale System Not Operating 160 58.6 0.38 74 182 68.4 0.34 76 166 61.7 0.36 75
3 Infiltration (NMCWD Rules) in
Redevelopment Areas2 162 59.7 0.37 74 199 76.2 0.32 77 129 45.1 0.45 72
4 42" RCP outlet from Swimming Pool
Pond to North Cornelia2 151 54.8 0.39 73 177 66.2 0.35 75 126 43.6 0.46 71
5
42" RCP outlet from Swimming Pool
Pond to North Cornelia & Infiltration of
1" of Runoff From All Impervious
Surfaces in the Watershed2
135 47.7 0.43 72 244 96.5 0.27 79 132 46.1 0.44 72
Future Conditions: Infiltration
Secchi Disc Transparency, and TSISD for All Management Alternatives Analyzed
Table 8-2 Lake Cornelia Predicted Total Phosphorus and Chlorophyll a Concentration,
Scenario
Number
Best Management Practice (BMP)
Strategy
Dry Climatic Conditions (2007-2008) Average Climatic Conditions (2003-2004) Wet Climatic Conditions (2001-2002)
Summer Average Summer Average Summer Average
6
Future Conditions: Infiltration
(NMCWD Rules) in Redevelopment
Areas & 42" RCP outlet from
Swimming Pool Pond to North
Cornelia2
159 58.1 0.38 74 201 76.9 0.31 77 128 44.4 0.45 71
7 Future Conditions & NURP Pond in NC-
62a 142 50.8 0.41 73 197 75.3 0.32 77 124 42.6 0.46 71
8
Future Conditions & Alum Treatment
Plant at the outlet of Swimming Pool
Pond3
135 47.6 0.43 72 174 65.1 0.35 75 114 38.1 0.50 70
9
Future Conditions & Iron-Enhanced
Sand Filter at the outlet of Swimming
Pool Pond4
142 50.6 0.41 73 182 68.5 0.34 76 118 40.2 0.48 71
10 Future Conditions & In-Lake Alum
Treatment of North Cornelia 139 49.4 0.42 72 136 48.2 0.43 72 115 38.7 0.49 70
11
Future Conditions, NURP Pond in NC-
62a, Alum Treatment Plant at outlet of
Swimming Pool Pond3, & Alum
Treatment of North Cornelia
99 31.5 0.55 68 106 34.7 0.52 69 97 30.7 0.56 68
1 - Reflects the 2004 dredging of Point of France Pond and Swim Pool Pond
2 - Assumes the Southdale System in NOT Operating
3 - Assumes treatment of 5 cfs of discharge
4 - Assumes treatment of 3.5 cfs
South Lake Cornelia Dry Climatic Conditions (2007-2008)Average Climatic Conditions (2003-2004)Wet Climatic Conditions (2001-2002)South Lake Cornelia
TP CHLa SD TSISD TP CHLa SD TSISD TP CHLa SD TSISD
(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)(µµµµg/L) (µµµµg/L)(m)
1 Existing (2008) Watershed Conditions1
with Southdale System Operating 150 67.2 0.24 81 176 79.8 0.21 83 133 58.7 0.26 79
2 Existing (2008) Watershed Conditions1
with Southdale System Not Operating 154 69.0 0.23 81 188 85.8 0.19 84 147 65.8 0.24 81
3 Infiltration (NMCWD Rules) in
Redevelopment Areas2 151 67.9 0.23 81 190 86.4 0.19 84 133 58.7 0.26 79
4 42" RCP outlet from Swimming Pool
Pond to North Cornelia2 149 67.0 0.24 81 183 83.3 0.20 83 133 59.1 0.26 79
5
42" RCP outlet from Swimming Pool
Pond to North Cornelia & Infiltration of
1" of Runoff From All Impervious
Surfaces in the Watershed2
149 66.5 0.24 81 117 51.3 0.29 78 129 56.9 0.27 79
6
Future Conditions: Infiltration
(NMCWD Rules) in Redevelopment
Areas & 42" RCP outlet from
Swimming Pool Pond to North
Cornelia2
152 68.0 0.23 81 185 84.2 0.20 83 133 59.2 0.26 79
Summer Average Summer Average Summer Average
Scenario
Number
Best Management Practice (BMP)
Strategy
Dry Climatic Conditions (2007-2008)Average Climatic Conditions (2003-2004)Wet Climatic Conditions (2001-2002)
7 Future Conditions & NURP Pond in NC-
62a 139 61.6 0.25 80 185 84.5 0.20 83 135 59.7 0.26 79
8
Future Conditions & Alum Treatment
Plant at the outlet of Swimming Pool
Pond3
131 58.0 0.26 79 146 65.2 0.24 80 125 54.9 0.28 79
9
Future Conditions & Iron-Enhanced
Sand Filter at the outlet of Swimming
Pool Pond4
138 61.2 0.25 80 158 70.9 0.23 81 128 56.7 0.27 79
10 Future Conditions & In-Lake Alum
Treatment of North Cornelia 149 66.7 0.24 81 154 69.0 0.23 81 115 50.1 0.30 78
11
Future Conditions, NURP Pond in NC-
62a, Alum Treatment Plant at outlet of
Swimming Pool Pond3, & Alum
Treatment of North Cornelia
115 50.4 0.30 78 115 50.3 0.30 78 107 46.4 0.32 77
1 - Reflects the 2004 dredging of Point of France Pond and Swim Pool Pond
2 - Assumes the Southdale System in NOT Operating
3 - Assumes treatment of 5 cfs of discharge
4 - Assumes treatment of 3.5 cfs
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106
8.2.2 Selection and Effectiveness of Alternatives
Three types of BMPs were considered for recommendation in this plan:
1. Structural
2. Nonstructural
3. In -Lake
Each of these types are defined and discussed in Section 8.1. Specific BMP alternatives that were
considered for the Lake Cornelia watershed are discussed below. Not all of the BMP alternatives
discussed below are recommended for implementation in the Lake Cornelia watershed. Figure 8-1
shows the location of these potential sites. Estimated “budgeting” costs reflect 2010 dollars and do
not include costs to acquire land or easements or obtain permits (concept level cost estimates are
provided in Appendix G).
8.2.2.1 Site-Specific Structural BMPs
8.2.2.1.1 Add Pond NC_62A designed to meet MPCA/NURP criteria
The first step in identifying potential structural BMPs to help improve the water quality of Lake
Cornelia was to assess the existing wet detention ponds and wetlands within the watershed to ensure
they provide adequate dead storage volume for water quality treatment. As discussed previously, the
treatment effectiveness of a pond is directly related to its dead storage volume. Current MPCA- (i.e.,
Protecting Water Quality in Urban Areas, 1989) and NURP- (Nationwide Urban Runoff Program)
design criteria require a minimum permanent pool or dead storage volume for each pond based upon
its watershed size and land use. In addition to these considerations, the volume of the pond accounts
for sedimentation over time, which tends to fill in the pond’s dead storage volume and reduce the
pond water quality treatment effectiveness. The MPCA and NURP criteria used to assess the
permanent pool volume of the existing ponds was a wet detention volume equal to the runoff from a
2.0 inch rainfall over the individual subwatershed, in addition to sediment storage to contain 25 years
of sediment accumulation. Table 8-3 summarizes the results of the dead storage volume analysis of
existing ponds.
"/!.
NC_4
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SC_1
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NC_88
NC_30
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Figure 8-1
Location of BMP Alternatives
Lake Cornelia UAA
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109
Based on wetland inventories, SWMPs, field surveys conducted in the summer of 2004, and dredging
plans provided by the City of Edina, most of the existing wet detention ponds within the Lake
Cornelia watershed provide sufficient permanent pool volume to achieve effective water quality
treatment based on MPCA and NURP criteria. However, North Cornelia’s direct subwatershed is
10.5 acre-ft deficient in dead storage. This means runoff from the 289-acre watershed, including
runoff from the Highway 100/Highway 62 intersection, enter North Cornelia untreated. Adding a
pond upstream from North Cornelia to treat the direct watershed inflow before it reaches the lake
would result in a reduced phosphorus loading to Lake Cornelia.
The addition of the pond NC_62a (Figure 8-1) upstream of North Cornelia to provide water quality
treatment storage based on the criteria established in the National Urban Runoff Program (NURP) for
full-development watershed conditions will have a noticeable effect on the external phosphorus load
to Lake Cornelia. These phosphorus loading changes to Lake Cornelia translate into minimal
changes in the summer average total phosphorus and chlorophyll a concentrations in the lakes and
will not noticeably improve the summer average water clarity in either lake (see Scenario 7;
Figures 8-2 through 8-4). As shown in Table 8-4, for North Cornelia approximately 51to 70 lbs of
phosphorus and for South Cornelia approximately 0 to 10 lbs of phosphorus would be removed
during the water year, depending on climatic condition.
This BMP scenario is estimated to have a capitol cost of $435,000, including engineering and design.
Actual cost for the pond would depend on the unique conditions at the site and a more precise
determination of those costs would have to be done. Additionally, the location of the proposed pond
NC_62a, is located within a wetland, requiring wetland mitigation. Typical wetland replacement
mitigation costs typically range from $50,000 to $100,000 per acre (not including land acquisition
costs). Wetland bank credits can also be purchased at less expense; however, wetland replacement is
the preferred approach. The proposed pond surface area is about 2.6 acres so an expected wetland
mitigation area is estimated to be 6.5 acres, resulting in an average wetland mitigation cost of
approximately $490,000.
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110
Table 8-4 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of NURP Pond NC_62a
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual Total
Phosphorus Load for
Future Conditions +
NURP pond in
NC_62a
Scenario 7
Change in
Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 261 69 21
Wet (2001-02) 432 362 70 16
Dry (2007-2008) 290 239 51 18
South Cornelia
Average (2003-04) 260 260 0 0.1
Wet (2001-02) 368 365 3 0.8
Dry (2007-2008) 240 230 10 4
8.2.2.1.2 Add Alum Treatment Plant to treat inflows from NC_3 (Swimming Pool Pond)
As Figures 5-2a, 5-2b, and 5-2c indicate, North Cornelia receives approximately 32 to 38 percent of
the phosphorus loading from NC_3, or Swimming Pool Pond. A scenario was evaluated where an
alum treatment plant was added to treat the inflows from Swimming Pool Pond. Table 8-3 shows the
results of the dead storage volume analysis of existing ponds. Adding the alum treatment plant will
reduce the external phosphorus load to Lake Cornelia. These phosphorus loading changes to Lake
Cornelia translate into changes in the summer average total phosphorus, chlorophyll a
concentrations, and secchi disc transparency in both lakes (see Scenario 8; Figures 8-2 through 8-4).
As shown in Table 8-5, for North Cornelia approximately 34 to 46 lbs of phosphorus and for South
Cornelia approximately 17 to 30 lbs of phosphorus would be removed during the water year annual
period, depending on climatic condition. This scenario assumes treatment of up to 5 cfs of flow
before bypassing the treatment plant.
This BMP scenario is estimated to have a capital cost of $1,000,000 including engineering and
design. Actual cost for the alum treatment plant would depend on the unique conditions at the site
and a more precise determination of those costs would have to be done. Additionally, there are
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111
annual operations and maintenance costs associated with an alum treatment system, which will be
dependent on the rate and amount of flow being treated as well as the phosphorus concentration
being treated. The Ramsey-Washington Metro Watershed district has been operating an alum dosing
plant, located just upstream of Tanners Lake since 1998. This system treats 1.5 cfs of flow at phosphorus
concentrations upward s of 300 ug/L. Approximately 30,000 gallons of alum is used each year, costing
approximately $30,000 to $40,000 depending upon the cost of alum. General maintenance costs have
been estimated to range from $5,000 to $10,000 per year and includes costs to operate the facility,
equipment repair (e.g., new dosing pumps, control panel repairs), and cleaning of the mixing chamber
sump. Spent alum floc removal is the primary maintenance cost and has ranged from $25,000 a year
when direct discharge to the sanitary sewer is conducted to as high as $100,000 a year when the alum floc
is disposed in a landfill.
Table 8-5 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of Alum Treatment Plant treating inflow from NC_3 (Swimming Pool
Pond)
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual
Total Phosphorus
Load for Future
Conditions + Alum
Treatment Plant
Scenario 8
Change
in Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 290 40 12
Wet (2001-02) 432 387 46 11
Dry (2007-2008) 290 256 34 12
South Cornelia
Average (2003-04) 260 231 30 11
Wet (2001-02) 368 348 20 6
Dry (2007-2008) 240 223 17 7
8.2.2.1.3 Add Iron-Enhanced Sand Filter to treat inflows from NC_3 (Swimming Pool Pond)
As Figures 5-2a, 5-2b, and 5-2c indicate, North Cornelia receives approximately 32 to 38 percent of
the phosphorus loading from NC_3, or Swimming Pool Pond. A scenario was evaluated where an
iron enhanced sand filter was used to treat the inflows from Swimming Pool Pond. Adding the iron-
enhanced sand filter will reduce the external phosphorus load to Lake Cornelia. These phosphorus
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112
loading changes to Lake Cornelia translate into changes in the summer average total phosphorus,
chlorophyll a concentrations, and secchi disc transparency in both lakes (see Scenario 9; Figures 8-2
through 8-4). As shown in Table 8-6, for North Cornelia approximately 24 to 32 lbs of phosphorus
and for South Cornelia approximately 10 to 21 lbs of phosphorus would be removed during the water
year annual period, depending on climatic condition. There are approximately 0.5 acres available in
the park north of the discharge pipe from NC_3, resulting in treatment of up to 3.5 cfs of flow before
bypassing the filter.
This BMP scenario is estimated to have a capital cost of $700,000 including engineering and design.
Actual cost for the iron enhanced sand filter would depend on the unique conditions at the site and a
more precise determination of those costs would have to be done. Additionally, there are operations
and maintenance costs typically associated with a filtration system which can include cleaning of
pre-treatment basin/vault at least every 5 years, surface scraping 1 to 2 times a year to remove
buildup and promote filtrations, potentially installation of a back flushing system could be installed
to prevent clogging from incoming sediment, rototilling of surface may be necessary every year to
break up surface layer of sediment and maintain hydraulic capacity if clogging is a problem, and
replace filter media every 10-20 years. In the case of a filter just downstream of Swimming Pool
Pond, much of the inflows will likely be sufficiently pretreated (most particulates will be settled) in
Swimming Pool Pond and all the upstream ponds within the watershed. The maintenance costs were
estimated to be $47,000 (10% of estimated construction costs).
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113
T able 8-6 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Construction of an Iron-Enhanced Sand Filter treating inflow from NC_3 (Swimming
Pool Pond)
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual
Total Phosphorus
Load for Future
Conditions + Iron-
Enhanced Sand
Filter
Scenario 9
Change
in Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 304 26 8
Wet (2001-02) 432 400 32 7
Dry (2007-2008) 290 266 24 8
South Cornelia
Average (2003-04) 260 240 21 8
Wet (2001-02) 368 356 12 3
Dry (2007-2008) 240 230 10 4
8.2.2.1.4 Infiltration of 1-inch of Runoff from ALL Impervious Surfaces Watershed-Wide
Infiltration practices have become a more prominent type of stormwater BMP, not only helping to
reduce TP loads but to reduce runoff volumes as well. The NMCWD rules currently have an on-site
retention requirement for runoff from new development and redevelopment. A scenario was
evaluated to assess the impact of the implementation of watershed-wide infiltration, assuming 1 inch
of runoff from all impervious surfaces was infiltrated. This scenario assumes that infiltrated water
will not intercept the groundwater and the infiltrated volume will not reach Lake Cornelia.
Implementing infiltration throughout the watershed will reduce the external phosphorus load to Lake
Cornelia, as well as the water loads reaching the lake. These phosphorus loading changes to Lake
Cornelia translate into changes in the summer average total phosphorus, chlorophyll a
concentrations, and secchi disc transparency in both lakes (see Scenario 5; Figures 8-2 through 8-4).
As shown in Table 8-7, for North Cornelia approximately 159 to 217 lbs of phosphorus and for South
Cornelia approximately 17 to 173 lbs of phosphorus would be removed during the water year annual
period, depending on climatic condition.
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114
This scenario was evaluated to evaluate the impact of watershed-wide infiltration only. No costs
have not been determined for this scenario.
Table 8-7 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
Infiltration of 1-inch of Runoff from ALL Impervious Surfaces Watershed-Wide
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual
Total Phosphorus
Load for Future
Conditions +
Infiltration of 1-inch
of Runoff Watershed
Wide
Scenario 5
Change
in Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 113 217 66
Wet (2001-02) 432 243 190 44
Dry (2007-2008) 290 131 159 55
South Cornelia
Average (2003-04) 260 87 173 67
Wet (2001-02) 368 223 145 40
Dry (2007-2008) 240 223 17 7
In addition to evaluating the impact of watershed –wide infiltration on the water quality in Lake
Cornelia, the water balance models were used to estimate the expected lake levels in both North and
South Cornelia with the implementation of infiltration throughout the watershed. Table 8-7
summarizes the predicted water surface elevations for the existing conditions scenario, the future
conditions scenario, and the scenario evaluating the infiltration of 1-inch of runoff from all
impervious surfaces across the watershed.
Table 8-8 Lake Cornelia Average Annual Water Level Summary – 1-inch of Infiltration from
ALL Impervious Surfaces Watershed-Wide
Scenario 1 - Existing
Conditions
Scenario 6 – Future
Conditions
Scenario 5 – Future
Conditions with
Infiltration of 1-inch
of Runoff Watershed
Wide
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115
North Cornelia
Average (2003-2004) 859.4 859.3 859.0
Wet (2001-2001) 859.5 859.4 859.2
Dry (2007-2008) 859.4 859.3 859.0
South Cornelia
Average (2003-2004) 859.2 859.1 858.7
Wet (2001-2001) 859.2 859.2 859.1
Dry (2007-2008) 859.2 859.1 859.1
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8
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3
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f
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(
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4
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2
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RC
P
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5
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RC
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6
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(
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P
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5
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\
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(
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P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
122
8.2.2.2 In-Lake Treatments
8.2.2.2.1 Treat - Application of Alum to the Entire Lake Surface Area of North Cornelia
There is evidence to suggest that internal loading may be impacting summer average TP
concentrations in Lake Cornelia. The results of the sediment core analysis suggests that the potential
TP loading rate from the sediments is much higher in North Cornelia than in South Cornelia and the
results of the in-lake modeling also supports this. Because North Cornelia is the major source of TP
to South Cornelia, an alum treatment in North Cornelia will likely improve water quality in South
Cornelia as well.
Alum treatment of the lake is expected to diminish the extent of the internal loading, and may result
in significant long-term declines in summer average TP concentrations. This prediction is based on
the assumption that application of alum to the lake sediments will decrease the internal phosphorus
load by 80 percent (Welch and Cook, 1999).
In -lake alum treatment of the lake is expected to provide both a temporary and a long-term
improvement in the water quality of the lakes. The temporary benefit (lasting from 1 to 2 years)
results from the alum’s ability to remove phosphorus from the water column. The phosphorus
removal inhibits algal growth by depriving the algae of phosphorus, a required nutrient.
Additionally, temporary improvements in water clarity result from the “cleansing” of the water
column that occurs as the alum floc settles and removes suspended particulate matter. Long-term
benefits to the lake are expected to result from the alum’s ability to bind phosphorus after the alum
comes to rest on the lake sediment surface, thus preventing transfer of sediment-bound phosphorus
back to the water column (i.e., preventing internal loading).
Over time, the effectiveness of the thin alum blanket on the sediment surface diminishes. Estimates
of the effective duration of a single alum treatment in preventing sediment phosphorus release vary
from 7 to 10 years. This effective duration can be affected by several factors, including homogeneity
of treatment, wind-driven mixing and sediment resuspension, changes in the sediment-water
chemical exchange dynamics that may result from the treatment itself and the impact of benthivorous
fish such as carp. Despite the uncertainties, it is reasonable to assume that for Lake Cornelia, the
alum treatment would be conducted at approximately 10-year intervals. If necessary, the treatment
interval could be adjusted based on the results of ongoing water quality monitoring.
In -lake application of alum to prevent sediment phosphorus release in North Cornelia during the
summer and fall months is another BMP scenario analyzed. Following an alum treatment of North
Cornelia, modeling simulations indicate the internal summer phosphorus load would be reduced by
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
123
about 80 percent. This reduction in internal phosphorus release would reduce the total annual
loadings to North Cornelia by 40 to 53 lbs and to South Cornelia by 2 to 27 lbs depending on the
climatic conditions (see Table 8-9 ). This reduction in summer phosphorus loading results in an
improvement in the summer average in-lake total phosphorus concentrations. Associated with the
total phosphorus reductions would be a decline in the chlorophyll a levels and improvement in the
water clarity (Figures 8-2 through 8-4).
The cost of alum treatment depends on the surface area of the lake to be treated and the amount of
releasable phosphorus in the lake sediments. Based on the sediment core analysis for North Cornelia,
the required dose of alum (and the required buffer) could be estimated. For North Cornelia, the
estimated cost of a whole-lake alum treatment is $90,000. The alum treatment may need to be
repeated in the future to maintain the predicted water quality. In addition, the presence of
benthivorous fish, such as carp and bullhead, may reduce the effectiveness and longevity of an
in-lake alum treatment because of their tendency to stir up the lake bottom. The MDNR 2005 fishery
indicates that there are significant numbers of benthivorous fish present in Lake Cornelia.
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124
Table 8-9 Lake Cornelia Total Phosphorus Loading Reduction for Future Development with
In-Lake Alum Treatment in North Cornelia
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual Total
Phosphorus Load for
Future Conditions + In-
Lake Alum Treatment in
North Cornelia
Scenario 10
Change in
Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 287 44 13
Wet (2001-02) 432 392 40 9
Dry (2007-2008) 290 237 53 18
South Cornelia
Average (2003-04) 260 243 17 7
Wet (2001-02) 368 341 27 7
Dry (2007-2008) 240 238 2 1
8.3 Combination of BMP Scenarios
One combination of the individual BMPs was developed and analyzed as part of this UAA to achieve
increased phosphorus removal. The elements making up the BMP combination and their associated
costs are summarized below.
• BMP Scenario 11 = A combination of Scenario 7 + Scenario 8 + Scenario 10
Based on the water quality analysis of the BMP Scenario 11, this combination will provide the most
significant water quality improvement to North and South Cornelia of all the scenarios evaluated. As
shown in Table 8-10, for North Cornelia approximately 138 to 156 lbs of phosphorus and for South
Cornelia approximately 28 to 54 lbs of phosphorus would be removed annually, depending, on the
climatic condition. This reduced phosphorus load translates to a 31 to 95 µg/L reduction for North
Cornelia and a 26 to 70 µg/L reduction for South Cornelia in summer average total phosphorus
concentration in Lake Cornelia (see Table 8-2). The estimated capital cost for this BMP combination
is $2,020,000 (not including annual operation and maintenance costs for the alum treatment plant).
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125
Table 8-10 Lake Cornelia Total Phosphorus Loading Reduction for BMP Scenario 11
Climatic Condition
Modeled Annual
Total Phosphorus
Load for Future
Conditions
Scenario 6
Modeled Annual Total
Phosphorus Load for
Future Conditions +
Combined BMPs
Scenario 11
Change in
Load
(lbs)
Percent
Decrease
(%)
North Cornelia
Average (2003-04) 330 181 149 45
Wet (2001-02) 432 276 156 36
Dry (2007-2008) 290 153 138 48
South Cornelia
Average (2003-04) 260 213 47 18
Wet (2001-02) 368 314 54 15
Dry (2007-2008) 240 212 28 12
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126
9.0 Discussion and Recommendations
9.1 Attainment of Stated Goals
The NMCWD Plan (Barr, 2007) currently lists the water quality conditions (and corresponding TSI
indices) for both the North and South basins of Lake Cornelia, and has established the water quality
goals for both basins as a Level III, with desired uses as fishing and aesthetic viewing. Table 9-1
lists the water quality, recreational-use, and ecological classifications for Lake Cornelia, along with
the MPCA shallow lake criteria. The table also lists total phosphorus (TP) and chlorophyll a
concentrations, Secchi disc (SD) transparencies, and Carlson’s Trophic State Index (TSI) based on
Secchi disc depth. The NMCWD’s management strategy typically is to “protect” the resource.
According to the Plan, “protect” means “to avoid significant degradation from point and nonpoint
sources and wetland alterations to maintain existing beneficial uses, aquatic and wetland habitats,
and the level of water quality necessary to protect these uses in receiving waters.” A discussion of
the goals follows.
In addition to the goals established by the NMCWD, the MPCA has developed assessment
methodologies, conducted extensive sampling of lakes, and ultimately derived ecoregion-based lake
eutrophication standards for deep and shallow lakes for total phosphorus, chlorophyll-a, and Secchi
depths (MPCA, 2008). These standards are outlined in Minnesota Rules, Chapter 7050 (Standards
for the Protection of Waters of the State) and are summarized in Table 9-1.
9.1.1 Water Quantity Goal
The water quantity goal for Lake Cornelia is to provide sufficient water storage during a regional
flood. Currently the lake provides sufficient storage so the water quantity goal is attainable with no
additional action.
9.1.2 Water Quality Goal
The NMCWD Water Management Plan (Barr, 2007) lists water quality goals for both the North and
South basins of Lake Cornelia. Current water quality levels place Lake Cornelia at a Level IV
classification, which indicates the lake is generally intended for runoff management and has limited
recreational use value. The specific NMCWD goal for this lake classification is to achieve and
maintain a TSISD greater than 70. However, the Minnesota Department of Natural Resources
(MDNR) stocks the lake annually with approximately 350 bluegill for the Fishing in the
Neighborhood Program. To account for this level of recreational use, the NMCWD has assigned a
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127
Level III classification which fully supports recreational activities that include fishing and aesthetic
viewing appears to be a reasonable goal. The specific NMCWD goal for Level III classification is to
achieve and maintain a TSISD between 60 and 70. Table 9-2 summarizes the overall NMCWD water
quality goal criteria.
For shallow lakes in the North Central Hardwood Forests (NCHF) ecoregion, the total phosphorus
standard established by the MPCA is 60 μg/L. The MPCA’s chlorophyll-a standard is less than 20
µg/L and the Secchi disc transparency standard is greater than 1.0 meters.
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P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
129
Table 9-2 NMCWD Water Quality Management Goals
Water Quality Management
Category Desired TSI
Desired TP
(µg/L)
Desired Chl a
(µg/L)
Desired
Transparency
(m)
Level I
Level I water bodies will support aquatic
life and recreation including full-body
contact aquatic activities (swimming,
snorkeling, etc.)
<50 <45 <20 >2.0
Level II
Level II water bodies will support aquatic
life and recreation except those
activities that require full-body contact
with the water. Activities may include
sailboating, water skiing, canoeing, jet-
skiing, wind-surfing, etc.
50-60 45-75 20-40 2.0-1.0
Level III
Level III water bodies will support
waterfowl or other wildlife, and may be
used for non-contact recreational use
(boating, fishing, etc.)
60-70 75-105 40-60 1.0-0.6
Level IV
Level IV water bodies are generally
suitable for aesthetic enjoyment and
may be used for runoff management
(i.e., stormwater detention).
>70 >105 >60 <0.5
Modeling results suggest a Level III water quality goal can be achieved for all climatic in North
Cornelia through BMP Scenario 11 but cannot be achieved with any BMP scenarios for South
Cornelia. Additionally, for all BMP scenarios and climatic conditions evaluated, neither North
Cornelia nor South Cornelia would be expected to meet the current MPCA shallow lake standard for
TP, Chla, or Secchi depth.
Figures 9-1a and 9-1b compare costs and water quality benefits (TSISD) of the various BMPs
analyzed under varying climatic conditions. Also shown on the figures are the NMCWD water
quality standards as well as the TSISD that corresponds to the MPCA shallow lake criterion for Secchi
depth.
9.1.3 Aquatic Communities Goal
In 1992, the MDNR categorized many Minnesota lakes according to the type of fishery each lake
might reasonably be expected to support (An Ecological Classification of Minnesota Lakes with
Associated Fish Communities; Schupp, 1992). The MDNR’s ecological classification system takes
P:\Mpls\23 MN\27\2327634\WorkFiles\Lake Cornelia\Report_2009Update\Text\UAA_LakeCornelia_January2010.docx
130
into account factors such as the lake area, percentage of the lake surface area that is littoral,
maximum depth, degree of shoreline development, Secchi disc transparency, and total alkalinity.
Since the MDNR did not specify the ecological classification for Lake Cornelia there is no specific
fisheries related TSI goal. However, the lake is stocked with fish and it is the goal of the NMCWD
to achieve water quality that will result in a diverse and balanced native ecosystem. This includes a
diverse growth of native aquatic macrophytes.
9.1.4 Recreational-Use Goal
Lake Cornelia is a wildlife lake, indicating the lake is generally intended for wildlife habitat,
aesthetic viewing, and runoff management (i.e., stormwater detention, providing sufficient
pretreatment of runoff to remove coarse suspended particles). T herefore, the recreational use goal
for Lake Cornelia is to achieve water quality that supports these functions as well as to maintain a
balanced eco system. In accordance with the NMCWD’s non degradation policy, the lake shall be
protected from significant degradation from point and nonpoint sources and shall maintain existing
water uses, aquatic habits, and the necessary water quality to protect these uses. The implementation
of possible BMPs (Scenarios 8, 9, 10, 11) all achieve the goal of nondegradation and enhance the
lake’s recreational uses.
9.1.5 Wildlife Goal
The wildlife goal for Lake Cornelia is to protect existing, beneficial wildlife uses. The wildlife goal
can be achieved with no action, especially if the wetlands and natural areas surrounding the lake
remain intact. However, the invasion of non-native macrophyte species, purple loosestrife and
Curlyleaf pondweed, may pose a threat to the wildlife’s use of Lake Cornelia, especially if these
invasive species begin replacing native species. Therefore, macrophyte surveys should continue on
Lake Cornelia to monitor the growth of the exotic species. A general macrophyte survey costs
approximately $3,000 per lake.
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9.2 Recommendations
In -lake improvement scenarios and site-specific structural BMPs were evaluated for feasibility and
cost-effectiveness. It is important that all BMPs currently required by the NMCWD continue to be
implemented in addition to those recommended below. The following BMP recommendations were
developed in the course of this study. While the implementation of structural and in-lake BMPs are
usually given priority, it is important to note that source control through the implementation of
nonstructural BMPs is crucial to protecting the lakes’ water quality.
9.2.1 Aquatic Weed Management
Macrophyte surveys should continue on this lake to monitor the development and growth of
undesirable non-native species. A decline in native aquatic plant species reduces available habitat
for wildlife, invertebrates, and other food organisms for small fish. Species of special concern in
Lake Cornelia are purple loosestrife (Lythrum salicaria) and Curlyleaf pondweed (Pomatogeton
crispus).
Curlyleaf pondweed was not observed in Lake Cornelia during the 2004 macrophyte survey;
however, it small areas were present in both North and South Cornelia in 2008. The appearance of
the small patches of the nonnative Curlyleaf pondweed should continue to be monitored in both
North and South Cornelia. Once a lake becomes infested with Curlyleaf pondweed, the plant
typically replaces native vegetation, increasing its coverage and density. Curlyleaf pondweed begins
growing in late-August and grows throughout the winter at a slow rate, grows rapidly in the spring,
and dies early in the summer (Madsen et al. 2002). Native plants that grow from seed in the spring
are unable to grow in the areas already occupied by the Curlyleaf pondweed, and are displaced by
this plant. Curlyleaf pondweed dies off in early to mid summer, releasing phosphorus into the water
column, and often resulting in increased algal growth for the remainder of the summer.
Macrophyte surveys should be conducted regularly to evaluate the change and distribution of these
notnative species. A general macrophyte survey costs approximately $3,000 per lake.
Both the 2004 and 2008 macrophyte surveys also indicated that the dominant emergent vegetation in
the North Cornelia is the cattail (Typha sp.) which is found in low densities along the entire
shoreline. Cattail is also found in patches along the shoreline of South Cornelia. In some locations,
recreational access to Lake Cornelia is affected by the presence of the cattails along the shoreline. In
order to harvest any emergent vegetation (including cattails) to create a recreational access to Lake
Cornelia, an aquatic plant management control permit from the MDNR is required. Currently, the
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MDNR only permits the removal of these plants only in a small area to provide boat access to deeper
lake water. It is important to note that the MDNR does not grant aquatic plant management control
permits automatically, and site inspections are required for first time permits. For more information
related to aquatic plant management, see the following website:
http://www.dnr.state.mn.us/shorelandmgmt/apg/permits.html
9.2.2 In-Lake Management
Water quality simulations using the P8 model and an in-lake model indicated that the internal release
of phosphorus accounts for approximately 10 to 19 percent of existing phosphorus loading to North
Cornelia and roughly 5 to 11 percent of phosphorus loading to South Cornelia during the various
climatic conditions. The sources of these internal phosphorus loads are likely attributed to two key
sources: the release of phosphorus from anoxic sediments and the resuspension of the bottom
sediments (and associated phosphorus) into the water column by the activities of benrhivorous fish
and other mixing events (e.g., wind) in the lake.
9.2.2.1 Internal Sediment Release
The 2008 sediment core analysis indicated that phosphorus release from anoxic sediment in Lake
Corneria is possible, given the right conditions. In-lake application of alum (aluminum sulfate) to
prevent sediment phosphorus release in the lake during the summer and fall months was scenario
analyzed. This BMP Scenario (Scenario 10) assumed alum application only to North Cornelia and
the alum dosing was based on the results of the sediment core analysis. The estimated to cost for
alum treatment of North Cornelia is $90,000 (which includes the cost of the alum as well as the
buffer, sodium aluminate). Scenario 10 (North Cornelia in-lake alum treatment) is the most cost
effective alternative and does improve the water quality in both North and South Cornelia. However,
even with this improvement both lakes still remain in NMCWD’s Level IV and above the MPCA’s
shallow lake criteria.
Because benthivorous fish (e.g. carp) populations are abundant in Lake Cornelia, the alum treatment
of North Cornelia should follow any fisheries management activities as the longevity of an alum
treatment may be reduced as the result of the resuspension of sediments by these fish species.
9.2.2.2 Management of Benthivorous Fish Populations
Carp, along with other benthivorous (bottom-feeding) fish, can have a direct influence on the
phosphorus concentration in a lake or water body (LaMarra, 1975). They can also cause
resuspension of sediments in shallow ponds and lakes, causing reduced water clarity and poor aquatic
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plant growth, as well as high phosphorus concentrations (Cooke et al., 1993). Because of the
abundance of carp in Lake Cornelia, along with other rough fish species, their feeding and spawning
activities may have a significant impact on the water quality in the lake. Additionally, information
from the MDNR indicates that winter fish kills are very likely in Lake Cornelia.
Lake Cornelia is part of the Fishing in the Neighborhood Program and has been stocked by the
MDNR with bluegill from 2000 through 2009. The 2005 MDNR fisheries survey indicates that
bluegills and black crappies were the primary species sampled in Lake Cornelia. Common carp were
also abundant in Lake Cornelia. Other species present included black bullheads, yellow perch, green
sunfish, hybrid sunfish, pumpkinseeds, and gold fish. The MDNR will complete a new fishery
survey in 2010.
To better understand the carp activity in the system and the potential contribution of carp to the
phosphorus loads to Lake Cornelia, a study is recommended to better understand the fishery,
focusing mainly on carp and other benthivorous fish. This includes understanding where the carp in
Lake Cornelia spawn, and if there are carp located in any of the water bodies located upstream of
North Cornelia. Potential items to be considered when evaluating the impact of carp on water
quality should include:
• Quantifying carp population in North and South Cornelia as well as upstream water bodies
• Tracking carp movement between the water bodies in the system, throughout the course of a
year (Dr. Peter Sorenson from the University of Minnesota has done similar tracking of carp
in several west metro area lakes)
• Identification of the key carp spawning locations within the system
• Understanding of how other fish populations may use the Lake Cornelia (spawning, feeding,
etc.)
Potential partnerships with the University of Minnesota and the MDNR may be possible as there is
significant interest in carp management in Lake Cornelia, and there is currently research being
conducted to better understand this invasive fish.
If the review of the fishery indicates that carp management may be an option, a typical management
strategy would include the combination of the following key steps: elimination of reinfestation,
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suppressment of recruitment, and removal of adult carp (Sorenson, 2009). Removal and management
of carp would require permitting and guidance from the MDNR.
Supressment of recruitment involves preventing the eggs from hatching or preventing the young from
surviving. This can be achieved by preventing adult carp from spawning in nursery areas along with
removal of adult carp. A single female carp can lay up to 2 million eggs during spawning (Sorensen,
2009). Elimination of reinfestation means “blocking” the movement of carp between waterbodies.
Both the suppressment of recruitment and the elimination of reinfestation can be achieved through
the use of fish barriers. Physical barriers and electric barriers have been used to control the
movement of carp between water bodies. More recently, sonic barriers (using bubble curtains) are
being studied and implemented to control carp movement.
Many electric fish barriers have been installed to control the movement of carp between water
bodies. Although these barriers can be fully effective at preventing the movement of carp, their
success is linked to the maintenance of the electrical current. As a result, automatic back-up
generators are required to maintain the electric field during power outages. Also, a dropping fine
screen is recommended should there be complete power failure. Electric barriers require a budget for
monthly operation and maintenance costs, as they need to be constantly supplied with electricity.
Current cost estimates for installations of electric fish barriers on two lakes in southern Minnesota
ranged from $250,000 to $300,000. This cost includes equipment and installation but does not
include the estimated monthly operation and maintenance costs.
The final step in carp management includes the harvesting of adult carp in the lakes. Carp harvesting
has been performed on many lakes in the Twin Cities metropolitan area. It is important to note that
carp harvesting, and its potential impact on the long term management of carp populations, may not
always be an option for a lake (Sorensen, 2009). A study of the carp within the Lake Owasso system
should provide a better understanding of the carp population as well as the potential to manage this
species.
9.2.3 Watershed Management
Several watershed management BMPs were considered for this UAA. However, model simulations
indicated that even with the implementation of several combined BMPs (Scenario 11), it may not be
possible to meet the Level III Classification goal based on TSI or the MPCA shallow lake standards
in neither North nor South Cornelia. While it was predicted that water quality will improve with the
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implementation of the various BMPs, model simulations indicate the water quality will typically
remain in the Level IV classification.
9.2.4 Public Participation
Finally, it should be mentioned that it is a general NMCWD goal to encourage public participation in
all NMCWD activities and decisions that may affect the public. In accordance with this goal, the
NMCWD seeks to involve the public in the discussion of this UAA. This goal is expected to be
achieved through a public meeting to obtain comments on the Lake Cornelia UAA.
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Bannerman, R., K. Baun, M. Bohn, P. Hughes, and D. Graczyk. 1983. Evaluation of Urban
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Barr Engineering Co. 1992. Minneapolis Chain of Lake Monitoring Study. Prepared for the
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Barr Engineering Co. 1996. Nine Mile Creek Watershed District Water Management Plan.
Prepared for Nine Mile Creek Watershed District
Barr Engineering Co. 1999a. City of Minnetonka Water Resources Management Plan. Prepared for
the City of Minnetonka.
Barr Engineering Co. 1999b. Round Lake Use Attainability Analysis. Prepared for Nine Mile Creek
Watershed District.
Barr Engineering Co. 2001. Big Lake Protection Grant LPT-67: Big Lake Macrophyte Management
Plan Implementation, Volume 1: Report,
Barr Engineering Co. 2003. Bryant Lake Use Attainability Analysis. Prepared for Nine Mile Creek
Watershed District.
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Barr Engineering Co. 2003. Southeast, Southwest, and Northwest Anderson Lake Use Attainability
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Barr Engineering Co. 2007. Nine Mile Creek Watershed District Water Management Plan.
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Barten, J. 1995. Quantity and Quality of Runoff from Four Golf Course in the Twin Cities
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chlorophyll-a, and Secchi depths in natural and artificial lakes. Can. J. Fish. Aquat. Sci. 38:
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Carlson, R. 1977. “A Trophic Status Index for Lakes.” Limnology Oceanography 22(2): 361-9.
Catling, P.M. and I. Dobson. 1985. “The Biology of Canadian Weeds. 69. Potamogeton crispus L.”
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Chapra, S.C., and S.J. Tarapchak, 1976. “A Chlorophyll a Model and its Relationship to Phosphorus
loading plots for Lakes.” Water Res. Res. 12(6): 1260-1264.
Cooke, G.D., E.B. Welch, S.A. Peterson, and P.R. Newroth. 1993. Restoration and Management of
Lakes and Reservoirs, Second Edition. Lewis Publishers, Boca Raton, FL. 548 pp.
Dillon, P.J. and F.H. Rigler. 1974. “A test of a simple nutrient budget model predicting the
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Erickson, A.J., J.S. Gulliver and P.T. Weiss. 2006. “Enhanced sand filtration for stormwater
phosphorus removal. Journal of Environmental Engineering, Vol 133 (5), pp 485-497
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Applications for Trend Assessment, Model Verification, and Development of Nutrient Criteria for
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and sediment in the Minneapolis Chain of Lakes, Minnesota, USA. Lake and Reserv.
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I.E.P., Inc. 1990. P8 Urban Catchment Model. Version 2.4. Prepared for the Narragansett Bay
Project. Providence, Rhode Island.
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Growth of Curly-leaf Pondweed, Potamogeton crispus.” Verh. Internat. Verein Limnol.
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440/5-88-002
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Vollenweider, R. A. 1976. Advances in Defining Critical Loading Levels for Phosphorus in Lake
Eutrophication. Mem. 1st. Ital. Idrobiol. 33:53-83.
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Management: Volume III. North American Lake Management Society.
Welch, E.B. and G.D. Cooke. 1999. “Effectiveness and Longevity of Phosphorus Inactivation with
Alum.” Journal of Lake and Reservoir Management. 15(1):5-27
Wilson, C.B. and W.W. Walker, The Minnesota Lake Eutrophication Analysis Procedure
(MNLEAP), MPCA, 1988.
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Appendices
Appendix A
Data Collection Methods
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Methods
The Lake Cornelia UAA included the collection and analysis of data from the lake and its watershed.
The methods discussion includes:
• Lake water quality data collection
• Ecosystem data collection
A.1 Lake Water Quality Data Collection
In 2004, a representative Lake Cornelia sampling station was selected (i.e., located at the deepest
location in the lake basin). Samples were collected monthly between the end of April and beginning
of September. During August samples were collected biweekly. Samples were also collected in
2008 from the end of April to the end of September. Table A-1 lists the water quality parameters that
were sampled and specifies at what depths samples or measurements were collected. Dissolved
oxygen, temperature, specific conductance, turbidity and Secchi disc were measured in the field,
whereas water samples were analyzed in the laboratory for total phosphorus, soluble reactive
phosphorus, total Kjeldahl nitrogen, nitrate + nitrite nitrogen, chlorophyll a, and pH. Additionally, a
single alkalinity sample was collected in 2008. The procedures for chemical analyses of the water
samples are shown in Table A-2. Generally, the methods can be found in Standard Methods for
Water and Wastewater Analysis.
A.2 Ecosystem Data Collection
Ecosystem describes the community of living things within Lake Cornelia and their interaction with
the environment in which they live and with each other. During June through September 2004, and
again in June through September 2008, ecosystem data collection included:
• Phytoplankton – A composite 0-2 meter sample was collected during each water quality
sampling event described in the previous section.
• Zooplankton – A zooplankton sample was collected (i.e., bottom to surface) during each
water quality sampling event described in the previous section.
• Macrophytes – Macrophyte surveys were collected during June and August 2004.
Macrophyte surveys were not conducted in 2008.
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Table A-1a. Lake Cornelia Water Quality Parameters (2004)
Parameters
Depth
(Meters)
Sampled or Measured
During Each Sample
Event
Dissolved Oxygen Surface to bottom profile X
Temperature Surface to bottom profile X
Specific Conductance Surface to bottom profile X
Secchi Disc — X
Total Phosphorus 0-2 Meter Composite Sample X
Orthophosphate 0-2 Meter Composite Sample X
Total Kjeldahl Nitrogen (TKN) 0-2 Meter Composite Sample X
Nitrate + Nitrite Nitrogen 0-2 Meter Composite Sample X
pH 0-2 Meter Composite Sample X
Turbidity 0-2 Meter Composite Sample X
Chlorophyll a 0-2 Meter Composite Sample X
Table A-1b. Lake Cornelia Water Quality Parameters (2008)
Parameters
Depth
(Meters)
Sampled or Measured
During Each Sample
Event
Dissolved Oxygen Surface to bottom profile X
Temperature Surface to bottom profile X
Specific Conductance Surface to bottom profile X
Secchi Disc — X
Total Phosphorus 0-2 Meter Composite Sample X
Total Dissolved Phosphorus 0-2 Meter Composite Sample X
Orthophosphate 0-2 Meter Composite Sample X
pH 0-2 Meter Composite Sample X
Turbidity 0-2 Meter Composite Sample X
Chlorophyll a 0-2 Meter Composite Sample X
Alkalinity 0-2 Meter Composite Sample Measured on 7/7/08 only
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Table A-2. Procedures for Chemical Analyses Performed on Water Samples
Analysis Procedure Reference
Total Phosphorus Persulfate digestion, manual
ascorbic acid
Standard Methods, 18th Edition (1992)
modified per Eisenreich, et al., Environmental
Letters 9(1), 43-53 (1975)
Soluble Reactive
Phosphorus
Manual ascorbic acid Standard Methods, 18th Edition modified per
Eisenreich, et al., Environmental Letters 9(1),
43-53 (1975)
Total Dissolved Phosphours
Total Nitrogen Persulfate digestion,
scanning
spectrophotometric
Bachman, Roger W. and Daniel E. Canfield,
Jr., 1991. A Comparability Study of a New
Method for Measuring Total Nitrogen in
Florida Waters. Report submitted to the
Florida Department of Environmental
Regulation.
Total Kjeldahl Nitrogen
Nitrate + Nitrite Nitrogen
Chlorophyll a Spectrophotometric Standard Methods, 18th Edition, 1992,
10200 H
pH Potentiometric
measurement, glass
electrode
Standard Methods, 16th Edition, 1985, 423
Specific Conductance Wheatstone bridge Standard Methods, 16th Edition, 1985, 205
Temperature Thermometric Standard Methods, 16th Edition, 1985, 212
Dissolved Oxygen Electrode Standard Methods, 16th Edition, 1985, 421F
Turbidity
Alkalinity
Phytoplankton Identification
and Enumeration
Inverted Microscope Standard Methods, 16th Edition, 1985, 1002F
(2-d), 1002H (2)
Zooplankton Identification
and Enumeration
Sedgewick Rafter Standard Methods, 16th Edition, 1985, 1002F
(2-d), 1002H
Transparency Secchi disc
Phytoplankton and zooplankton samples were identified and enumerated to provide information on
species diversity and abundance. The macrophyte community was surveyed to determine species
location, composition, and abundance.
Appendix B
P8 Model Parameter Selection
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P8 Model Parameter Selection
Because no inflow water quantity or quality data was collected for this UAA, P8 modeling
parameters could not be calibrated to any great extent. However, from the data that were collected for
the Lake Cornelia UAA, model calibration afforded the opportunity to select P8 parameters that
resulted in a good fit between modeled and observed data. The parameters selected for the Lake
Cornelia P8 model are discussed in the following paragraphs. P8 parameters not discussed in the
following paragraphs were left at the default setting. P8 version 2.4 was used for the modeling.
Time Step, Snowmelt, & Runoff Parameters (Case-Edit-Other)
• Time Steps Per Hour (Integer)— 5. Selection was based upon the number of time steps required
to eliminate continuity errors greater than two percent.
• Minimum Inter-Event Time (Hours)— 10. The selection of this parameter was based upon an
evaluation of storm hydrographs to determine which storms should be combined and which
storms should be separated to accurately depict runoff from the lake’s watershed. It should be
noted that the average minimum inter-event time for the Minneapolis area is 6. In a more typical
climatic year a value of 6 would be used.
• Snowmelt Factors—Melt Coef (Inches/Day-Deg-F)—0.03. The P8 model predicts snowmelt
runoff beginning and ending earlier than observed snowmelt. The lowest coefficient of the
recommended range was selected to minimize the disparity between observed and predicted
snowmelt (i.e., the coefficient minimizes the number of inches of snow melted per day and
maximizes the number of snowmelt runoff days).
• Snowmelt Factors— Scale Factor For Max Abstraction—1. This factor controls the quantity of
snowmelt runoff (i.e., controls losses due to infiltration). Selection was based upon the factor that
resulted in the closest fit between modeled and observed runoff volumes.
• Growing Season AMC—II = .05 and AMC—III = 100. Selection of this factor was based upon
the observation that the model accurately predicted runoff water volumes from monitored
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watersheds when the Antecedent Moisture Condition II was selected (i.e., curve numbers selected
by the model are based upon antecedent moisture conditions).
Particle Scale Factor (Case-Edit-Components)
• Scale Fac.—TP—1.0. The particle scale factor determines the total phosphorus load generated
by the particles predicted by the model in watershed runoff. The factor for total phosphorus was
selected as 1.0. Further discussion in Section 6.2.2.
Particle File Selection (Case—Read—Particles)
• NURP50.PAR. The NURP 50 particle file was found to most accurately predict phosphorus
loading to Lake Cornelia.
Precipitation File Selection (Case—Edit—First—Prec. Data File)
• Mtb4908.pcp. The precipitation file Mtb4908.pcp was used for all the P8 simulations. The file is
comprised of hourly precipitation measured at the NMCWD Metro Blvd. station (when available)
and augmented with data from the Minneapolis–St. Paul International Airport for all other time
periods. Individual events were adjust based on comparison with the daily precipitation recorded
as part of the High Density Network.
Air Temperature File Selection (Case—Edit—First—Air Temp. File)
• MSP4908.tmp. The MSP4908.tmp file was used for all simulations. The temperature file was
comprised of temperature data from the Minneapolis–St. Paul International Airport during the
period from 1949 through 2008.
Devices Parameter Selection (Case—Edit—Devices—Data—Select Device)
• Detention Pond— Permanent Pool— Area and Volume— The surface area and dead storage
volume of each detention pond was determined and entered here.
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• Detention Pond— Flood Pool— Area and Volume— The surface area and storage volume under
flood conditions (i.e., the storage volume between the normal level and flood elevation) was
determined and entered here.
• Detention Pond— Infiltration Rate (in/hr)— Only infiltration from landlocked (i.e., no piped outlet)
was included in the model. This was done to provide a better water balance model. An infiltration
rates of 0.015 in/hr was used, based on soil type.
• Detention Pond— Orifice Diameter and Weir Length— The orifice diameter or weir length was
determined from field surveys or development plans of the area for each detention pond and
entered here.
• Detention Pond or Generalized Device— Particle Removal Scale Factor— Particle Removal
Scale Factor— 0.3 for ponds less than two feet deep and 1.0 for all ponds three feet deep or
greater. For ponds with normal water depths between two and three feet, a particle removal factor
of 0.6 was selected. The particle removal factor for watershed devised determines the particle
removal by device. The factors were selected based on similar work in the Round Lake Use
Attainability Analysis, Barr Engineering, March 1999.
• Detention Pond or Generalized Device— Outflow Device Nos.— The number of the downstream
device receiving water from the detention pond outflow was entered.
• Generalized Device— Infiltration Outflow Rates (cfs)— Although the infiltration rates listed
under the detention pond category are the same, the outflow rates at each pond depth were
calculated in cfs and entered.
• Pipe/Manhole— Time of Concentration— The time of concentration for each pipe/manhole
device was determined and entered here. A “dummy” pipe/manhole was installed in the network
to represent Lake Cornelia. This forced the model to total all loads (i.e., water, nutrients, etc.)
entering the lake. Failure to enter the “dummy” pipe requires the modeler to manually tabulate
the loads entering the lake.
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Watersheds Parameter Selection (Case—Edit—Watersheds—Data—Select Watershed)
• Outflow Device Number— The Device Number of the device receiving runoff from the
watersheds was selected to match the watershed number. For example, subwatershed NC-2 flows
into device 9 (labeled NC_2).
• Pervious Curve Number— A weighted SCS Curve number was used, as outlined in the following
procedure. The Hennepin County Soils Survey was consulted to determine the soil types within
each subwatershed and a pervious curve number was selected for each subwatershed based upon
soil types, land use, and hydrologic conditions (e.g., if watershed soils are type B and pervious
areas are comprised of grassed areas with >75% cover, then a Curve Number of 61 would be
selected). A pervious curve number of 61 was selected for all subwatersheds. The pervious curve
number was then weighted with indirect (i.e., disconnected) impervious areas in each
subwatershed as follows:
The assumptions for direct, indirect, and total impervious were based upon measurements from the
Lake Cornelia watershed and areas with similar land use.
The following assumptions shown in Table B-1, for direct impervious and total impervious, were
used to determine the weighted curve numbers.
Area Total
Number)] Curve (Pervious* Area) [(Pervious +(98)] * Area] Impervious [(Indirect = WCN
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Table B-1 Direct, Indirect and Total Impervious Fractions Based on Land Use
Land Use Direct
Impervious
Indirect
Impervious
Total
Impervious
Natural/Park/Open 0.00 0.02 0.02
High Density Residential (>8 units/ac) 0.40 0.30 0.70
Institutional- High Impervious 0.50 0.20 0.70
Highway 0.50 0.00 0.50
Commercial 0.80 0.10 0.90
Industrial/Office 0.80 0.10 0.90
Open Water 1.00* 0.00 1.00
Wetland 1.00* 0.00 0.00
Developed Park 0.00 0.02 0.02
* Using 100% impervious may skew model results. Therefore open water and wetland areas were not accounted for while
determining the pervious curve number.
• Swept/Not Swept—An “Unswept” assumption was made for the entire impervious watershed
area. A Sweeping Frequency of 0 was selected. Selected parameters were placed in the
“Unswept” column since a sweeping frequency of 0 was selected.
• Impervious Fraction—The direct or connected impervious fraction for each subwatershed was
determined and entered here. The direct or connected impervious fraction includes driveways and
parking areas that are directly connected to the storm sewer system. The previous table indicates
was used to determine the direct impervious fractions for each land use type. Then, the average
direct impervious fraction was determined by weighting the acres of each land use with the direct
impervious fraction to obtain a weighted average.
• Depression Storage— 0.03
• Impervious Runoff Coefficient— 0.94
Passes Through the Storm File (Case—Edit—First—Passes Through Storm File)
• Passes Through Storm File—5. The number of passes through the storm file was determined after
the model had been set up and a preliminary run completed. The selection of the number of
passes through the storm file was based upon the number required to achieve model stability.
Multiple passes through the storm file were required because the model assumes that dead
storage waters contain no phosphorus. Consequently, the first pass through the storm file results
in lower phosphorus loading than occurs with subsequent passes. Stability occurs when
subsequent passes do not result in a change in phosphorus concentration in the pond waters. To
determine the number of passes to select, the model was run with three passes, five passes, and
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ten passes. A comparison of phosphorus predictions for all devices was evaluated to determine
whether changes occurred between the three scenarios. If there is no difference between three and
five passes, three passes are sufficient to achieve model stability. If differences are noted
between three and five passes and no differences are noted between five and ten passes, then five
passes are sufficient to achieve model stability. Several differences were noted between three and
five passes and no differences were noted between five and ten passes. Therefore, it was
determined that five passes through the storm file resulted in model stability for the Lake
Cornelia project.
Appendix C
Pond Data
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n
d
i
x
C
La
k
e
C
o
r
n
e
l
i
a
E
x
i
s
t
i
n
g
P
o
n
d
I
n
f
o
r
m
a
t
i
o
n
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
R
e
p
o
r
t
_
2
0
0
9
U
p
d
a
t
e
\
A
p
p
e
n
d
i
c
e
s
\
a
p
p
e
n
d
i
c
e
s
2
.
x
l
s
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
R
e
p
o
r
t
_
2
0
0
9
U
p
d
a
t
e
\
A
p
p
e
n
d
i
c
e
s
\
a
p
p
e
n
d
i
c
e
s
2
.
x
l
s
C-1
Appendix D
Southdale Center Water Inflow
D-1
D-2
D-3
D-4
Appendix E
Lake Cornelia 2004 & 2008 Water Quality Data
Da
t
e
Ma
x
De
p
t
h
(
m
)
Sa
m
p
l
e
De
p
t
h
(
m
)
Se
c
c
h
i
De
p
t
h
(
m
)
Ch
l
.
a
(u
g
/
L
)
Tu
r
b
i
d
i
t
y
(N
T
U
'
s
)
D.
O
.
(m
g
/
L
)
Te
m
p
(°
C
)
Sp
.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
P
(m
g
/
L
)
Or
t
h
o
P
(m
g
/
L
)
To
t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)
4/
2
1
/
0
4
1
.
5
0
-
1
0
.
5
6
7
.
0
1
1
.
6
-
-
-
-
-
-
0
.
0
7
8
<
0
.
0
0
6
1
.
8
<
0
.
0
2
0
8
.
5
0.
0
9.
0
1
3
.
2
1
6
4
2
-
-
--
1.
0
8.
8
1
3
.
2
1
6
5
5
-
-
--
6/
1
0
/
0
4
1
.
8
0
-
1
.
5
0
.
6
2
4
.
0
1
1
.
0
-
-
-
-
-
-
0
.
1
2
0
0
.
0
3
3
1
.
4
0
.
0
3
3
7
.
4
0.
0
4.
0
2
1
.
0
4
8
6
-
-
--
1.
0
3.
8
2
1
.
0
4
8
6
-
-
--
1.
5
3.
7
2
1
.
0
4
8
6
-
-
--
7/
7
/
0
4
1
.
8
0
-
1
.
5
0
.
6
1
1
.
0
9
.
6
-
-
-
-
-
-
0
.
2
0
0
0
.
0
4
6
1
.
2
<
0
.
0
2
0
7
.
3
0.
0
1.
3
2
1
.
1
5
0
7
-
-
--
1.
0
1.
2
2
1
.
2
5
0
7
-
-
--
8/
1
1
/
0
4
1
.
8
0
-
1
.
5
0
.
2
2
0
0
.
0
2
9
.
3
-
-
-
-
-
-
0
.
2
0
0
<
0
.
0
0
6
2
.
3
<
0
.
0
2
0
7
.
5
0.
0
6.
1
1
8
.
3
4
4
0
-
-
--
1.
0
6.
1
1
8
.
3
4
4
0
-
-
--
8/
2
4
/
0
4
1
.
8
0
-
1
.
5
0
.
4
6
5
.
0
1
5
.
4
-
-
-
-
-
-
0
.
1
7
0
<
0
.
0
0
6
1
.
6
<
0
.
0
2
0
7
.
8
0.
0
5.
3
2
0
.
8
4
8
2
-
-
--
1.
0
5.
2
2
0
.
8
4
8
2
-
-
--
1.
5
4.
0
2
0
.
8
4
8
0
-
-
--
9/
1
0
/
0
4
1
.
8
0
-
1
.
5
0
.
4
5
1
.
0
1
7
.
1
-
-
-
-
-
-
0
.
1
3
0
<
0
.
0
0
6
1
.
0
<
0
.
0
2
0
7
.
9
0.
0
8.
0
2
0
.
7
4
9
6
-
-
--
1.
0
7.
6
2
0
.
5
4
9
6
-
-
--
1.
5
7.
5
2
0
.
5
4
9
6
-
-
--
Co
r
n
e
l
i
a
(
N
o
r
t
h
B
a
s
i
n
)
-
2
0
0
4
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
W
a
t
e
r
Q
u
a
l
i
t
y
D
a
t
a
\
C
o
r
n
e
l
i
a
_
W
Q
_
S
u
m
m
a
r
y
.
x
l
s
E-1
L
a
k
e
C
o
r
n
e
l
i
a
(
N
o
r
t
h
B
a
s
i
n
)
-
2
0
0
8
Da
t
e
M ax
De
p
t
h
(
m
)
Sa
m
p
l
e
De
p
t
h
(
m
)
Se
c
c
h
i
De
p
t
h
(
m
)
Ch
l
.
a
(u
g
/
L
)
Tu
r
b
i
d
i
t
y
(N
T
U
'
s
)
D.
O
.
(m
g
/
L
)
Te
m
p
(°
C
)
Sp
.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
)
To
t
a
l
Di
s
s
o
l
v
e
d
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
)
Or
t
h
o
Ph
o
s
p
h
a
t
e
as
P
,
Di
s
s
o
v
l
e
d
(m
g
/
L
)
To
t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)ORP (mv)
4/
1
0
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
7
2
'
4/
2
5
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
6
0
.
1
4
'
4/
3
0
/
0
8
1
.
5
0
-
1
0
.
7
1
1
.
0
8
.
3
-
-
-
-
-
-
0
.
0
8
1
--
<
0
.
0
0
6
0
0
.
6
5
<
0
.
0
2
0
-
-
-
-
0.
0
12
.
8
1
0
.
5
1
5
3
1
--
--
--
-
-
-
-
8
.
6
2
2
1
1.
0
13
.
0
1
0
.
4
1
5
2
7
--
--
--
-
-
-
-
8
.
6
2
2
1
Wa
t
e
r
L
e
v
e
l
:
8
6
0
.
0
4
'
5/
3
0
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
2
2
'
6/
5
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
4
7
'
6/
1
6
/
0
8
1
.
8
0
-
1
.
5
0
.
3
3
3
.
0
3
4
.
0
-
-
-
-
-
-
0
.
1
6
0
0
.
0
4
1
0
.
0
0
9
5
1
.
8
0
<
0
.
0
2
0
-
-
-
-
0.
0
8.
0
2
1
.
3
8
5
8
--
--
--
-
-
-
-
8
.
5
1
3
4
1.
0
7.
5
2
1
.
2
8
5
8
--
--
--
-
-
-
-
8
.
3
1
3
6
7.
4
2
1
.
2
8
5
8
--
--
--
-
-
-
-
8
.
1
1
3
8
Wa
t
e
r
L
e
v
e
l
:
8
6
0
.
5
0
'
7/
1
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
7
5
'
7/
7
/
0
8
1
.
4
0
-
1
0
.
3
4
9
.
0
2
3
.
3
-
-
-
-
-
-
0
.
1
4
0
0
.
0
2
3
-
-
-
-
-
-
-
-
-
-
0.
0
8.
6
2
5
.
5
9
3
0
--
--
--
-
-
-
-
8
.
4
2
4
9
1.
0
7.
6
2
5
.
4
9
3
1
0
.
1
4
0
0
.
0
2
2
-
-
-
-
-
-
8
.
3
2
5
0
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
3
7
'
T
o
t
a
l
A
l
k
a
l
i
n
i
t
y
:
1
3
0
m
g
/
L
(
0
-
1
.
5
M
)
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
W
a
t
e
r
Q
u
a
l
i
t
y
D
a
t
a
\
C
o
r
n
e
l
i
a
_
W
Q
_
S
u
m
m
a
r
y
.
x
l
s
E-2
L
a
k
e
C
o
r
n
e
l
i
a
(
N
o
r
t
h
B
a
s
i
n
)
Da
t
e
M ax
De
p
t
h
(
m
)
Sa
m
p
l
e
De
p
t
h
(
m
)
Se
c
c
h
i
De
p
t
h
(
m
)
Ch
l
.
a
(u
g
/
L
)
Tu
r
b
i
d
i
t
y
(N
T
U
'
s
)
D.
O
.
(m
g
/
L
)
Te
m
p
(°
C
)
Sp
.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
)
To
t
a
l
Di
s
s
o
l
v
e
d
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
)
Or
t
h
o
Ph
o
s
p
h
a
t
e
as
P
,
Di
s
s
o
v
l
e
d
(m
g
/
L
)
To
t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)ORP (mv)
7/
2
1
/
0
8
1
.
5
0
-
1
0
.
4
2
8
.
0
2
2
.
5
-
-
-
-
-
-
0
.
1
2
0
0
.
0
1
9
-
-
-
-
-
-
-
-
-
-
0.
0
7.
0
2
5
.
4
6
4
6
--
--
--
-
-
-
-
8
.
2
2
0
2
1.
0
8.
6
2
5
.
4
6
4
5
--
--
--
-
-
-
-
8
.
1
2
0
1
Wa
t
e
r
L
e
v
e
l
:
8
6
0
.
4
0
'
7/
3
1
/
2
0
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
9
3
'
8/
4
/
0
8
1
.
5
0
-
1
0
.
3
6
4
.
0
4
.
0
-
-
-
-
-
-
0
.
2
0
0
0
.
0
2
6
-
-
-
-
-
-
-
-
-
-
0.
0
6.
2
2
4
.
1
6
6
4
--
--
--
-
-
-
-
7
.
5
1
9
0
1.
0
6.
1
2
4
.
1
6
6
4
--
--
--
-
-
-
-
7
.
6
1
9
1
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
7
5
'
8/
1
8
/
0
8
1
.
2
0
-
1
0
.
2
4
9
.
0
3
2
.
0
-
-
-
-
-
-
0
.
2
1
0
0
.
0
2
6
-
-
-
-
-
-
-
-
-
-
0.
0
7.
4
2
4
.
6
6
3
3
--
--
--
-
-
-
-
8
.
1
2
1
3
1.
0
7.
2
2
4
.
6
6
3
3
--
--
--
-
-
-
-
8
.
1
2
1
0
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
6
7
'
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
6
3
4
\
W
o
r
k
F
i
l
e
s
\
L
a
k
e
C
o
r
n
e
l
i
a
\
W
a
t
e
r
Q
u
a
l
i
t
y
D
a
t
a
\
C
o
r
n
e
l
i
a
_
W
Q
_
S
u
m
m
a
r
y
.
x
l
s
E-3
L
a
k
e
C
o
r
n
e
l
i
a
(
N
o
r
t
h
B
a
s
i
n
)
Da
t
e
M ax
De
p
t
h
(
m
)
Sa
m
p
l
e
De
p
t
h
(
m
)
Se
c
c
h
i
De
p
t
h
(
m
)
Ch
l
.
a
(u
g
/
L
)
Tu
r
b
i
d
i
t
y
(N
T
U
'
s
)
D.
O
.
(m
g
/
L
)
Te
m
p
(°
C
)
Sp
.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
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To
t
a
l
Di
s
s
o
l
v
e
d
Ph
o
s
p
h
o
r
u
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as
P
(
m
g
/
L
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Or
t
h
o
Ph
o
s
p
h
a
t
e
as
P
,
Di
s
s
o
v
l
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d
(m
g
/
L
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To
t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)ORP (mv)
8/
2
9
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
6
0
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3
5
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5
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2
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6
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2
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M
p
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2
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N
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2
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2
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2
7
6
3
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W
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S
u
m
m
a
r
y
.
x
l
s
E-4
Da
t
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Ma
x
De
p
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(
m
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Sa
m
p
l
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p
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(
m
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c
c
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(
m
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a
(u
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d
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y
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T
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s
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D.
O
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(m
g
/
L
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m
p
(°
C
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Sp
.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
P
(m
g
/
L
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Or
t
h
o
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(m
g
/
L
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t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
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Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)
4/
2
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0
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1
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5
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4
6
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(
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p
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u
m
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x
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t
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x
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p
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h
(
m
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m
p
l
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p
t
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(
m
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c
c
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p
t
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(
m
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l
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a
(u
g
/
L
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r
b
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d
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t
y
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T
U
'
s
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O
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g
/
L
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m
p
(°
C
)
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.
C
o
n
d
.
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m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
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s
s
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l
v
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d
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o
s
p
h
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r
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s
(m
g
/
L
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t
h
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o
s
p
h
a
t
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as
P
,
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s
s
o
v
l
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d
(m
g
/
L
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To
t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)ORP (mv)
4/
1
0
/
0
8
Wa
t
e
r
L
e
v
e
l
:
8
5
9
.
3
2
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4/
2
5
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0
8
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t
e
r
L
e
v
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l
:
8
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3
5
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3
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p
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2
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u
m
m
a
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x
l
s
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Da
t
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x
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p
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h
(
m
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m
p
l
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p
t
h
(
m
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c
c
h
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p
t
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(
m
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l
.
a
(u
g
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L
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r
b
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d
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y
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T
U
'
s
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O
.
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g
/
L
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m
p
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C
)
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.
C
o
n
d
.
(µ
m
h
o
/
c
m
@
2
5
°
C
)
To
t
a
l
Ph
o
s
p
h
o
r
u
s
as
P
(
m
g
/
L
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s
s
o
l
v
e
d
Ph
o
s
p
h
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r
u
s
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g
/
L
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t
h
o
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o
s
p
h
a
t
e
as
P
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s
s
o
v
l
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d
(m
g
/
L
)
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t
a
l
Kj
e
l
d
a
h
l
Ni
t
r
o
g
e
n
(m
g
/
L
)
Nitrate + Nitrite Nitrogen (mg/L)pH (S.U.)ORP (mv)
7/
2
1
/
0
8
1
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5
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2
7
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Appendix F
Lake Cornelia Biological and Fisheries Data
Name: Cornelia
Public Access Information
Lake Characteristics
Fish Sampled up to the 2005 Survey Year
Normal Ranges represent typical catches for lakes with similar physical and chemical characteristics.
Length of Selected Species Sampled for All Gear for the 2005 Survey Year
Nearest Town: Edina
Primary County: Hennepin
Survey Date: 06/29/2005
Inventory Number: 27-0028-00
Ownership Type Description
City Carry-in No improved access for boats canoes or small watercraft on the
north basin is in the city park.
Lake Area (acres): 51.50
Littoral Area (acres): 51.50
Maximum Depth (ft): 6.50
Water Clarity (ft): 1.00
Dominant Bottom Substrate: N/A
Abundance of Aquatic Plants: N/A
Maximum Depth of Plant Growth (ft): N/A
Species Gear Used Number of fish per net Average Fish
Weight (lbs)
Normal Range
(lbs) Caught Normal Range
Black Bullhead Gill net 12.0 N/A - N/A 0.20 N/A - N/A
Trap net 20.5 N/A - N/A 0.13 N/A - N/A
Black Crappie Gill net 20.0 N/A - N/A 0.15 N/A - N/A
Trap net 20.2 N/A - N/A 0.22 N/A - N/A
Bluegill Trap net 12.7 N/A - N/A 0.08 N/A - N/A
Common Carp Gill net 33.0 N/A - N/A 1.04 N/A - N/A
Trap net 26.8 N/A - N/A 0.24 N/A - N/A
Goldfish Trap net 0.3 N/A - N/A ND N/A - N/A
Green Sunfish Trap net 3.8 N/A - N/A 0.09 N/A - N/A
Hybrid Sunfish Trap net 1.2 N/A - N/A 0.16 N/A - N/A
Pumpkinseed
Sunfish Trap net 1.3 N/A - N/A 0.04 N/A - N/A
Painted Turtle Trap net 0.5 N/A - N/A ND N/A - N/A
Snapping Turtle Trap net 1.2 N/A - N/A ND N/A - N/A
Yellow Perch Gill net 35.0 N/A - N/A 0.15 N/A - N/A
Trap net 2.5 N/A - N/A 0.14 N/A - N/A
Page 1 of 4
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F-1
Fish Consumption Guidelines
These fish consumption guidelines help people make choices about which fish to eat and how often.
Following the guidelines enables people to reduce their exposure to contaminants while still enjoying
the many benefits from fish.
Pregnant Women, Women who may become pregnant and Children under age 15
General Population
DOWID - MN DNR, Divion of Waters' lake ID number.
Contaminants listed were measured at levels high enough to warrant a recommendation to limit
consumption.
Listing of consumption guidelines do not imply the fish are legal to keep, MN DNR fishing regulations
should be consulted.
Dioxin
Mercury
PCBS - Polychlorinated biphenyls
Species Number of fish caught in each category (inches)
0-5 6-8 9-11 12-14 15-19 20-24 25-29 30+Total
Black Bullhead 67 21 3 0 0 0 0 0 91
Black Crappie 66 53 22 0 0 0 0 0 141
Bluegill 65 11 0 0 0 0 0 0 76
Green Sunfish 21 2 0 0 0 0 0 0 23
Hybrid Sunfish 3 4 0 0 0 0 0 0 7
Pumpkinseed Sunfish 8 0 0 0 0 0 0 0 8
Yellow Perch 9 39 2 0 0 0 0 0 50
LAKE NAME
County, DOWID Species
Meal Advice
Contaminants
Unrestricted 1
meal/week
1
meal/month
Do not
eat
CORNELIA
Hennepin Co.,
27002800
Carp All sizes
Crappie All sizes
LAKE NAME
County, DOWID Species
Meal Advice
Contaminants
Unrestricted 1
meal/week
1
meal/month
Do not
eat
CORNELIA
Hennepin Co.,
27002800
Carp All sizes
Crappie All sizes
Page 2 of 4
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F-2
PFOS - Perfluorooctane sulfanate
Status of the Fishery (as of 06/29/2005)
A fish population assessment was conducted at Lake Cornelia, Edina on the 29-30 of June 2005. Lake
Cornelia is a small lake in Edina; it is divided into an 18.9-acre northern and a 32.6-acre southern basin
by West 66th Street. Rosland Park is located on the east side of the northern basin. Anglers can try their
luck fishing at the pier in Rosland Park or from shore off 66th Street. Since 2001, Cornelia Lake has
been managed by the Fishing in the Neighborhood Program (FiN), in cooperation with the City of
Edina, and the northern basin has received annual stockings of adult bluegill.
Bluegills and black crappies were the primary species sampled in Lake Cornelia. The trap net catch of
bluegills was 12.7 fish per net, above median levels for the lake type. Bluegills ranged in length from
2.6 to 8.0 inches in length, with a mean length of 4.1 inches. Most of the bluegills sampled during the
survey were in the northern basin.
The average catch of black crappies was 20.2 fish per trap net for both basins combined; black crappies
were more abundant on the southern basin than on the northern basin. Black crappies were 4.6 to 10.3
inches, with a mean length of 6.7 inches. Many large crappies were sampled, with about 30% of
catchable-sized crappies over 8 inches.
Common carp were abundant in Lake Cornelia (33 per gill net, 26.8 per trap net), and were 9.6 inches
mean length. Dissolved oxygen readings indicate probable winterkills most winters; therefore though
carp migrate into the lake annually, they do not survive most winters.
Other species sampled included black bullheads, and low numbers of yellow perch, green sunfish,
hybrid sunfish, pumpkinseeds, and gold fish. Seven snapping turtles and three painted turtles were also
captured during the survey.
Water quality measurements were taken on both the southern and northern basins in the deepest holes
found. In the southern basin, the sampling site was in 5.5 feet of water. Dissolved oxygen ranged from
6.1 to 4.6 ppm and the water temperature was 23.5 C. Water clarity was low, with a 0.75-foot secchi
disk reading. In the northern basin, the sampling site was in 4.25 feet of water. Dissolved oxygen ranged
from 7.2 to 4.1 ppm and the water temperature was 23.8 C. The secchi disk reading was 1.25 feet.
Rosland Park has many amenities in addition to Lake Cornelia. The Park is a great place to spend a day
fishing, swimming in the pool, and picnicking. More information about the Rosland Park can be found
at: gis.logis.org/edina/parkfinder.
For more information about the FiN program or to see what FiN has done in your neighborhood, please
visit us at: www.dnr.state.mn.us/fishing/fin.
For Additional Information
For more information on this lake, contact:
Area Fisheries Supervisor
9925 VALLEY VIEW ROAD
Lake maps can be obtained from:
Minnesota Bookstore
660 Olive Street
Page 3 of 4
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F-3
EDEN PRAIRIE, MN 55344
(952) 826-6771
St. Paul, MN 55155
(651) 297-3000 or (800) 657-3757
To order, use 0000 for the map-id.
For general DNR Information, contact:
DNR Information Center
500 Lafayette Road
St. Paul, MN 55155-4040
(651) 296-6157 or (888) MINNDNR
TDD: (651) 296-5484 or (800) 657-3929
E-Mail: info@dnr.state.mn.us
Turn in Poachers (TIP):
Toll-free: (800) 652-9093
Page 4 of 4
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F-4
CORNELIA (NORTH BASIN)
SAMPLE: 0-2 METERS
STANDARD INVERTED MICROSCOPE ANALYSIS METHOD
4/21/2004 6/10/2004 7/7/2004 8/11/2004 8/24/2004 9/10/2004
DIVISION TAXON units/mL units/mL units/mL units/mL units/mL units/mL
CHLOROPHYTA (GREEN ALGAE)Actinastrum Hantzschii 0 0 0 0 65 62
Ankistrodesmus falcatus 0 0 78 154 1,043 803
Chlamydomonas globosa 72,078 18,804 8,237 5,097 8,930 6,117
Closterium sp.331 0 0 0 0 0
Coelastrum microporum 0 1,886 234 0 326 62
Cosmarium sp.0 0 0 0 65 0
Elakotothrix gelatinosa 0 0 0 0 0 124
Oocystis parva 0 9,795 156 232 0 62
Pandorina morum 0 0 0 77 0 0
Pediastrum Boryanum 331 52 156 309 0 0
Pediastrum duplex 0 157 0 0 130 62
Rhizoclonium hieroglyphyicum 0 0 39 77 0 0
Schroederia Judayi 0 1,152 0 154 130 124
Scenedesmus dimorphus 331 0 234 0 196 371
Scenedesmus quadricauda 2,976 1,886 1,718 1,236 2,282 3,707
Scenedesmus sp.0 943 0 77 0 494
Selenastrum minutum 0 0 586 541 1,499 1,606
Sphaerocystis Schroeteri (Colony)496 0 0 0 130 432
Staurastrum sp.0 0 117 0 0 62
Tetraedron minimum 0 0 0 0 0 62
Tetraedron muticum 0 0 0 0 326 618
Tetraedron sp.165 0 117 77 7,105 62
CHLOROPHYTA TOTAL 76,707 34,675 11,673 8,032 22,228 14,828
CHRYSOPHYTA (YELLOW-BROWN ALGAE)Dinobryon sociale 0 0 0 0 0 1,297
CHRYSOPHYTA TOTAL 0 0 0 0 0 1,297
CYANOPHYTA (BLUE-GREEN ALGAE)Anabaena affinis 0 0 0 7,491 130 62
Anabaena flos-aquae 0 0 0 463 326 618
Cylindrospermopsis raciborski 0 0 0 154 0 0
Aphanizomenon flos-aquae 0 52 234 8,264 782 0
Coelosphaerium Naegelianum 0 0 39 0 0 0
Merismopedia tenuissima 0 210 664 154 0 309
Merismopedia sp.0 0 273 0 0 309
Microcystis aeruginosa 0 1,886 1,171 541 65 124
Microcystis incerta 0 0 117 541 130 556
Oscillatoria limnetica 0 52 0 4,170 1,890 556
Phormidium mucicola 0 0 39 0 0 0
CYANOPHYTA TOTAL 0 2,200 2,499 21,779 3,324 2,533
BACILLARIOPHYTA (DIATOMS)Amphora ovalis 0 0 0 77 0 0
Asterionella formosa 165 105 0 0 0 62
Cymbella sp.0 0 0 0 65 62
Melosira granulata 661 314 703 1,699 3,911 7,600
Navicula sp.0 105 0 154 130 62
Pinnularia sp.0 105 0 0 0 0
Rhoicosphenia curvata 0 0 0 0 0 62
Stephanodiscus Hantzschii 331 0 351 5,792 5,736 4,449
Stephanodiscus sp.165 210 0 77 0 0
Synedra acus 1,323 0 39 0 0 0
Synedra ulna 4,960 105 312 927 326 309
BACILLARIOPHYTA TOTAL 7,605 943 1,405 8,727 10,169 12,604
CRYPTOPHYTA (CRYPTOMONADS)Cryptomonas erosa 7,109 3,719 2,420 2,394 2,151 2,595
CRYPTOPHYTA TOTAL 7,109 3,719 2,420 2,394 2,151 2,595
EUGLENOPHYTA (EUGLENOIDS)Euglena sp.0 52 508 232 847 124
Phacus sp.0 0 429 154 587 432
Trachelomonas sp.0 0 0 0 130 0
EUGLENOPHYTA TOTAL 0 52 508 232 847 124
PYRRHOPHYTA (DINOFLAGELLATES)Ceratium hirundinella 0 0 0 77 130 309
Peridinium cinctum 0 0 0 0 130 0
PYRRHOPHYTA (DINOFLAGELLATES) 0 0 0 77 261 309
TOTALS 91,420 41,589 18,505 41,241 38,981 34,291
F-5
CORNELIA LAKE NORTH BASIN
SAMPLE: 0-1 METERS
STANDARD PHYTOPLANKTON CLUMP COUNT
6/16/2008 7/7/2008 7/21/2008 8/4/2008 8/19/2008 9/3/2008 9/17/2008 9/30/2008
DIVISION TAXON units/mL units/mL units/mL units/mL units/mL units/mL units/mL units/mL units/mL units/mL units/mL
CHLOROPHYTA (GREEN
ALGAE)Ankistrodesmus Brauni 0 107 0 0 0 57 0 230 0 0 0
Ankistrodesmus falcatus 0 320 0 67 74 115 227 517 0 0 0
Chlamydomonas globosa 689 3,840 901 1,805 1,777 1,321 3,062 1,953 0 0 0
Closterium sp.0 0 0 0 74 0 113 0 0 0 0
Coelastrum microporum 1,034 320 270 334 592 0 454 0 0 0 0
Cosmarium sp.0 0 0 334 0 0 113 0 0 0 0
Crucigenia tetrapedia 57 0 1,531 602 0 115 340 689 0 0 0
Elakotothrix gelatinosa 0 0 0 67 0 0 0 0 0 0 0
Elakotothrix sp.57 0 90 134 0 0 0 0 0 0 0
Lagerheimia sp.0 0 0 0 0 57 227 57 0 0 0
Micractinium sp.0 0 0 0 0 57 0 0 0 0 0
Oocystis parva 1,551 1,920 2,341 1,070 592 402 794 0 0 0 0
Pandorina morum 0 0 0 0 74 919 0 0 0 0 0
Pediastrum Boryanum 3,159 1,173 1,441 802 74 0 1,021 57 0 0 0
Pediastrum duplex 0 0 0 0 1,111 0 0 0 0 0 0
Pediastrum simplex 0 320 360 0 148 172 340 345 0 0 0
Pediastrum tetras 0 0 0 0 74 0 0 0 0 0 0
Rhizoclonium hieroglyphicum 0 107 0 0 74 0 0 0 0 0 0
Scenedesmus dimorphus 172 533 0 134 74 0 227 287 0 0 0
Scenedesmus quadricauda 6,720 9,173 3,422 4,614 4,221 2,470 4,990 7,179 0 0 0
Scenedesmus sp.345 320 1,441 602 1,407 574 3,176 287 0 0 0
Schroederia Judayi 0 1,173 0 0 0 0 0 230 0 0 0
Selenastrum minutum 0 0 270 267 0 0 1,928 459 0 0 0
Selenatrum sp.230 320 540 669 74 0 113 0 0 0 0
Sphaerocystis schroeteri 57 0 180 0 0 0 113 57 0 0 0
Staurastrum sp.115 107 0 0 0 0 113 0 0 0 0
Tetraedron muticum 402 0 90 1,003 518 517 567 172 0 0 0
Tetraedron sp.0 747 0 67 74 0 0 57 0 0 0
CHLOROPHYTA TOTAL 14,589 20,480 12,877 12,571 11,033 6,777 17,920 12,578 0 0 0
CHRYSOPHYTA (YELLOW-
BROWN ALGAE)CHRYSOPHYTA TOTAL 0 0 0 0 0 0 0 0 0 0 0
CYANOPHYTA (BLUE-GREEN
ALGAE)Anabaena affinis 0 0 0 401 7,331 0 0 0 0 0 0
Anabaena flos-aquae 0 0 0 0 0 0 113 0 0 0 0
Anabaena spiroides v. crassa 0 320 540 0 0 0 0 0 0 0 0
Anabaena sp.0 0 0 468 0 57 113 0 0 0 0
Aphanizomenon flos-aquae 0 2,773 810 4,413 148 0 340 287 0 0 0
Cylindrospermopsis raciborskii 0 0 0 0 74 0 0 0 0 0 0
Coelosphaerium Naegelianum 0 107 90 0 370 115 113 0 0 0 0
Merismopedia tenuissima 115 1,280 810 401 74 115 340 402 0 0 0
Merismopedia sp.172 213 1,261 0 0 0 0 57 0 0 0
Microcystis aeruginosa 115 2,240 2,431 1,003 592 1,034 794 747 0 0 0
Microcystis incerta 0 8,533 0 6,352 7,701 4,021 14,291 3,389 0 0 0
Oscillatoria Agardhii 0 0 9,906 0 148 0 113 0 0 0 0
Oscillatoria limnetica 0 0 0 0 148 0 0 0 0 0 0
Phormidium mucicola 0 320 0 334 74 0 0 0 0 0 0
Unidentified Blue Green Algae 0 213 0 0 0 0 0 0 0 0 0
CYANOPHYTA TOTAL 402 16,000 15,849 13,373 16,661 5,342 16,219 4,882 0 0 0
BACILLARIOPHYTA
(DIATOMS)Asterionella formosa 1,264 0 0 0 0 0 0 0 0 0 0
Cyclotella glomerata 0 0 0 0 0 57 0 0
Cymbella sp.0 0 0 67 148 57 0 0 0 0 0
Melosira granulata 804 107 1,171 1,404 1,407 172 340 402 0 0 0
Navicula sp.57 107 90 0 74 0 0 0 0 0 0
Nitzschia sp.172 0 0 0 0 0 0 0 0 0 0
Pinnularia sp.115 0 0 0 74 0 0 115 0 0 0
Rhoicosphenia curvata 0 0 0 67 0 0 0 0 0 0 0
Stephanodiscus Hantzschii 13,440 13,653 14,948 8,158 9,330 14,014 22,003 20,160 0 0 0
Stephanodiscus sp.57 533 0 134 0 115 227 115 0 0 0
Synedra ulna 0 0 0 201 296 0 0 287 0 0 0
BACILLARIOPHYTA TOTAL 15,910 14,400 16,209 10,030 11,330 14,416 22,570 21,079 0 0 0
CRYPTOPHYTA
(CRYPTOMONADS)Cryptomonas erosa 230 747 991 936 592 402 227 115 0 0 0
CRYPTOPHYTA TOTAL 230 747 991 936 592 402 227 115 0 0 0
EUGLENOPHYTA
(EUGLENOIDS)Euglena sp.107 0 0 0 172 0 57 0 0 0
Phacus sp.0 0 90 0 0 0 0 0 0 0
EUGLENOPHYTA TOTAL 107 0 90 0 172 0 57 0 0 0 0
PYRRHOPHYTA
(DINOFLAGELLATES)Ceratium hirundinella 0 0 0 0 74 57 0 0 0 0 0
Peridinium cinctum 0 107 0 0 0 0 0 0 0 0 0
PYRRHOPHYTA TOTAL 0 107 0 0 74 57 0 0 0 0 0
TOTALS 31,237 51,733 46,016 36,910 39,863 26,995 56,993 38,654 0 0 0
F-6
CORNELIA (SOUTH BASIN)
SAMPLE: 0-2 METERS
STANDARD INVERTED MICROSCOPE ANALYSIS METHOD
4/21/2004 6/10/2004 7/7/2004 8/11/2004 8/24/2004 9/10/2004
DIVISION TAXON units/mL units/mL units/mL units/mL units/mL units/mL
CHLOROPHYTA (GREEN ALGAE)Actinastrum Hantzschii 0 0 0 0 0 0
Ankistrodesmus falcatus 264 39 0 0 147 0
Chlamydomonas globosa 1,345 898 781 159 537 156
Closterium sp.26 0 0 0 0 0
Coelastrum microporum 26 781 0 53 0 0
Cosmarium sp.26 0 0 0 0 0
Elakotothrix gelatinosa 0 39 0 0 0 156
Elakotothrix sp.0 0 0 0 0 0
Oocystis parva 290 2,069 78 0 49 39
Pediastrum Boryanum 0 0 586 583 391 820
Pediastrum duplex 923 586 0 0 0 0
Pediastrum simplex 0 273 0 0 0 0
Quadrigula sp.0 78 0 53 0 0
Rhizoclonium hieroglyphyicum 0 0 0 0 49 0
Schroederia Judayi 132 273 39 0 0 0
Scenedesmus dimorphus 185 78 0 0 0 0
Scenedesmus quadricauda 2,110 2,225 898 424 342 117
Scenedesmus sp.26 351 39 0 0 0
Selenastrum minutum 158 547 0 0 49 0
Sphaerocystis Schroeteri (Colony)79 78 0 0 0 0
Staurastrum sp.0 39 0 53 98 0
Tetraedron muticum 26 0 0 0 0 0
Tetraedron sp.0 78 0 0 0 0
CHLOROPHYTA TOTAL 5,617 8,433 2,420 1,326 1,661 1,288
CHRYSOPHYTA (YELLOW-BROWN ALGAE)Dinobryon sociale 0 0 0 0 0 0
CHRYSOPHYTA TOTAL 0 0 0 0 0 0
CYANOPHYTA (BLUE-GREEN ALGAE)Anabaena affinis 0 0 0 7,264 5,812 0
Anabaena flos-aquae 0 0 78 477 293 156
Anabaena spiroides v. crassa 0 0 0 583 0 0
Anabaenopsis raciborski 0 0 0 1,167 4,005 0
Aphanizomenon flos-aquae 0 508 9,721 1,114 488 39
Coelosphaerium Naegelianum 53 0 78 106 98 0
Lyngbya limnetica 0 0 0 424 293 0
Lyngbya cordata 0 0 0 106 98 0
Merismopedia tenuissima 105 390 508 371 147 195
Microcystis aeruginosa 1,450 1,132 4,412 5,621 5,910 5,895
Microcystis incerta 0 39 586 954 440 117
Oscillatoria limnetica 105 0 0 4,666 1,319 0
Phormidium mucicola 0 0 234 1,538 3,663 8,355
CYANOPHYTA TOTAL 1,714 2,069 15,382 22,853 18,903 6,403
BACILLARIOPHYTA (DIATOMS)Amphora ovalis 26 0 0 53 0 0
Asterionella formosa 158 1,249 39 0 0 0
Cocconeis placentula 26 39 0 0 0 0
Cyclotella glomerata 0 0 0 0 0 117
Cymbella sp.0 0 39 0 0 0
Fragilaria capucina 369 0 351 424 244 39
Fragilaria crotonensis 0 0 0 0 0 0
Melosira granulata 158 78 273 265 49 234
Navicula sp.26 0 156 0 0 0
Stephanodiscus Hantzschii 607 156 117 106 147 351
Stephanodiscus sp.79 859 1,913 371 195 195
Synedra acus 422 0 0 0 0 0
Synedra ulna 817 39 78 0 98 0
BACILLARIOPHYTA TOTAL 2,690 2,420 2,967 1,220 733 937
CRYPTOPHYTA (CRYPTOMONADS)Cryptomonas erosa 3,771 2,460 429 477 244 117
CRYPTOPHYTA TOTAL 3,771 2,460 429 477 244 117
EUGLENOPHYTA (EUGLENOIDS)Euglena sp.0 117 0 0 0 0
Phacus sp.26 39 0 0 0 0
EUGLENOPHYTA TOTAL 0 117 0 0 0 0
PYRRHOPHYTA (DINOFLAGELLATES)Peridinium cinctum 26 0 0 106 0 0
PYRRHOPHYTA (DINOFLAGELLATES)26 0 0 106 0 0
TOTALS 13,818 15,499 21,199 25,982 21,540 8,745
F-7
CORNELIA LAKE SOUTH BASIN
SAMPLE: 0-1.5 METERS
STANDARD PHYTOPLANKTON CLUMP COUNT
6/16/2008 7/7/2008 7/21/2008 8/4/2008 8/19/2008 9/3/2008 9/17/2008 9/30/2008
DIVISION TAXON units/mL units/mL units/mL units/mL units/mL units/mL units/mL
CHLOROPHYTA (GREEN ALGAE)Ankistrodesmus falcatus 0 0 0 0 172 0 89 115
Chlamydomonas globosa 115 517 922 862 1,723 402 4,101 919
Closterium sp.172 0 0 0 0 0 0 287
Coelastrum microporum 115 115 132 230 115 172 89 0
Cosmarium sp.115 57 66 57 0 57 89 0
Crucigenia quadrata 0 0 0 0 172 0 0 0
Crucigenia tetrapedia 0 0 0 57 0 57 0 0
Elakotothrix gelatinosa 0 0 66 0 115 0 0 0
Eudorina elegans 0 0 0 0 0 0 0 0
Lagerhei;mia sp.0 0 0 57 0 0 0 57
Micractinium sp.0 0 0 0 0 0 0 0
Oocystis parva 976 402 264 287 862 632 267 287
Pandorina morum 0 57 0 0 0 0 0 0
Pediastrum Boryanum 1,206 0 527 574 517 1,436 446 1,149
Pediastrum duplex 0 0 0 0 57 0 0 0
Pediastrum duplex var. clathratum 0 0 0 0 57 0 0 0
Pediastrum simplex 57 0 66 57 172 287 0 230
Pediastrum tetras 0 0 0 0 0 0 0 0
Rhizosolenia sp.0 0 0 0 0 0 0 0
Rhizoclonium hieroglyphicum 0 0 0 0 115 0 0 0
Scenedesmus dimorphus 0 0 0 0 287 0 89 0
Scenedesmus quadricauda 1,149 287 856 1,149 1,838 1,321 624 1,551
Scenedesmus sp.0 230 527 230 976 230 178 57
Schroederia Judayi 57 115 0 0 172 0 0 0
Selenastrum minutum 0 57 0 0 574 459 1,337 230
Selenastum sp.402 57 66 57 0 0 0 57
Sphaerocystis schroeteri 0 0 0 0 57 0 0 0
Starurastrum sp.0 0 0 0 0 0 0 0
Tetraedron minimum 0 0 0 0 0 0 0 0
Tetraedron muticum 0 0 0 57 115 115 89 0
Tetraedron sp.0 0 0 0 115 57 0 0
Treubaria setigerum 0 0 66 0 0 0 0 0
CHLOROPHYTA TOTAL 4,365 1,895 3,558 3,676 8,213 5,227 7,400 4,939
CHRYSOPHYTA (YELLOW-BROWN
ALGAE)CHRYSOPHYTA TOTAL 0 0 0 0 0 0 0 0
CYANOPHYTA (BLUE-GREEN
ALGAE)Anabaena affinis 0 0 0 57 919 0 0 0
Anabaena flos-aquae 57 0 0 57 172 0 0 57
Anabaena spiroides v. crassa 0 115 922 517 402 0 0 230
Aphanizomenon flos-aquae 57 689 1,845 1,493 287 0 267 517
Cylindrospermopsis raciborskii 0 0 0 57 0 0 89 0
Coelosphaerium Naegelianum 0 57 66 0 172 57 0 0Coelosphaerium Naegelianum 0 57 66 0 172 57 0 0
Lyngbya limnetica 0 0 0 0 0 0 0 0
Merismopedia tenuissima 1,034 2,987 2,042 1,034 1,149 402 2,853 632
Microcystis aeruginosa 3,331 4,595 6,391 5,801 919 3,216 713 747
Microcystis incerta 3,159 8,443 0 6,433 8,845 4,250 18,187 4,480
Oscillatoria Agardhii 57 0 0 0 115 0 0 0
Oscillatoria limnetica 0 0 66 0 574 115 0 0
Phormidium mucicola 4,193 1,953 1,581 3,389 287 1,206 357 0
Rhabdoderma lineare 0 0 0 115 0 0 0 0
Unidentified Blue Green Algae 0 0 0 57 0 0 0 0
CYANOPHYTA TOTAL 11,889 18,839 12,913 19,011 13,842 9,247 22,467 6,663
BACILLARIOPHYTA (DIATOMS)Cymbella sp.0 0 0 0 0 57 0 0
Fragilaria capucina 57 0 0 172 57 115 89 0
Fragilaria crotonensis 0 0 0 0 0 0 0 0
Melosira granulata 0 0 198 459 172 115 0 0
Navicula sp.57 57 0 57 459 172 89 0
Nitzschia sp.0 0 0 0 0 57 0 0
Pinnularia sp.0 0 0 0 0 57 0 0
Rhizosolenia sp.0 0 0 0 0 0 0 0
Stephanodiscus Hantzschii 1,091 574 791 0 2,068 4,595 14,800 18,265
Stephanodiscus sp.0 0 0 172 115 0 0 0
Synedra ulna 230 57 0 0 0 57 0 172
BACILLARIOPHYTA TOTAL 1,378 689 988 862 2,872 5,227 14,978 18,437
CRYPTOPHYTA (CRYPTOMONADS)Cryptomonas erosa 287 0 264 345 574 0 624 345
CRYPTOPHYTA TOTAL 287 0 264 345 574 0 624 345
EUGLENOPHYTA (EUGLENOIDS)Phacus sp.0 0 0 0 0 115 0 0
EUGLENOPHYTA TOTAL #REF! #REF!0 0 0 115 0 0
PYRRHOPHYTA
(DINOFLAGELLATES)Ceratium hirundinella 57 57 0 0 0 57 0 0
PYRRHOPHYTA TOTAL 57 57 0 0 0 57 0 0
TOTALS #REF! #REF! 17,722 23,893 25,501 19,873 45,469 30,384
F-8
CORNELIA LAKE (N. BASIN)
ZOOPLANKTON ANALYSIS
4/21/2004 6/11/2004 7/7/2004 8/11/2004 8/24/2004 9/10/2004
DIVISION TAXON #/m2 #/m2 #/m2 #/m2 #/m2 #/m2
CLADOCERA Bosmina longirostris 50,841 305,577 19,452 40,673 19,452 108,933
Ceriodaphnia sp.0 152,789 0 0 0 0
Chydorus sphaericus 10,168 9,549 0 10,168 0 0
Daphnia ambigua 0 38,197 0 0 0 0
Daphnia galeata mendotae 0 66,845 0 0 0 0
Daphnia pulex 0 0 0 0 0 0
Daphnia retrocurva 0 0 0 0 0 0
Diaphanosoma leuchtenbergianum 0 0 0 0 0 0
Immature Cladocera 0 0 0 0 0 9,903
CLADOCERA TOTAL 61,009 572,958 19,452 50,841 19,452 118,836
COPEPODA Cyclops sp.498,243 133,690 68,083 40,673 29,178 79,224
Diaptomus sp.0 38,197 0 20,336 0 0
Nauplii 498,243 496,563 126,440 71,178 58,357 217,865
Copepodid 0 0 0 0 0 0
COPEPODA TOTAL 996,487 668,451 194,523 132,187 87,535 297,089
Asplanchna priodonta 0 19,099 0 0 0 0
Brachionus sp.0 38,197 233,427 50,841 106,987 79,224
Filinia longiseta 0 0 0 0 29,178 29,709
Lecane sp.0 9,549 0 0 0 0
Keratella cochlearis 50,841 525,211 1,274,124 264,374 3,112,363 5,149,547
Keratella quadrata 30,505 143,239 9,726 10,168 0 0
Kellicottia sp.0 0 0 0 0 0
Polyarthra vulgaris 0 47,746 165,344 721,945 719,734 1,307,193
ROTIFERA Trichocerca cylindrica 0 0 0 0 0 0
Trichocerca multicrinis 0 0 0 10,168 204,249 29,709
ROTIFERA TOTAL 81,346 783,042 1,682,621 1,057,496 4,172,512 6,595,381
TOTALS 1,138,842 2,024,451 1,896,596 1,240,524 4,279,500 7,011,306
F-9
CORNELIA LAKE (NORTH BASIN)
ZOOPLANKTON ANALYSIS
6/16/2008 7/7/2008 7/21/2008 8/4/2008 8/19/2008 9/3/2008 9/17/2008 9/30/2008
Vertical Tow (m)
DIVISION TAXON #/m2 #/m2 #/m2 #/m2 #/m2 #/m2 #/m2 #/m2
CLADOCERA Bosmina longirostris 1,091,272 186,477 82,053 588,431 1,875,685 259,776 19,275 237,937
Ceriodaphnia sp.85,590 68,702 205,133 128,385 141,029 59,948 19,275 31,035
Chydorus sphaericus 0 88,331 133,336 0 197,441 479,587 48,189 144,831
Daphnia galeata mendotae 21,397 29,444 71,797 64,192 14,103 9,991 0 10,345
Daphnia pulex 0 0 0 0 0 0 9,638 10,345
Daphnia rosea 0 0 0 10,699 0 19,983 0 10,345
Diaphanosoma leuchtenbergianum 0 0 10,257 21,397 0 0 0 0
Immature Cladocera 0 29,444 0 0 0 9,991 0 0
CLADOCERA TOTAL 1,198,260 402,397 502,576 813,105 2,228,258 839,277 96,377 444,838
COPEPODA Cyclops sp.32,096 147,218 153,850 235,372 380,778 239,793 134,928 124,141
Diaptomus sp.10,699 19,629 30,770 106,987 56,412 29,974 48,189 10,345
Nauplii 64,192 294,437 512,833 0 1,142,335 489,578 279,494 113,796
Copepodid 0 0 0 620,527 0 0 0 0
COPEPODA TOTAL 106,987 461,284 697,452 962,887 1,579,524 759,346 462,610 248,282
ROTIFERA Asplanchna priodonta 0 0 0 21,397 112,823 9,991 0 0
Brachionus havanaensis 567,034 0 0 0 0 0 0 0
Brachionus plicatilis 1,433,632 29,444 471,806 1,134,067 0 369,682 106,015 196,556
Brachionus calyciflorus 310,264 9,815 0 0 0 0 0 0
Brachionus sp.0 0 0 0 282,058 0 0 0
Filinia longiseta 128,385 0 20,513 353,059 437,190 59,948 19,275 41,380
Keratella cochlearis 331,661 9,815 892,329 2,321,629 2,073,126 1,009,131 790,293 620,704
Keratella quadrata 85,590 0 0 0 0 0 0 0
Mytilinia sp.0 0 0 10,699 0 0 0 0
Polyarthra vulgaris 246,071 78,516 143,593 374,456 705,145 69,940 106,015 248,282
Trichocerca cylindrica 0 0 0 0 28,206 19,983 19,275 0
Trichocerca multicrinis 10,699 58,887 0 117,686 155,132 19,983 0 10,345
ROTIFERA TOTAL 3,113,336 186,477 1,528,241 4,332,993 3,793,679 1,558,657 1,040,873 1,117,268
TOTALS 4,418,583 1,050,157 2,728,269 6,108,986 7,601,461 3,157,280 1,599,861 1,810,387
F-10
CORNELIA LAKE (S. BASIN)
ZOOPLANKTON ANALYSIS
4/21/2004 6/11/2004 7/7/2004 8/11/2004 8/24/2004 9/10/2004
DIVISION TAXON #/m2 #/m2 #/m2 #/m2 #/m2 #/m2
CLADOCERA Bosmina longirostris 0 400,009 53,936 189,394 489,578 891,268
Ceriodaphnia sp.0 153,850 0 0 0 10,610
Chydorus sphaericus 0 133,336 53,936 0 0 0
Daphnia ambigua 0 20,513 0 0 0 0
Daphnia galeata mendotae 0 102,567 0 0 29,974 0
Daphnia pulex 0 0 0 0 0 0
Daphnia retrocurva 0 0 0 0 0 0
Diaphanosoma leuchtenbergianum 0 0 0 0 9,991 10,610
Immature Cladocera 0 30,770 0 0 0 0
CLADOCERA TOTAL 0 841,045 107,872 189,394 529,544 912,488
COPEPODA Cyclops sp.408,498 328,213 21,574 42,088 89,923 42,441
Diaptomus sp.0 71,797 43,149 52,610 49,957 0
Nauplii 380,646 451,293 118,659 147,307 299,742 137,934
Copepodid 0 0 0 0 0 0
COPEPODA TOTAL 789,143 851,302 183,382 242,004 439,621 180,376
Asplanchna priodonta 9,284 30,770 21,574 0 0 0
Brachionus sp.120,692 225,646 819,825 94,697 9,991 10,610
Filinia longiseta 9,284 0 172,595 115,741 169,854 42,441
Lecane sp.0 10,257 0 31,566 89,923 0
Keratella cochlearis 3,416,526 1,159,002 1,682,798 252,526 939,191 233,427
Keratella quadrata 547,758 153,850 10,787 0 0 0
Kellicottia sp.9,284 0 0 0 0 0
Polyarthra vulgaris 9,284 92,310 140,233 441,920 529,544 95,493
ROTIFERA Trichocerca cylindrica 0 0 53,936 31,566 59,948 21,221
Trichocerca multicrinis 0 10,257 43,149 84,175 219,811 21,221
ROTIFERA TOTAL 4,122,113 1,682,091 2,944,897 1,052,191 2,018,262 424,413
TOTALS 4,911,256 3,374,438 3,236,151 1,483,589 2,987,427 1,517,277
F-11
CORNELIA LAKE (SOUTH BASIN)
ZOOPLANKTON ANALYSIS
6/16/2008 7/7/2008 7/21/2008 8/4/2008 8/19/2008 9/3/2008 9/17/2008 9/30/2008
Vertical Tow (m)
DIVISION TAXON #/m2 #/m2 #/m2 #/m2 #/m2 #/m2 #/m2 #/m2
CLADOCERA Bosmina longirostris 65,784 76,394 37,136 31,831 586,574 378,789 90,188 244,038
Ceriodaphnia sp.43,856 19,099 83,556 95,493 378,435 136,785 99,207 63,662
Chydorus sphaericus 197,352 190,986 213,533 10,610 18,922 957,494 108,225 222,817
Daphnia galeata mendotae 32,892 38,197 9,284 0 56,765 10,522 9,019 0
Daphnia pulex 21,928 9,549 9,284 0 0 0 0 0
Daphnia rosea 0 19,099 9,284 31,831 0 0 9,019 10,610
Diaphanosoma leuchtenbergianum 0 0 0 0 9,461 0 0 0
Immature Cladocera 0 0 0 0 0 0 0 10,610
CLADOCERA TOTAL 361,812 353,324 362,077 169,765 1,050,157 1,483,589 315,657 551,737
COPEPODA Cyclops sp.10,964 66,845 120,692 180,376 283,826 157,829 27,056 116,714
Diaptomus sp.21,928 0 83,556 0 18,922 42,088 9,019 95,493
Nauplii 98,676 76,394 250,669 360,751 709,566 778,621 162,338 74,272
Copepodid 0 334,225 0 0 0 0 0 0
COPEPODA TOTAL 131,568 477,465 454,918 541,127 1,012,314 978,538 198,413 286,479
ROTIFERA Asplanchna priodonta 0 0 0 0 9,461 10,522 0 0
Brachionus havanaensis 0 9,549 0 0 28,383 0 0 0
Brachionus plicatilis 372,776 171,887 492,054 509,296 0 252,526 45,094 180,376
Brachionus calyciflorus 10,964 0 9,284 0 0 10,522 0 0
Brachionus sp.0 0 0 0 236,522 0 0 0
Filinia longiseta 10,964 57,296 74,272 21,221 113,531 94,697 36,075 21,221
Mytilinia sp.0 9,549 0 0 0 0 0 0
Keratella cochlearis 285,064 362,873 232,101 297,089 425,739 631,315 270,563 318,310
Keratella quadrata 164,460 0 0 0 0 0 0 0
Polyarthra vulgaris 21,928 28,648 0 84,883 406,818 42,088 0 148,545
Trichocerca cylindrica 0 0 0 0 9,461 10,522 0 0
Trichocerca multicrinis 10,964 19,099 37,136 42,441 56,765 0 9,019 0
Immature Rotifera 0 0 0 0 0 0 0 21,221
ROTIFERA TOTAL 877,121 658,901 844,847 954,930 1,286,679 1,052,191 360,751 689,671
TOTALS 1,370,501 1,489,690 1,661,843 1,665,822 3,349,151 3,514,318 874,822 1,527,887
F-12
Appendix G
BMP Cost Estimates
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x
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s
G-4
Appendix H
Lake Cornelia 2004 & 2008 Macrophyte Surveys
Not to Scale
LAKE CORNELIA
(NORTH BASIN)
MACROPHYTE SURVEY
JUNE 5, 2008
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Water Quality
Monitoring
Location
Lythrum salicaria
Ceratophyllum demersum
Potamogeton crispus
Typha sp.
Scirpus sp.
Lythrum salicaria
Coontail
Curlyleaf pondweed
Cattail
Bullrush
Purple loosestrife
No macrophytes found in water > 3.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
Water depths drop to 4-5 feet at edge of Cattails.
Typha sp.
Typha sp.
Scirpus sp.
Ceratophyllum demersum 1
Potamogeton crispus
Typha sp.
Fishing
Pier
Typha sp.
Typha sp.
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
0
0
3
\
M
o
v
e
d
F
r
o
m
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p
l
s
_
P
\
L
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a
c
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e
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a
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s
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n
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l
i
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h
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a
s
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n
\
2
0
0
8
M
a
p
s
\
L
a
k
e
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r
n
e
l
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a
N
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J
U
N
E
2
0
0
8
.
C
D
R
R
L
G
0
6
-
1
7
-
0
8
Ceratophyllum demersum 1
Potamogeton crispus 1
H-1
Not to Scale
LAKE CORNELIA
(NORTH BASIN)
MACROPHYTE SURVEY
AUGUST 13, 2008
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Water Quality
Monitoring
Location
Lythrum salicaria
Ceratophyllum demersum
Potamogeton crispus
Typha sp.
Scirpus sp.
Lythrum salicaria
Coontail
Curlyleaf pondweed
Cattail
Bullrush
Purple loosestrife
No macrophytes found in water > 3.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
Water depths drop to 4-5 feet at edge of Cattails.
Algal bloom
Typha sp.
Typha sp.
Scirpus sp.
Ceratophyllum demersum 1
Typha sp.
Fishing
Pier
Typha sp.
Typha sp.
P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
0
0
3
\
M
o
v
e
d
F
r
o
m
M
p
l
s
_
P
\
L
a
k
e
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a
c
r
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p
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e
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a
p
s
\
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n
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l
i
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h
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a
s
i
n
\
2
0
0
8
M
a
p
s
\
L
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k
e
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o
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e
l
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a
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A
U
G
U
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T
2
0
0
8
.
C
D
R
R
L
G
0
8
-
2
6
-
0
8
Ceratophyllum demersum 1-2
Potamogeton crispus 1
Potamogeton crispus
Potamogeton crispus
H-2
Not to Scale
LAKE CORNELIA
(SOUTH BASIN)
MACROPHYTE SURVEY
JUNE 5, 2008P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
0
0
3
\
M
o
v
e
d
F
r
o
m
M
p
l
s
_
P
\
L
a
k
e
M
a
c
r
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p
h
y
t
e
M
a
p
s
\
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o
r
n
e
l
i
a
S
o
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h
B
a
s
i
n
\
2
0
0
8
M
a
p
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
B
J
U
N
E
2
0
0
8
.
C
D
R
R
L
G
0
6
-
1
7
-
0
8
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Potamogeton pectinatus
Potamogeton crispus
Typha sp.
Scirpus sp.
Lythrum salicaria
Iris vericolor
Sago pondweed
Curlyleaf pondweed
Cattail
Bullrush
Purple loosestrife
Blue flag iris
No macrophytes found in water > 1.5'
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy
Lythrum salicaria (Purple loosestrife) sporadically located along entire north shoreline
Water Quality
Monitoring
Location
Typha sp.
Lythrum salicaria
Iris vericolor
Typha sp.
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Potamogeton pectinatus 1
Typha sp.
Lythrum salicaria
Scirpus sp.
Lythrum salicaria
Typha sp.
Lythrum salicaria
Typha sp.
Typha sp.
Outflow
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Lythrum salicaria
Potamogeton crispus 1
H-3
Not to Scale
LAKE CORNELIA
(SOUTH BASIN)
MACROPHYTE SURVEY
AUGUST 13, 2008P:
\
M
p
l
s
\
2
3
M
N
\
2
7
\
2
3
2
7
0
0
3
\
M
o
v
e
d
F
r
o
m
M
p
l
s
_
P
\
L
a
k
e
M
a
c
r
o
p
h
y
t
e
M
a
p
s
\
C
o
r
n
e
l
i
a
S
o
u
t
h
B
a
s
i
n
\
2
0
0
8
M
a
p
s
\
L
a
k
e
C
o
r
n
e
l
i
a
S
B
A
U
G
U
S
T
2
0
0
8
.
C
D
R
R
L
G
0
8
-
2
6
-
0
8
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Potamogeton pectinatus
Potamogeton nodosus
Typha sp.
Scirpus sp.
Lythrum salicaria
Iris vericolor
Sagittaria sp.
Sago pondweed
Longleaf pondweed
Cattail
Bullrush
Purple loosestrife
Blue flag iris
Arrowhead
No macrophytes found in water > 1.5'
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy
Lythrum salicaria (Purple loosestrife) sporadically located along entire north shoreline
Algal bloom
Water Quality
Monitoring
Location
Typha sp.
Lythrum salicaria
Iris vericolor
Typha sp.
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Potamogeton pectinatus 1
Typha sp.
Lythrum salicaria
Scirpus sp.
Lythrum salicaria
Typha sp.
Typha sp.
Typha sp.
Outflow
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Lythrum salicaria
Potamogeton nodosus 1
Lythrum salicaria
Lythrum salicaria
Lythrum salicaria
Sagittaria sp.
H-4
Not to Scale
LAKE CORNELIA
(NORTH BASIN)
MACROPHYTE SURVEY
JUNE 14, 2004P:
2
3
\
2
7
\
0
0
3
\
L
a
k
e
M
a
c
r
o
p
h
y
t
e
M
a
p
s
\
C
O
R
N
E
L
I
A
N
O
R
T
H
B
A
S
I
N
\
2
0
0
4
\
J
U
N
E
2
0
0
4
.
C
D
R
R
L
G
0
8
-
0
4
-
0
4
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Water Quality
Monitoring
Location
Lythrum salicaria
Ceratophyllum demersum
Typha sp.
Scirpus sp.
Lythrum salicaria
Coontail
Cattail
Bullrush
Purple loosestrife
No macrophytes found in water > 3.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
Water depths drop to 4-5 feet at edge of Cattails.
Typha sp.
Typha sp.
Scirpus sp.
Ceratophyllum demersum 1
Typha sp.
Fishing
Pier
Typha sp.
Typha sp.
H-5
Not to Scale
LAKE CORNELIA
(NORTH BASIN)
MACROPHYTE SURVEY
AUGUST 23, 2004P:
2
3
\
2
7
\
0
0
3
\
L
a
k
e
M
a
c
r
o
p
h
y
t
e
M
a
p
s
\
C
O
R
N
E
L
I
A
N
O
R
T
H
B
A
S
I
N
\
2
0
0
4
\
A
U
G
U
S
T
2
0
0
4
.
C
D
R
R
L
G
0
1
-
2
0
-
0
5
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Water Quality
Monitoring
Location
Lythrum salicaria
Ceratophyllum demersum
Potamogeton sp. (narrowleaf)
Potamogeton pectinatus
Typha sp.
Scirpus sp.
Lythrum salicaria
Coontail
Narrowleaf pondweed
Sago pondweed
Cattail
Bullrush
Purple loosestrife
No macrophytes found in water > 3.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
Water depths drop to 4-5 feet at edge of Cattails.
Typha sp.
Typha sp.
Scirpus sp.
Ceratophyllum demersum 1
Typha sp.
Fishing
Pier
Typha sp.
Typha sp.
Scirpus sp.
Ceratophyllum demersum 1
Potamogeton sp. (narrowleaf)
Potamogeton pectinatus 1
Potamogeton sp. (narrowleaf)
Potamogeton pectinatus 1
H-6
Not to Scale
LAKE CORNELIA
(SOUTH BASIN)
MACROPHYTE SURVEY
JUNE 14, 2004P:
2
3
\
2
7
\
0
0
3
\
L
a
k
e
M
a
c
r
o
p
h
y
t
e
M
a
p
s
\
C
O
R
N
E
L
I
A
N
O
R
T
H
B
A
S
I
N
\
2
0
0
4
\
J
U
N
E
2
0
0
4
.
C
D
R
R
L
G
0
8
-
0
4
-
0
4
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Potamogeton pectinatus
Potamogeton sp. (narrowleaf)
Typha sp.
Scirpus sp.
Lythrum salicaria
Iris vericolor
Sago pondweed
Narrowleaf pondweed
Cattail
Bullrush
Purple loosestrife
Blue flag iris
No macrophytes found in water > 2.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
sporadically located along entire northLythrum salicaria (Purple loosestrife)
Water Quality
Monitoring
Location
Typha sp.
Lythrum salicaria
Iris vericolor
Typha sp.
Potamogeton sp. (narrowleaf) 1
Typha sp.
Potamogeton pectinatus 1
Potamogeton pectinatus 1
Lythrum salicaria
Typha sp.
Potamogeton sp. (narrowleaf) 1
Scirpus sp.
Potamogeton pectinatus 1
Potamogeton sp. (narrowleaf) 1
Typha sp.
Lythrum salicaria
Scirpus sp.
Lythrum salicaria
Typha sp.
Lythrum salicaria
Potamogeton pectinatus 1
Potamogeton sp. (narrowleaf) 1
Typha sp.
Typha sp.
Outflow
Potamogeton pectinatus 1
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Lythrum salicaria
Potamogeton pectinatus 1-2
H-7
Not to Scale
LAKE CORNELIA
(SOUTH BASIN)
MACROPHYTE SURVEY
AUGUST 23, 2004P:
2
3
\
2
7
\
0
0
3
\
L
a
k
e
M
a
c
r
o
p
h
y
t
e
M
a
p
s
\
C
O
R
N
E
L
I
A
N
O
R
T
H
B
A
S
I
N
\
2
0
0
4
\
A
U
G
U
S
T
2
0
0
4
.
C
D
R
R
L
G
0
1
-
2
0
-
0
5
Submerged Aquatic Plants:
Floating Leaf:
Emergent:
No Aquatic Vegetation Found:
Common Name Scientific Name
Potamogeton pectinatus
Potamogeton sp. (narrowleaf)
Potamogeton natans
Typha sp.
Scirpus sp.
Lythrum salicaria
Iris vericolor
Sago pondweed
Narrowleaf pondweed
Floating leaf pondweed
Cattail
Bullrush
Purple loosestrife
Blue flag iris
No macrophytes found in water > 2.0'.
Macrophyte densities estimated as follows: 1 = light; 2 = moderate; 3 = heavy.
sporadically located along entire north shorelineLythrum salicaria (Purple loosestrife)
Water Quality
Monitoring
Location
Typha sp.
Lythrum salicaria
Iris vericolor
Typha sp.
Potamogeton natans
Typha sp.
Lythrum salicaria
Lythrum salicaria
Typha sp.
Scirpus sp.
Potamogeton pectinatus 1
Potamogeton sp. (narrowleaf) 1
Typha sp.
Lythrum salicaria
Scirpus sp.
Lythrum salicaria
Typha sp.
Lythrum salicaria
Typha sp.
Typha sp.
Outflow
Typha sp.
Lythrum salicaria
Typha sp.
Scirpus sp.
Lythrum salicaria
Lythrum salicaria
Lythrum
salicaria
H-8
Appendix I
Lake Cornelia Sediment Core Analysis
Appendix J
Lake Cornelia Trend Analyses
Da
t
e
:
1
/
1
3
/
1
0
Fa
c
i
l
i
t
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:
L
a
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T
r
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d
A
n
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s
i
s
Ti
m
e
:
7
:
5
9
A
M
Da
t
a
F
i
l
e
:
N
C
O
R
N
Vi
e
w
:
N
o
r
t
h
C
o
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n
Co
n
s
t
i
t
u
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n
t
:
C
h
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(
u
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/
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)
v.
1
.
5
6
.
C
A
S
#
n
/
a
WQStat Plus TM
SE
N
'
S
S
L
O
P
E
E
S
T
I
M
A
T
O
R
NC
050
10
0
15
0
20
0
Ju
l
2
0
0
3
Ju
l
2
0
0
8
De
c
2
0
0
5
C
o
n
c
e
n
t
r
a
t
i
o
n
(
u
g
/
L
)
n
=
6
Sl
o
p
e
=
-
9
.
1
8
7
un
i
t
s
p
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r
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a
r
.
Ma
n
n
K
e
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d
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l
l
st
a
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=
-
7
Al
p
h
a
C
r
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t
i
c
a
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S
i
g
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f
.
0.
0
1
-
1
4
N
o
0.
0
5
-
1
2
N
o
0.
1
-
1
0
N
o
0.
2
-
9
N
o
J-1
Da
t
e
:
1
/
1
3
/
1
0
Fa
c
i
l
i
t
y
:
L
a
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T
r
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d
A
n
a
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s
i
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Ti
m
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:
7
:
5
9
A
M
Da
t
a
F
i
l
e
:
N
C
O
R
N
Vi
e
w
:
N
o
r
t
h
C
o
r
n
Co
n
s
t
i
t
u
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n
t
:
S
D
(
m
)
v.
1
.
5
6
.
C
A
S
#
n
/
a
WQStat Plus TM
SE
N
'
S
S
L
O
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S
T
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M
A
T
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NC
0.
0
0.
1
0.
2
0.
3
0.
4
0.
5
0.
6
Ju
l
2
0
0
3
Ju
l
2
0
0
8
De
c
2
0
0
5
C
o
n
c
e
n
t
r
a
t
i
o
n
(
m
)
n
=
6
Sl
o
p
e
=
-
0
.
0
4
un
i
t
s
p
e
r
y
e
a
r
.
Ma
n
n
K
e
n
d
a
l
l
st
a
t
i
s
t
i
c
=
-
1
2
Al
p
h
a
C
r
i
t
i
c
a
l
S
i
g
n
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f
.
0.
0
1
-
1
4
N
o
0.
0
5
-
1
2
D
o
w
n
0.
1
-
1
0
D
o
w
n
0.
2
-
9
D
o
w
n
J-2
Da
t
e
:
1
/
1
3
/
1
0
Fa
c
i
l
i
t
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:
L
a
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T
r
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n
d
A
n
a
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s
i
s
Ti
m
e
:
7
:
5
8
A
M
Da
t
a
F
i
l
e
:
N
C
O
R
N
Vi
e
w
:
N
o
r
t
h
C
o
r
n
Co
n
s
t
i
t
u
e
n
t
:
T
P
(
m
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/
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)
v.
1
.
5
6
.
C
A
S
#
n
/
a
WQStat Plus TM
SE
N
'
S
S
L
O
P
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E
S
T
I
M
A
T
O
R
NC
050
10
0
15
0
20
0
25
0
30
0
Ju
l
2
0
0
3
Ju
l
2
0
0
8
De
c
2
0
0
5
C
o
n
c
e
n
t
r
a
t
i
o
n
(
m
g
/
L
)
n
=
6
Sl
o
p
e
=
-
4
.
1
1
un
i
t
s
p
e
r
y
e
a
r
.
Ma
n
n
K
e
n
d
a
l
l
st
a
t
i
s
t
i
c
=
-
5
Al
p
h
a
C
r
i
t
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S
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g
n
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f
.
0.
0
1
-
1
4
N
o
0.
0
5
-
1
2
N
o
0.
1
-
1
0
N
o
0.
2
-
9
N
o
J-3