HomeMy WebLinkAboutArrowhead_Indianhead_WQ_Study_09.15.2022_FINAL_wApp
4300 MarketPointe Drive, Suite 200 Minneapolis, MN 55435
952.832.2600 www.barr.com
Arrowhead and Indianhead Lakes Water Quality Study
Prepared for
Nine Mile Creek Watershed District
August 2022
REPORT
SUMMARY
Arrowhead and
Indianhead Lakes
Water Quality Study
August 2022
Prepared for
Nine Mile Creek
Watershed District
Protecting and Enhancing Water Quality
Arrowhead Lake and Indianhead Lake are shallow lakes located in the southwestern portion of the city
of Edina, south of Highway 62 and east of Highway 169. The shallow, urban lakes suffer from moderate
to poor water quality. The Nine Mile Creek Watershed District (NMCWD), a local unit of government
that works to address water-related problems, conducted a study of Arrowhead and Indianhead lakes in
2021 to evaluate current water quality and identify protection and improvement strategies. Additional
information on the current lake conditions, water quality challenges, and recommended management
strategies are summarized in this project overview, including proposed implementation timelines.
Protecting and enhancing the water quality of the lakes within the Nine Mile Creek watershed is one of
the primary goals of the Nine Mile Creek Watershed District. The NMCWD’s lake management program
includes data collection (monitoring), assessment (e.g., studies), and implementation of projects and
programs to protect and improve water quality and aquatic habitat. Using monitoring data collected
by NMCWD in recent years (2019 and 2020), the objectives of this study were to assess or “diagnose”
the lakes’ water quality problems, understand the cause or sources of the problems, and recommend
management strategies to improve the water quality and overall health of the lakes.
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
1
Arrowhead Lake, October 2020
IMPROVING
LAKE WATER
QUALITY
REPORT SUMMARY CONTENTS
• Protecting and Enhancing Water
Quality
• Looking at Current Lake Conditions
• Managing to Protect and Improve
Our Lakes
For this study, the primary goals are to achieve the water quality
standards for shallow lakes, attain a diverse, native macrophyte
(aquatic plant) population, and support a healthy, balanced
fishery.
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
2
Lake Management Goals
When assessing the ecological health
of a lake, it is important to take
a holistic approach, considering
factors such as in-lake water quality
(e.g., phosphorus and nitrogen
concentrations), the health and quality
of the aquatic communities, and water
quantity (see Figure 1). How recreation
and wildlife habitat affect and are affected
by overall lake health are also considered.
Numerical goals exist for some of these
factors, such as state water quality standards.
However, other factors are assessed relative to
narrative criteria that describe the desired condition
and do not have strict numerical goals. For this study, the
primary goals are to achieve the water quality standards for
shallow lakes; attain a diverse, native macrophyte (aquatic plant)
population; and support a healthy, balanced aquatic ecosystem.
Indianhead Lake, June 2019
Looking at Current Lake Conditions
Healthy Shallow Lakes
Shallow lakes are unique ecosystems that differ from deeper lakes. Shallow lakes have depths that allow
for light to reach the lake bottom throughout most or all of the lake (often less than 10 feet deep). These
lakes also tend to be more nutrient-rich than other deeper lakes, especially in an urban setting where
they receive nutrients (e.g., phosphorus and nitrogen) from stormwater. A healthy shallow lake will have
abundant aquatic plant growth due to the shallowness and nutrients. However, excess nutrients can lead
to algal growth that creates turbid (murky-looking, low clarity) water and limits or prevents aquatic plant
growth. Aquatic plants are good for shallow lake ecosystems. Healthy shallow lakes have plants growing
throughout the entire lake, with a variety of species such as coontail, native pondweed, and water lily.
The plants can take phosphorus and nitrogen from the lake water, reducing the amount of nutrients
available for algae. Aquatic plants also provide excellent habitat for insects, zooplankton, fish, waterfowl
and other wildlife.
One measure of a lake’s health is the community of plants, fish and aquatic life it sustains. For aquatic
plants, the Minnesota Department of Natural Resources (MNDNR) has developed an index of biological
integrity (IBI), which is a score that compares the types and numbers of plants observed in a lake to
what is expected for a healthy lake. As shown on page 4, the number of plant species in Arrowhead and
Indianhead lakes in recent years are well below the DNR’s threshold of at least 11 species for a healthy
lake. In 2020, only 2–3 species were found in the lakes.
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
3
Arrowhead Lake, August 2019
Arrowhead and Indianhead Lakes are below the MNDNR threshold for healthy
number of plant species in the lakes, indicating a degraded plant community.
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
4
Indianhead Lake Macrophyte Species Richness Compared with
Plant IBI Threshold for Species Richness
Arrowhead Lake Macrophyte Species Richness Compared with
Plant IBI Threshold for Species Richness
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
5
Urban Watersheds
A lake watershed is all the land area that drains
to the lake through overland flow, channels, and
storm pipes. Land use practices within a lake’s
watershed impact the lake and its water quality
by altering the amount of stormwater runoff,
sediment, and nutrients (namely phosphorus and
nitrogen) that reaches the lake. Each type of land
use contributes a different amount of runoff and
pollutants to the lake, thereby impacting the lake’s
water quality differently. Land use within the highly
developed Arrowhead and Indianhead watersheds
is primarily single family residential, highway, open
water, and public open space, with smaller areas of
multi-family residential and churches. Arrowhead
and Indianhead lakes can be particularly sensitive
to land use impacts on stormwater quantity and
quality because both are land-locked with no
surface outlets.
Arrowhead
Lake
Indianhead
Lake
Map showing watersheds for Arrowhead Lake
(shaded purple) and Indianhead Lake
(shaded green).
Arrowhead Lake, June 2019
Sources of Nutrients
Nutrients (phosphorus and nitrogen) are a food source for algae. An overabundance of these nutrients
in a lake can result in nuisance algal blooms and threaten the health of the aquatic plant community.
In Minnesota, phosphorus is most commonly the “limiting nutrient,” although nitrogen can also be
limiting for portions of the growing season. Whether phosphorus or nitrogen is the “limiting nutrient”
this means the available quantity of this nutrient tends to control the amount of algae and aquatic plants
produced. The two primary sources are summarized below:
• Phosphorus and nitrogen in stormwater runoff from the direct watershed—
Stormwater runoff conveys phosphorus and nitrogen from streets, lawns, and
parking lots within the direct watersheds to Arrowhead and Indianhead lakes
via a series of drainage channels and storm drain pipes. This study confirmed
that stormwater runoff is a major contributor of phosphorus and nitrogen to
Arrowhead and Indianhead lakes.
• Nutrient-rich sediment—Phosphorus builds up over time in lake bottom
sediments as a result of sedimentation and die-off of vegetation and algae.
In general, two forms of sediment phosphorus can release back into the
water column when certain environmental conditions are met. When oxygen
levels are low at the lake bottom (typically periodically throughout the
summer), the form of phosphorus called “mobile-P” is released from the
sediment into the water column. “Organic-P” can also release from bottom
sediments, where the release rate is controlled by lake water temperature.
This study confirmed that phosphorus release from lake bottom sediments,
typically termed “internal loading,” is a major contributor of phosphorus to
Arrowhead and Indianhead Lakes.
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
6
Indianhead Lake 2020
Total Phosphorus Sources
Watershed/
Groundwater Inflow
16%
Lake Bottom
Sediment
84%
Arrowhead Lake 2020
Total Phosphorus Sources
Watershed
Inflow
46%
Lake Bottom
Sediment
54%
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
7
Arrowhead Lake Water Quality
Challenges
Review of historic data indicates that water
quality in Arrowhead Lake is poor, with summer
average total phosphorus and chlorophyll-a
concentrations generally above the state
standard for shallow lakes. The poor water
quality is primarily due to excess nutrients
in the lake, which fuels algal growth and
decreases water clarity. The phosphorus in
Arrowhead Lake comes from several sources,
including stormwater runoff from the watershed
and internal sources such as nutrient-rich
sediments. Additionally, the decrease in
the number of plant species as well as the
quantity of plants in the lake since 2014 is likely
contributing to the decrease in water quality.
Summer average total phosphorus concentrations measured in Arrowhead Lake between 2004 and 2020
Arrowhead Lake, September 2020
Too Much Salt
Observed chloride concentrations in Arrowhead Lake in April 2019
were moderately high (185 mg/L). The MPCA chloride standard is 230
mg/L. While chloride occurs naturally in lakes and streams, too much
chloride can be harmful to fish and other aquatic life. The primary
source of chlorides in our lakes and streams is road salt, which is
commonly used in the winter to minimize the amount of ice on our
roadways, parking lots, and sidewalks. With Arrowhead Lake receiving
stormwater runoff from several highways, local roadways, private
parking lots, and an area of developed residential properties, the lake
is especially vulnerable to chloride pollution. NMCWD works to provide training and other resources to
reduce the harmful impacts of chloride on our local waterbodies. For more information about chloride,
visit: www.pca.state.mn.us/water/chloride-salts
Indianhead Lake Water Quality Challenges
Review of historic data indicates that water quality in Indianhead Lake has been declining since 2004,
with summer average total phosphorus above the state standards for shallow lakes in 2019 and 2020
and chlorophyll-a concentrations generally above the state standard for shallow lakes since 2011. The
degradation in water quality is primarily due to excess nutrients in the lake, which fuels algal growth
and decreases water clarity. The phosphorus in Indianhead Lake comes from several sources, including
stormwater runoff from the watershed and internal sources such as nutrient-rich sediments. Additionally,
vegetation management reducing the number of plant species as well as the quantity of plants in the
lake is likely contributing to the decrease in water quality.
Summer average total phosphorus concentrations measured in Indianhead Lake between 2004 and 2020
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
8
Managing to Protect and Improve Our Lakes
Water quality in Arrowhead and Indianhead Lakes has declined in the past decade. The lakes currently
do not meet water quality and ecological health goals and given this, future management efforts should
focus on improving lake water quality and ecosystem health, monitoring for changes, and continuing water
quality and ecosystem health protection measures as improvements are obtained. The recommended
management and protection strategies for Arrowhead and Indianhead Lakes are summarized on the next
page.
Planning-level opinions of probable cost were developed for several new management alternatives
evaluated as part of this study. These opinions of cost are intended to provide assistance in evaluating and
comparing alternatives and should not be considered as absolute values. All estimated costs are presented
in 2021 dollars and include costs for engineering and project administration.
• Arrowhead Lake Bottom Sediment Treatment: $125,000
• Indianhead Lake Bottom Sediment Treatment: $120,000
• Arrowhead and Indianhead Lakes Street Sweeping Program: $250,000
• Arrowhead and Indianhead Lakes Fertilization Optimization Program: $20,000
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
9
Indianhead Lake, August 2019
REPORT SUMMARY Prepared for the
Arrowhead and Indianhead Lakes Water Quality Study Nine Mile Creek Watershed District / August 2022
10
Management/Protection Action Basis Estimated Timeline
Address
Internal Bottom
Sediment
Loading
Continuous dissolved
oxygen monitoring
Determine aeration capacity
of existing system 2022 - 2024
Alum and iron treatment
Reduce bottom sediment
phosphorus load
2023/2024
Modify aeration system,
as needed 2024
Sediment release
monitoring
Assess management
effectiveness 2024 - 2025+
Address External
Nutrient Loading
Enhanced street
sweeping program
Reduce pollutant loading
from stormwater
2022 - 2023 (Planning
begins)
Fertilizer management
program
Reduce nitrogen sources
from excess fertilizer use
2022 - 2023 (Planning
begins)
Chloride monitoring
Continue to identify/track
chloride levels from winter
salt use
As part of continued
lake monitoring
program
Promote NMCWD
cost-share grants to
watershed residents
In a fully developed
watershed, opportunities for
largescale BMPs are limited
2022+
Aquatic Invasive
Species
Curly-leaf pondweed
management
Continue to monitor and
treat curly-leaf pondweed
growth
2022+
Promote
Sustainable
Management
Discontinue copper
sulfate treatments
Evaluate timeline to
discontinue copper sulfate
treatments after internal
loading management
2025
Promote native aquatic
plant growth
Encourage native plants
to promote clear water
conditions and competition
with algae
2022
Discontinue blue dye
applications
Unnecessary addition of
chemicals 2022
REPORT SUMMARY:
Arrowhead and Indianhead Lakes Water Quality Study
Prepared for Nine Mile Creek Watershed District
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xiii
Arrowhead and Indianhead Lakes Water Quality Study
August 2022
Contents
Report Summary .................................................................................................................................................................................... i
1.0 Introduction ............................................................................................................................................................................... 1
1.1 Water Quality Study Approach.................................................................................................. 1
2.0 Shallow Lake Characteristics and Water Quality ......................................................................................................... 3
2.1 Eutrophication ........................................................................................................................... 3
2.2 Nutrients .................................................................................................................................... 5
2.2.1 Stratification Impacts on Internal Phosphorus Loading .............................................................. 5
2.2.2 pH Impacts on Internal Phosphorus Loading .................................................................................. 6
2.2.3 Organism Impacts on Internal Phosphorus Loading .................................................................... 6
2.2.4 Curly-leaf Pondweed Impacts on Internal Phosphorus Loading ............................................. 7
2.2.5 Nitrogen Inputs and Limitations ........................................................................................................... 7
2.3 Climate Change Considerations ................................................................................................ 8
2.3.1 Projected Changes to the Hydrologic Cycle .................................................................................... 8
2.3.2 Projected Changes to Waterbodies (Physical and Chemical).................................................... 9
2.3.3 Projected Changes to Waterbodies (Biological) ............................................................................. 9
3.0 Identification of Goals and Expectations ......................................................................................................................11
3.1 NMCWD Goals for Lake Management .................................................................................... 11
3.1.1 Water Quality Goals .................................................................................................................................11
3.1.2 Other Lake Health Goals ........................................................................................................................12
3.2 NMCWD Adaptive Management Approach ............................................................................ 13
4.0 Lake Basin and Watershed Characteristics ..................................................................................................................14
4.1 Arrowhead Lake Basin Characteristics .................................................................................... 14
4.2 Arrowhead Lake Watershed Characteristics ........................................................................... 17
4.2.1 Land Use .......................................................................................................................................................17
4.3 Indianhead Lake Basin Characteristics .................................................................................... 20
4.4 Indianhead Lake Watershed Characteristics ........................................................................... 22
4.4.1 Land Use .......................................................................................................................................................22
5.0 Existing Water Quality and Ecological Health ............................................................................................................25
5.1 Water Quality .......................................................................................................................... 25
5.1.1 Eutrophication Parameters - Phosphorus, Chlorophyll-a, and Clarity .................................25
5.1.2 Nitrogen .......................................................................................................................................................29
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xiv
5.1.3 Chlorides ......................................................................................................................................................30
5.1.4 Dissolved Oxygen & Aeration..............................................................................................................30
5.2 Sediment Quality ..................................................................................................................... 32
5.3 Aquatic Communities .............................................................................................................. 33
5.3.1 Aquatic Plants.............................................................................................................................................33
5.3.2 Phytoplankton ............................................................................................................................................37
5.3.3 Zooplankton ...............................................................................................................................................42
5.3.4 Fish ..................................................................................................................................................................44
5.4 Water Levels ............................................................................................................................ 45
6.0 Water Quality Modeling ......................................................................................................................................................47
6.1 P8 Model Runoff and Phosphorus Loading ............................................................................. 47
6.1.1 P8 Model Updates ....................................................................................................................................48
6.2 Water Balance Calibration....................................................................................................... 48
6.2.1 Precipitation and Runoff ........................................................................................................................48
6.2.2 Stormwater Volume Calibration (Water Balance) ........................................................................48
6.3 In-Lake Modeling ..................................................................................................................... 50
6.3.1 In-Lake Water Quality Model Calibration .......................................................................................51
6.3.2 In-Lake Water Quality (Phosphorus) Model Calibration Loading Summaries ..................54
6.3.3 In-Lake Water Quality Additional Observations ...........................................................................54
7.0 Public Engagement ...............................................................................................................................................................60
7.1 Public Stakeholder Meetings ................................................................................................... 60
7.1.1 Public Engagement Meeting #1- May 25, 2021 ...........................................................................60
7.1.2 Public Engagement Meeting #2 – April 19, 2022 ........................................................................60
7.2 Resident Survey ....................................................................................................................... 60
8.0 Conclusions and Recommendations ..............................................................................................................................62
8.1 Conclusions .............................................................................................................................. 62
8.2 Recommendations .................................................................................................................. 64
8.2.1 Reduce Phosphorus Loading from Lake Bottom Sediment (Internal Loading) ...............64
8.2.2 Reduce Pollutant Loading from Stormwater Runoff ..................................................................67
8.2.3 Continue to Monitor Growth and Impacts from Curly-leaf Pondweed ..............................70
8.2.4 Determine Timeline to Discontinue Copper Sulfate Treatments ...........................................70
8.2.5 Encourage Residents to Promote Healthy Aquatic and Shoreline Plant Growth ............71
8.2.6 Encourage Residents to Discontinue Lake Dye Applications ..................................................71
8.2.7 Encourage Residents to Apply for NMCWD Cost-Share Grants ............................................72
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xv
9.0 Cost – Benefit Analysis .........................................................................................................................................................73
9.1 Opinion of Probable Cost ........................................................................................................ 73
9.1.1 Cost Details .................................................................................................................................................73
9.2 Cost Benefit Analysis ............................................................................................................... 75
10.0 References ...............................................................................................................................................................................78
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xvi
List of Tables
Table 3-1 NMCWD water quality goals for shallow lakes ........................................................................................ 12
Table 3-2 NMCWD holistic lake health assessment evaluation factors .............................................................. 13
Table 4-1 Stage-storage-discharge relationships for Arrowhead Lake............................................................... 15
Table 4-2 Land use classifications in the Arrowhead Lake watershed ................................................................. 17
Table 4-3 Stage-storage-discharge relationships for Indianhead Lake .............................................................. 20
Table 4-4 Land use classifications in the Indianhead Lake watershed ................................................................ 22
Table 6-1 Modeled total precipitation for the 2020 Growing Season (May 1 through Sept. 30) ............. 48
Table 8-1 Growing season estimated pounds of phosphorus removed through management of internal loading from lake bottom sediments .......................................................................................... 66
Table 8-2 Summer average total phosphorus and chlorophyll-a concentrations with management of internal loading from bottom sediments ................................................................................................... 67
Table 9-1 Planning-level cost estimates for evaluated management alternatives ......................................... 73
Table 9-2 Cost-benefit summaries for Arrowhead and Indianhead evaluated management alternatives .............................................................................................................................................................. 77
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xvii
List of Figures
Figure 2-1 Depiction of shallow lake states ........................................................................................................................ 4
Figure 2-2 Generalized thermal lake stratification diagram ......................................................................................... 6
Figure 3-1 NMCWD Holistic Lake Health Assessment Factors (NMCWD, 2017, amended 2019) ............. 11
Figure 4-1 Arrowhead Lake Bathymetry ............................................................................................................................ 16
Figure 4-2 Arrowhead Lake Subwatersheds & Stormwater Conveyance ............................................................ 18
Figure 4-3 Land Use, Arrowhead Lake Watershed ........................................................................................................ 19
Figure 4-4 Indianhead Lake Bathymetry ........................................................................................................................... 21
Figure 4-5 Indianhead Lake Subwatersheds & Stormwater Conveyance ............................................................ 23
Figure 4-6 Land Use, Indianhead Lake Watershed ........................................................................................................ 24
Figure 5-1 Total phosphorus, chlorophyll-a, and Secchi disk transparency from 2004 through 2020 in Arrowhead Lake. The black “x” indicates the summer average (June through September). .. 27
Figure 5-2 Total phosphorus, chlorophyll-a, and Secchi disk transparency from 2004 through 2020 in Indianhead Lake. The black “x” indicates the summer-average (June through September). . 28
Figure 5-3 Total Kjehdahl Nitrogen 2019 through 2020 in Arrowhead Lake. The black “x” indicates the summer-average (June through September). ................................................................................... 29
Figure 5-4 Total Kjehdahl Nitrogen 2019 through 2020 in Indianhead Lake. The black “x” indicates the summer-average (June through September). ................................................................................... 29
Figure 5-5 Arrowhead Lake dissolved oxygen concentrations near the aerators (east end) ....................... 31
Figure 5-6 Arrowhead Lake dissolved oxygen concentrations away from aerators (west end) .................. 31
Figure 5-7 Arrowhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Species Richness ................................................................................................................................................... 35
Figure 5-8 Arrowhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Floristic Quality Index (FQI) .............................................................................................................................. 35
Figure 5-9 Indianhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Species Richness ................................................................................................................................................... 36
Figure 5-10 Indianhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Floristic Quality Index (FQI) .............................................................................................................................. 36
Figure 5-11 Top, Arrowhead Lake 2004-2020 summer average phytoplankton numbers and bottom, microscopic pictures of phytoplankton species, from left to right, Chlamydomonas globosa (green algae) Dolichospermum affine (blue-green algae), Fragilaria crotonensis (diatom), and Cryptomonas erosa (cryptomonad).................................................................................. 40
Figure 5-12 Arrowhead Lake blue-green algae data compared with the World Health Organization’s Thresholds for Adverse Health Effects Guidelines................................................................................... 40
Figure 5-13 Top, Indianhead Lake 2004-2020 summer average phytoplankton numbers and bottom, microscopic pictures of phytoplankton species, from left to right, Chlamydomonas globosa (green algae) Dolichospermum affine (blue-green algae), Fragilaria crotonensis (diatom), and Cryptomonas erosa (cryptomonad).................................................................................. 41
Figure 5-14 Indianhead Lake blue-green algae data compared with the World Health Organization’s Risk of Adverse Health Effects Guidelines .................................................................................................. 41
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xviii
Figure 5-15 A) Arrowhead Lake 2004-2020 zooplankton numbers, B) Indianhead Lake 2004 – 2020 zooplankton numbers, and C) microscopic pictures of zooplankton species, from left to right, Bosmina longirostris. (cladoceran), Ceriodaphnia sp. (cladoceran), Diaptomus sp. (copepod), and Keratella cochlearis (rotifer). ............................................................................................ 43
Figure 5-16 Zooplankton abundance and community changes in Indianhead Lake compared to timing of algal copper sulfate treatment in 2020 .................................................................................................. 44
Figure 5-17 Observed Water Surface Elevations on Arrowhead Lake ..................................................................... 46
Figure 5-18 Observed Water Surface Elevations on Indianhead Lake ..................................................................... 46
Figure 6-1 Arrowhead Lake (2020) Water Balance ........................................................................................................ 49
Figure 6-2 Indianhead Lake (2020) Water Balance ....................................................................................................... 49
Figure 6-3 Arrowhead Lake and Indianhead Lake water balance summaries .................................................... 50
Figure 6-4 Arrowhead Lake In-Lake Total Phosphorus Calibration ........................................................................ 52
Figure 6-5 Arrowhead Lake In-Lake Total Kjeldahl Nitrogen Calibration ............................................................ 52
Figure 6-6 Indianhead Lake In-Lake Total Phosphorus Calibration ....................................................................... 53
Figure 6-7 Indianhead Lake In-Lake Total Kjeldahl Nitrogen Calibration ............................................................ 53
Figure 6-8 2020 Total Phosphorus Loading Summaries (Watershed and Internal Loading from Lake Bottom Sediment) from Arrowhead and Indianhead Lakes In-Lake Calibration Models ........ 54
Figure 6-9 Indianhead Lake Chlorophyll-a calibration impacted by copper sulfate ....................................... 55
Figure 6-10 Impact of copper sulfate on Indianhead Lake total phosphorus calibration ............................... 55
Figure 6-11 Impact of copper sulfate on Indianhead Lake total nitrogen concentrations ............................. 56
Figure 6-12 Phytoplankton Growth Limitation in Arrowhead Lake in 2020 .......................................................... 58
Figure 6-13 Phytoplankton Growth Limitation in Indianhead Lake in 2020 .......................................................... 58
Figure 8-1 Summer average total phosphorus and chlorophyll-a concentrations and Secchi disk depth measured in Arrowhead Lake between 2004 and 2020 .......................................................... 63
Figure 8-2 Summer average total phosphorus and chlorophyll-a concentrations and Secchi disk depth measured in Indianhead Lake between 2004 and 2020 .......................................................... 64
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xix
List of Appendices
Appendix A Aquatic Plant Surveys
Appendix B Fisheries Assessment (2021)
Appendix C In-Lake Water Quality Calibration Plots
Appendix D Arrowhead Lake and Indianhead Lake Public Survey
Appendix E In-Lake Water Quality Proposed Best Management Plots
Appendix F Opinions of Probable Costs
P:\Mpls\23 MN\27\2327634\WorkFiles\Indianhead Lake\2021 Arrowhead_Indianhead UAA\Workfiles\Report\_FINAL Report Submittal\Arrowhead_Indianhead_UAAUpdate_2021_FINAL.docx xx
Acronyms
Acronym Description
AIS Aquatic Invasive Species
AACE Association for the Advancement of Cost Engineering
BMP Best Management Practice
FQI Floristic Quality Index
IBI Index of Biological Integrity
MCES Metropolitan Council of Environmental Services
MNDNR Minnesota Department of Natural Resources
MPCA Minnesota Pollution Control Agency
NGVD29 National Geodetic Vertical Datum of 1929
NMCWD Nine Mile Creek Watershed District
NOAA National Oceanic and Atmospheric Administration
N-P-K Nitrogen-Phosphorus-Potassium
P8 Program for Predicting Polluting Particle Passage through Pits, Puddles and Ponds
TKN Total Kjeldahl Nitrogen
TP Total Phosphorus
WHO World Health Organization
UAA Use Attainability Analysis
1
1.0 Introduction
This report describes the results of the water quality study for Arrowhead and Indianhead Lakes in Edina,
Minnesota. The study represents a scientific assessment of the physical, chemical, and biological
conditions of these lakes, and includes both a water quality assessment and a prescription of protective
and/or remedial measures for Arrowhead and Indianhead Lakes and the lakes’ tributary watersheds. The
work presented in this report provides an update of analyses that were previously completed for a water
quality study developed by Nine Mile Creek Watershed District (NMCWD) for Arrowhead and Indianhead
Lakes in 2006 (Barr Engineering Co., 2006).
The conclusions and recommendations presented in this report are based on historical water quality data,
a fisheries survey conducted in 2021, several years of aquatic plant surveys, and the results of intensive
lake water quality monitoring in 2020. Lake water quality and ecological models were developed and
calibrated to the 2020 dataset to gain a better understanding of the relative and absolute effect of various
nutrient (e.g., nitrogen and phosphorus) sources on lake water quality.
1.1 Water Quality Study Approach
The Nine Mile Creek Watershed District (NMCWD) has historically used a process referred to as a Use
Attainability Analysis (UAA) to assess the water quality condition of its lakes relative to the desired
beneficial uses that can be reasonably achieved and maintained with implementation of management
recommendations. The objective of a UAA is to provide a scientific foundation for a lake-specific
management plan that will permit maintenance of, or attainment of, the intended beneficial uses of a
waterbody. The UAA process addresses a wide range of goals (e.g., water quantity, aquatic communities,
recreational use, and wildlife), with the primary focus being achievement of water quality goals.
As part of the Nine Mile Creek Watershed District Water Management Plan (Plan) adopted in 2017 and
amended in 2018 and 2019 (NMCWD, 2017, amended 2019), the NMCWD adopted the Minnesota
eutrophication standards. In addition, the NMCWD expanded its emphasis on the role of ecological
indicators (aquatic plants, phytoplankton, fish, etc.) in overall lake health, as well as the feedback
mechanisms between these indicators. A properly functioning ecosystem supports the attainment of good
water quality.
While the UAA terminology is not included in the title of this water quality study, a similar analysis process
was employed, utilizing observed data, watershed modeling and in-lake modeling to understand and
diagnose lake health issues and evaluate protective or remedial management activities. The water quality
study utilized a watershed runoff model and an in-lake water quality and ecological model to quantify
pollutants from various sources and to quantify the benefits of management efforts. The in-lake water
quality model predicts changes in lake water quality based on the results of the watershed runoff model
(external inputs) as well as internal processes such as sediment phosphorus release due to anoxia,
submerged vegetation death and decay, phytoplankton growth and decay, and nutrient settling to lake
sediments. Using these models, various watershed and lake management strategies can be evaluated to
determine their likely effects on lake water quality. The resulting lake water quality can then be compared
2
with the water quality goals to see if the management strategies are able to produce the desired changes
in the lake. Using the modeling tools, the cost-effectiveness of the management strategies can also be
evaluated.
3
2.0 Shallow Lake Characteristics and Water Quality
Shallow lakes are unique ecosystems that differ from deeper lakes. Shallow lakes are lakes that generally
have well mixed water columns throughout most of the year and have depths that potentially allow for
light penetration to reach most of the lake bottom. Shallow lakes can support macrophyte growth across
the entire lake surface when lake clarity is reasonably high. Shallow lakes classically exist in two states:
(1) clear water with extensive coverage of submerged and emergent macrophytes and low phytoplankton
(algae) abundance; and (2) turbid water where phytoplankton dominate and macrophyte coverage is
limited due to phytoplankton shading. The concentration of nutrients entering the shallow water system
(from stormwater or from lake bottom sediments), fishery balance and composition, the presence or
absence of invasive species (such as curly-leaf pondweed, carp, and goldfish), and dissolved oxygen
concentrations are primary drivers that determine the state of shallow lakes (Figure 2-1).
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.
2.1 Eutrophication
Eutrophication, or lake degradation, is the accumulation of sediments and nutrients in lakes. As a lake
naturally becomes more fertile, biological production enhances and sediment inflow accumulates filling
the lake’s basin. Over a period of hundreds to thousands of years, a lake can successively become 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 processes and is caused by human activities. Nutrient and sediment inputs from stormwater
runoff can far exceed the natural inputs to a lake. Nutrient enrichment in lakes often intensifies algal
blooms. Enhanced sediment loadings can attenuate light and reduce lake transparency, which can limit
macrophyte growth. Since macrophytes assist in creating a stable water state (e.g., improved clarity,
reduced sediment resuspension, improved habitat for aquatic organisms), especially in shallow lakes, high
suspended sediment and enhanced nutrients can often lead to impaired water quality.
Clear Water Turbid Water
2
3 4 2
3 4 2
3 4
1 1 1
Shoreline BufferShoreline BufferShoreline Buffer
2
3
4
1 Good fishery balance
Numerous and diverse native plants in the lake and within shoreline buffers; low invasive species present
Algae blooms rare
Diverse prey options and healthy habitat for birds
Less balanced fishery, more rough fish (e.g., carp)
Less diverse native plants in the lake and within shoreline buffers; invasive species present
Algae blooms moderate
Less prey options and habitat for birds
Fishery not balanced, mostly rough fish, winter fish kills
Low diversity and quantity of native plants in the lake and within shoreline buffers; invasive species present
Algae blooms dominant, blue-green algae possible
Limited prey options and habitat for birds
2
3
4
1
2
3
4
1
Figure 2-1 Depiction of shallow lake states
5
2.2 Nutrients
Biological production in an aquatic ecosystem is limited by the concentrations of essential nutrients. The
“limiting nutrient” concept is a widely applied principle in ecology and in the study of eutrophication. It is
based on the idea that phytoplankton and plants require many nutrients to grow, but the nutrient with
the lowest availability, relative to the amount needed by the phytoplankton or plant, will limit growth. It
follows then, that identifying the limiting nutrient will point the way to controlling aquatic plant and algal
growth. Nitrogen (N) and phosphorus (P) are generally the two growth-limiting macronutrients in most
natural waters. Thus, efforts to improve water quality typically focus on reducing the growth-limiting
nutrient concentration in the waterbody; however, it is often difficult to identify and control all the
nutrient loadings to a specific waterbody.
Two primary sources, external and internal loads, are responsible for elevated nutrient concentrations in
lakes. Nutrients that enter lakes through watershed runoff, groundwater inputs, or atmospheric deposition
are considered external loads. As urbanization has occurred, more areas of impermeable surfaces have
been developed causing increased stormwater runoff and pollutant transport during storm and spring
thaw events. In urbanized areas, stormwater runoff typically flows through storm sewer systems to the
downstream waterbody, which generally results in faster velocities than natural channel flow and can
result in higher suspended loadings. Implementation of the NMCWD’s stormwater management rules for
new development and redevelopment and efforts to install retrofit best management practices (BMPs) are
helping to reduce external loads to nearby waterbodies. However, for many shallow lakes, internal load
reduction measures (e.g., alum treatment, aquatic plant management, fish management) are also required
to meet water quality goals.
Once external nutrient loads enter a lake, over time, the nutrients accumulate in the sediment through the
settling of particulates and through organism decay. Natural lake processes such as sediment
resuspension, chemical dissolution, or microbial reduction can reintroduce these nutrients to the overlying
water body resulting in internal loading. This is specifically common for phosphorus, which can be found
bound to the sediment under oxidized conditions. The binding of phosphorus to iron in sediments allows
the sediment to act as a sink or source depending on the lake’s physical and chemical conditions.
Therefore, understanding the chemical and physical conditions and the timing of these conditions will be
important considerations when developing an internal loading management plan.
2.2.1 Stratification Impacts on Internal Phosphorus Loading
Lake stratification, the separating of an upper, well mixed warm layer (epilimnion) from a cool, bottom
layer (hypolimnion) (Figure 2-2), can lead to low oxygen concentrations in lake bottom waters and trigger
internal phosphorus loading. For shallow lakes like Arrowhead and Indianhead Lakes, stratification is
typically irregular and can happen on a daily, weekly, or longer timescale. Mixing likely occurs regularly in
Arrowhead and Indianhead Lakes and phosphorus released from sediments is then made available to
phytoplankton during these frequent mixing events.
6
Figure 2-2 Generalized thermal lake stratification diagram
2.2.2 pH Impacts on Internal Phosphorus Loading
The pH of the water column can also play a vital role in affecting the phosphorus release rate under
conditions when oxygen is present in the water column (oxic conditions). Photosynthesis by macrophytes
(aquatic plants) 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 phosphorus release at elevated pH
(pH > 8.2) is thought to occur through replacement of the phosphate ion (PO4-3) with the excess hydroxyl
ion (OH-) on the oxidized iron compound (James, Barko, & Eakin, 2001). Large increases in pH are often
the consequence of phytoplankton blooms (e.g., cyanobacteria harmful algal blooms).
2.2.3 Organism Impacts on Internal Phosphorus Loading
Benthivorous, rough 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 (bottom-feeding) fish can also cause resuspension of
sediments in shallow ponds and lakes, transporting phosphorus from sediment into the water column,
causing reduced water clarity and poor aquatic plant growth, as well as high phosphorus concentrations
(Cooke, Welch, Peterson, & Newroth, 1993). In some cases, the water quality impairment caused by
benthivorous fish can negate the positive effects of BMPs and lake restoration.
The critical difference between biological (e.g., benthivorous fish feeding) and physical (e.g., wind and
waves) sediment resuspension is the area and the frequency to which these components can induce
impacts. The volume of sediment impacted by physical resuspension is largely influenced by the geometry
of the lake (e.g., size, fetch, bathymetry) and wind events (e.g., direction, velocity). For example, a wind
event may develop wave induced sediment resuspension along a portion of the shoreline. However,
biological resuspension from feeding or mating activities of fish can occur over a much larger area and is
7
impacted by the number of organisms in the aquatic ecosystem. Additionally, while physical resuspension
occurs in a periodic, episodic-based fashion, benthivorous fish resuspension can be more continuous.
2.2.4 Curly-leaf Pondweed Impacts on Internal Phosphorus Loading
Another potential source of internal phosphorus loading is the growth and die-off of curly-leaf
pondweed. Curly-leaf pondweed is an invasive (i.e., non-native) aquatic plant that is common in many
Twin Cities metropolitan area lakes. Curly-leaf pondweed grows under the ice during the winter and gets
an early start in the spring, crowding out native species. It releases a small reproductive pod that
resembles a small pinecone in late-June, and then begins its die-back in late-June and early-July. The
biomass sinks to the bottom of the lake and begins to decay, releasing nutrients into the water column
and causing oxygen depletion, exacerbating the internal sediment release of phosphorus. This cycle can
result in an increase in nutrient concentrations in the lake in late-June or early-July in lakes with a higher
percentage of invasive growth.
2.2.5 Nitrogen Inputs and Limitations
Nitrogen is a nutrient required for phytoplankton growth and hence nitrogen management also needs to
be considered as an important component of lake management. Increases in nitrogen concentrations in
lakes can be attributed to a combination of factors in the watershed, including increased fertilizer
application rates and frequency, increased impervious surface areas, expansion of storm sewer systems,
and loss of riparian wetlands. Land use changes and increased nitrogen loading can result in a decreased
natural capacity for nitrogen uptake and assimilation by plants and decreased cycling back to the
atmosphere as nitrogen gas (N2) through natural nitrification and denitrification processes. Thus, this can
result in high nitrogen concentrations in open water systems.
For the last couple of decades, phosphorus reduction has generally been the primary focus for lake
management in Minnesota based on the premise that phosphorus limitation is dominant in freshwater
lakes (e.g., reducing phosphorus inputs alone will limit primary productivity and algal bloom growth).
While phosphorus management has been successful or partially successful in a number of lake
management projects, recent research is showing that nitrogen limitation or dual nitrogen-phosphorus
limitation may be more significant than initially anticipated (Paerl et. al, 2016). This is particularly true for
shallow lakes. The nutrient that limits phytoplankton/algal growth can vary geographically, but limitation
can also vary seasonally in a single lake. Some lakes have been shown to display phosphorus limitation in
the spring but switch to nitrogen limitation in the summer and fall. Furthermore, an additional benefit of
managing nitrogen in upstream ecosystems is that this reduces some of the burden in vulnerable
ecosystems further downstream that are nitrogen limited (e.g., Gulf of Mexico). Given that recent research
is showing higher evidence of dual nitrogen-phosphorus limitation in freshwater lakes, there is a benefit
for determining whether source control programs that target both phosphorus and nitrogen will provide
greater ecosystem benefits.
8
2.3 Climate Change Considerations
Considerable studies have been devoted to predicting the impacts of a warming climate on the
hydrologic cycle. Of particular concern are the changes to atmospheric moisture content, evaporation,
precipitation intensity, and the possibility of increased risk for drought and flooding extremes (Trenberth,
1999; Trenberth, Smith, Qian, Dai, & Fasullo, 2003; Giorgi, et al., 2011; Trenberth, 2011).
Alterations to the hydrologic cycle will consequently impact freshwater ecosystems. Observational records
and climate model projections show evidence of freshwater vulnerability to a warming climate (Dokulil &
Teubner, Eutrophication and climate change: Present situation and future scenarios, 2011). Freshwater
characteristics such as lake stratification and mixing, ice coverage, and river flow could see discernable
changes by the end of the 21st century (Dokulil & Teubner, 2011; Dokulil, 2013). Increases in nutrient
loadings and water temperatures, changes to water levels, and amplified eutrophication could impact
aquatic organisms and influence biodiversity.
2.3.1 Projected Changes to the Hydrologic Cycle
Larger concentrations of greenhouse gases in the atmosphere, such as carbon dioxide and methane,
create an increased downwelling of longwave radiation to the earth’s surface (Trenberth, 1999). This
enhanced downwelling not only escalates surface temperature warming, but also induces changes to the
atmospheric moisture content and evaporation. Higher atmospheric temperatures allow for an expanded
water holding-capacity of the atmosphere and enhanced radiation causes elevated rates of evaporation.
This results in increases to the atmospheric moisture content, which, consequently, will impact
precipitation (Trenberth, 1999; Trenberth, Smith, Qian, Dai, & Fasullo, 2003; Kharin, Zwiers, Zhang, &
Wehner, 2013).
While changes to precipitation amounts and intensity are expected on a global scale, the changes will be
geographically disproportionate. According to the National Oceanic and Atmospheric Administration’s
(NOAA’s) 2013 assessment of climate trends for the Midwest (NOAA, 2013), upward trends in annual and
summer precipitation amounts have been observed. The frequency of higher intensity storms has also
been noted. Specifically in Minnesota, climatologists have identified four significant climate trends
(MNDNR, 2017):
• Increasing annual precipitation
• Increasing frequency and size of extreme rainfall events
• Increasing temperatures, with winter temperatures warming the fastest
• Decline in severity and frequency of extreme cold weather
Overall, the changes to precipitation induced by atmospheric warming pose difficult challenges. The shift
to more frequent, high intensity precipitation events in Minnesota indicates a risk for extreme flood
events. Higher intensity precipitation events typically produce more runoff than lower intensity events
with similar amounts of precipitation because higher intensity rainfall can overwhelm the capacity of the
land surface to infiltrate and attenuate runoff.
9
Not only do these hydrologic changes pose challenges for agriculture, infrastructure, and human safety;
but also has the potential to induce changes to aquatic environments. The subsequent section describes
the anticipated impacts to aquatic ecosystems if atmospheric warming trends continue.
2.3.2 Projected Changes to Waterbodies (Physical and Chemical)
In freshwater lakes, one of the most important atmospheric variables influencing the lake’s physical and
chemical parameters is temperature. Due to enhanced air temperatures and the projected increasing
trends, lake water temperature and the number of ice-free days are projected to change in most inland
waters globally. Increases in lake temperature will affect mixing regimes, the length and depth of summer
stratification in deep lakes, and the oxygen concentration in the hypolimnion (Dokulil, 2013; Dokulil, 2014;
Dokulil, 2016), as well as phytoplankton growth rates, and phosphorus cycling (e.g., release of phosphorus
from bottom sediments). As water temperature rises, lake stability enhances, which results in longer
thermal stratification and shorter mixing periods (Dokulil, 2013). Resistance to mixing, particularly in deep
lakes, between the nutrient rich hypolimnion and nutrient poor epilimnion across the thermocline
increases considerably at temperature gradients of only a few degrees Fahrenheit (Sahoo, et al., 2016).
Prolonged lake stability and a lower thermocline may enhance the risk of oxygen depletion in the
hypolimnion (Jeppesen, et al., 2009; Sahoo, et al., 2016). Anoxic conditions in the hypolimnion can cause
nutrient release from the sediments, which raises the potential for algal blooms. Additionally, overall
oxygen concentrations in the lake can be reduced as solubility decreases when the water temperature
warms, which can impact fishery balance (Dokulil & Teubner, 2011).
In mid-latitudes where precipitation is likely to increase, with the heighted chance for extreme events,
other concerns are warranted. Intense rainfalls resulting in flooding could raise the loading of suspended
sediments associated with larger areas experiencing soil erosion (Dokulil & Teubner, 2011; Dokulil, 2016).
The combination of longer dry periods and extreme precipitation events could create episodic and intense
pulse flows affecting aquatic habitats, bank stability, and species (Dokulil, 2016). Additionally, the increase
in the number of extreme, high intensity rain events is likely to increase the runoff driven phosphorus
transfers from the land to the water (Jeppesen, et al., 2009).
2.3.3 Projected Changes to Waterbodies (Biological)
The potential for increased erosion and nutrient inputs from large runoff rates combined with higher
water temperatures and prolonged lake stratification in summer could lead to widespread, climate-related
eutrophication based on the results of existing studies (Dokulil & Teubner, 2011; Dokulil, 2013). Nutrient
enrichment, whether through external or internal loading, stimulates the development of phytoplankton
biomass. This resulting surface biomass absorbs light, can shade out benthic algae or macrophytes, and
can produce negative lake aesthetics (Dokulil & Teubner, 2011). Unfortunately, not only has previous
research projected larger biomasses of phytoplankton in a warmer climate, but research also predicts that
a higher proportion of these phytoplankton biomasses will consist of potentially toxic cyanobacteria
assemblages (Jeppesen, et al., 2009; Dokulil & Teubner, 2011; Jeppesen, et al., 2014; Dokulil, 2016).
Multiple regression analyses on data from 250 Danish lakes sampled during the month of August
indicated higher dominance of cyanobacteria with a warming climate. Studies during heat waves in the
10
northern hemisphere also showed that higher percentages of cyanobacteria correlated with rises in
temperature (Huisman, Matthijs, & Visser, 2005).
Changes in the seasonal pattern and dynamics of freshwater productivity could also be a consequence of
a changing climate. With the earlier onset of warmer air temperatures in the spring, the timing of the
phytoplankton peak is likely to shift forward. If the phytoplankton blooms contain a larger percentage of
cyanobacteria species or if the timing of algal production falls out of synchrony with the food demands of
zooplankton and fish, then upper levels of the food chain could be negatively impacted (Dokulil, 2016).
Enhanced phytoplankton biomasses can also induce thermal feedback mechanisms for lakes. A large area
of phytoplankton biomass can result in greater surface temperatures and stronger stratification (Dokulil,
2013). Additionally, increased light attenuation at the surface will reduce light availability at the lake
bottom influencing macrophyte growth (Jeppesen, et al., 2014).
This water quality study did not directly assess potential impacts to lake responses due to a changing
climate. However, any current and/or future management efforts for waterbodies will be affected by
changing climate conditions. Continued monitoring of lake conditions will be important as management
efforts are implemented and as changing climate conditions progress. Long-term studies of waterbodies
will be essential to create the most effective plans to overcome climate-induced impacts.
11
3.0 Identification of Goals and Expectations
3.1 NMCWD Goals for Lake Management
The NMCWD’s approach to evaluating and improving lake health includes numerous health assessment
factors, as illustrated in Figure 3-1. The primary factors identified as affecting lake ecological health
include chemical water quality (e.g., nutrient concentrations), aquatic communities, and water quantity
(groundwater and surface water). The effects of recreation and wildlife habitat on overall lake health are
also considered.
Figure 3-1 NMCWD Holistic Lake Health Assessment Factors (NMCWD, 2017, amended 2019)
3.1.1 Water Quality Goals
One of the primary goals of the NMCWD is to “ensure the water quality of the lakes and streams of the
NMCWD is protected and enhanced.” In 1996, the NMCWD established lake water quality management
goals based on designated uses for a waterbody (i.e., full-contact recreational activities such as swimming;
non-full body contact recreational activities such as boating, canoeing, or water skiing; fishing and
aesthetic viewing; runoff management). In 2008, the Minnesota Pollution Control Agency (MPCA) adopted
eutrophication water quality standards for Minnesota lakes, which vary by ecoregion and include criteria
for both shallow and deep lakes. The MPCA defines “shallow” lakes as having a maximum depth of 15 feet
12
or less or having at least 80% of the lake area shallow enough to support aquatic plants (referred to as
“littoral area”).
In their 2017 Plan, the NMCWD adopted the state’s lake eutrophication standards as their lake water
quality goals, as well as the state water quality standards for Escherichia coli and chloride. The water
quality goals for shallow lakes (including Arrowhead and Indianhead Lake) are presented in Table 3-1.
Table 3-1 NMCWD water quality goals for shallow lakes
Water Quality Parameter Water Quality Standard for Shallow Lakes1, 2
Total Phosphorus (summer average, μg/L) 60
Chlorophyll-a (summer average, μg/L) 20
Secchi Disk Transparency (summer average, m) 1.0
Total Suspended Solids (mg/L) NA
Daily Dissolved Oxygen Flux (mg/L) NA
Biological Oxygen Demand (5 day) (mg/L) NA
Escherichia coli (# per 100 mL) 126 3
Chloride (mg/L) 2304
1 NMCWD goals are based on MPCA standards included in MN Rules 7050. Revisions to MN Rules 7050 will supersede NMCWD standards. Note that MN Rule 7050.0220 includes standards for additional parameters that are enforced by the MPCA. 2 Shallow lakes have a maximum depth less than 15 feet or littoral area greater than 80% of the total lake surface area. 3 126 organisms per 100 mL as a geometric mean of not less than five samples within any month, nor shall more than 10% of all samples within a month exceed 1,260 organisms per 100 mL. 4 The MPCA has established a chronic exposure chloride standard of 230 mg/L or less and considers two or more exceedances of the chronic standard in three years to be an impairment.
3.1.2 Other Lake Health Goals
In addition to the water quality goals presented in Table 3-1, the NMCWD’s 2017 Plan expresses the
desire to establish holistic lake health targets for NMCWD-managed lakes. The holistic lake health targets
consider a wide range of factors, with an increased emphasis on the role of ecological factors in overall
lake health and the interrelated nature of these factors.
Table 3-2 lists the evaluation factors used by the NMCWD to holistically assess lake health. Numerical
goals exist for some of the factors presented in this table (e.g., MPCA water quality standards), while other
holistic health factors are assessed qualitatively by comparing to narrative criteria. The NMCWD
collaborates with stakeholders and regulatory agencies (e.g., MPCA, Minnesota Department of Natural
Resources (MNDNR)) to develop lake-specific numerical goals for ecological indicators where appropriate.
13
Table 3-2 NMCWD holistic lake health assessment evaluation factors
Lake Health Assessment Factors Evaluation Factors
Chemical Water Quality
• Nutrients
• Sediment
• Clarity
• Chlorophyll-a
• Chloride
Aquatic Communities
• Aquatic Plant IBI1- species richness and floristic quality
• Invasive Species Presence
• Phytoplankton Populations
• Cyanobacteria/Blue-green Algae Presence
• Zooplankton Populations
Water Quantity • Water Levels
• Water Level Bounce
• Groundwater Levels
Recreation
• Shore Access
• Navigation Potential
• Aesthetics
• Use Metrics
Wildlife • Upland biodiversity
• Buffer extent/width
1 Lake plant eutrophication Index of Biotic Integrity (IBI) methodology developed by the MNDNR and MPCA
3.2 NMCWD Adaptive Management Approach
The NMCWD implements an adaptive management approach to improve lake health based on water
quality and assessment of the other holistic lake health factors. While striving to achieve the state
standards for shallow lakes, the NMCWD recognizes that achieving the water quality goals may not be
feasible for some lakes or may require a timeframe that extends several decades. For these situations, the
NMCWD’s objective is to make reasonable and measurable progress towards meeting the water quality
goals and other holistic lake health targets.
The NMCWD reviews lake monitoring data annually to assess progress toward lake management goals.
For lakes that are meeting the goals, the NMCWD continues periodic monitoring to track variations in
water quality and potential trends. If water quality declines or if water quality does not meet NMCWD
goals, a lake-specific water quality study is conducted (or updated) to identify additional protection and
improvement measures, as is being completed in this report for Arrowhead and Indianhead Lakes.
14
4.0 Lake Basin and Watershed Characteristics
The following sections describe the unique characteristics of the Arrowhead and Indianhead Lakes and
watersheds. Both lakes are located in the southwestern portion of the City of Edina, south of Highway 62
and east of Highway 169.
4.1 Arrowhead Lake Basin Characteristics
Arrowhead Lake has a water surface area of approximately 22 acres, a maximum depth of approximately
8 feet, and a mean depth of 3.2 feet at a 10-year average water surface elevation of 874.8 (NGVD29). At
this elevation the lake volume is approximately 83 acre-feet (Figure 4-1). Arrowhead Lake is land-locked
with no surface outlets. Thus, the water level in the lake depends on weather conditions (snowmelt,
rainfall, evaporation) and groundwater flow. The stage-storage relationship that was used in this study for
Arrowhead Lake is shown in Table 4-1 and was based on bathymetric measurements completed by the
City of Edina in 2017 and LiDAR collected in 2011 by the MNDNR. The approximate natural overflow
elevation from Arrowhead Lake is 882.5 feet.
Since Arrowhead Lake is shallow, the lake may be prone to frequent wind-driven mixing of the lake’s
shallow waters during the summer. Additionally, lake mixing may be influenced by the existing aeration
system as well as nighttime cooling. Therefore, one would expect Arrowhead Lake 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 precisely characterize the mixing
dynamics of a lake, but the current data gathered from Arrowhead Lake strongly suggests that the lake is
polymictic.
15
Table 4-1 Stage-storage-discharge relationships for Arrowhead Lake
Elevation Area (acres) Cumulative Storage (ac-ft) Comment
867.0 0.08 0.0
Wet Detention Storage Volume
868.0 0.55 0.3
869.0 1.40 1.3
870.0 3.68 3.8
871.0 9.58 10.5
872.0 16.65 23.6
873.0 21.58 42.7
874.8 22.33 82.6 Average 10-year WSE
875.8 22.99 105.3
Available Live Storage to Natural Overflow
876.8 23.74 128.7
877.8 24.55 152.8
878.8 25.35 177.8
879.8 26.09 203.5
880.8 26.78 229.9
881.8 27.50 257.0
882.5 27.96 276.0
B r e n d a nCt Post La
IndianHills CirMccauley TrIndian Hills Rd
Dakota Tr
T i m b e r R d g
Iroquois TrArrowhead PassMohawk TrM ccauley CirPaw nee R dTimber Tr WMc I
nt
yr
e Ct
ARROWHEAD LAKEBATHYMETRY
FIGURE 4-1
Barr Footer: ArcGIS 10.8.1, 2022-02-25 11:04 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-1_Arrowhead_Bathymetry_elev.mxd User: kjn20 250
Feet
!;N
City of Edina Bathymetry(2017)
Elevation, NGVD29
867
868
869
870
871
872
873
874
875
Hennepin County Imagery Spring 2020
17
4.2 Arrowhead Lake Watershed Characteristics
Arrowhead Lake’s direct watershed is approximately 178 acres, including the surface area of the lake
(22 acres). The watershed area compared to the lake surface area is relatively small (approximately 8:1
acres). Runoff from the watershed enters Arrowhead Lake through overland flow and from several storm
sewer outfalls at various points along the lakeshore. Subwatersheds and locations of the major
stormwater conveyance features are shown on Figure 4-2.
4.2.1 Land Use
Land use practices within a lake’s watershed impact the lake and its water quality by altering the volume
of stormwater runoff, sediment load, and nutrient load (namely phosphorus and nitrogen) that reach the
lake from the lake’s watershed. Each land use contributes a different amount of runoff and nutrients 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 Arrowhead Lake 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.
Based on the 2016 Met Council Land Use Dataset, the watershed of Arrowhead Lake is near fully
developed (Metropolitan Council, 2016). Table 4-2 provides a summary of the land use classifications
within the watershed. The major land use classification in the Arrowhead Lake watershed is single family
detached residential. The watershed also includes major highway, and to a lesser extent open water, single
family attached residential, undeveloped/open space, parks and recreational, and institutional land uses.
Figure 4-3 shows a map of the land use classifications within the Arrowhead Lake watershed.
Table 4-2 Land use classifications in the Arrowhead Lake watershed
Land Use Classification Percent of Watershed
Single Family Detached1 45%
Major Highway 21%
Open Water 12%
Single Family Attached1 11%
Undeveloped/Open Space 4%
Park and Recreational 3%
Institutional 3%
Multi-Family 0.1%
Total Watershed Area (ac) 178
1 Single family residential homes sharing no exterior walls with another home or building are considered “detached.” Attached housing shares walls on one or more sides with other homes.
£¤169
£¤212
62
4567158
AH_30
AH_8
AH_9
AH_10
AH_19
AH_20
AH_3
AH_7
AH_15
AH_5
AH_16
AH_13
AH_22
AH_21
AH_24
AH_1
AH_6
AH_26
AH_27
AH_18
AH_11
AH_17
AH_31
AH_4
AH_23
AH_12
AH_28
AH_29
AH_25
AH_33
AH_32
ARROWHEAD LAKESUBWATERSHEDS &STORMWATER CONVEYANCE
FIGURE 4-2
Barr Footer: ArcGIS 10.8.1, 2022-01-31 13:23 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-2_Arrowhead_StormConveyance.mxd User: kjn20 600
Feet
!;N
P8 Model Treatment Devices
Subwatersheds
Storm SewerNational Wetland Inventory (NWI) Wetlands
Freshwater Emergent Wetland
Freshwater Pond
Lake
Hennepin County Imagery Spring 2020
Arrrowhead Lake
£¤169
£¤212
62
4567158
AH_30
AH_8
AH_9
AH_10
AH_19
AH_20
AH_3
AH_7
AH_15
AH_5
AH_16
AH_13
AH_22
AH_21
AH_24
AH_1
AH_6
AH_26
AH_27
AH_18
AH_11
AH_17
AH_31
AH_4
AH_23
AH_12
AH_28
AH_29
AH_25
AH_33AH_32
LAND USEARROWHEAD LAKEWATERSHED
FIGURE 4-3
Barr Footer: ArcGIS 10.8.1, 2022-01-26 08:56 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-3_Arrowhead_LandUse.mxd User: kjn20 600
Feet
!;N
SubwatershedsLand Use (Met Council 2016)
Industrial and Utility
Institutional
Major Highway
Multifamily
Open Water
Park, Recreational, or Preserve
Single Family Attached
Single Family Detached
Undeveloped
Hennepin County Imagery Spring 2020
Arrrowhead Lake
20
4.3 Indianhead Lake Basin Characteristics
Indianhead Lake has a water surface area of approximately 14.3 acres, a maximum depth of approximately
5.1 feet, and a mean depth of 3.1 feet at a 10-year average water surface elevation of 863.1 (NGVD29). At
this elevation the lake volume is approximately 49.4 acre-feet (Figure 4-4). Indianhead Lake is land-locked
with no surface outlets. Thus, the water level in the lake depends on weather conditions (snowmelt,
rainfall, evaporation) and groundwater flow. The stage-storage relationship that was used in this study for
Indianhead Lake is shown in Table 4-3 and was based on bathymetric measurements completed by the
City of Edina in 2017 and MNDNR LiDAR collected in 2011. The approximate natural overflow elevation is
881.4 feet.
Since Indianhead Lake is shallow, the lake may be prone to frequent wind-driven mixing of the lake’s
shallow waters during the summer. Additionally, lake mixing may be influenced by the existing aeration
system as well as nighttime cooling. Therefore, one would expect Indianhead Lake 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 precisely characterize the
mixing dynamics of a lake, but the current data gathered from Indianhead Lake strongly suggests that the
lake is polymictic.
Table 4-3 Stage-storage-discharge relationships for Indianhead Lake
Elevation Area (acres) Cumulative Storage (ac-ft) Comment
858 3.59 0
Wet Detention Storage Volume
859 6.74 5.2
860 9.08 13.1
861 10.50 22.9
862 12.47 34.3
863 14.16 47.7
863.1 14.29 49.4 Average 10-year WSE
864 15.21 62.4
Available Live Storage to Natural Overflow
866.8 17.15 108.1
868.8 18.42 143.6
870.8 19.56 181.6
872.8 20.74 221.9
874.8 22.11 264.7
876.8 23.73 310.6
878.8 25.22 359.5
881.4 26.90 426.8
Dakota TrValley View RdShaw n e e C irCheyenne Cir Black Foot PassMark Terrace DrCheyenne TrINDIANHEAD LAKEBATHYMETRY
FIGURE 4-4
Barr Footer: ArcGIS 10.8.1, 2022-02-25 11:10 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-4_Indianhead_Bathymetry_elev.mxd User: kjn20 200
Feet
!;NCity of Edina Bathymetry(2017)
Elevation, NGVD29
858
859
860
861
862
863
864
Hennepin County Imagery Spring 2020
22
4.4 Indianhead Lake Watershed Characteristics
Indianhead Lake’s direct watershed is approximately 107 acres, including the surface area of the lake
(14.3 acres). The watershed area compared to the lake surface area is relatively small (approximately 8:1
acres). Runoff from the watershed enters Indianhead Lake through overland flow and from several storm
sewer outfalls at various points along the lakeshore. Subwatersheds and locations of the major
stormwater conveyance features are shown on Figure 4-5.
4.4.1 Land Use
Land use within a lake’s watershed impact the lake and its water quality by altering the volume of
stormwater runoff, sediment load, and nutrient load (namely phosphorus and nitrogen) that reaches the
lake from the lake’s watershed. Each land use contributes a different amount of runoff and nutrients 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.
Similar to Arrowhead Lake, historically, the Indianhead Lake 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.
Based on the 2016 Metropolitan Council of Environmental Services (MCES) Land Use Dataset, the
watershed of Indianhead Lake is near fully-developed (Metropolitan Council, 2016). Table 4-4 provides a
summary of the land use classifications within the watershed. The major land use classification in the
Indianhead Lake watershed is single family detached residential. To a lesser extent, the land use also
includes open water, undeveloped/open space, and institutional. Figure 4-6 shows a map of the land use
classifications within the Indianhead Lake watershed.
Table 4-4 Land use classifications in the Indianhead Lake watershed
Land Use Classification Percent of Watershed
Single Family Detached1 82%
Open Water 13%
Undeveloped/Open Space 6%
Institutional 1%
Total Watershed Area (ac) 107
1 Single family residential homes sharing no exterior walls with another home or building are considered “detached.” Attached housing shares walls on one or more sides with other homes.
Scandia RdPaiuteCir
ScandiaCt
IroquoisTr
CheyenneCir
Cherokee Tr
DakotaTrIndian Hills RdValley View RdGleason RdDakota TrS c o t i a D r
GleasonTerIndian Hills RdSaint Albans Cir
MarkTerraceCirPaiute DrS h a w nee C irGleason CirMoc
c
a
si
n
Vall
e
y
RdIroquois CirCheyenne TrOverholt PassB e l l o D r Bl
ackFootPas
sBalder La
Mark Terrace DrMohawk TrNavaho Tr
IH_10
IH_1
IH_6
IH_14
IH_15
IH_5
IH_12
IH_13
IH_7
IH_8
IH_3
IH_11
INDIANHEAD LAKESUBWATERSHEDS &STORMWATER CONVEYANCE
FIGURE 4-5
Barr Footer: ArcGIS 10.8.1, 2022-01-31 13:38 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-5_Indianhead_StormConveyance.mxd User: kjn20 400
Feet
!;N
P8 Model Treatment Devices
Subwatersheds
Storm Sewer
National Wetland Inventory (NWI) Wetland
Freshwater Emergent Wetland
Freshwater Pond
Hennepin County Imagery Spring 2020
Indianhead Lake
Scandia RdPaiuteCir
ScandiaCt
IroquoisTr
Cherokee Tr
DakotaTrIndian Hills RdValley View RdGleason RdDakota TrS c o t i a D r
Gleason TerIndian Hills RdSaint Albans Cir
Mark Terrace CirPaiute DrS h a w nee C irGleason CirMocc
asi
n Va
ll
e
y
RdIroquois CirCheyenne TrOverholt PassB e l l o D r Bl
ackFootPas
sBalder La
Mark Terrace DrMohawk TrNavaho Tr
IH_10
IH_1
IH_6
IH_14
IH_15
IH_5
IH_12
IH_13
IH_7
IH_8
IH_3
IH_11
LAND USEINDIANHEAD LAKEWATERSHED
FIGURE 4-6
Barr Footer: ArcGIS 10.8.1, 2022-01-26 08:59 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\2021_Arrowhead_Indianhead_UAA\Maps\Report\Figure4-6_Indianhead_LandUse.mxd User: kjn20 400
Feet
!;N
SubwatershedsLand Use (Met Council 2016)
Institutional
Open Water
Single Family Detached
Undeveloped
Hennepin County Imagery Spring 2020
Indianhead Lake
25
5.0 Existing Water Quality and Ecological Health
5.1 Water Quality
The NMCWD conducted intensive water quality monitoring in Arrowhead and Indianhead Lakes in 2019
and 2020 in support of this water quality study. The NMCWD also collected data in 2004, 2011, and 2014.
5.1.1 Eutrophication Parameters - Phosphorus, Chlorophyll-a, and Clarity
The NMCWD intensive monitoring included the lake eutrophication parameters of total phosphorus (TP),
chlorophyll-a, and Secchi disk transparency depth to assess water clarity. Data are presented using box
plots. The box plots show averages (black ‘x’), median values (straight horizontal line), minimum and
maximum values (whiskers), as well as the region where 50 percent of the data lie (the area within the
boxes). Box plots shown on Figure 5-1 display the observed summer-average TP and chlorophyll-a
concentrations and the Secchi disk transparency depths from 2004 through 2020 for Arrowhead Lake.
Figure 5-2 shows the observed summer-average TP and chlorophyll-a concentrations and the Secchi disk
transparency depths from 2004 through 2020 for Indianhead Lake.
There is variability in TP and chlorophyll-a concentrations and the Secchi disk transparency depths in
Arrowhead and Indianhead Lakes from year to year, as well as within a given year. The variability can be a
reflection of numerous factors, including climatic variability, changing aquatic plant and other aquatic
community populations, management efforts, and changes in external pollutant loadings from the direct
watershed.
For Arrowhead Lake, summer average TP and chlorophyll-a concentrations have remained fairly consistent
between 2004 and 2020. Monitoring year 2011 was the only observed year where the summer average TP
concentration met the MPCA water quality standard of 60 μg/L at a concentration of 52 μg/L. For the
other years monitored, summer average TP concentrations ranged from 65 – 82 μg/L. Monitoring of
chlorophyll-a concentrations showed that summer average concentrations met the MPCA water quality
standard (20 μg/L) in 2004 and 2019 at concentrations of 19 and 18 μg/L, respectively. For the other years
monitored, summer average chlorophyll-a concentrations exceeded the standard, ranging from 23 –
38 μg/L. Secchi disk transparency measurements have shown a decrease in transparency since 2011, with
summer average Secchi disk transparency depths decreasing from 1.2 meters in 2011 to 0.5 meters in
2020.
For Indianhead Lake, water quality has generally declined between 2004 and 2020. Summer average TP
and chlorophyll-a concentrations have generally increased between 2004 and 2020. In 2004 and 2011, the
summer average TP concentrations met the MPCA water quality standard of 60 μg/L at concentrations of
46 and 53 μg/L, respectively. In 2014, the summer average TP concentration was only slightly above the
MPCA standard at 61 μg/L. In 2019 and 2020, the monitoring data showed a significant increase in TP
concentrations, with summer average concentrations of 146 and 115 μg/L, respectively. Summer average
chlorophyll-a concentrations met the MPCA water quality standard (20 μg/L) in 2004 and 2019 at
concentrations of 9 and 19 μg/L, respectively. For the other years monitored, summer average
chlorophyll-a concentrations exceed the standard, ranging from 25 – 35 μg/L. Monitoring of Secchi disk
26
transparency depths has shown a decrease in transparency since 2011, with observed summer average
Secchi disk transparency depths decreasing from 1.3 meters in 2011 to 0.5 meters in 2020.
27
Figure 5-1 Total phosphorus, chlorophyll-a, and Secchi disk transparency from 2004 through 2020 in Arrowhead Lake. The black “x” indicates the summer average (June through September).
28
Figure 5-2 Total phosphorus, chlorophyll-a, and Secchi disk transparency from 2004 through 2020 in Indianhead Lake. The black “x” indicates the summer-average (June through September).
29
5.1.2 Nitrogen
The NMCWD intensive monitoring in 2019 and 2020 included Total Kjehdahl Nitrogen (TKN) and
nitrate/nitrite concentrations. TKN data are presented using box plots. The box plots show averages (black
‘x’), median values (straight horizontal line), minimum and maximum values (whiskers), as well as the
region where 50 percent of the data lie (the area within the boxes). Box plots shown on Figure 5-3 and
Figure 5-4 display the observed summer-average TKN concentrations in 2019 and 2020 for Arrowhead
Lake and Indianhead Lake, respectively. Most observed nitrate/nitrite concentrations in Arrowhead and
Indianhead Lakes were below the detection limit (~5 μg/L). The highest observed nitrate/nitrite
concentrations in Arrowhead (16 μg/L) and Indianhead (13 μg/L) Lakes occurred in mid-August 2020.
These nitrate/nitrite concentrations represent 0.9% and 0.8% of the TKN concentrations, respectively.
Figure 5-3 Total Kjehdahl Nitrogen 2019 through 2020 in Arrowhead Lake. The black “x” indicates the summer-average (June through September).
Figure 5-4 Total Kjehdahl Nitrogen 2019 through 2020 in Indianhead Lake. The black “x” indicates the summer-average (June through September).
30
5.1.3 Chlorides
Chloride concentrations in area lakes have increased since the early 1990s when many government
agencies switched from sand or sand/salt mixtures to salt for winter road maintenance. When snow and
ice melts, the salt goes with it, washing into lakes, streams, wetlands, and groundwater. Once chlorides
reach downstream waterbodies, they are considered permanent pollutants since there is no way to
remove chloride without extensive financial implications.
To protect fish and plant life, the MPCA has established a chronic exposure chloride standard of 230 mg/L
or less and considers two or more exceedances of the chronic standard in 3 years to be an impairment.
Based on the Arrowhead Lake monitoring data collected in 2011, 2014, 2019, and 2020, chloride
concentrations have not been observed to exceed 230 mg/L. The highest concentration recorded was 185
mg/L in April 2019. Average chloride concentrations from 2011 – 2020 remained fairly consistent (average
yearly concentrations (April – October) ranged from 120 – 150 mg/L). Based on the Indianhead Lake
monitoring data collected in 2011, 2014, 2019, and 2020, chloride concentrations have not been observed
to exceed 230 mg/L. The highest concentration recorded was 66 mg/L in April 2019. Average chloride
concentrations from 2011 – 2020 remained fairly consistent (average yearly concentrations (April –
October) ranged from 34 – 57 mg/L). Arrowhead Lake chloride concentrations are significantly higher than
Indianhead Lake, which may be due to highway land use within the Arrowhead Lake watershed.
5.1.4 Dissolved Oxygen & Aeration
5.1.4.1 Arrowhead Lake
Dissolved oxygen measured in Arrowhead Lake in 2020 at the routine monitoring location ranged from
9.3 to 5.3 mg/L in the surface waters. For the most part, oxygen was fairly uniform from the surface to the
bottom. This is likely due to the operation of three aerators in Arrowhead Lake. The minimum bottom
oxygen concentration was 3.8 mg/L. These dissolved oxygen concentrations are high enough to prevent
phosphorus release from lake bottom sediments that are dominated by iron-bound phosphorus (see
Section 5.2 for a more complete discussion of phosphorus release from lake bottom sediments).
To confirm the conclusion that dissolved oxygen is high enough in Arrowhead Lake to control internal
loading from iron-bound phosphorus release, two dissolved oxygen probes were placed mid-depth in the
lake in August 2021 and operated through the third week of September. The purpose of placing these
probes in the lake was to determine if oxygen was high enough during the night when phytoplankton
consume oxygen and dissolved oxygen can become quite low. Dissolved oxygen measurements for the
probe placed on the west end of the lake away from the aerators indicate that there were significant
changes in dissolved oxygen from day to night (change as high as 8 mg/L), but that dissolved oxygen did
not drop below a key level of 2 mg/L (Figure 5-5). For the probe placed near the aerators on the east end
of the lake, dissolved oxygen did not change as notably from day to night and the concentrations were
above 2 mg/L for all the measurements (Figure 5-6). Dissolved oxygen measurements taken across the
lake for one event during August 2021 also demonstrated that dissolved oxygen concentrations were
similar across the entire lake surface.
31
Given these monitoring results, internal load management strategies can be crafted assuming that oxygen
concentrations are high enough to prevent iron-phosphate release under most conditions.
Figure 5-5 Arrowhead Lake dissolved oxygen concentrations near the aerators (east end)
Figure 5-6 Arrowhead Lake dissolved oxygen concentrations away from aerators (west end)
32
5.1.4.2 Indianhead Lake
Dissolved oxygen measured in Indianhead Lake in 2020 at the routine monitoring location ranged from 19
to 4.3 mg/L in the surface waters. For the most part, oxygen was fairly uniform from the surface to the
bottom except for the measurement on August 4, 2020 where the bottom dissolved oxygen was 2.7 mg/L.
This may have been a result of a copper sulfate treatment completed on July 26, 2020 to treat for high
concentrations of algae (permit applied for by the Indianhead Lake Association). For additional discussion
on copper sulfate treatments, see Sections 5.3.2 and 6.3.3.1. Outside of observed low dissolved oxygen
concentrations on August 4, 2020, higher dissolved oxygen concentrations in Indianhead Lake are likely
due to the operation of four aerators.
Additional dissolved oxygen measurements taken across Indianhead Lake on August 24, 2021 were
consistently high in the surface samples (approximately 10 mg/L) with bottom measurements ranging
from 7 to 9 mg/L. These concentrations are high enough to prevent phosphorus release from lake bottom
sediments that are dominated by iron-bound phosphorus (see Section 5.2 for a more complete discussion
of phosphorus release from lake bottom sediments).
5.2 Sediment Quality
Phosphorus in lake bottom sediments is often bound to a range of different elements such as iron and
manganese (often referred to as mobile phosphorus), aluminum, or calcium. It is the mobile phosphorus
fraction that releases from sediment during low oxygen conditions. Phosphorus can also be found
incorporated into organic matter in the sediment (organically bound phosphorus). Organically bound
phosphorus can also release phosphorus from lake sediment but typically at a slower rate than mobile
phosphorus; release is controlled by lake water temperature. Phosphorus release from sediment is
typically termed as “internal phosphorus loading”.
Sediment cores from Arrowhead and Indianhead Lakes were collected in 2021 and used to inform the
potential internal phosphorus loading potential of the mobile and organically bound phosphorus
fractions. In both Arrowhead and Indianhead Lake the amount of mobile phosphorus was low; however,
the amount of organically bound phosphorus in the sediments was high, indicating potential for internal
phosphorus loading. In both lakes, the amount of organically bound phosphorus was significantly higher
than the mobile phosphorus fraction. The average concentration of organically bound phosphorus and
mobile phosphorus in the top 4 centimeters of three cores taken from Arrowhead Lake was 36.1 and 4.1
μg P/cm3 wet sediment, respectively. The average concentration of organically bound phosphorus and
mobile phosphorus in the top 4 centimeters of two cores taken from Indianhead Lake was 39.6 and
5.6 μg P/cm3 wet sediment, respectively. These observed concentrations indicate that a significantly larger
percentage of internal phosphorus loading in both lakes is due to organically bound phosphorus
(organic-P) rather than mobile phosphorus (mobile-P).
33
5.3 Aquatic Communities
The fish, zooplankton, phytoplankton, and aquatic plants residing in lakes are all linked, and the
composition and abundance of biota observed in the lakes provide indication of lake health and if
biological management should be considered to improve water quality.
5.3.1 Aquatic Plants
Macrophytes, also called aquatic plants, grow in aquatic systems such as streams and lakes. There is a
wide range of macrophytes including species attached to the lake bottom, species unattached and
floating, submerged species, and emergent species (e.g., cattails). Macrophytes are an important part of a
shallow lake ecosystem and provide critical habitat for aquatic insects and fish. A healthy native plant
community contributes to the overall health of the lake. However, a dense non-native plant community
can create problems, including recreational use impairment, fluctuating water quality, and a less than ideal
fisheries habitat, which has adverse impacts on the fish community. The dense growth can make it difficult
for invertebrates and other organisms that fish eat to survive. So, with less to eat and less open water, fish
populations decrease (MPCA, Eurasian Water Milfoil, 2019). The dense growth can also make it difficult for
fish to catch food. When fish are less effective at controlling prey species, an unbalanced fishery results
(Indiana Department of Natural Resources, 2019).
The NMCWD conducted qualitative macrophyte monitoring as part of its routine monitoring of
Arrowhead and Indianhead Lakes in 2004, 2011, 2014, 2019, and 2020. The macrophyte monitoring
consisted of conducting qualitative plant surveys in June and August of each of the monitored years, with
qualitative notation of plants observed and their density throughout the lakes.
The Minnesota Department of Natural Resources (MNDNR) developed the Lake Plant Eutrophication
Index of Biological Integrity (IBI) to develop thresholds to indicate plant degradation (communities likely
stressed from anthropogenic eutrophication). The Lake Plant Eutrophication IBI includes two metrics to
measure the response of a lake plant community to eutrophication. The first metric is species richness—
the estimated number of species in a lake. The second metric is floristic quality index (FQI), which
distinguishes the quality of the plant community and can be a reflection of the quantity of nutrients in the
lake.
The MNDNR’s Lake Plant Eutrophication IBI was used to assess the health of the Arrowhead and
Indianhead Lake plant communities, based on results of the macrophyte surveys. Aquatic plant data
collected by NMCWD from 2004 through 2020 was used to determine species richness and Floristic
Quality Index (FQI) scores. The scores were then compared with MNDNR Lake Plant Eutrophication IBI
thresholds for shallow lakes (a minimum of 11 species and an FQI score of at least 17.8) to assess the
health of the Arrowhead and Indianhead Lake plant communities.
The Arrowhead Lake plant community failed to meet the MNDNR Lake Plant Eutrophication IBI criteria for
measurements taken in 2004, June 2011, 2014, 2019, and 2020 (Figure 5-7). The Arrowhead Lake plant
community met the MNDNR Lake Plant Eutrophication IBI criteria in August 2011 (i.e., at least 11 plant
species). The number of species observed in Arrowhead Lake generally increased from 2004 to 2014. In
June 2004, six plant species were found during survey. From August 2004 to August 2014, 10 – 11 plant
34
species were observed in Arrowhead Lake. However, the number of plant species found in 2019 and 2020
showed a significant decrease, which reflects the lake’s poor water quality during that time period (i.e.,
total phosphorus and chlorophyll-a concentrations above Minnesota State shallow lake water quality
standards). The number of species observed in Arrowhead Lake in 2019 ranged from 6 – 7 species and the
number of species observed in 2020 was 2 species. The decrease in observed species can be reflective of
degrading water quality, but may also be a reflection of plant management conducted by lake residents.
The FQI values follow a similar trend to the number of plant species observed in Arrowhead Lake over
time. FQI values were near or above the MDNR plant IBI threshold of 17.8 from August 2004 through
August 2014 and ranged from 17.1 to 19.9 (Figure 5-8). FQI values from 2019 to 2020 decreased, ranging
from 9.2 to 12.9, which is lower than the plant IBI threshold for FQI of at least 17.8 (Figure 5-8).
The Indianhead Lake plant community failed to meet the MNDNR Lake Plant Eutrophication IBI criteria for
measurements taken in 2004, 2011, 2014, 2019, and 2020, with all observed data falling below the desired
threshold of 11 plant species (Figure 5-9). The number of species observed in Indianhead Lake generally
remained consistent from 2004 to 2020, likely due to plant management efforts conducted by residents.
From 2004 to 2020 the number of plant species observed in Indianhead Lake ranged from 3 – 5 species.
The decrease in observed species may be reflective of degrading water quality conditions, but this
correlation is difficult to quantify due to yearly plant management efforts.
The FQI values in Indianhead Lake show a decreasing trend over time. FQI values were below the MNDNR
plant IBI threshold of 17.8 for all years monitored (2004 – 2020). FQI values were the highest in 2004 at
15.2 and have been decreasing over time where FQI values monitored in 2020 were approximately 11.5
(Figure 5-10).
35
Figure 5-7 Arrowhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Species Richness
Figure 5-8 Arrowhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Floristic Quality Index (FQI)
36
Figure 5-9 Indianhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Species Richness
Figure 5-10 Indianhead Lake Macrophyte Species Richness Compared with Plant IBI Threshold for Floristic Quality Index (FQI)
37
Two non-native aquatic invasive species (AIS) are currently present in Arrowhead Lake: Purple loosestrife
and curly-leaf pondweed. Eurasian watermilfoil has been observed in the past but was not present in the
most recent survey completed in 2020.
Purple loosestrife has been observed in Arrowhead Lake since 2011. Purple loosestrife has been observed
along the south and southwest shorelines. Curly-leaf pondweed has been observed in Arrowhead Lake
since 2004. Although curly-leaf pondweed is not depicted in the June 2004 macrophyte survey map
completed by NMCWD, herbicide treatment documentation indicates curly-leaf pondweed was present in
early spring. In 2011, curly-leaf pondweed was found in northern, eastern, and western portions of the
lake. In 2014, curly-leaf pondweed was more widespread with observations not only in the northern,
eastern, and western portions of the lake, but also in the southern portions. In June 2019 and 2020, less
curly-leaf pondweed was observed during the June macrophyte surveys due to management efforts
completed by the City of Edina in spring 2019 and 2020. The City of Edina has been managing for curly-
leaf pondweed in Arrowhead Lake since spring 2017. Eurasian watermilfoil was found in Arrowhead Lake
in the first recorded survey in 2004 in the eastern, western, and southern portions of the lake. By 2011,
Eurasian watermilfoil was more widespread with observations not only in the eastern, western, and
southern portions, but also in the north. Similar extents of Eurasian watermilfoil were also observed in
2014. The extent of Eurasian watermilfoil decreased in 2019, with observations noted in northern portions
of the lake. No observations of Eurasian watermilfoil were noted in the June and August 2020 surveys. The
NMCWD will continue to track invasive species’ growth in Arrowhead Lake.
Three non-native AIS are currently present in Indianhead Lake: Purple loosestrife, curly-leaf pondweed,
and yellow iris.
Purple loosestrife has been observed in Indianhead Lake since a macrophyte survey was completed in
2019. Purple loosestrife has been observed along the southwestern and southeastern shorelines. A
macrophyte survey in 2014 identified a widespread curly-leaf pondweed population in Indianhead Lake. In
June 2019 and 2020, less curly-leaf pondweed was observed during the June macrophyte surveys due to
management efforts completed by the City of Edina in spring 2019 and 2020. Yellow iris was observed
along the northern, eastern, and southern portions of the Indianhead Lake shoreline in the first recorded
survey in 2004. By 2011, yellow iris was more widespread with observations not only in the northern,
eastern, and southern portions, but also in the west. Similar extents of yellow iris were also observed in
2019 and 2020. The NMCWD will continue to track invasive species’ growth in Indianhead Lake.
Aquatic plant maps from 2004 through 2020 are provided in Appendix A.
5.3.2 Phytoplankton
Samples of phytoplankton, microscopic aquatic algae, were collected from Arrowhead and Indianhead
Lakes in 2004, 2011, 2014, 2019, and 2020 as part of NMCWD’s routine monitoring to evaluate water
quality and the quality of food available to zooplankton (microscopic animals).
Phytoplankton numbers in Arrowhead Lake generally increased during the monitoring period of 2004
through 2020. In 2004, the summer average phytoplankton number was 13,350 per milliliter. In 2020, the
38
summer average phytoplankton number increased to 48,845 per mL. Blue-green algae numbers have also
increased from 2004 to 2020. In 2004, the summer average blue-green algae numbers were approximately
240 per mL. In 2020, the blue-green algae summer average numbers increased to approximately 38,880
per mL (Figure 5-11). The highest observed concentration of blue-green algae from the routine
monitoring location was 76,960 per mL in July 2020.
Blue-green algae are associated with water quality problems and can be a source of health concerns. The World Health Organization (WHO) has established the following thresholds for assessing the probability of adverse health effects to lake users from exposure to blue-green algae (World Health Organization, 2003):
• Low Probability of Adverse Health Effects: Exposure to lakes with blue-green algae density levels between 20,000 and 100,000 cells per milliliter poses a low probability of adverse health effects (i.e., skin irritation or allergenic effects such as watery eyes).
• Moderate Probability of Adverse Health Effects: Exposure to lakes with blue-green algae densities greater than 100,000 cells per milliliter poses a moderate probability of adverse health effects (i.e., long-term illness from algal toxins is possible).
• High Probability of Adverse Health Effects: Exposure to lakes with blue-green scum in areas where whole body contact or ingestion/aspiration occur poses a high probability of adverse health effects (i.e., acute poisoning from algal toxins is possible).
Figure 5-12 shows the observed blue-green algae counts in Arrowhead Lake in comparison with the WHO
thresholds for probability of adverse health effects. From July through August 2020, observed blue-green
algae counts were above the threshold for low probability of adverse health effects level. Observed blue-
green algae counts in Arrowhead Lake in August 2014 and August 2019 were also above the threshold for
low probability of adverse health effects from exposure to blue green algae.
Phytoplankton numbers in Indianhead Lake during the monitoring period of 2004 through 2020 followed
a pattern similar to that of the water quality parameters (e.g., total phosphorus, chlorophyll-a, Secchi disk
depth), both reflecting degrading water quality over time. In 2004, the summer average phytoplankton
number was 16,550 per milliliter. In 2020, the summer average phytoplankton number increased to 76,430
per mL. Blue-green algae numbers have also increased from 2004 to 2020. In 2004, the summer average
blue-green algae numbers were approximately 190 per mL, whereas in 2020, the blue-green algae
summer average count increased to approximately 56,500 per mL (Figure 5-13). The highest observed
concentration of blue-green algae from the routine monitoring location was 144,740 per mL in July 2020.
Figure 5-14 shows the observed blue-green algae counts in Indianhead Lake in comparison with the WHO
thresholds for probability of adverse health effects. In July and August 2020, blue-green algae counts
were above the thresholds for moderate and low probability of adverse health effects levels, respectively.
Prior to 2020, blue-green algae cell counts were consistently below the WHO threshold for low probability
of adverse health effects.
39
5.3.2.1 Copper Sulfate Treatments
Copper sulfate treatments have been applied to Arrowhead and Indianhead Lakes in the past to control
algal blooms. The Arrowhead Lake Association and Indianhead Lake Association have worked with the
City of Edina to coordinate these treatments with licensed contractors and apply for the appropriate
permits from the MnDNR. The approximate dates of the most recent algal treatments based on records
available from the City of Edina are as follows:
• Arrowhead Lake: 9/19/2019, 6/11/2020, 8/6/2020
• Indianhead Lake: 7/26/2019, 7/8/2020
40
Figure 5-11 Top, Arrowhead Lake 2004-2020 summer average phytoplankton numbers and bottom, microscopic pictures of phytoplankton species, from left to right, Chlamydomonas globosa (green algae) Dolichospermum affine (blue-green algae), Fragilaria crotonensis (diatom), and Cryptomonas erosa (cryptomonad).
Figure 5-12 Arrowhead Lake blue-green algae data compared with the World Health Organization’s Thresholds for Adverse Health Effects Guidelines
41
Figure 5-13 Top, Indianhead Lake 2004-2020 summer average phytoplankton numbers and bottom, microscopic pictures of phytoplankton species, from left to right, Chlamydomonas globosa (green algae) Dolichospermum affine (blue-green algae), Fragilaria crotonensis (diatom), and Cryptomonas erosa (cryptomonad).
Figure 5-14 Indianhead Lake blue-green algae data compared with the World Health
Organization’s Risk of Adverse Health Effects Guidelines
42
5.3.3 Zooplankton
Zooplankton are microscopic animals that feed on phytoplankton (algae) and organic matter that are a
source of food for fish (e.g., bluegills, crappies). Samples of zooplankton were collected from Arrowhead
and Indianhead Lakes in 2004, 2011, 2014, 2019, and 2020 as part of NMCWD’s routing monitoring
program.
In general, the average quantity of zooplankton has increased since 2004 in Arrowhead Lake. In 2004, the
yearly average total number of zooplankton per square meter was less than 1 million. In 2020, the yearly
average total number of zooplankton increased to over 3 million per square meter. Since 2004, the
percentage of rotifers observed in Arrowhead Lake has decreased while the percentage of cladocerans
and copepods has increased (Figure 5-15). The data indicate the zooplankton community provided an
abundant supply of food for planktivorous fish in the lake.
In Indianhead Lake, the average quantity of zooplankton per square meter increased from 2004 (2.2
million) to 2011 (4.7 million). From 2011 – 2014, the average zooplankton quantity and community
composition stayed fairly consistent with the dominant zooplankton group being rotifers. From 2014 to
2019, the average zooplankton quantity per square meter decreased. Numbers of cladocerans and
copepods were, on average, higher in 2019 and 2020 than previous years resulting in a more even
distribution between the 3 groups of zooplankton. The total number of zooplankton in 2020 was, on
average, higher than 2019, but lower than numbers observed in 2011 and 2014. Nonetheless, the 2020
data indicate the zooplankton community provided an abundant supply of food for planktivorous fish in
the lake.
43
Figure 5-15 A) Arrowhead Lake 2004-2020 zooplankton numbers, B) Indianhead Lake 2004 – 2020 zooplankton numbers, and C) microscopic pictures of zooplankton species, from left to right, Bosmina longirostris. (cladoceran), Ceriodaphnia sp. (cladoceran), Diaptomus sp. (copepod), and Keratella cochlearis (rotifer).
A)
B)
C)
44
5.3.3.1 Impact of Copper Sulfate on Zooplankton
Research has shown that copper sulfate treatments do not only reduce algal abundance, but treatments
can deplete food availability for zooplankton and copper toxicity can affect zooplankton health and
survival. Results of zooplankton monitoring in Indianhead Lake in 2020 indicates a probable impact of a
copper sulfate treatment on the zooplankton community. All three zooplankton groups showed a
decrease in abundance between mid-July and early-August; however, rotifers showed the largest decrease
in abundance (Figure 5-16). Rotifer abundance was approximately 4.2 million per square meter on July 14,
2020 and decreased to 95,500 per square meter by August 4, 2020. A copper sulfate treatment was
applied on July 8, 2020. Future monitoring should be completed to confirm direct cause and effect of
copper sulfate on zooplankton communities and rule out other factors impacting growth (e.g., fish
predation changes).
Figure 5-16 Zooplankton abundance and community changes in Indianhead Lake compared
to timing of algal copper sulfate treatment in 2020
5.3.4 Fish
The environmental consulting firm WSB completed a fisheries assessment of Arrowhead and Indianhead
Lakes in fall 2021. Between September 19 through 21, 2021 WSB completed a standard lake survey of
Arrowhead and Indianhead Lakes using three standard double frame fyke trap nets and three mini fyke
trap nets.
During the standard lake survey in early September 2021, a variety of species were sampled in Arrowhead
Lake, including bluegill, black bullhead, green sunfish, hybrid sunfish, and largemouth bass. Bluegill were
found to be the most prominent fish in the lake with an average size of 5.8 inches. Largemouth bass was
found to be the most prominent predator fish in the lake with an average size of 13.1 inches. Prior to the
45
2021 fisheries assessment, the MNDNR completed a standard fisheries assessment of Arrowhead Lake in
1995. In 1995, black bullhead and green sunfish were the most prominent fish species in Arrowhead Lake,
which is a stark contrast to the observed species in 2021. The increase in blue gill and large mouth bass
species is likely due to a recorded fish stocking event in 2016. Recorded fish stocking reports are available
from the MNDNR. Within the last 10 years, Arrowhead Lake was stocked in 2016 (Bluegills – 1,000
fingerlings, 1,000 yearlings; Largemouth Bass – 430 fingerlings, 90 yearlings).
During the standard lake survey in early September 2021, a variety of species were sampled in Indianhead
Lake, including bluegill, hybrid sunfish, black crappie, golden shiner, and largemouth bass. Bluegill were
found to be the most prominent fish in the lake with an average size of 6.7 inches. Largemouth bass was
found to be the most prominent predator fish in the lake with an average size of 10.6 inches. Prior to the
2021 fisheries assessment, no standard MNDNR fisheries assessments have been completed on
Indianhead Lake. Recorded fish stocking reports are available from the MNDNR. Within the last 10 years,
Indianhead Lake was stocked in 2013 (Black Crappie – 50 adults; Bluegill Sunfish – 200 adults; Largemouth
Bass – 200 yearlings) and 2016 (Black Crappie – 2,000 yearlings; Bluegill Sunfish – 5,000 yearlings; Hybrid
Sunfish – 1,000 yearlings; Largemouth Bass – 900 fingerlings, 1,000 yearlings). The 2021 fisheries
assessment indicates high survival of the stocked fish, although the lack of abundant small fish (< 3
inches) may suggest low recruitment (low survival of fish spawned within the lake).
In spring 2022, WSB plans to conduct follow-up fish surveys of Arrowhead and Indianhead Lakes using
electrofishing. Electrofishing data should expand upon the data collected in fall 2021 using the fyke trap
nets. A final report will be developed following this survey with results of the fall 2021 and spring 2022
surveys.
The official 2021 fisheries assessment reports can be found in Appendix B.
5.4 Water Levels
Arrowhead and Indianhead lakes are land-locked with no surface outlets. Thus, the water levels in the
lakes depend on weather conditions (snowmelt, rainfall, evaporation) and groundwater flow. The observed
water surface elevations in Arrowhead and Indianhead lakes monitored since 2010 by the NMCWD are
shown in Figure 5-17 and Figure 5-18, respectively. Both lakes experienced significantly higher water
levels in 2014, 2017, and 2019 due to above average precipitation and high groundwater levels. Since
mid-2020 water surface elevations have been falling in both lakes due to below average precipitation in
2020 and 2021 and changes in groundwater levels.
Predicting how water quality conditions will change in land-locked lakes due to water level variations can
be difficult. While watershed models, such as P8, can be used to predict changes in stormwater inflow
concentrations due to above or below average precipitation, estimating the changes to in-lake processes
can be more challenging. For example, in some lakes, high water levels may result in improved water
quality because high water levels correspond to more water volume and lower nutrient concentrations
(i.e., nutrients are diluted by more water volume). However, in other lakes, high water levels may result in
degrading water quality because high water levels may increase erosion in upland areas or water may
46
extend into upland areas that are heavily fertilized. How water quality responds to changing water levels
may also vary from year to year.
Figure 5-17 Observed Water Surface Elevations on Arrowhead Lake
Figure 5-18 Observed Water Surface Elevations on Indianhead Lake
47
6.0 Water Quality Modeling
Computer modeling was used in this study to estimate stormwater runoff and pollutant contributions
from the watershed and link water and nutrient loading to observed nutrient concentrations in the water
column of the lake (e.g., total phosphorus, orthophosphate, Total Kjeldahl Nitrogen (TKN), nitrate/nitrite).
In-lake modeling included simulation of dynamic internal lake processes such as phosphorus release from
lake sediments (internal sediment loads), phytoplankton/macrophyte nutrient uptake, and
phytoplankton/macrophyte death and decay. The in-lake model was also updated to include algorithms
to calculate effects of in-lake management efforts such as copper sulfate treatments to reduced algal
abundance. The watershed and in-lake models were used to simulate conditions in 2020. Model year 2020
was typical of the variability that Arrowhead or Indianhead Lake may experience from a watershed
loading, in-lake loading, and biological variability perspective.
6.1 P8 Model Runoff and Phosphorus Loading
Central to a lake water quality analysis is the use of a water quality model that has the capacity to predict
the amount of runoff and pollutants that reach a lake via stormwater runoff (external loading). The P8
(Program for Predicting Polluting Particle Passage through Pits, Puddles and Ponds) modeling software
was used to estimate watershed loads to the lake (I.E.P, Inc., 1990). The P8 model incorporates hourly
precipitation and daily temperature data. The P8 model was used to calculate the daily water volume and
nutrient loads introduced from each tributary subwatershed in the Arrowhead and Indianhead Lake
watersheds.
P8 model inputs included:
• Climate Data: hourly precipitation (source: Bryant Lake precipitation gages) and daily
temperature (source: National Weather Service gage at Minneapolis-St. Paul International Airport,
MSP)
• Watershed: tributary land areas (both pervious and impervious), soil conditions
• Conveyance: storm sewer system
• Best management practices: ponds, including the water storage and solids and phosphorus
settling functionalities
The P8 model was run for the Arrowhead and Indianhead Lake watersheds for water year 2020.
Since inflow water quantity or quality data were not collected for Arrowhead or Indianhead Lakes on a
subwatershed-scale, detailed calibration of the P8 models was not conducted. Therefore, the accuracy of
P8 model outputs, used as inputs for the in-lake model (described below) were critically evaluated
through the in-lake modeling process. In-lake model calibrations confirmed that total phosphorus
concentrations predicted by the P8 model were best-suited for considering relative changes in loading
under varying watershed conditions. However, the total nitrogen and orthophosphate concentrations
48
predicted by the P8 model needed to be modified during the in-lake calibration process. The inflow
orthophosphate concentrations were reduced by 90% for the entire modeling period (April – October). P8
nitrogen inflow concentrations were increased by applying a multiplier on a month-by-month basis to
match in-lake concentrations (e.g., Arrowhead Lake P8 nitrogen inflow concentrations increased by 1 – 5
times, Indianhead Lake P8 nitrogen inflow concentrations increased by 10 times).
6.1.1 P8 Model Updates
A P8 watershed model was developed for the previous Arrowhead and Indianhead Lake UAA that was
based on City of Edina land use information from 2003. Since then, a limited number of permit
applications have been submitted to NMCWD for projects within the Arrowhead and Indianhead Lake
watersheds. This is not surprising since the watersheds were nearly fully developed in 2003. The permit
applications submitted since 2003 were reviewed and no changes were made to the existing P8 model.
6.2 Water Balance Calibration
6.2.1 Precipitation and Runoff
The annual water and watershed nutrient loads to Arrowhead and Indianhead Lake under existing land
use conditions were estimated for model year 2020. Precipitation totals during model year 2020 are
summarized in Table 6-1 (source: Bryant Lake precipitation gages).
Table 6-1 Modeled total precipitation for the 2020 Growing Season (May 1 through Sept. 30)
Model Year Growing Season (May 1 through Sept 30) Precipitation (inches)
2020 21.2
6.2.2 Stormwater Volume Calibration (Water Balance)
Water balance models were developed for Arrowhead and Indianhead Lake. The changes in water
volumes of the lake over time were calibrated by matching the modeled surface elevations to monitored
data. To translate the water loadings into water surface elevations, a water balance model was utilized.
The model uses estimated daily watershed runoff inflows (predicted by P8 models), daily precipitation,
daily evaporation, estimated groundwater inflow or outflow, and observed lake levels to estimate changes
in the water level of the lake. Since both lakes are land locked, no discharge rating curves were used.
Figure 6-1 shows the water balance calibration that was completed for Arrowhead Lake for model year
2020. The predicted water levels, shown by the orange line on the plot, were calibrated to match as
closely as possible to the observed monthly water levels, indicated by the blue circles. Model calibration
showed groundwater outflow in model year 2020 for Arrowhead Lake.
Figure 6-2 shows the water balance calibration that was completed for Indianhead Lake for model year
2020. The predicted water levels, shown by the orange line on the plot, were calibrated to match as
49
closely as possible to the observed monthly water levels, indicated by the blue circles. Model calibration
showed groundwater inflow from April through June in model year 2020 for Indianhead Lake.
Figure 6-1 Arrowhead Lake (2020) Water Balance
Figure 6-2 Indianhead Lake (2020) Water Balance
50
Overall, the water balance calibrations for both Arrowhead Lake and Indianhead Lake correlate well with
the observed monitored data. Figure 6-3 provides a water balance volume comparison for Arrowhead and
Indianhead lakes for 2020. Since both lakes are landlocked, in-lake nutrient processes as well as the
quality and quantity of watershed inflows, will have an impact on the lakes’ overall water quality.
Figure 6-3 Arrowhead Lake and Indianhead Lake water balance summaries
6.3 In-Lake Modeling
The purpose of in-lake modeling is to establish a relationship between the amount of nutrients that enter
a lake and the concentration of these nutrients that remain in a lake. Generally, for freshwater lakes,
phosphorus is the main nutrient of concern and is discussed in greater detail in this report. However,
nitrogen also plays a role in limiting growth in lakes and is also discussed.
There are several processes that dynamically increase or decrease the concentration of phosphorus in the
lake water column, including (the “-“ or “+” indicates that the mechanism generally either reduces or
increases phosphorus):
• Watershed Runoff (+): Phosphorus enters the lake through natural channels, sheet flow from turfed backyards, and discharge from storm sewer pipes following precipitation or snow melt events.
• Atmospheric Deposition (+): Phosphorus deposits into the water body from the atmosphere
• Settling (-): Phosphorus in phytoplankton and attached to particles settles out of the lake water column to the sediments.
• Flushing (-): Typically represents the phosphorus that is discharged through an outlet structure. Since Arrowhead and Indianhead Lakes are land-locked, this includes phosphorus that is discharged to groundwater.
• Lake Bottom Sediment Loading (+): Mobile phosphorus from lake bottom sediments may release into the water column during low oxygen conditions. Organic phosphorus will release as
51
bacteria breakdown debris in the lake sediment that contains phosphorus (e.g., decaying leaves, plants, and algae). This is typically referred to as internal loading.
• Phytoplankton and macrophyte growth (-): Phosphorus will be removed from the water column and the sediment through uptake by phytoplankton and macrophytes during the growth phase.
• Phytoplankton and macrophyte die-off and decay (+): Phosphorus in the phytoplankton and plant tissues is released into the water column when the species die and decay.
• Curly-leaf pondweed die-off and decay (+): Phosphorus in the plant tissue is released into the water column when curly-leaf pondweed dies and decays. Curly-leaf pondweed die-off and decay occurs much earlier than other native plant species (typically in late June and July), so this species is modeled separately.
• Copper sulfate treatment (-): Copper sulfate is applied as an algal management technique. Monitoring data indicates that the type of copper sulfate application used in Arrowhead and Indianhead not only removed algae from the water column, but also coagulated and flocculated out total phosphorus from the water column.
The in-lake model used for this study is a finite difference lake model developed by Barr Engineering Co.
The model integrates the phosphorus inputs and losses described above on an hourly time-step. The lake
model is considered to be zero-dimensional, meaning, it is assumed that every input to the model is
completely mixed both vertically and horizontally in the lake water column. Biological components, as
discussed above, include phytoplankton and macrophytes (aquatic plants and attached filamentous algae)
and growth is dependent upon phosphorus, nitrogen, light, and temperature. Macrophytes can derive
nutrients from the sediment and the water column. Each of these processes occur at different levels
during different periods and hence they are quantified (e.g., calibrated) by matching the in-lake
phosphorus and nitrogen concentrations with the field-measured phosphorus and nitrogen
concentrations.
6.3.1 In-Lake Water Quality Model Calibration
Calibration is a process in which model parameters and coefficients are reasonably adjusted such that the
model predictions are similar to in-lake measurements. The Arrowhead and Indianhead Lake models were
calibrated to the following water quality parameters:
• Total Phosphorus (TP)
• Orthophosphate (Ortho-P)
• Chlorophyll-a
• Total Kjeldahl Nitrogen (TKN)
• Nitrate + Nitrite
Example in-lake model calibrations for Arrowhead Lake and Indianhead Lake are provided below. Figure 6-4
and Figure 6-5 show the 2020 calibrations for TP and TKN concentrations in Arrowhead Lake, respectively. The
orange line represents the modeled in-lake concentrations, and the blue circles represent the monitored
concentrations. Figure 6-6 and Figure 6-7 show the TP and TKN in-lake model calibrations for Indianhead Lake
in 2020. Plots showing all parameters used for calibration can be found in Appendix C.
52
Figure 6-4 Arrowhead Lake In-Lake Total Phosphorus Calibration
Figure 6-5 Arrowhead Lake In-Lake Total Kjeldahl Nitrogen Calibration
53
Figure 6-6 Indianhead Lake In-Lake Total Phosphorus Calibration
Figure 6-7 Indianhead Lake In-Lake Total Kjeldahl Nitrogen Calibration
54
6.3.2 In-Lake Water Quality (Phosphorus) Model Calibration Loading Summaries
After the in-lake water quality model calibrations were finalized, loading summaries were developed.
Figure 6-8 shows the total phosphorus loading summaries for Arrowhead and Indianhead Lakes during
the 2020 growing season (June – Sept). The percentage of total phosphorus loading from the watershed
and the sediment were similar for Arrowhead Lake. The in-lake calibration shows that approximately 54%
of the total phosphorus load to Arrowhead Lake during the modeled period of 2020 was from the
sediment (internal loading). The remaining 46% of the total phosphorus load entered from watershed
runoff. For Indianhead Lake, a much larger percentage of the total phosphorus load came from the
sediment (84%) and a smaller portion entered from watershed runoff and groundwater inflow (16%).
Figure 6-8 2020 Total Phosphorus Loading Summaries (Watershed and Internal Loading from Lake Bottom Sediment) from Arrowhead and Indianhead Lakes In-Lake
Calibration Models
6.3.3 In-Lake Water Quality Additional Observations
6.3.3.1 Copper Sulfate Impacts to In-Lake Water Quality
Water quality monitoring data collected approximately monthly from Arrowhead and Indianhead Lakes in
2020 indicates that the copper sulfate treatments applied to both lakes not only impacted phytoplankton
(i.e., chlorophyll-a concentrations), but also impacted the total nitrogen and total phosphorus
concentrations. The in-lake model calibrations from Indianhead Lake are shown below as an example.
A contractor was hired to apply a copper sulfate treatment to Indianhead Lake on July 8, 2020. Figure 6-9
shows the impact to chlorophyll-a concentrations due to the copper sulfate treatment. The orange line
represents the modeled in-lake concentrations, and the blue circles represent the monitored
concentrations. As expected, chlorophyll-a concentrations decreased after the copper sulfate treatment
because of the toxic effect on algal species.
55
Figure 6-9 Indianhead Lake Chlorophyll-a calibration impacted by copper sulfate
Unexpectedly, the copper sulfate treatment also decreased the total phosphorus concentrations in
Indianhead Lake following the application. The orange line in Figure 6-10 shows the calibrated total
phosphorus concentrations compared to the monitored data represented with the blue circles. The purple
line shows the expected total phosphorus concentrations if a copper sulfate treatment was not applied to
the lake. From this purple line, we can see that the total phosphorus concentrations in late-summer and
early-fall would have been significantly higher without the copper sulfate treatment. Therefore, it is
hypothesized that the type of copper sulfate treatment applied to Indianhead Lake in early-July 2020
coagulated and flocculated phosphorus suspended in the water column.
Figure 6-10 Impact of copper sulfate on Indianhead Lake total phosphorus calibration
56
Investigation of the monitoring data also indicated that a copper sulfate treatment has the potential to
increase TKN concentration in Indianhead Lake. The orange line in Figure 6-11 shows the calibrated TKN
concentrations compared to the monitored data represented with the blue circles. The purple line shows
the expected TKN concentrations if a copper sulfate treatment was not applied to the lake. The purple line
indicates that TKN concentrations in late-summer and early-fall would likely have been significantly lower
without a copper sulfate treatment. Therefore, it is hypothesized that the type of copper sulfate treatment
applied to Indianhead Lake was likely chelated. Chelation allows copper sulfate, which is normally in a
solid form, to remain in a liquid state for spray applications. Chelated copper can also remain in the water
column for longer periods, which can increase the toxicity to algae and extends the target application
area. Several chelating agents can have high concentrations of nitrogen, and this is likely why we are
seeing a large increase in nitrogen concentrations around the timing of the copper sulfate application.
This was not confirmed as information on the application procedure and products was not available.
The impacts of copper sulfate treatment on chlorophyll-a, total phosphorus, and TKN were very similar in
Arrowhead Lake.
To better understand and quantify the impacts of copper sulfate on water quality parameters (e.g.,
chlorophyll-a, TKN, total phosphorus), more rigorous monitoring could be employed before, during, and
after future copper sulfate applications.
Figure 6-11 Impact of copper sulfate on Indianhead Lake total nitrogen concentrations
57
6.3.3.2 Macrophyte Nutrient Uptake
Macrophytes provide many benefits to lake ecosystems, including the uptake of nutrients. Model
results indicate that phosphorus uptake by aquatic plants in Arrowhead Lake in 2020 likely created
competition for phytoplankton and kept phytoplankton concentrations lower than they would be with
fewer aquatic plants.
Macrophyte management through herbicide treatments or mechanical removal has been completed in
Indianhead Lake for a number of years. Although, lake-wide submerged macrophyte removal was
stopped in spring 2019, macrophyte surveys in 2019 and 2020 indicate limited submerged
macrophytes throughout the lake. As such, macrophytes are not available to utilize nutrients in the
lake providing minimal competition with phytoplankton (algae).
6.3.3.3 Phytoplankton Limitation
Throughout the growing season, various factors can influence the rate and volume of phytoplankton
growth, such as phosphorus, nitrogen, light, and temperature. The model uses Michaelis Menten kinetics
to determine which factor or combination of factors limit growth throughout the modeled time period.
As part of the calibration process, plots were developed that show which factors limited phytoplankton
growth over the model period. Figure 6-12 and Figure 6-13 show the phytoplankton limitation plots for
Arrowhead Lake and Indianhead Lake, respectively. A phytoplankton limitation value of 0 indicates
complete limitation and a value of 1 indicates no limitation. Therefore, the closer a line approaches the x-
axis, the more limiting the factor. The limitation factors summarized include light, phosphorus
(orthophosphate, organic phosphorus), and nitrogen (nitrates).
In Arrowhead Lake, nitrogen, phosphorus, and light showed similar phytoplankton limitation during the
spring of 2020. From May through mid-June, nitrogen was the most limiting factor, although not
significantly more than phosphorus. For the remainder of the summer, phosphorus was the most limiting
factor for phytoplankton growth in Arrowhead Lake.
For Indianhead Lake, nitrogen and light were limiting phytoplankton growth from April through early June
2020 due to excess orthophosphate in the water column in spring and early summer. From early-June
through late-July, nitrogen was the most limiting factor. From late-July through early-fall, the most
limiting factor changed from nitrogen to phosphorus. Review of the data suggests that the stronger
nitrogen limitation in Indianhead Lake is likely because the growth rate of phytoplankton is greater than
the degradation rate of nitrogen (slow decomposition from organic nitrogen forms to ammonia and/or
slow nitrification rate changing ammonia to nitrite and nitrate). In other words, the phytoplankton
continue to grow until they have used up nitrate in the water column, which limits how much
phytoplankton biomass is produced. Monitoring data in 2020 also show high concentrations of total
Kjeldahl nitrogen in Indianhead Lake (summer average 2.1 mg/L), which further suggests that the nitrogen
limitation in the lake is influenced more by the rate of degradation of nitrogen into different forms rather
than the total mass of nitrogen in the lake.
58
The phytoplankton growth limitations developed during model calibration reflect which parameters are
currently limiting growth. As management is implemented, the phytoplankton growth limitations will
change. For example, if phosphorus loading from lake bottom sediment is reduced, phosphorus limitation
may become more dominant throughout the growing season. However, since the calibrated models
indicate that the lakes are partially limited by nitrogen for portions of the growing season under current
conditions, this indicates that nitrogen management can be a complementary management approach
with phosphorus reduction.
Figure 6-12 Phytoplankton Growth Limitation in Arrowhead Lake in 2020
Figure 6-13 Phytoplankton Growth Limitation in Indianhead Lake in 2020
59
6.3.3.4 Curly-leaf Pondweed as a Phosphorus Source
The presence of curly-leaf pondweed and its mid-summer die-off can negatively impact the water quality
of a shallow lake. When lakes start to accumulate a prolific growth of curly-leaf pondweed, a spike in in-
lake total phosphorus concentration is generally observed during the same period of curly-leaf pondweed
die-off and decay. The City of Edina has been monitoring and treating for curly-leaf pondweed in
Arrowhead Lake since 2017 and Indianhead Lake since 2019. Therefore, curly-leaf pondweed did not
influence water quality in Arrowhead and Indianhead Lakes in 2020.
60
7.0 Public Engagement
Public engagement is an important part of completing and implementing water quality studies for lakes in
the Nine Mile Creek watershed. For this study, public engagement included two public meetings and a
survey of residents living adjacent to the lakes, both discussed further below.
7.1 Public Stakeholder Meetings
Because the recommendations that stem from this study will impact residents adjacent to Arrowhead and
Indianhead Lakes, input from residents was sought at two public engagement meetings. The meetings
allowed NMCWD to gain further insight on lake use and historic management through comments,
photos, and data provided by residents. The meetings also presented an opportunity to get feedback
from the public on lake management options and willingness to participate in various activities to
improve lake water quality.
7.1.1 Public Engagement Meeting #1- May 25, 2021
The first public stakeholder engagement meeting was held virtually due to the ongoing Covid-19
pandemic and public safety concerns. In early May 2021, a postcard was mailed to Arrowhead Lake and
Indianhead Lake residents informing them of a planned virtual community meeting held via Zoom on
May 25, 2021. At this meeting, the NMCWD staff and engineers, as well as City of Edina staff provided an
overview of the upcoming study and goals for future management of the lakes. Following the background
presentation on the study, the remainder of the meeting involved open discussion with residents
regarding their observations and concerns regarding lake health. During the meeting, residents were
informed that a formal survey would be mailed to all residents living on the lakes and made available
online so that the NMCWD could gather additional feedback from residents. Comments provided during
the virtual community meeting in May 2021 were considered during the development of management
recommendations and will continue to be considered during implementation of recommended lake
management activities.
7.1.2 Public Engagement Meeting #2 – April 19, 2022
In early April 2021, a postcard was mailed to Arrowhead Lake and Indianhead Lake residents informing
them of a planned community meeting held at Edina Public Works on April 19, 2022. At this meeting, the
NMCWD staff and engineers, as well as City of Edina staff provided an overview of the study conclusions
and anticipated timeline of the proposed lake management activities. Following the background
presentation on the study, the remainder of the meeting involved open discussion with residents to
answer questions and address concerns. Comments provided during the community meeting in April
2022 were considered during development of the final water quality report and will continue to be
considered during implementation of recommended lake management activities.
7.2 Resident Survey
NMCWD developed a survey for residents living adjacent to Arrowhead and Indianhead Lakes to better
understand residents’ lake use, values and perceptions related to the lakes, concerns and issues, current
61
management activities, and willingness to participate in lake improvement efforts. Residents were able to
participate in the survey via a paper survey received in the mail or online. The online survey was active
from July 9 through August 16, 2021, and paper surveys were mailed to residents before July 9, 2021.
Thirty-five (35) surveys were mailed to Arrowhead Lake residents and 33 surveys were mailed to
Indianhead Lake residents. Of the 68 surveys mailed to residents, 31 responses were received (either
mailed back or answers provided online). Of the 31 responses, 14 responses were received from
Arrowhead Lake, and 17 responses were received from Indianhead Lake.
The survey was intended to provide additional community feedback to assist in the evaluation of
management strategies and to provide additional observations, photos, and data to help define lake
health. A summary of the survey questions and provided responses can be found in Appendix D.
Comments provided in the survey were considered during the development of management
recommendations and will continue to be considered during implementation of recommended lake
management activities.
62
8.0 Conclusions and Recommendations
8.1 Conclusions
Recent monitoring data indicates that Arrowhead Lake and Indianhead Lake are not meeting Minnesota’s
water quality standards for shallow lakes.
The summer average (June 1-Sept 30) total phosphorus concentrations measured in 2004, 2014, 2019,
and 2020 in Arrowhead Lake were above the shallow lake standard of 60 µg/L. The Arrowhead Lake
summer average chlorophyll-a concentrations measured in 2011, 2014, and 2020 were also above the
shallow lake standard of 20 µg/L and the summer average Secchi disk transparency depths in 2019 and
2020 were less than the 1.0 meter Secchi depth standard (Figure 8-1).
The plant surveys completed from 2014 through 2020 in Arrowhead Lake indicate declining health of the
macrophyte plant community. In August 2014, 10 plant species were observed in Arrowhead Lake. The
number of species observed in Arrowhead Lake in 2019 ranged from 6 – 7 species, while 2 species were
observed in 2020. The decrease in observed species may be the result of degrading water quality (e.g.,
reduced lake clarity) and plant management activities.
Phytoplankton (microscopic aquatic algae) populations in Arrowhead Lake generally increased from 2004
through 2020. In 2004, the summer average phytoplankton abundance was 13,350 per milliliter. In 2020,
the summer average phytoplankton abundance increased to 48,845 per milliliter. Blue-green algae
abundance increased from 2004 to 2020. The highest concentration of blue-green algae was sampled in
July 2020 at 76,960 per milliliter, which is above the low probability of adverse health effects level set by
the World Health Organization (WHO).
63
Figure 8-1 Summer average total phosphorus and chlorophyll-a concentrations and Secchi disk depth measured in Arrowhead Lake between 2004 and 2020
For Indianhead Lake, water quality has generally declined between 2004 and 2020. The summer average
(June 1-Sept 30) total phosphorus concentrations measured in 2019 and 2020 in Indianhead Lake were
above the shallow lake standard of 60 µg/L. The Indianhead Lake summer average chlorophyll-a
concentrations measured in 2011, 2014, and 2020 were also above the shallow lake standard of 20 µg/L
and the summer average Secchi disk depths in 2014, 2019, and 2020 were less than the 1.0 meter Secchi
depth standard (Figure 8-2).
The plant surveys completed from 2004 through 2020 in Indianhead Lake indicate poor health of the
macrophyte plant community. The number of plant species observed in Indianhead Lake from 2004 to
2020 was consistently low, ranging from 3 – 5 species. The observed lower species count may be caused
by degraded water quality (e.g., reduced lake clarity); however, this correlation is difficult to ascertain due
to yearly plant management efforts.
Changes in phytoplankton populations monitored from 2004 through 2020 corresponded with water
quality (e.g., total phosphorus, chlorophyll-a, Secchi disk depth) changes, both reflecting degrading water
quality in Indianhead Lake over time. In 2004, the summer average phytoplankton abundance was
16,550 per milliliter. In 2020, the summer average phytoplankton abundance increased to 76,430 per
milliliter. Blue-green algae abundance increased from 2004 to 2020. The highest concentration of blue-
green algae was sampled in July 2020 at 144,740 per milliliter, which is above the WHO threshold for
moderate probability of adverse health effects.
64
Figure 8-2 Summer average total phosphorus and chlorophyll-a concentrations and Secchi disk depth measured in Indianhead Lake between 2004 and 2020
8.2 Recommendations
Water quality in Arrowhead and Indianhead Lakes has declined in the past decade and the lakes currently
do not meet water quality standards and ecological health goals. Given this, future management efforts
should be focused on improving lake water quality and ecosystem health with monitoring to assess
progress toward goals and overall changes. The following sections summarize the recommended
monitoring and management strategies for Arrowhead and Indianhead Lakes. These recommended
management efforts are based on a review of available monitoring data and in-lake modeling to predict
improvements resulting from management activities. The modeled water quality improvements can be
viewed in Appendix E (i.e., changes to in-lake phosphorus, nitrogen, and chlorophyll-a concentrations).
8.2.1 Reduce Phosphorus Loading from Lake Bottom Sediment (Internal Loading)
In-lake modeling for this water quality study demonstrated that phosphorus release from bottom
sediments (typically termed internal phosphorus loading) significantly affects lake water quality in both
Arrowhead Lake and Indianhead Lake. Internal phosphorus loading represented 54% and 84% of the total
phosphorus load to Arrowhead Lake and Indianhead Lake, respectively, for the summer growing period of
June through September 2020.
65
For both lakes, most of the internal sediment loading was due to the release of organically bound
phosphorus rather than the mobile phosphorus fraction. Phosphorus in lake bottom sediments is often
bound to a range of different elements such as iron and manganese (often referred to as mobile
phosphorus), aluminum, or calcium. It is the mobile phosphorus fraction that releases from sediment
during low oxygen conditions. Phosphorus can also be found incorporated into organic matter
(organically bound phosphorus). Organically bound phosphorus also releases phosphorus from lake
sediment but typically at a slower rate than mobile phosphorus and the release rate is controlled by lake
water temperature.
Sediment cores collected from Arrowhead and Indianhead Lakes in 2021 showed that the average
concentration of organically bound phosphorus in the top 4 centimeters of sediment was significantly
higher than mobile phosphorus. In Arrowhead Lake the average concentration of organically bound
phosphorus was 36.1 mg P/cm3 wet sediment, while the mobile fraction was 4.1 mg/cm3 wet sediment.
Similarly, for Indianhead Lake the average concentration of organically bound phosphorus was 39.6 mg
P/cm3 wet sediment, while the mobile fraction was 5.6 mg/cm3 wet sediment. These observed
concentrations indicate that a significantly larger percentage of internal phosphorus loading in both lakes
is due to organically bound phosphorus (organic-P) rather than mobile phosphorus (mobile-P). Also,
because Arrowhead and Indianhead Lakes are shallow, have small water volumes, and have no existing
outlets, even a low internal loading rate can significantly increase phosphorus concentrations in the lake
water column.
Because a higher proportion of the internal sediment loading is due to organic-P instead of mobile-P,
internal phosphorus loading will need to be controlled with the addition of iron as well as alum. The iron
addition is designed to capture phosphorus as it is released from the organic-P fraction. Iron is only
effective when oxygen is high enough to keep the iron activated (i.e., in chemistry terminology the iron is
oxidized). Hence, adequate oxygen levels in the lake are important for a successful iron treatment.
In summary, the following sediment management approach is recommended:
• Year 1 (May – September) - Monitor the effectiveness of the existing aerators in Arrowhead and
Indianhead Lakes to determine the extent of bottom sediment aeration and decide if additional
aeration is needed to cover a larger percentage of the bottom sediments. By enhancing the
existing aeration systems, sediment treatments that require adequate dissolved oxygen
concentrations can be applied to the lakes (e.g., iron).
• Year 2 or 3 (Spring) – Apply ferric chloride and alum (as sodium aluminate) to the lake to prevent
internal load from organic phosphorus in lake bottom sediments. Install additional aerator in the
north-west lobe of Arrowhead Lake and the south lobe of Indianhead if needed.
The in-lake models for Arrowhead and Indianhead Lakes were used to predict improvements in lake water
quality by implementing the recommended sediment management approach. Since a sediment
management approach that specifically targets organically bound phosphorus has not been widely
applied in Twin Cities lakes, two assumptions for effectiveness of the internal load reduction from lake
bottom sediment were applied (50% and 70% reduction in internal phosphorus loading from lake bottom
66
sediments). Table 8-1 summarizes the estimated pounds of phosphorus removed from each lake during
the growing season assuming the application of a sediment treatment. Table 8-2 summarizes the
estimated reduction in 2020 summer-average total phosphorus and chlorophyll-a concentrations
assuming a sediment treatment was applied to the lakes. The results presented in these tables assume
copper sulfate treatments are no longer applied to manage algae.
In Arrowhead Lake, assuming a 50% - 70% reduction in internal loading from sediments, modeling
indicates a reduction of 21 – 30 pounds of total phosphorus. This reduction in phosphorus load translates
to a reduction in the summer average total phosphorus and chlorophyll-a concentrations. Modeling
indicates that the 2020 summer average total phosphorus concentration of 80 μg/L in Arrowhead Lake
would be reduced to 51 – 67 μg/L. The MPCA shallow lake total phosphorus water quality standard is 60
μg/L. A reduction in total phosphorus concentrations also leads to a reduction in chlorophyll-a
concentrations. Modeling indicates that the 2020 summer average chlorophyll-a concentration of 27 μg/L
would be reduced to 16 – 20 μg/L. The MPCA shallow lake chlorophyll-a water quality standard is 20 μg/L.
In Indianhead Lake, assuming a 50% - 70% reduction in internal loading from sediments, modeling
indicates a reduction of 37 – 52 pounds of total phosphorus. This reduction in phosphorus load translates
to a reduction in the summer average total phosphorus and chlorophyll-a concentrations. Modeling
indicates that the 2020 summer average total phosphorus concentration of 115 μg/L in Indianhead Lake
would reduce to 71 – 108 μg/L. The MPCA shallow lake total phosphorus water quality standard is 60
μg/L. A reduction in total phosphorus concentrations also lead to a reduction in chlorophyll-a
concentrations. Modeling indicates that the 2020 summer average chlorophyll-a concentration of 34 μg/L
would reduce to 20 – 30 μg/L. The MPCA shallow lake chlorophyll-a water quality standard is 20 μg/L.
Table 8-1 Growing season estimated pounds of phosphorus removed through management of internal loading from lake bottom sediments
Lake
Pounds of Phosphorus Removed (Growing Season) Reduced Internal Loading from Lake Bottom Sediments by 50% Reduced Internal Loading from Lake Bottom Sediments by 70% Arrowhead Lake 21 30 Indianhead Lake 37 52
67
Table 8-2 Summer average total phosphorus and chlorophyll-a concentrations with management of internal loading from bottom sediments
Lake
Summer Average Concentrations Total Phosphorus (μg/L) Chlorophyll-a (μg/L)
Existing Conditions1
Reduced Internal Loading from Lake Bottom Sediments by 50%2
Reduced Internal Loading from Lake Bottom Sediments by 70%2
Existing Conditions1
Reduced Internal Loading from Lake Bottom Sediments by 50%2
Reduced Internal Loading from Lake Bottom Sediments by 70%2 Arrowhead Lake 80 67 51 27 20 16
Indianhead Lake 115 108 71 34 30 20
1 Existing conditions summer average concentrations from observed 2020 monitoring data 2 Summer average concentrations reported assuming copper sulfate treatments no longer applied to manage algae.
8.2.2 Reduce Pollutant Loading from Stormwater Runoff
Watershed and in-lake modeling demonstrated that pollutant loading from the watershed contributes to
water quality concerns in Arrowhead and Indianhead Lakes. Increased impervious areas and storm sewer
systems in the highly residential watersheds allow plant debris, sediment, and fertilizer residuals to flow
towards Arrowhead and Indianhead Lakes at higher volumes.
8.2.2.1 Reduce External Phosphorus Load
Watershed loading represented approximately 46% and 16% of the total phosphorus load to Arrowhead
Lake and Indianhead Lake, respectively, during the summer growing season period of June – September
2020. This suggests that phosphorus management strategies should also focus on reducing external
loading within the direct watershed, when feasible. Since the watershed is mostly fully developed, there
may be limited opportunities for external loading management. NMCWD has stormwater management
rules in place for land development activities. As additional development or re-development occurs in the
watershed, it is recommended that NMCWD consider partnering with landowners to add additional
and/or enhanced BMPs, where feasible and cost effective. Additionally, close monitoring of construction
projects within the watershed is recommended to ensure adequate erosion control practices are in place
and maintained. The NMCWD should also consider seeking out and/or prioritizing project opportunities
through their cost share program (Section 8.2.7).
Cross View Lutheran Church was originally investigated as a potential location to install external BMPs in
the Arrowhead Lake watershed as a part of this water quality study. However, in 2018/2019 Cross View
Lutheran Church applied for a NMCWD permit to install a building addition and complete parking lot
modifications. As part of this construction project, subsurface storage and rain gardens were installed to
retain and treat stormwater runoff from portions of the site. A geotechnical investigation was completed
as part of the permit application and indicated that the underlying soils are clay. Given the poor,
underlaying soils, the site qualified as restricted. Because Cross View Lutheran Church has already installed
68
BMPs as part of the NMCWD redevelopment rules and given the underlying soils are not conducive to
infiltration, no further BMPs were assessed for this parcel as a part of this water quality study. If in the
future, Cross View Lutheran Church reaches out to the NMCWD or the City of Edina with interest in
providing additional water quality treatment, considerations can be made for partnership opportunities at
that time.
As an alternative to largescale BMPs, a more rigorous street sweeping program within the Arrowhead and
Indianhead watersheds is an external management practice that could reduce external phosphorus
loading. An advantage of such a program, especially in a fully developed watershed, is that the
management practice can be implemented rapidly and is not dependent upon uncontrollable factors such
as redevelopment timelines or land ownership practices. Street sweeping is a source control practice that
directly reduces the potential for plant debris and sediment discharges to downstream lakes. The City of
Edina has expressed interest in a targeted public street sweeping program as follows: Sweeping two times
a month in spring and fall (May, October, November) and sweeping one time per month in summer (June,
July, August, September). While implementation of this enhanced sweeping frequency would capture
more debris and sediment than the City’s existing program (twice a year), a disadvantage of street
sweeping is that pollutants can still build-up and wash off between sweepings depending on climate
conditions. It is recommended that NMCWD continue to work with the City of Edina to evaluate public
street sweeping options and the most appropriate way to track success of an enhanced street sweeping
program.
Published research on street sweeping effectiveness has largely focused on the mass of solids removed
from impervious surfaces rather than impacts to stormwater runoff concentrations and downstream
waterbodies. Due to limited quantification of street sweeping’s impacts to stormwater runoff
concentrations, the effectiveness of street sweeping as a BMP could not be applied to the models used in
this study. Therefore, no specific estimates of phosphorus removal or impacts to summer average
concentrations are reported for street sweeping.
8.2.2.2 Reduce External Nitrogen Loads
External nitrogen loading, in the form of plant debris and fertilizer residues, can also affect lake water
quality by supporting algal growth. A targeted street sweeping program that reduces phosphorus will also
reduce nitrogen. It is recommended that the NMCWD continue to work with the City of Edina to evaluate
public street sweeping options and the most appropriate way to track nitrogen and phosphorus source
control outcomes in the watersheds.
Fertilizer application to residential lawns is a source of nitrogen to Arrowhead and Indianhead Lakes and
reduced fertilizer application can improve the water quality of these lakes. It is recommended that the
NMCWD continue to educate citizens on fertilization best practices for downstream water quality
protection. One program that the NMCWD could consider is to promote/coordinate testing of residential
soils. Testing of residential soils could help residents to better understand the need for nitrogen
fertilization on their lawns and help avoid over-fertilization practices.
69
The University of Minnesota Soil Testing Laboratory offers lawn analysis testing (Regular test $17). Soil
samples collected from existing lawns and tested by the laboratory are intended to aid in evaluating the
fertility and chemical condition of the soils. Based on the test results, fertilization recommendations are
calculated to assist residents to provide adequate levels of nutrients for healthy plant growth without
adversely affecting the environment. Fertilization recommendations include:
• Fertilization Ratio (N-P-K)
• Total amount of each nutrient to apply each year
• Recommendations on when to fertilize and how much to apply each application
• Amount of lime to apply each year
If residents increase their knowledge on existing lawn health, fertilization practices can be reduced and/or
optimized in the watershed. The University recommends performing a soil test approximately every 3
years to reassess if lawn management practices should change.
While reducing external nitrogen inputs to downstream waterbodies is always a best practice, decreasing
the nitrogen load from the Arrowhead and Indianhead watersheds will likely not result in short-term water
quality benefits. Review of the monitoring and modeling data indicates that when phytoplankton
experienced growth limitation due to nitrogen, this correlated with phytoplankton growth rates exceeding
nitrogen degradation rates to bioavailable forms rather than the total mass of nitrogen in the lake. In both
Arrowhead and Indianhead Lakes the total Kjeldahl nitrogen (TKN) concentrations were high compared to
nitrate concentrations (bioavailable form). Since there already are high existing concentrations of TKN in
Arrowhead and Indianhead Lakes, reductions in external nitrogen loading will have limited impact on
phytoplankton growth in the short-term. However, enacting management efforts to control nitrogen can
have long-term water quality benefits, especially when tied with external phosphorus control, such as
street sweeping.
8.2.2.3 Reduce External Chloride Loads
Observed chloride concentrations in Arrowhead Lake are higher than chloride concentrations in
Indianhead Lake. This is likely due to the larger proportion of highway land use in the Arrowhead Lake
watershed. Because high concentrations of chloride can harm fish and plant life, the MPCA has
established a chronic exposure chloride standard of 230 mg/L or less and considers two or more
exceedances of the chronic standard in 3 years to be an impairment. Of the Arrowhead Lake monitoring
data collected in 2011, 2014, 2019, and 2020, chloride concentrations have not been observed to exceed
230 mg/L. The highest concentration recorded was 185 mg/L in April 2019. Average chloride
concentrations in Arrowhead Lake from 2011 – 2020 remained fairly consistent (average yearly
concentrations (April – October) ranged from 120 – 150 mg/L). Comparatively, the highest concentration
recorded in Indianhead Lake was 66 mg/L in April 2019. Average chloride concentrations in Indianhead
Lake from 2011 – 2020 remained fairly consistent (average yearly concentrations (April – October) ranged
from 34 – 57 mg/L). Continued periodic water quality monitoring of chloride concentrations is
recommended. NMCWD should also consider seeking opportunities to work with MnDOT and other
70
property owners and/or management companies, especially within the Arrowhead Lake watershed, to
reduce winter salt usage.
8.2.3 Continue to Monitor Growth and Impacts from Curly-leaf Pondweed
The presence of curly-leaf pondweed and its mid-summer die-off can negatively impact lake water
quality. The City of Edina has been managing curly-leaf pondweed in Arrowhead Lake since 2017 and
Indianhead Lake since 2019 to reduce species growth and proliferation. The invasive species growth
should continue to be tracked with periodic surveys to assess if conditions are changing and management
should continue as needed.
8.2.4 Determine Timeline to Discontinue Copper Sulfate Treatments
Copper sulfate treatments have been used in Arrowhead and Indianhead Lakes to manage algal growth.
Review of the Arrowhead Lake and Indianhead Lake monitoring data collected before and after copper
treatments provides the following observations and conclusions regarding the effects of copper treatment
on lake water quality:
• Chlorophyll-a concentrations decreased following treatment due to toxicity of copper to
phytoplankton species
• Total phosphorus concentrations decreased based on monitoring data and modeling results. The
hypothesis regarding this observation is that the type of copper treatment applied to the lakes
coagulated and flocculated phosphorus suspended in the water column, resulting in reduced total
phosphorus concentrations.
• Total nitrogen concentrations significantly increased at the time of application based on
monitoring data and modeling results. The hypothesis regarding this observation is that the type
of copper sulfate treatment applied to the lakes was chelated. Chelation allows copper sulfate,
which is normally in a solid form, to remain in a liquid state for spray applications. Chelated
copper sulfate can also remain buoyant in the water column for longer periods, which can
increase the toxicity to algae and extends the target application area. Several chelating agents can
have high concentrations of nitrogen, and this is likely why there was a large increase in nitrogen
concentrations around the timing of the copper sulfate application. This has not been confirmed,
as the application procedure and products used were not disclosed.
The NMCWD does not typically recommend conducting copper treatments to manage algae, preferring
to focus on long-term strategies to reduce nutrients (algal food source) versus short-term removal of
excessive algae. However, the observed decreases in total phosphorus following treatments were
unanticipated. Due to the unexpected impacts of copper sulfate treatments on phosphorus and nitrogen,
the following are recommended for consideration:
• To better quantify the impacts of copper sulfate on water quality parameters (e.g., chlorophyll-a,
total nitrogen, total phosphorus), more rigorous monitoring is recommended before, during, and
after a copper sulfate application. Monitoring observations could then be used to inform future
in-lake water quality modeling and develop prescriptive management recommendations for
copper sulfate treatments.
71
• In-lake modeling shows that copper sulfate treatments (following best practices) reduced
phosphorus concentrations in Arrowhead and Indianhead Lakes in 2020. While ultimately it is
recommended that the copper treatments be discontinued, it may be beneficial to wait to
discontinue until internal loading has been controlled (by alum and iron treatments).
• A quantitative and qualitative assessment will be conducted by NMCWD after one year of lake
monitoring data has been collected following the final internal load treatment. If observations
indicate that summer average chlorophyll-a concentrations have fallen below 20 μg/L, NMCWD
will recommend that copper treatments be discontinued.
8.2.5 Encourage Residents to Promote Healthy Aquatic and Shoreline Plant Growth
The Arrowhead and Indianhead Lake Associations have participated in submerged macrophyte removal
programs in the past by making requests to the City of Edina. Although the City has recommended that
these macrophyte removal practices stop, the City has accommodated these requests in the past and has
coordinated contractors to apply for appropriate permits from the MNDNR and conduct the treatments.
Due to numerous benefits of healthy aquatic macrophyte communities (e.g., phytoplankton competition,
invasive macrophyte competition, fisheries habitat, increased water clarity), it is recommended that
NMCWD and the City continue to educate residents regarding the benefits of macrophytes in lakes and
discourage removal practices.
Residents have expressed concerns about lily pads impeding lake recreation to the City of Edina and
during public open house events attended by NMCWD and the City. The MNDNR allows lakeshore
residents to maintain a channel a maximum of 15 feet wide to open water by cutting or pulling floating-
leaf plants by hand. Any other destruction of floating-leaf vegetation requires a permit with the MNDNR.
Lakeshore residents can work with the City of Edina to discuss City policies regarding lily pad removal.
Due to the high value of aquatic plants to lake ecosystems, NMCWD does not encourage the removal of
native submerged or floating-leaf vegetation beyond the extent allowed by MNDNR.
Promoting healthy shoreline vegetation and increasing buffer widths can help to improve wildlife habitat
and decrease overland stormwater inflow into lakes. The invasive species, purple loosestrife, was found in
shoreline buffers surrounding Arrowhead Lake. The invasive species, purple loosestrife and yellow iris,
were found in shoreline buffers surrounding Indianhead Lake. It is recommended to encourage residents
to apply for NMCWD cost-share grants to assist with the invasive species removal and native species
restoration of their shorelines. Please see Section 8.2.7 for additional information.
8.2.6 Encourage Residents to Discontinue Lake Dye Applications
The Arrowhead and Indianhead Lake Associations have participated in dye applications (Aquashade, Sky
Blue) in the past. Pond dyes are sold as products that block light and restrict algal photosynthesis and
submerged macrophyte growth. Typically, the dyes are used in smaller applications, such as ornamental
ponds, fountains, and golf course ponds. The effectiveness of using pond dyes on larger lake scales is not
well documented and the impacts of these dyes on aquatic organisms (e.g., reproduction, toxicity, food
web changes) are not well understood. It is recommended that the dye applications be discontinued.
72
8.2.7 Encourage Residents to Apply for NMCWD Cost-Share Grants
Because the Arrowhead and Indianhead Lake watersheds are almost fully developed, opportunities for
large-scale external BMPs will be limited. It is recommended that NMCWD continue to promote their cost
share grant programs to residents, associations, nonprofits, schools, and businesses for smaller-scale
projects. NMCWD Stewardship Grants can help individuals install projects that prevent stormwater
pollution to downstream lakes, such as rain gardens, shoreline buffer improvements, and permeable
pavers. Native Habitat Restoration Grants are also available to assist with project costs associated with
restoring native plant and wildlife habitat, such as prairie and woodland restorations.
Additional information on NMCWD Cost-Share Grants can be found at
https://www.ninemilecreek.org/get-involved/grants/
73
9.0 Cost – Benefit Analysis
9.1 Opinion of Probable Cost
Planning-level opinions of probable cost were developed for the evaluated management alternatives that
have the greatest potential for water quality improvement in Arrowhead and Indianhead Lakes, as
discussed in Section 8.2. These opinions of cost are intended to provide assistance in evaluating and
comparing alternatives and should not be assumed as absolute values. The estimated costs are
summarized in Table 9-1. Detailed opinions of probable cost are included in Appendix F.
The opinions of probable cost summarized in Table 9-1 generally correspond to standards established by
the Association for the Advancement of Cost Engineering (AACE). Class 5 planning-level opinions of costs
were used based on the limited project definition, wide-scale use of parametric models to calculate
estimated costs (i.e., making extensive use of order-of-magnitude costs from similar projects), and
uncertainty, with an acceptable range of between -30% and +50% of the estimated project cost.
Table 9-1 Planning-level cost estimates for evaluated management alternatives
Description Planning-Level Cost Estimate1 Planning-Level Cost Range
Estimated Life of Project
Arrowhead Lake Bottom Sediment Treatment (alum, iron, aerator optimization, monitoring) $125,000 $87,000 - $186,000 10 years
Indianhead Lake Bottom Sediment Treatment (alum, iron, aerator optimization, monitoring) $120,000 $85,000 -$182,000 10 years
Arrowhead and Indianhead Lake Watershed Targeted Street Sweeping Program $250,0002 $176,000 - $377,000 10 years
Soil Sampling Program for Resident Fertilization Assessment $20,000 $14,000 – $30,000 3 years
1 Rounded to the nearest $5,000.
2The planning-level cost estimate for a targeted street sweeping program includes capital costs for purchasing a regenerative air sweeper and includes operations and maintenance costs for a one-year trial run of enhanced sweeping in the Arrowhead and Indianhead lakes watersheds.
9.1.1 Cost Details
9.1.1.1 Lake Bottom Sediment Treatments
The opinions of probable cost for the lake bottom sediment treatments of Arrowhead and Indianhead
Lakes are based on correspondence with alum application contractors, ferric chloride application
74
contractors, and aeration installation and management contractors. The primary assumptions for the
sediment treatment opinions of cost are:
• Mobilization/Demobilization approximately $15,000
• Arrowhead Lake aluminum treatment:
o 3954 gallons alum
o 1977 gallons sodium aluminate
• Indianhead Lake aluminum treatment:
o 4273 gallons alum
o 2136 gallons sodium aluminate
• Dissolved oxygen monitoring to assess aeration needs
• Addition of 1 aerator to Arrowhead Lake and 1 aerator to Indianhead Lake
• Arrowhead Lake iron treatment
o 4,300 gallons ferric chloride
• Indianhead Lake iron treatment
o 5,580 gallons ferric chloride
• 150 hours per lake for project planning, design, data review, field observation, and monitoring
It should be noted that some laboratory experimental work will need to be conducted as part of the
feasibility study to determine the gallons of sodium aluminate (a base / buffer) needed to balance the
acidity of ferric chloride (an acid).
9.1.1.2 Targeted Street Sweeping
Unit costs for targeted street sweeping in the Arrowhead and Indianhead Lake watersheds were based, in
part, on the values summarized in the City of Edina MN Street Sweeping Management Plan (Emmons &
Olivier Resources, Inc. (EOR), 2015). The assumptions used to develop the opinion of cost are:
• The cost of a new Crosswind 4-Wheel Regenerative Air Sweeper is approximately $210,000 and the buy-back cost after 10 years of use is approximately $20,000. It was assumed a new Sweeper is needed to account for the additional area.
• Within the Arrowhead and Indianhead Lake watersheds there is approximately 9.6 miles of sweepable public street curb.
• Sweeper operation speed is estimated at 4.5 miles per hour and average fuel consumption is 5 miles per gallon.
• The sweeping path width of a high efficiency, two-sided broom sweeper with a pick-up head is approximately 12 feet.
• 1.5 hours of labor is needed for every 4 hours of sweeping time.
• Total transit (brush off) is about 3 times the total amount of swept miles.
• The maximum number of hours worked in one week by a single worker is 40 hours.
• Sweeping frequency is as follows:
o Twice a month in May, October, and November
o Once a month from June - September
• Labor cost = $75/hour
75
• Fuel cost = $3.50/gallon
• Sweeper Maintenance cost = $4,800/year
• The City of Edina is responsible for the operations and maintenance of the street sweeping program.
Using the outlined assumptions, to sweep the public streets in the Arrowhead and Indianhead Lake
watersheds 10 times per year, one high efficiency regenerative air sweeper would be needed. Since the
City of Edina currently owns one high-efficiency regenerative air sweeper that is used all over the city, the
opinion of cost assumes one additional high-efficiency regenerative sweeper would be purchased. Vehicle
maintenance, labor, and fuel costs are summarized as annual costs.
9.1.1.3 Soil Sampling for Resident Fertilization Assessment
The primary opinion of cost assumptions for the soil sampling program to assess resident fertilization
practices and target nitrogen reductions are:
• University of Minnesota Standard Soil Testing per sample = $17/sample
• 50% participation of residents adjacent to Arrowhead and Indianhead Lakes (68 total residential
properties adjacent to Arrowhead and Indianhead Lakes) = 34 residential properties
o NMCWD can consider expanding sampling efforts to non-lakeshore residents living
within the watersheds.
• 3 hours of labor per residential property needed to provide project background, schedule soil
sampling field work, and discuss results summary
• 1 hour of labor per residential property needed to complete field soil sample collection
• 8 hours of project-wide data review by project engineer
• 16 hours of initial team project planning
9.2 Cost Benefit Analysis
The management strategies considered to help improve water quality in Arrowhead and Indianhead Lakes
range in type, scale, cost, and effectiveness. Some strategies have larger, upfront capital costs, whereas
others are more programmatic or may require periodic or annual recurrence. To account for these
variations, a comparison of cost-benefit of the potential management strategies was conducted, where
reasonably feasible. Results of the cost-benefit analysis can help to understand the value derived and
associated costs, for each management practice and combinations thereof.
Estimated costs for the evaluated management activities were annualized to help compare the cost-
benefit ratio. The annualized cost for each management alternative is based on anticipated maintenance,
replacement costs, and anticipated useful life span of the projects/treatments. A 3% inflation rate was
assumed. The annualized cost for each alternative is calculated as the value of ‘n’ equal, annual payments,
where ‘n’ is the anticipated useful life span of the project or treatment. The annualized cost estimates for
each management alternative are summarized in
76
Table 9-2. For the cost-benefit analysis, the benefit is in terms of phosphorus removed (in pounds) during
the time period of June through September (i.e., phosphorus that did not enter the lake system as a result
of the management practice).
77
Table 9-2 Cost-benefit summaries for Arrowhead and Indianhead evaluated management alternatives
Description Management Type
Estimated Annualized Cost
Average Pounds of TP Load Removed
Annualized Cost per Pound of TP Removed
(June - Sept) (June - Sept)
Arrowhead Lake Bottom Sediment Treatment Internal $14,000 - $15,000 21 - 30 $500 - $700
Indianhead Lake Bottom Sediment Treatment Internal $14,000 - $15,000 37 - 52 $300 - $400
Arrowhead and Indianhead Lake Watershed Targeted Street Sweeping Program External $42,000 Not Modeled -
Soil Sampling Program for Resident Fertilization Assessment External $7,000 Targets Nitrogen Reduction -
78
10.0 References
Barr Engineering Co. (2006). Arrowhead and Indianhead Lakes - Use Attainability Analysis.
Barr Engineering Co. (2007). Kohlman Lake Dredging Feasibility Study. Prepared for Ramsey-Washington
Metro Watershed District.
Barr Engineering Co. (2018). Lake Cornelia and Lake Edina Water Quality Report (UAA).
Barr Engineering Co. (2020). Lake Smetana Water Quality Study - Use Attainability Analysis.
Cayan, D. (2013). Future climate: projected average. Assessment of climate change in the southwest United
States: a report prepared for the National Climate Assessment., 101-125.
Cooke, G., Welch, E., Peterson, S., & Newroth, P. (1993). Restoration and Management of Lakes and
Reservoirs, Second Edition. Boca Raton, FL: Lewis Publishers.
Dettinger, M., Udall, M., & Georgakakos, A. (2015). Western water and climate change. Ecological
Applications, 2069-2093.
Dokulil, M. (2013). Old wine in new skins - eutrophication reloaded: Glogal perspectives of potential
amplification by climate warming, altered hydrological cycle and human interference.
Eutrophication: Causes, Economic Implications and Future Challenges, 95-125.
Dokulil, M. (2014). Impact of climate warming on European inland waters. Inland Waters, 4, 27-40.
Dokulil, M. (2016). Climate impacts on ecohydrological process in aquatic systems. Ecohydrology and
Hydrobiology, 16, 66-70.
Dokulil, M., & Teubner, K. (2011). Eutrophication and climate change: Present situation and future
scenarios. Eutrophication: Causes, Consequences, and Control, 1-16.
Emmons & Olivier Resources, Inc. (EOR). (2015). City of Edina, MN Street Sweeping Management Plan. City
of Edina, MN.
Giorgi, F., Im, E., Coppola, E., Diffenbaugh, N., Gao, X., Mariotti, L., & Shi, Y. (2011). Higher hydroclimatic
intensity with global warming. Journal of Climate, 24, 5309-5324.
Hope, D., Naegeli, M., Chan, A., & Grimm, N. (2004). Nutrients on asphalt parking sufaces in an urban
environment. Water, Air, and Soil Pollution, 4, 371-390.
Huisman, J., Matthijs, H., & Visser, P. (2005). Harmful cyanobacteria. Springer.
79
Huser, B., & Pilgrim, K. (2014). A simple model for predicting aluminum bound phosphorus formation and
internal loading reduction in lakes after aluminum addition to lake sediment. Water Research, 53,
378-385.
I.E.P, Inc. (1990). p8 Urban Catchment Model. Version 3.5. Providence, RI: Prepared for the Narragansett
Bay Project. .
Indiana Department of Natural Resources. (2019, April 13). Aquatic Invasive Species (AIS) Eurasian Water
Milfoil. Retrieved from https://www.in.gov/dnr/files/EURASIAN_WATERMILFOIL.pdf
James, W., Barko, J., & Eakin, H. (2001). Direct and Indirect Impacts of Submerged Aquatic Vegetation on the
Nutrient Budget of an Urban Oxbow Lake. U.S. Army Research and Development Center,
Vicksburg, MS: APCRP Technical Notes Collection (ERDC TN-APCRP-EA-02).
Jeppesen, E., Kronvang, B., Meerhoff, M., Søndergaard, M., Hansen, K., Andersen, T., . . . Olesen, J. (2009).
Climate change effects on runoff, catchment phosphorus loading and lake ecological state, and
potential adaptations. Journal of Environmental Quality, 38, 1930-1941.
Jeppesen, E., Meerhoff, M., Davidson, T., Trolle, D., Søndergaard, M., Lauridsen, T., . . . Nielsen, A. (2014).
Climate change impacts on lakes: An integrated ecological perspective based on a multi-faceted
approach, with special focus on shallow lakes. Journal of Limnology, 73, 88-111.
Kharin, V., Zwiers, F., Zhang, X., & Wehner, M. (2013). Changes in temperature and precipitation extremes
in the CMIP5 ensemble. Climatic Change, 119, 345-357.
LaMarra, V. J. (1975). Digestive activities of carp as a major contributor to the nutrient loading of lakes.
Verh. Int. Verein. Limnol. 19, 2461-2468.
Metropolitan Council. (2016). Metropolitan Council Land Use Coverage Dataset (GIS database).
MNDNR. (2017). How the Climate of Minnesota is and is not Changing. (K. Blumenfeld, Performer) State
Climatologist Office, at the City Engineers Association of Minnesota (CEAM) Annual Meeting,
Minnesota.
MPCA. (2008). Minnesota Rules Chapter 7050: Standards for Protection of Water of the State.
MPCA. (2019, April 13). Eurasian Water Milfoil. Retrieved from https://www.pca.state.mn.us/eurasian-
water-milfoil
NMCWD. (2017, amended 2019). Nine Mile Creek Watershed District Water Management Plan.
NOAA, N. O. (2013). Atlas 14. Volume 8.
Paerl et. al, H. W. (2016). It Takes Two to Tango: When and Where Dual Nutrient (N&P) Reductions Are
Needed to Protect Lakes and Downstream Ecosystems. Environmental Science and Technology.
80
Passeport, E., & Hunt, W. (2009). Asphalt parking lot runoff nutrient characterization for eight sites in
North Carolina, USA. Jounral of Hydrologic Engineering, 14(4), 352-361.
Pilgrim, K., Huser, B., & Brezonik, P. (2007). A method for comparative evaluation of whole-lake and inflow
alum treatment. Water Research, 41, 1215-1224.
Sahoo, G., Forrest, A., Schladow, S., Reuter, J., Coats, R., & Dettinger, M. (2016). Climate change impacts on
lake thermal dynamics and ecosystem vulnerabilities. Limnology and Oceanography, 61, 496-507.
Schueler, T. (1987). Controlling Urban Runoff: A practical manual for planning and designing urban BMPs.
Washington D.C., USA: Prepared for Washington Metropolitan Water Resources Planning Board.
Metropolitan Washinton Council of Governments.
Trenberth, K. (1999). Conceptual framework for changes of extremes of the hydrological cycle with climate
change. Climatic Change, 42, 327-339.
Trenberth, K. (2011). Changes in precipitation with climate change. Climate Research, 47, 123-138.
Trenberth, K., Smith, L., Qian, T., Dai, A., & Fasullo, J. (2003). The changing character of precipitation.
Bulletin of the American Meteorological Society, 84, 1205-1217.
Vighi, M., & Chiaudani, G. (1985). A Simple Method to Estimate Lake Phosphorus Concentrations Resulting
from Natural, Background, Loadings. Water Resources, 19(8), 987-991.
Walsh, J. (2014). Our changing climate. In Climate Change Impacts in the United States: the Third National
Climate Assessment. Washington D.C., USA: U.S. Global Change Research Climate Program.
Wei, Q., Zhu, G., Wu, P., Cui, L., Kaisong, Z., Zhou, J., & Zhang, W. (2010). Distributions of typical
contaminant species in urban short-term storm runoff and their fates during rain events: A case of
Xiamen City. Journal of Environemntal Sciences, 22(4), 533-539.
World Health Organization. (2003). Guidelines for Safe Water Environments. In Coastal and Fresh Waters.
Volume 1 (p. 219). Geneva, Switzerland.
Appendices
Appendix A
Aquatic Plant Surveys
!?Nymphaea odorataCeratopyllum demersum 1-2Potamogeton crispus 1Myriophyllum spicatum 1-2Potamogeton sp. (narrow) 2-3Nymphaea odorataNuphar luteaChara sp. 1Myriophyllum spicatum 1-2Chara sp. 3PotamogetoncrispusZosterella dubiaMyriophyllumspicatum 1-2Chara sp.Potamogeton crispus 2-3Myriophyllum spicatum 2-3+Chara sp. 3+Nymphaea odorata (sparse)Typha sp.Nymphaea odorataNuphar lutea (sparse)Nymphaea odorataNuphar lutea (sparse)Scirpus sp.Scirpus sp.Typha sp.Typha sp.Nymphaea odorata (sparse) Lythrum salicariaChara sp. 2-3Myriophyllum spicatum 1-2Lythrum salicariaTypha sp.Typha sp.Water QualityMonitoring Location!;N0 75 150Meters0 300 600FeetBarr Footer: ArcGIS 10.0, 2011-09-07 14:59:33.700000 File: I:\Projects\23\27\634\Macrophyte_Maps\2011\Arrowhead_Lake\ArrowheadLk_Macrophytes_Base - 20110602.mxd User: kac2Imagery Source: 2009 AEARROWHEAD LAKE MACROPHYTESURVEYJune 2, 2011Nine Mile Creek Watershed DistrictLegend!?Water Quality Monitoring LocationEmergent PlantsFloating Leaf PlantsSubmerged Aquatic PlantsNo Aquatic Vegetation*Note: Bold red name indicates extremely aggressive/invasive introduced species.FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Ceratophyllum demersum observed - sporadic, light densityTypha sp.Typha sp.Scirpus sp.Typha sp.Typha sp.Typha sp.Typha sp.Scirpus sp.Iris versicolorIris versicolorNymphaea odorata(sparse)Common NameScientific NameEurasion watermilfoilMyriophyllum spicatumStonewortNitella sp.CoontailCeratophyllum demersumWater stargrassZosterella dubiaNarrowleaf pondweedPotamogeton sp.Curlyleaf pondweedPotamogeton crispusMuskgrassChara sp.Water stargrassZosterella dubiaCommon NameScientific NameWhite waterlilyNymphaea odorataYellow waterlilyNuphar luteaCommon NameScientific NameCattailTypha sp.Blue flag irisScirpus sp.Iris blueflagIris versicolorBullrushScirpus sp.Purple loosestrifeLythrum salicariaSubmerged Aquatic PlantsEmergent PlantsFloating Leaf PlantsNitella sp. 3Nymphaeaodorata
!?Chara sp. 3+Myriophyllum spicatum 1Chara sp. 2-3+Nymphaea odorataCeratopyllum demersum 1-2Potamogeton sp. (narrow) 2-3Nymphaea odorataNuphar luteaChara sp. 1Riccia fluitans 1Myriophyllum spicatum 1Chara sp. 3Zosterella dubiaPotamogeton sp. 3Chara sp. 2-3Chara sp. 3+Nymphaea odorataTypha sp.Nymphaea odorataNuphar luteaNymphaea odorataNuphar lutea (sparse)Scirpus sp.Scirpus sp.Typha sp.Typha sp.Nymphaea odorata (sparse) Lythrum salicariaLythrum salicariaTypha sp.Typha sp.Water QualityMonitoring Location!;N0 75 150Meters0 300 600FeetBarr Footer: ArcGIS 10.0, 2011-09-07 16:18:07.221000 File: I:\Projects\23\27\634\Macrophyte_Maps\2011\Arrowhead_Lake\ArrowheadLk_Macrophytes August 2011.mxd User: kac2Imagery Source: 2009 AEARROWHEAD LAKE MACROPHYTESURVEYAugust 16, 2011Nine Mile Creek Watershed DistrictLegend!?Water Quality Monitoring LocationEmergent PlantsFloating Leaf PlantsSubmerged Aquatic PlantsNo Aquatic Vegetation*Note: Bold red name indicates extremely aggressive/invasive introduced species.FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy-Ceratophyllum demersumobserved - sporadic, light density-Nuphar microphyllapresent throughout lake- Copper sulfate treatment on August 8, 2011- Lake has probably been treated for milfoil, density has droppedsince June - found in one area onlyTypha sp.Typha sp.Scirpus sp.Typha sp.Typha sp.Typha sp.Typha sp.Scirpus sp.Iris versicolorIris versicolorNymphaea odorataNitella sp. 3Common NameScientific NameEurasion watermilfoilMyriophyllum spicatumStonewortNitella sp.CoontailCeratophyllum demersumWater stargrassZosterella dubiaNarrowleaf pondweedPotamogeton sp.Curlyleaf pondweedPotamogeton crispusMuskgrassChara sp.Water stargrassZosterella dubiaSlender ricciaRiccia fluitanaCommon NameScientific NameWhite waterlilyNymphaea odorataYellow waterlilyNuphar luteaSmall yellow pond lilyNuphar microphyllaCommon NameScientific NameCattailTypha sp.Blue flag irisScirpus sp.Iris blueflagIris versicolorBullrushScirpus sp.Purple loosestrifeLythrum salicariaSubmerged Aquatic PlantsFloating Leaf PlantsEmergent PlantsPotamogeton sp. 3Nymphaea odorataChara sp. 3
!?
Typha sp.
Typha sp.
Typha sp.
Scirpus sp.
Iris versicolor
Chara sp. 1Myriophyllum spicatum 1-2Potamogeton crispus 1-2
Nymphaea odorata
Ceratopyllum demersum 1Potamogeton crispus 1-2Myriophyllum spicatum 1-2Potamogeton sp. (narrow) 2Chara sp. 3 Nymphaea odorataNuphar lutea (sparse)
Chara sp. 2-3Potamogeton crispus 2-3
Potamogetoncrispus 2-3+
Zosterella dubia
Myriophyllumspicatum 1-2
Chara sp. 1 Potamogeton crispus 2-3+Myriophyllum spicatum 2-3
Chara sp. 1-2
Nymphaea odorata (sparse)
Typha sp.
Nymphaea odorataNuphar lutea (sparse)
Nymphaea odorataNuphar lutea (sparse)
Scirpus sp.
Typha sp.
Typha sp.
Nymphaea odorata (sparse)
Chara sp. 1-2Myriophyllum spicatum 1-2
Lythrum salicaria
Typha sp.
Typha sp.
Chara sp. 1-2
Typha sp.
Typha sp.
Typha sp.Scirpus sp.
Nitella sp. 3
Iris versicolor
Nymphaea odorata (sparse)
Myriophyllumspicatum 1-2
Potamogeton crispus 1-2
Chara sp. 1
Iris versicolor
Water QualityMonitoring Location
!;N
0 75 150
Meters
0 300 600
Feet
Barr Footer: ArcGIS 10.3, 2015-05-12 14:31 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Arrowhead Lake Macrophytes_20140616.mxd User: kac2ARROWHEAD LAKE MACROPHYTESURVEY
June 16, 2014Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Ceratophyllum demersum observed - sporadic, light density- High water level- Dense algal mats (submerged and floating)- Iris versicolor sporatic along entire lake perimeter- Aerators on
Imagery Source: 2012 Twin Citites - USGS(MNGeo WMS)
Common Name Scientific Name
Coontail Ceratophyllum demersumCurlyleaf pondweed Potamogeton crispusEurasion watermilfoil Myriophyllum spicatumMuskgrassChara sp.Narrow leaf pondw eed Potamogeton sp.Stonew ort Nitella sp.Water stargrass Zosterella dubia
Common Name Scientific Name
White w aterlily Nymphaea odorataYellow w aterlily Nuphar lutea
Common Name Scientific Name
Bulrush Scirpus sp.Cattail Typha sp.Iris blueflag Iris versicolorPurple loosestrife Lythrum salicaria
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?
Typha sp.
Typha sp.
Typha sp.
Scirpus sp.
Iris versicolor
Chara sp. 1Myriophyllum spicatum 1Potamogeton sp. 1-2Ceratophyllum demersum 1
Nymphaea odorata
Ceratopyllum demersum 1Potamogeton sp. (narrow) 2Chara sp. 3Nitella sp. 1-2Najas sp. 1 Nymphaea odorataNuphar lutea (sparse)
Chara sp. 2Najas sp. 1-2
Zosterella dubia 1
Nitella sp. 1
Chara sp. 1Najas sp. 1Potamogeton sp. 1-3+Nitella sp. 1-3
Chara sp. 1Nitella sp. 1-3Potamogeton sp. 2-3
Nymphaea odorata (sparse)
Typha sp.
Nymphaea odorataNuphar lutea (sparse)
Nymphaea odorataNuphar lutea (sparse)
Scirpus sp.
Typha sp.
Typha sp.
Nymphaea odorata (sparse)
Chara sp. 1-2
Lythrum salicaria
Typha sp.
Typha sp.
Chara sp. 1
Typha sp.
Typha sp.
Typha sp.Scirpus sp.
Nitella sp. 3+
Iris versicolor
Nymphaea odorata (sparse)
Potamogeton sp. 2-3
Nitella sp. 2-3
Chara sp. 1Nitella sp. 2-3
Iris versicolor
Water QualityMonitoring Location
!;N
0 75 150
Meters
0 300 600
Feet
Barr Footer: ArcGIS 10.3, 2015-05-12 14:33 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Arrowhead Lake Macrophytes_20140811.mxd User: kac2ARROWHEAD LAKE MACROPHYTESURVEY
August 11, 2014Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Ceratophyllum demersum observed - sporadic, light density- High water level- Algal mats (submerged and floating), less dense than June- Iris versicolor sporatic along entire lake perimeter- Aerators off- Lake treated with Tribune and Copper sulfate on 6/25 and 7/25- Myriophyllum spicatum: no visual or sampled specimens exceptsouthwest basin- Potamogeton crispus: no visual or sampled specimens
Imagery Source: 2012 Twin Citites - USGS(MNGeo WMS)
Common Nam e Scientific Name
Bushy pondweed Najas sp.Coontail Ceratophyllum demersumEurasion watermilfoil Myriophyllum spicatumMuskgrassChara sp.Narrow leaf pondw eed Potamogeton sp.Stonew ort Nitella sp.Water stargrass Zosterella dubia
Common Nam e Scientific Name
White w aterlily Nymphaea odorataYellow w aterlily Nuphar lutea
Common Nam e Scientific Name
Bulrush Scirpus sp.Cattail Typha sp.Iris blueflag Iris versicolorPurple loosestrife Lythrum salicaria
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?Typha sp.Typha sp.Typha sp.Scirpus sp.Iris versicolor Ceratophyllum demersum 1Polygonum amphibiumLythum salicariaNitella sp. 1-2Potamogeton crispusPolygonum amphibiumLythrum salicariaCeratophyllum demersum 1Myriophyllum spicatum 1Nymphaea odorataCeratopyllum demersum 1Myriophyllum spicatum - 1-2Nymphaea odorataNuphar lutea (sparse)Myriophyllum spicatum 1Nymphaea odorata (sparse)Typha sp.Nymphaea odorataNuphar lutea (sparse)Nymphaea odorata (sparse)Typha sp.Nymphaea odorata (sparse)Lythrum salicariaTypha sp.Typha sp. (sparse)Scirpus sp.Typha sp.Typha sp.Scirpus sp.Nitella sp. 1-2Iris versicolor Nymphaea odorata (sparse) Iris versicolorWater QualityMonitoring Location!;N0 75 150Meters0 300 600FeetBarr Footer: ArcGIS 10.6.1, 2019-07-08 08:41 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2019\Arrowhead Lake Macrophytes_20190614.mxd User: MJM3ARROWHEAD LAKE MACROPHYTESURVEYJune 14, 2019Nine Mile Creek Watershed District!?Water Quality Monitoring LocationEstimated Survey RouteEmergent PlantsFloating Leaf PlantsSubmerged Aquatic PlantsNo Aquatic Vegetation*Note: Bold red name indicates extremely aggressive/invasive introduced species.FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Ceratophyllum demersum observed - sporadic, light density- High water level- Iris versicolor sporatic along entire lake perimeter- Aerators on- Lake treated 5-14-18Imagery Source: Nearmap 1ft imagery April, 2019Common NameScientific NameEurasion watermilfoilMyriophyllum spicatumStonewortNitella sp.CoontailCeratophyllum demersumCurlyleaf pondweedPotamogeton crispusCommon NameScientific NameWhite waterlilyNymphaea odorataYellow waterlilyNuphar luteaCommon NameScientific NameCattailTypha sp.Iris blueflagIris versicolorBullrushScirpus sp.Purple loosestrifeLythrum salicariaWater smartweed Polygonum amphibiumSubmerged Aquatic PlantsFloating Leaf PlantsEmergent Plants
!?
Typha sp.
Typha sp.
Typha sp.
Scirpus sp.
Iris versicolor
Ceratophyllum demersum 1
Polygonum amphibium
Lythum salicaria
Nitella sp. 1
Polygonum amphibium
Lythrum salicaria
Ceratophyllum demersum 1
Polygonum amphibium
Nymphaea odorata
Nymphaea odorata
Ceratopyllum demersum 1Myriophyllum spicatum - 1-2
Nymphaea odorataNuphar lutea (sparse)
Nymphaea odorata
Typha sp.
Nymphaea odorataNuphar lutea (sparse)
Nymphaea odorata
Typha sp.
Nymphaea odorata
Lythrum salicaria
Typha sp.
Typha sp. (sparse)
Scirpus sp.Typha sp.
Typha sp.Scirpus sp.
Nitella sp. 1
Iris versicolor
Nymphaea odorata (sparse)
Iris versicolor
Water QualityMonitoring Location
!;N
0 75 150
Meters
0 300 600
Feet
Barr Footer: ArcGIS 10.7.1, 2019-09-03 13:14 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2019\Arrowhead Lake Macrophytes_20190815.mxd User: RCS2ARROWHEAD LAKE MACROPHYTESURVEY
August 15, 2019
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
GPS Survey Route
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'
- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Ceratophyllum demersum observed - sporadic, light density- High water level- Iris versicolor sporatic along entire lake perimeter- Aerators on- Lake treated 5-14-18
Imagery Source: Nearmap 1ft imagery April, 2019
Common Name Scientific Name
Eurasion watermilfoil Myriophyllum spicatumStonewortNitella sp.Coontail Ceratophyllum demersum
Common Name Scientific Name
White waterlily Nymphaea odorataYellow waterlily Nuphar lutea
Common Name Scientific Name
Cattail Typha sp.Iris bluefl ag Iris versicolorBullrushScirpus sp.Purple loosestrife Lythrum salicariaWater s martweed Polygonum a mphibium
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?
Polygonumamphibium
Lythum salicaria
Nitella sp. 1-2
Polygonum amphibium (sparse)
Nymphaea odorata
Nymphaea odorata (sparse)
Nymphaea odorata
Nymphaea odorata (sparse)
Typha sp.
Nymphaea odorata (sparse)
Typha sp.
Nitella sp. 1-2
Nymphaea odorata (sparse)
Water QualityMonitoring Location
!;N
0 75 150
Meters
0 250 500
Feet
Barr Footer: ArcGIS 10.7.1, 2020-07-30 21:50 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2020\Arrowhead Lake Macrophytes_20200611.mxd User: kac2ARROWHEAD LAKE MACROPHYTESURVEY
June 11, 2020
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Estimated Survey Route
Emergent Plants
Floating Leaf Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Iris versicolor sporatic along entire lake perimeter- Aerators on
- Lake treated recently and was being treated onJune 11 as survey was ending.
Imagery Source: Nearmap 1ft imagery April, 2019
Common Name Scientific Name
Stonewort Nitella sp.
Common Name Scientific Name
White wa terlily Nymphaea odorata
Common Name Scientific Name
Cattail Typha sp.Purple loosestrife Lythum salicaria
Wa ter smartweed Polygonum amphibium
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?
Polygonumamphibium
Lythrum salicaria
Nitella sp. 1
Polygonum amphibium (sparse)
Nymphaea odorata
Lythrumsalicaria
Lythrumsalicaria
Nymphaea odorata
Nymphaea odorata (numerous patches,dense in areas)
Nymphaea odorata
Nymphaea odorata
Typha sp.
Nymphaea odorata(numerous patches)
Typha sp.
Nitella sp. 1
Nymphaea odorata(numerous patches)
Water QualityMonitoring Location
!;N
0 75 150
Meters
0 250 500
Feet
Barr Footer: ArcGIS 10.7.1, 2020-09-14 21:27 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2020\Arrowhead Lake Macrophytes_20200820.mxd User: kac2ARROWHEAD LAKE MACROPHYTESURVEY
August 20, 2020
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Estimated Survey Route
Emergent Plants
Floating Leaf Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- No macrophytes found in water > 6.0 to 7.0'- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy
- Iris versicolor sporatic along entire lake perimeter- Aerators on- Lake treated on June 11 as survey was ending.
Imagery Source: Nearmap 1ft imagery April, 2019
Common Name Scientific Name
Stonewort Nitella sp.
Common Name Scientific Name
White wa terlily Nymphaea odorata
Common Name Scientific Name
Cattail Typha sp.Purple loosestrife Lythrum salicaria
Wa ter smartweed Polygonum amphibium
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?!;N0 75 150Meters180 0 180FeetBarr Footer: ArcGIS 10.0, 2011-07-19 12:09:48.341000 File: I:\Projects\23\27\634\Macrophyte_Maps\2011\Indianhead_Lake\Indianhead Lake Macrophytes June 2011.mxd User: kac2Imagery Source: 2009 AEINDIANHEAD LAKE MACROPHYTESURVEYJune 2, 2011Nine Mile Creek Watershed DistrictLegend!?Water Quality Monitoring LocationEmergent PlantsFloating Leaf PlantsSubmerged Aquatic PlantsNo Aquatic Vegetation*Note: Bold red name indicates extremely aggressive/invasive introduced species.FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Macrophytes found in entire water body, less dense near centerof water body.- Water color indicates that "Aqua Shade" may have been used.Iris sp. (yellow flower)Scirpus sp.Iris sp. (yellow flower)Typha sp.Iris sp. (yellow flower) - sporadicTypha sp.Iris sp. (yellow flower)Nitella sp 3+Potamogeton sp. (narrowleaf) 2-3Iris sp. (yellow flower)Scirpus sp.Iris sp. (yellow flower)Riccia fluitansTypha sp.Nitella sp. 3Iris sp. (yellow flower)Nitella sp. 1Iris sp. (yellow flower)Nitella sp. 3+Iris sp. (yellow flower)Typha sp.Nitella sp. 2-3Potamogeton sp. (narrowleaf) 1-3Typha sp.Nitella sp. 3+Typha sp.Scirpus sp.Iris sp. (yellow flower)Schoenoplectus fluviatilisWater QualityMonitoring LocationCommon NameScientific NameSlender ricciaRiccia fluitansStonewortNitella sp.Narrowleaf pondweedPotamogeton sp. (narrowleaf)Common NameScientific NameCommon NameScientific NameYellow irisIris sp. (yellow flower)CattailTypha sp.BullrushScirpus sp.River bullrushSchoenoplectus fluviatilisArrowheadSagittaria sp.Submerged Aquatic PlantsFloating Leaf PlantsNone FoundEmergent Plants
!?!;N0 75 150Meters0 180 360FeetBarr Footer: ArcGIS 10.0, 2011-09-07 14:44:53.041000 File: I:\Projects\23\27\634\Macrophyte_Maps\2011\Indianhead_Lake\Indianhead Lake Macrophytes August 2011.mxd User: kac2Imagery Source: 2009 AEINDIANHEAD LAKE MACROPHYTESURVEYAugust 16, 2011Nine Mile Creek Watershed DistrictLegend!?Water Quality Monitoring LocationEmergent PlantsFloating Leaf PlantsSubmerged Aquatic PlantsNo Aquatic Vegetation*Note: Bold red name indicates extremely aggressive/invasive introduced species.FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Macrophytes found in entire water body, less dense near centerof water body.- Water color indicates that "Aqua Shade" may have been used.- Lake treated with copper sulfate August 2, 2011Iris sp. (yellow flower)Scirpus sp.Iris sp. (yellow flower)Typha sp.Iris sp. (yellow flower) - sporadicTypha sp.Iris sp. (yellow flower)Nitella sp 3+Potamogeton sp. (narrowleaf) 1Iris sp. (yellow flower)Scirpus sp.Iris sp. (yellow flower)Riccia fluitansTypha sp.Nitella sp. 3Iris sp. (yellow flower)Nitella sp. 1Iris sp. (yellow flower)Nitella sp. 3+Iris sp. (yellow flower)Typha sp.Nitella sp. 2-3Potamogeton sp. (narrowleaf) 1Typha sp.Nitella sp. 3+Typha sp.Scirpus sp.Iris sp. (yellow flower)Schoenoplectus fluviatilisWater QualityMonitoring LocationCommon NameScientific NameSlender ricciaRiccia fluitansStonewortNitella sp.Narrowleaf pondweedPotamogeton sp. (narrowleaf)Common NameScientific NameCommon NameScientific NameYellow irisIris sp. (yellow flower)CattailTypha sp.BullrushScirpus sp.River bullrushSchoenoplectus fluviatilisArrowheadSagittaria sp.Submerged Aquatic PlantsFloating Leaf PlantsNone FoundEmergent PlantsPotamogeton sp. 1-3Potamogeton sp. 1-3
!?
!;N
0 75 150
Meters
0 180 360
Feet
Barr Footer: ArcGIS 10.3, 2015-05-12 13:34 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140616.mxd User: kac2INDIANHEAD LAKE MACROPHYTESURVEY
June 16, 2014Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Macrophytes found in entire water body, less dense near centerof water body.- Aqua Shade has been added to lake.- High water level- Aerators on.
Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp.Iris pseudacorus
Typha sp.
Iris pseudacorus
Nitella sp 3+Potamogeton crispus 1-2
Iris pseudacorus
Scirpus sp.Iris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. 3
Iris pseudacorus
Nitella sp. 1
Iris sp. (yellow flower)
Nitella sp. 3+
Iris pseudacorus
Typha sp.
Nitella sp. 2-3Potamogeton sp. crispus 1-2
Typha sp.
Nitella sp. 3+
Typha sp.Scirpus sp.Iris sp. (yellow flower)
Schoenoplectus fluviatilis
Water QualityMonitoring Location
Potamogeton crispus 1-2
Potamogeton crispus 1-2
Potamogeton crispus 1-2
Typha sp.
Imagery Source: 2012 Twin Citites - USGS(MNGeo WMS)
Com m on Name Scientific Nam e
Curlyleaf pondw eed Potamogeton crispusSlender riccia Riccia fluitansStonewortNitella sp.
Com m on Name Scientific Nam e
Com m on Name Scientific Nam e
Bulrush Scirpus sp.Cattail Typha sp.Iris Iris sp.River Bulrush Schoenoplectus fluviatilisYellow iris Iris pseudacorus
Submerged Aquatic Plants
Floating Leaf Plants
None Found
Emerge nt Plants
!?
!;N
0 75 150
Meters
0 180 360
Feet
Barr Footer: ArcGIS 10.3, 2015-05-12 13:39 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140811.mxd User: kac2INDIANHEAD LAKE MACROPHYTESURVEY
August 11, 2014Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely aggressive/invasive introduced species.
FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Macrophytes found in entire water body, less dense near centerof water body.- Aqua Shade has been added to lake.- High water level- Aerators on.- Lake treated with Tribune and Copper Sulfate on 6/22 and
Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp.Iris pseudacorus
Typha sp.
Iris pseudacorus
Nitella sp 1-2
Iris pseudacorus
Scirpus sp.Iris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. 3
Iris pseudacorus
Nitella sp. 1
Iris sp. (yellow flower)
Nitella sp. 1
Iris pseudacorus
Typha sp.
Nitella sp. 1
Typha sp.
Nitella sp. 1-2
Typha sp.Scirpus sp.Iris sp. (yellow flower)
Schoenoplectus fluviatilis
Water QualityMonitoring Location
Typha sp.
Imagery Source: 2012 Twin Citites - USGS(MNGeo WMS)
Common Name Scientific Name
Slender riccia Riccia fluitansStonewortNitella sp.
Common Name Scientific Name
Common Name Scientific Name
Bulrush Scirpus sp.Cattail Typha sp.Iris Iris sp.River Bulrush Schoenoplectus fluviatilisYellow iris Iris pseudacorus
Submerged Aquatic Plants
Floating Leaf Plants
None Found
Emergent Plants
!?Barr Footer: ArcGIS 10.3, 2015-05-12 13:34 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140616.mxd User: kac2Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp. (sparse)Iris pseudacorus
Typha sp.
Iris pseudacorus
Iris pseudacorus
Lythrum salicariaIris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. (sparse)
Iris versicolorIris pseudacorus
Nitella sp. (sparse)
Iris pseudacorus
Iris pseudacorus
Typha sp.
Typha sp.
Typha sp.Scirpus sp.Iris pseudacorus
Polygonum amphibium
Water QualityMonitoring Location
Typha sp.Iris pseudacorusLythrum salicaria
Lythrum salicaria
!;N
0 75 150
Meters
0 180 360
Feet
INDIANHEAD LAKE MACROPHYTESURVEY
June 14, 2019
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Estimated Survey Route
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely
aggressive/invasive introduced species.
FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy
- Aqua Shade has been added to lake.- High water level
- Aerators on.- Lake was treated last year 5-14-2018
- Submerged plants extremely sparse
Imagery Source: Nearmap 1 ft imagery April, 2019
Barr Footer: ArcGIS 10.6.1, 2019-08-22 09:51 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2019\Indianhead Lake Macrophytes_20190614.mxd User: MJM3Common Name Scientific Name
Stonewort Nitella sp.
Common Name Scientific Name
Common Name Scientific Name
Yellow iris Iris pseudacorusCattailTypha sp.Bullrush Scirpus sp.Purple loosestrife Lythrum salicariaNorthern blue flag Iris versicolorWater smartweed Polygonum amphibiumSlender Riccia Riccia fluitans
Submerged Aquatic Plants
Floating Leaf Plants
None Found
Emergent Plants
!?Barr Footer: ArcGIS 10.3, 2015-05-12 13:34 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140616.mxd User: kac2Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp. (sparse)Iris pseudacorus
Typha sp.
Iris pseudacorus
Iris pseudacorus
Lythrum salicariaIris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. (sparse)
Iris versicolorIris pseudacorus
Nitella sp. (sparse)
Iris pseudacorus
Iris pseudacorus
Typha sp.
Typha sp.
Typha sp.Scirpus sp.Iris pseudacorus
Polygonum amphibium
Water QualityMonitoring Location
Typha sp.Iris pseudacorusLythrum salicaria
Lythrum salicaria
!;N
0 75 150
Meters
0 180 360
Feet
INDIANHEAD LAKE MACROPHYTESURVEY
August 15, 2019
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
GPS Survey Path
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely
aggressive/invasive introduced species.
FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Aqua Shade has been added to lake.- High water level- Aerators on.- Lake was treated last year 5-14-2018- Submerged plants extremely sparse
-Potamogeton crispus turions observed floatingon water surface
-Lemna minor on water surface throughout lake
Imagery Source: Nearmap 1 ft imagery April, 2019
Barr Footer: ArcGIS 10.6.1, 2019-08-22 12:36 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2019\Indianhead Lake Macrophytes_20190815.mxd User: MJM3Common Name Scientific Name
Stonewort Nitella sp.
Common Name Scientific Name
Small duckweed Lemna minor
Common Name Scientific Name
Yellow iris Iris pseudacorusCattailTypha sp.Bullrush Scirpus sp.Purple loosestrife Lythrum salicariaNorthern blue flag Iris versicolorWater smartweed Polygonum amphibiumSlender Riccia Riccia fluitans
Submerged Aquatic Plants
Floating Leaf Plants
Emergent Plants
!?Barr Footer: ArcGIS 10.3, 2015-05-12 13:34 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140616.mxd User: kac2Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp. (sparse)Iris pseudacorus
Typha sp.
Iris pseudacorus
Iris pseudacorus
Lythrum salicariaIris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. (sparse)
Iris versicolorIris pseudacorus
Nitella sp. (sparse)
Iris pseudacorus
Iris pseudacorus
Typha sp.
Typha sp.
Typha sp.Scirpus sp.Iris versicolorIris pseudacorus
Polygonum amphibium
Water QualityMonitoring Location
Typha sp.Iris pseudacorusLythrum salicaria
Lythrum salicaria
Nitella sp. - 1
!;N
0 75 150
Meters
0 180 360
Feet
INDIANHEAD LAKE MACROPHYTESURVEY
June 11, 2020
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Estimated Survey Route
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely
aggressive/invasive introduced species.
FIELD NOTES:
- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy
- Aqua Shade has been added to lake- Aerators on- Submerged growth extremely sparse- Sporadic algal mats near shore
Imagery Source: Nearmap 1 ft imagery April, 2019
Barr Footer: ArcGIS 10.7.1, 2020-07-13 12:05 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2020\Indianhead Lake Macrophytes_20200611.mxd User: kac2Common Name Scientific Name
Slender riccia Riccia fluitans
Stonewort Nitella sp.
Common Name Scientific Name
Common Name Scientific Name
Yellow iris Iris pseudacorus
Cattail Typha sp.
Bullrush Scirpus sp.Purple loosestrife Lythrum salicaria
Northern blue flag Iris versicolor
Submerged Aquatic Plants
Floating Leaf Plants
None Found
Emergent Plants
!?Barr Footer: ArcGIS 10.3, 2015-05-12 13:34 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\23270634_Project\Maps\Macrophyte_Maps\2014\Indianhead Lake Macrophytes_20140616.mxd User: kac2Iris pseudacorus
Scirpus sp.Iris pseudacorus
Typha sp. (sparse)Iris pseudacorus
Typha sp.
Iris pseudacorus
Iris pseudacorus
Lythrum salicariaIris pseudacorus
Riccia fluitans
Typha sp.Nitella sp. (sparse)
Iris versicolorIris pseudacorus
Iris pseudacorus
Iris pseudacorus
Typha sp.
Typha sp.
Typha sp.Scirpus sp.Iris versicolorIris pseudacorus
Polygonum amphibium
Water QualityMonitoring Location
Typha sp.Iris pseudacorusLythrum salicaria
Lythrum salicaria
Nitella sp. - 1
!;N
0 75 150
Meters
0 180 360
Feet
INDIANHEAD LAKE MACROPHYTESURVEY
August 20, 2020
Nine Mile Creek Watershed District
!?Water Quality Monitoring Location
Estimated Survey Route
Emergent Plants
Floating Leaf Plants
Submerged Aquatic Plants
No Aquatic Vegetation
*Note: Bold red name indicates extremely
aggressive/invasive introduced species.
FIELD NOTES:- Macrophyte densities estimated as follows:1=light; 2=moderate; 3=heavy- Aerators on- Submerged growth extremely sparse
Imagery Source: Nearmap 1 ft imagery April, 2019
Barr Footer: ArcGIS 10.7.1, 2020-09-03 15:17 File: I:\Client\Nine_Mile_Creek_WD\Work_Orders\Macrophyte_Maps\2020\Indianhead Lake Macrophytes_20200820.mxd User: kac2Common Name Scientific Name
Slender riccia Riccia fluitans
Stonewort Nitella sp.
Common Name Scientific Name
Common Name Scientific Name
Yellow iris Iris pseudacorus
Cattail Typha sp.
Bullrush Scirpus sp.Purple loosestrife Lythrum salicaria
Northern blue flag Iris versicolor
Submerged Aquatic Plants
Floating Leaf Plants
None Found
Emergent Plants
Appendix B
Fisheries Assessment (2021)
K:\018641-000\Admin\Docs\018641-000 MEMO September 2021 Fisheries survey Draft 178 E 9TH STREET | SUITE 200 | SAIN | 55101 | 651.286.8450 | WSBENG.COM
Memorandum
To: Jessica Vanderwerff Wilson
From: Jordan Wein, WSB
Date: January 14, 2022
Re: Arrowhead Fisheries Survey
Edina, MN
WSB Project No. 018641-000
BACKGROUND
Arrowhead Lake (MN DNR DOW #27004500) located in Edina, MN is a 22-acre lake with an
average depth of 4.5 feet with a maximum of 7 feet. Hypoxia (lack of enough oxygen to support
living tissues) can occur in winter when ice and snow have prevented reintroduction of dissolved
oxygen to the lake. This can result in the observation of fish kills in springtime when ice melts off
the lake. In addition, in shallow lakes, hot and dry months in summer can deplete oxygen to the
point of summer fish kills. To prevent this, a common management option is to install aeration
systems to artificially add dissolved oxygen to the water column. An aeration system with 3
diffusers near the southeast area of the lake were installed in 1994 to attempt to maintain a
healthy fishery through conditions that usually result in hypoxia in the lake (winterkill). However,
a lack of knowledge of this fishery exists and thus the effect of the aerators is not well known.
This system is paid for by the lake association and maintenance is coordinated by the service
contractor through the City of Edina.
A standard MN DNR fishery was completed in 1995 and showed a species diversity of black
bullhead, green sunfish and fathead minnows using standard trap nets. This diversity seems to
suggest regular periods of hypoxia since these species are especially resistant to low levels of
dissolved oxygen. MN DNR permitted stocking of 400 bluegill sunfish and 600 largemouth bass
(both species susceptible to mortality in hypoxic conditions) occurred in 1994 by lake residents,
however no fish from that stock was recaptured indicating low or no survival of stocked species.
Since then, in 2016, the lake was stocked with 1000 bluegill fingerlings and 1000 yearlings as
well as 430 largemouth bass fingerlings and 90 yearlings. No MN DNR survey has been
conducted since then.
This memo describes the use of nets to conduct a standard fisheries survey at Arrowhead Lake in
Edina, MN. The results will give a baseline index for catch per unit effort (CPUE) for comparison
of subsequent surveys in order to understand population and diversity dynamics as well as
presence/absence of invasive species. This event was conducted between September 19, 2021
through September 21, 2021.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 2
ARROWHEAD TRAP NET SURVEYS: SEPTEMBER 2021
Methods
We used three (3) MN DNR standard double frame fyke trap nets with ¾” mesh and a 60’ lead
line. In addition, we used three (3) mini fyke trap nets with 3/8” mesh and a 30’ lead line (seen in
Figure 1). This style of traps targets the natural movement patterns of fish along the shorelines
during a 24-hour period. Fish swimming along the shore is guided toward funneled throats the
allow the fish in but is not able to escape. The contents of each trap are emptied, all fish are
identified, and a representative sample is measured for length for comparative purposes.
Figure 1: Example of mini fyke trap net set in a lake.
Results
Both standard trap nets and mini fyke trap nets resulted in the same diversity of species: black
bullhead, bluegill sunfish, green sunfish, hybrid sunfish, and largemouth bass as shown in Figure
2.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 3
Figure 2: Largemouth bass on left and bluegill on right from traps
Figure 3: Catch per unit effort (CPUE) by species and trap type in 2021.
0
20
40
60
80
100
120
Black bullhead Bluegill Green sunfish Hybrid sunfish Largemouth
bassNumber of fish caughtSpecies
Mini TrapNet
Standard TrapNet
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 4
Figure 4: Average length by species and trap type in 2021.
0
2
4
6
8
10
12
14
16
18
Black bullhead Bluegill Green sunfish Hybrid sunfish Largemouth
bassAverage length (inches)Species
Mini TrapNet
Standard TrapNet
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 5
Figure 5: CPUE comparison of MN DNR survey in 1995 and WSB survey in 2021 using standard trap nets.
For comparison purposes, the following will focus the CPUE only from standard trap nets since
both the 1995 and 2021 surveys used standard sizes. The most abundant species was bluegill
sunfish with a CPUE of 18.17 and an average size of 5.8 inches. Next most abundant was
largemouth bass with a CPUE of 2.17 and an average size of 13.1 inches. Black bullhead and
green sunfish showed the same abundance with CPUE of 0.17 and an average size of 9.8 and
6.2 inches respectively.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
Black bullhead Bluegill Green sunfish Largemouth bassCPUE
Species
1995 survey 2021 survey
Fall 2021 Fisheries Survey Memo
December 6, 2021
Page 6
K:\018641-000\Admin\Docs\018641-000 MEMO September 2021 Fisheries survey Draft 178 E 9TH STREET | SUITE 200 | SAIN | 55101 | 651.286.8450 | WSBENG.COM CONCLUSIONS
Preliminary results show a stark contrast between the two different surveys. The 1995 survey
captured species that are typical in lakes that suffer frequent winter kills due to hypoxia.
However, the turnover to species like bluegill and largemouth bass suggests stocking of these
species in 2016 was successful and there are normally abundant in Arrowhead Lake. Follow up
surveys in spring of 2022 will continue to establish the status of the fishery after an additional
winter has passed.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 7
APPENDIX:
Figure 4:Map of aeration diffusers in Arrowhead Lake
K:\018642-000\Admin\Docs\September 2021 Indianhead Fisheries survey Draft
Memorandum
To: Jessica Vanderwerff Wilson From: Jordan Wein, WSB Date: January 14, 2022 Re: Indianhead Fishery Survey Edina, MN WSB Project No. 018642-000
BACKGROUND
Indianhead Lake (MN DNR DOW #27004400) located in Edina, MN is a 14-acre lake with an
average depth of 4.5 feet with a maximum of 6 feet. Hypoxia (lack of enough oxygen to support living tissues) can occur in winter when ice and snow have prevented reintroduction of dissolved oxygen to the lake. This can result in the observation of fish kills in springtime when ice melts off the lake. In addition, in shallow lakes, hot and dry months in summer can deplete oxygen to the point of summer fish kills. To prevent this, a common management option is to install aeration systems to artificially add dissolved oxygen to the water column. An aeration system consisting of
4 aerators spread throughout the lake was installed in 1979 as part of a Clean-Flo system to control algae and submerged plants. Furthermore, the aeration system served to prevent conditions that usually result in hypoxia in the lake and fish winterkill. However, a lack of knowledge of this fishery exists and thus the effect of the aerators is not well known. This system
is paid for by the lake association and maintenance is coordinated by the service contractor through the City of Edina. To this point, there has not been a standard MN DNR fishery assessment using standard trap nets. Therefore, it is believed this is the first standardized survey efforts on the lake. In the last 10 years, MN DNR permitted stocking has occurred in 2013 and 2016, stocking native species
like bluegill sunfish (200 and 5000 respectively) black crappie, (50 and 2000 respectively) and largemouth bass (200 and 1900 respectively). This stocking was paid for by lake residents. The desire was to promote a healthy, native fisheries balanced for sustainable fish populations. The results of these surveys will give a baseline index for catch per unit effort (CPUE) for comparison of subsequent surveys in order to understand population and diversity dynamics as well as presence/absence of invasive species. This event was conducted between September 19, 2021 through September 21, 2021.
ARROWHEAD TRAP NET SURVEYS: SEPTEMBER 2021
Methods We used three (3) MN DNR standard double frame fyke trap nets with ¾” mesh and a 60’ lead line. In addition, we used three (3) mini fyke trap nets with 3/8” mesh and a 30’ lead line (seen in Figure 1). This style of traps targets the natural movement patterns of fish along the shorelines
Fall 2021 Fisheries Survey Memo January 14, 2022 Page 2
K:\018642-000\Admin\Docs\September 2021 Indianhead Fisheries survey Draft
during a 24-hour period. Fish swimming along the shore is guided toward funneled throats the allow the fish in but is not able to escape. The contents of each trap are emptied, all fish are identified, and a representative sample is measured for length for comparative purposes.
Figure 1: Example of mini fyke trap net set in a lake.
Results
Both standard trap nets and mini fyke trap nets resulted in the same diversity of species: black
crappie, bluegill sunfish, golden shiner, hybrid sunfish, and largemouth bass as shown in Figure 2. The most abundant by far were bluegill sunfish with an average size of 6.7 inches, followed by
hybrid sunfish at an average length of 8.2 inches, then black crappie at 7.3 inches, golden shiners at 6.9 inches and finally largemouth bass at 10.6 inches (see Figures 3 and 4 below).
Figure 2: On the left, snapping turtles were regularly caught in out traps as well as bluegills, black crappie
and golden shiners shown on the right.
Fall 2021 Fisheries Survey Memo January 14, 2022 Page 3
K:\018642-000\Admin\Docs\September 2021 Indianhead Fisheries survey Draft
Figure 3: Total fish captured by species and trap type in 2021.
Figure 4: Average length by species and trap type in 2021.
0
100
200
300
400
500
600
Black crappie Bluegill Golden shiner Hybrid sunfish LargemouthbassNumber of fish caughtSpecies
Mini TrapNet
Standard TrapNet
0
2
4
6
8
10
12
Black crappie Bluegill Golden shiner Hybrid sunfish Largemouth
bassAverage length (inches)Species
Mini TrapNet
Standard TrapNet
Fall 2021 Fisheries Survey Memo January 14, 2022 Page 4
K:\018642-000\Admin\Docs\September 2021 Indianhead Fisheries survey Draft
Figure 5: CPUE comparison of MN DNR survey in 1995 and WSB survey in 2021 using standard trap nets.
CONCLUSIONS Preliminary results support the assumption that the stocking efforts in 2013 and 2016 were successful and recruitment (survival of fish spawned within the lake) could be occurring. However, the lack of abundant small fish (<3 inches) may suggest low recruitment, but high survival of stocked fish. Regardless, the fishery seems to have benefitted from stocking efforts and the installation of aeration systems. However, data from dissolved oxygen surveys will help to study the effect over an entire year (data to come in final report). Follow up fishery surveys in spring of 2022 will continue to establish the status of the fishery after an additional winter has passed.
Fall 2021 Fisheries Survey Memo January 14, 2022 Page 5
K:\018642-000\Admin\Docs\September 2021 Indianhead Fisheries survey Draft
APPENDIX
Figure 4: Map of aerator diffusers in Indianhead Lake
Appendix C
In-lake Water Quality Calibration Plots
C-1
Figure C-1 Arrowhead Lake water surface elevation calibration
Figure C-2 Arrowhead Lake phytoplankton limitations calibration
C-2
Figure C-3 Arrowhead Lake total phosphorus calibration
Figure C-4 Arrowhead Lake orthophosphate calibration
C-3
Figure C-5 Arrowhead Lake total kjeldahl nitrogen (TKN) calibration
Figure C-6 Arrowhead Lake nitrate + nitrite calibration
C-4
Figure C-7 Arrowhead Lake chlorophyll-a calibration
C-5
Figure C-8 Indianhead Lake water surface elevation calibration
Figure C-9 Indianhead Lake phytoplankton limitations calibration
C-6
Figure C-10 Indianhead Lake total phosphorus calibration
Figure C-11 Indianhead Lake orthophosphate calibration
C-7
Figure C-12 Indianhead Lake total kjeldahl nitrogen (TKN) calibration
Figure C-13 Indianhead Lake nitrate + nitrite calibration
C-8
Figure C-14 Indianhead Lake chlorophyll-a calibration
Appendix D
Arrowhead Lake and Indianhead Lake Public Survey
Arrowhead Lake and
Indianhead Lake
Public Survey
Prepared September 2021
Nine Mile Creek Watershed District | 12800 Gerard Drive, Eden Prairie, MN 55346
| 952.358.2276 | ninemilecreek.org
The Nine Mile Creek Watershed District (NMCWD) sought to gather feedback from residents on
Arrowhead Lake and Indianhead Lake in Edina, through a survey that was mailed to those residents and
also made available to them online. This report summarizes the survey responses received.
Survey
The survey is meant to provide community feedback to NMCWD staff, engineers, and the board of
managers, along with the City of Edina to assist in the evaluation of management strategies designed to
improve the health of Arrowhead Lake and Indianhead Lake.
The survey was active July 9 - August 16, 2021. To encourage residents on Arrowhead Lake and
Indianhead Lake to take the survey, a paper survey was mailed to all lakeshore residents on July 9, 2021.
35 surveys were mailed to Arrowhead Lake residents and 33 surveys were mailed to Indianhead Lake
residents. An online survey link was provided, as well. The survey link and a
PDF copy of the survey was emailed to the Arrowhead Lake Association Board
and Indianhead Lake Association Board on July 9, 2021, by the City of Edina as
another method of distribution. Reminder postcards with the survey link were
sent out on July 29, 2021, to those that had not taken survey yet.
31 responses were received. Of the 31 responses, 24 were paper surveys that
were mailed back to NMCWD using the postage-paid envelopes provided, and
seven were online surveys. 14 responses were received from Arrowhead Lake,
and 17 responses were received from Indianhead Lake.
The survey instructed that no more than one survey could be completed per adult per household. There
were two paper surveys that did not have any contact information on them. One household took the
survey twice, and the rest of the surveys represented individual households.
ARROWHEAD/INDIANHEAD LAKE SURVEY
OVERVIEW
1
2
SURVEY RESULTS
1. Which lake do you live on in Edina?
Between the two surveys, 31 people responded, 17 (54.8%) lived on Indianhead Lake and 14 (45.2%) lived on
Arrowhead Lake. For clarity, the responses for the remaining questions were separated for each lake.
14 (45.2%)
17 (54.8%)
Arrowhead Lake
Indianhead Lake
6
ARROWHEAD SURVEY RESULTS
How was the survey submitted?
Of the 14 respondents, 8 (57.1%) completed the survey in a paper format and 6 (42.9%) completed the survey online.
3
6 (42.9%)
8 (57.1%)
Online
Paper
3 4
2. What kinds of activities do you do on or near the lake?
Of the 14 respondents, 13 (12 daily and 1 weekly, 92.9%) view wildlife/nature on Arrowhead Lake, 0 (0%) swim in
Arrowhead Lake, 9 (6 weekly and 3 monthly, 64.3%) boat/canoe/kayak in Arrowhead Lake, 7 (1 daily, 2 weekly, 4
monthly, 50%) fish on Arrowhead Lake, 2 (1 weekly and 1 monthly, 14.3%) ice fish on Arrowhead Lake, 9 (1 daily,
6 weekly, and 2 monthly, 64.3%) recreate on Arrowhead Lake in the winter, and 6 (42. 9%) do other activities on
Arrowhead Lake including lake bonfires.
13 (92.9%)
0 (0%)
9 (64.3%)
7 (50%)
2 (14.3%)
9 (64.3%)
6 (42.9%)
Viewing Wildlife/Nature
Swimming
Boating/Canoeing/Kayaking
Open Water Fishing
Ice Fishing
Winter Recreation
Other
5
3. How do you perceive the current health of the lake?
Of the 14 respondents, 4 (28.6%) were unsure how they perceived the current health of Arrowhead Lake, 3 (21.4%)
perceived Arrowhead Lake’s health as good, 2 (14.3%) perceived Arrowhead Lake’s health as neither good nor bad,
and 5 (35.7%) perceived Arrowhead Lake’s health as bad.
4. How has water clarity (how far you can see down into the water) changed since you have
lived on or near the lake?
Of the 14 respondents, 5 (35.7%) were unsure how the water clarity in Arrowhead Lake has changed since living on
or near the lake, 0 (0%) thought clarity in Arrowhead Lake has improved since living on or near the lake, 3 (21.4%)
thought clarity in Arrowhead Lake has remained constant since living on or near the lake, and 6 (42.9%) thought
clarity in Arrowhead Lake has declined since living on or near the lake.
5 (35.7%)
2 (14.3%)
3 (21.4%)
4 (28.6%)
Bad
Neither Good Nor Bad
Good
Unsure
6 (42.9%)
3 (21.4%)
0 (0%)
5 (35.7%)
Declined
Remained Constant
Improved
Unsure
6
5. What do you value and/or appreciate about the lake?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
We value the scenery, wildlife, boating and fishing on the lakeWe value the scenery, wildlife, boating and fishing on the lake
Looking at it. Also enjoy the wildlife that live by it.Looking at it. Also enjoy the wildlife that live by it.
The north woods feel of actually living on a lake with a dock and canoe and fishing! Awesome The north woods feel of actually living on a lake with a dock and canoe and fishing! Awesome
viewview
I love it- that’s why I am still here at 90 years old- still awed by what I see - deer (2 large bucks I love it- that’s why I am still here at 90 years old- still awed by what I see - deer (2 large bucks
7-21) cyotes. One killed my yorkie dog - the alfa female had her pups “7” under my screen 7-21) cyotes. One killed my yorkie dog - the alfa female had her pups “7” under my screen
porch (4&5-2014). Edina police great, helped me cage them and goodbye! We had (unclear) porch (4&5-2014). Edina police great, helped me cage them and goodbye! We had (unclear)
for the winter and they found a good home. Approxcimity to schools - church - freeways - for the winter and they found a good home. Approxcimity to schools - church - freeways -
shopping - (unclear). Good people - all ages kind (unclear) smart - 4 grandkids - now 4 great shopping - (unclear). Good people - all ages kind (unclear) smart - 4 grandkids - now 4 great
grandkids that love come here. Plus a neighborhood of kids that come from all over Edina to grandkids that love come here. Plus a neighborhood of kids that come from all over Edina to
fishfish
The ecosystem, wildlife, outdoor opportunitesThe ecosystem, wildlife, outdoor opportunites
It’s a beautiful setting with wildlife!It’s a beautiful setting with wildlife!
Diversity of Wildlife, Does not stink like Lake CorneliaDiversity of Wildlife, Does not stink like Lake Cornelia
We value the ability to engage in recreational water activities in our backyard. We have We value the ability to engage in recreational water activities in our backyard. We have
especially enjoyed the community aspect. When several families clear ice rinks.especially enjoyed the community aspect. When several families clear ice rinks.
The ability to have a great, peaceful view combined with the convenience of the city.The ability to have a great, peaceful view combined with the convenience of the city.
it’s calm and peacefulit’s calm and peaceful
We are very invested in the Lake because we live here & should be respectful and good We are very invested in the Lake because we live here & should be respectful and good
stewards for the creatures that live in and around the Lakestewards for the creatures that live in and around the Lake
The view of the lake is very beautiful and relaxing. The wildlife on and around the lake is The view of the lake is very beautiful and relaxing. The wildlife on and around the lake is
great. Watching the eagles and the cranes fishing. Also the spring migration of waterfowl is great. Watching the eagles and the cranes fishing. Also the spring migration of waterfowl is
spectacularspectacular
Love having the lake, love kayaking that there is fish, turtles, wildlifeLove having the lake, love kayaking that there is fish, turtles, wildlife
The beauty of the fact ot is a lake- a place of respite- even to just look out on. It’s a refuge for The beauty of the fact ot is a lake- a place of respite- even to just look out on. It’s a refuge for
birds as well as animals in the winter. It’s beauty in winter is very significant.birds as well as animals in the winter. It’s beauty in winter is very significant.
6
6. What specific features of the lake do you like?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
Generally, the esthetics, although we have a green scum on the lake in the last few weeks.
the shoreline and the wildlife
Shape Privacy fish
Trees, Water, Views
The natural beauty, aeroators
Just to be able to take in the terrific views everyday.
It makes our house fell unique because we have lakeshore. The bald eagles and our own personal
muskrat is pretty cool.
the clamness - the fact that it is non-motorized - the eagles/egrets/ducks that we see
The wildlife, views, neighborhood
not sure how to answer
Its irregular shoreline
The view of the lake is very beautiful and relaxing. The wildlife on and around the lake is The view of the lake is very beautiful and relaxing. The wildlife on and around the lake is
great. Watching the eagles and the cranes fishing. Also the spring migration of waterfowl is great. Watching the eagles and the cranes fishing. Also the spring migration of waterfowl is
spectacularspectacular
That it has water
That it winds around and the fact that you only see one house from the northwest side. You
could be up north. I don’t think people should be able to cut down trees.
7
8
7. What are some issues or concerns that you have regarding the lake?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
1) The water level. We now have a plan for high water levels but not for when the level is low.
2) Weeds - there is disagreement about what people call water quality. Many see that as less
weeds vs the actual quality of the water. How do we strike a balance? 3) Run off - not just from
the houses on the lake but from all of the surrounding area.
the water is merky. lilly pads. also right now the lake level is really low. i don’t think there is a
freshwater supply in to the lake.
Weeds, Lily Pads, Water Levels are too drastic from high to low
The lake being treated too late this year 2021 not done until July or late June?) Plus lake low
and hot temps - not good Please try to stay ahead of the summer - lets not lose the lake
Gets treated for weeds too late in the season. Need to address earlier and stay on top of the
weeds. Would like more aeration in the north end of the lake as opposed to just the south.
Weeds and water quality. Also maintaining a good environment for wildlife.
Algae blooms and preventing issues with nitrogen and phosphorous levels.
Significant amount of lily pads and lake weeds. This can make kyaking and paddle boating
difficult
Clarity, weeds. Are we doing all we can to keep the lake viable?
none
I find that hocky rinks extending into the Lake are not only visually disturbing, but not in
keeping with the character of the Lake
None so far
Yes, it’s a lake and has water, but can be over-run by lilypads - can’t even (unclear) or kayak
through them. Blue green, dirty color is very offputting. Lots of water run-off seems to be
directed there - city of Edina dumps a lot of salt on Indian Hills rd. Which in spring can go into
the lake. Could a fountain or additional aerators help? Wish is could be deeper, maybe dredged
or something? Aren’t lilypads dying and just settling on the bottom.
Lily pads are out of control.
9
8. What activities do you participate in to improve the water quality of the lake?
Of the 14 respondents, 1 (7.1%) did not do any activities listed to improve the water quality of Arrowhead Lake. 3
(21.4%) restored shoreline with native plants to improve the water quality of Arrowhead Lake, 2 (14.3%) replaced turf
grass with native plants to improve the water quality of Arrowhead Lake, 1 (7.1%) installed a rain garden to improve
the water quality of Arrowhead Lake, 13 (92.9%) limited salt use in winter to improve the water quality of Arrowhead
Lake, 13 (92.9%) limited fertilizer application to improve the water quality of Arrowhead Lake, 10 (71.4%) directed
downspouts to lawns to improve the water quality of Arrowhead Lake, 3 (21.4%) adopted a drain to improve the
water quality of Arrowhead Lake, and 12 (85.7%) keep leaves and grass off sidewalks and roads to improve the water
quality of Arrowhead Lake.
9.What activities are you willing to participate in to improve the water quality of the lake?
Of the 14 respondents, 1 (7.1%) will not do any of the listed activities to improve the health of Arrowhead Lake. 5
(35.7%) will apply for a cost share grant to improve the water quality of Arrowhead Lake, 7 (50%) will restore shoreline
with native plants to improve the water quality of Arrowhead Lake, 4 (28.6%) will replace turf grass with native plants
to improve the water quality of Arrowhead Lake, 2 (14.3%) will install a rain garden to improve the water quality of
Arrowhead Lake, 11 (78.6%) will limit salt use in winter to improve the water quality of Arrowhead Lake, 10 (71.4%) will
limit fertilizer application to improve water quality in Arrowhead Lake, 8 (57.1%) will direct downspouts to lawns to
improve the water quality of Arrowhead Lake, 5 (35.7%) will adopt a drain to improve the water quality of Arrowhead
Lake, and 11 (78.6%) will keep leaves and grass clippings off sidewalks and roads to improve the water quality of
Arrowhead Lake.
12 (85.7%)
3 (21.4%)
10 (71.4%)
13 (92.9%)
13 (92.9%)
1 (7.1%)
2 (14.3%)
3 (21.4%)
1 (7.1%)
Keeping leaves and grass clippings off sidewalks and roads
Adopting a storm drain and keeping it clear of debris
Directing downspouts to lawns instead of sidewalks/driveways
Limiting fertilizer application
Limiting salt use in winter
Installing a rain garden
Replacing turfgrass with native plants
Restoring shoreline with native plants
None
11 (78.6%)
5 (35.7%)
8 (57.1%)
10 (71.4%)
11 (78.6%)
2 (14.3%)
4 (28.6%)
7 (50%)
5 (35.7%)
1 (7.1%)
Keeping leaves and grass clippings off sidewalks and roads
Adopting a storm drain (grated drain along street curb) and…
Directing downspouts to lawns instead of sidewalks/driveways
Limiting fertilizer application
Limiting salt use in winter
Installing a rain garden
Replacing turfgrass with native plants
Restoring shoreline with native plants
Applying for a cost share grant
None
10
10. Do you fertilize your lawn?
Of the 14 respondents, 7 (50%) do not fertilize their lawn or hire someone to fertilize their lawn, 7 (50%) hire a
contractor to fertilize their lawn, and 0 (0%) fertilize their lawn themselves.
11. What time(s) of year do you fertilize your lawn?
Of the 14 respondents, 6 (42.9%) do not fertilize their lawn, 3 (21.4%) are unsure when they fertilize their lawn, 3
(21.4%) fertilize their lawn in October, 0 (0%) fertilize their lawn in September, 2 (14.3%) fertilize their lawn in August,
0 (0%) fertilize their lawn in July, 1 (7.1%) fertilize their lawn in June, 4 (28.6%) fertilize their lawn in May. Of the 6
respondents that fertilized their lawn and knew when they fertilized their lawn, 3 fertilized their lawn once a year, 2
fertilized their lawns twice a year, and 1 fertilized their lawn 4 times a year.
0 (0%)
7 (50%)
7 (50%)
Yes, I fertilize my lawn or someone in
my household fertilizes the lawn
Yes, I hire a contractor to fertilize my
lawn
No, I do not fertilize my lawn or hire
someone to fertilize my lawn
6 (42.9%)
3 ( 21.4%)
3 ( 21.4%)
0 (0%)
2 (14.3%)
0 (0%)
1 (7.1%)
4 (28.6%)
NA
Unsure
October
September
August
July
June
May
11
12. Do you use phosphorus-free fertilizer (noted by the zero in the middle number describing
the fertilizer blend)?
Of the 14 respondents, 6 (42.9%) did not fertilize their lawn, 2 (14.3%) were unsure if they use phosphorous-free
fertilizer on their lawn, 0 (0%) did not use phosphorous-free fertilizer on their lawn, 4 (28.6%) use phosphorous-free
fertilizer on their lawn.
13. Would you be interested to participate in a free soil sampling program to confirm optimal
fertilization needs for your lawn?
Of the 14 respondents, 2 (14.3%) were unsure if they would be willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn, 3 (21.4%) were not willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn, and 8 (57.1%) were willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn.
4 (28.6%)
0 (0%)
2 (14.3%)
6 (42.9%)
Yes
No
Unsure
NA
8 (57.1%)
3 (21.4%)
2 (14.3%)
Yes
No
Unsure
12
14. How would you prefer to receive information about the water quality study and future
projects?
Of the 14 respondents, 0 (0%) preferred to receive information about the water quality study and future projects
from the city of Edina webpage, 3 (21.4%) preferred to receive information about the water quality study and future
projects from the city of Edina e-newsletter, 6 (42.9%) preferred to receive information about the water quality study
and future projects from an in-person meeting, 1 (7.1%) preferred to receive information about the water quality
study and future projects from a virtual meeting, 0 (0%) preferred to receive information about the water quality study
and future projects from the Nine Mile Creek Watershed District Webpage, 6 (42.9%) preferred to receive information
about the water quality study and future projects from the Nine Mile Creek Watershed District e-newsletter, 9 (64.3%)
preferred to receive information about the water quality study and future projects from a mailing, 4 (28.6%) preferred
to receive information about the water quality study and future projects from neighbors/word of mouth, 0 (0%)
did not want to receive information on the water quality study or future projects, and 3 (21.4%) preferred to receive
information about the water quality study and future projects from an unlisted option. Other options included,
“Something that stands out from junk mail”, “email info”, and “from homeowners that live on the lake”.
0 (0%)
3 (21.4%)
6 (42.9%)
1 (7.1%)
0 (0%)
6 (42.9%)
9 (64.3%)
4 (28.6%)
0 (0%)
3 (21.4%)
City of Edina Webpage
City of Edina e-newsletter
In-Person Meeting
Virtual Meeting
Nine Mile Creek Watershed District Webpage
Nine Mile Creek Watershed District e-newsletter
Mailing
From Neighbors/Word of Mouth
I do not want to receive information on this topic
Other
13
15. How long have you lived at your current residence?
Of the 14 respondents, 5 (35.7%) have lived in their current residence for 0-4 years, 2 (14.3%) have lived in their current
residence for 5-10 years, 0 (0.0%) have lived in their current residence for 11-15 years, 1 (7.1%) have lived in their
current residence for 16-20 years, 1 (7.1%) have lived in their current residence for 21-25 years, 0 (0.0%) have lived in
their current residence for 26-30 years, 3 (21.4%) have lived in their current residence for 31-35 years, 1 (7.1%) have
lived in their current residence for 35-40 years, and 1 (7.1%) have lived in their current residence for 40+ years.
5 (35.7%)
2 (14.3%)
0 (0%)
1 (7.1%)
1 (7.1%)
0 (0%)
3 (21.4%)
1 (7.1%)
1 (7.1%)
0-4 years
5-10 years
11-15 years
16-20 years
21-25 years
26-30 years
31-35 years
36-40 years
41+ years
14
16. Do you have any additional comments, information, or stories about Arrowhead Lake
that you would like to add? You may also share a photo on the next question. Please describe
the photo here, if sharing one.
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
I would like to see the coy eliminated from the lake. This is the current state of the lake.
none. we just recently moved in.
I’ve watched a flood, 1987 sand bars, picnics, weddlings, grad photos, parties, a tornado, you
name it. It’s been a happy place to live. ( our house was ok)
none
no
When I studied for the GRE, I learned the word “riparian”. I can now feel cool. I want to know
about the person who died 20 years ago while trying to swim in the lake.
no
17. Would you like to share a photo of the lake? (separate question for online survey to
provide place to upload photos)
Respondents had the opportunity to send in pictures through the online survey and the paper survey. The pictures
submitted in the Arrowhead Lake are below
15
17. Continued
16
17. Continued
6
INDIANHEAD LAKE SURVEY RESULTS
How was the survey submitted?
Of the 17 respondents. 16 (94%) completed the survey in a paper format and 1 (5.9%) completed the survey online.
1 (5.9%)
16 (94%)
Online
Paper
17
17 18
2. What kinds of activities do you do on or near the lake?
Of the 17 respondents, 15 (14 daily and 1 weekly 88.2%) view wildlife/nature on Indianhead Lake, 2 (both monthly
11.8%) swim in Indianhead Lake, 9 (4 weekly and 5 monthly, 52.9%) boat/canoe/kayak in Indianhead Lake, 7 (5
weekly and 2 monthly, 41.2%) fish on Indianhead Lake, 2 (both monthly, 11.8%) ice fish on Indianhead Lake, 7 (1
daily, 4 weekly, and 2 monthly, 41.2%) recreate on Indianhead Lake in the winter, and 4 (23.5%) do other activities on
Indianhead Lake including lake bonfires, walking their dog on the frozen lake, and gardening.
15 (88.2%)
2 (11.8%)
9 (52.9%)
7 (41.2%)
2 (11.8%)
7 (41.2%)
4 (23.5%)
Viewing Wildlife/Nature
Swimming
Boating/Canoeing/Kayaking
Open Water Fishing
Ice Fishing
Winter Recreation
Other
19
3. How do you perceive the current health of the lake?
Of the 17 respondents, 1 (5.9%) were unsure how they perceived the current health of Indianhead Lake, 10 (58.8%)
perceived Indianhead Lake’s health as good, 5 (29.4%) perceived Indianhead Lake’s health as neither good nor bad,
and 0 (0.0%) perceived Indianhead Lake’s health as bad.
4. How has water clarity (how far you can see down into the water) changed since you have
lived on or near the lake?
Of the 17 respondents, 2 (11.8%) were unsure how the water clarity in Indianhead Lake has changed since living on
or near the lake, 1 (5.9%) thought clarity in Indianhead Lake has improved since living on or near the lake, 8 (47.1%)
thought clarity in Indianhead Lake has remained constant since living on or near the lake, and 5 (29.4%) thought
clarity in Indianhead Lake has declined since living on or near the lake.
0 (0%)
5 (29.4%)
10 (58.8%)
1 (5.9%)
Bad
Neither Good Nor Bad
Good
Unsure
5 (29.4%)
8 (47.1%)
1 (5.9%)
2 (11.8%)
Declined
Remained Constant
Improved
Unsure
20
5.What do you value and/or appreciate about the lake?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
It was a good fishing lake it no longer is it is beautiful
wildlife, scenic
From our middle of the lake vantage point from our deck it actually looks like a flowing river we
never get tired of it. Also the wildlife viewing is great
natural beauty and nature the neighbors use out dock and boat for fishing
#1 the quality of the water animal/bird/fish presence wildlife limited access
Aquatic Life: Bass Bluegills Crappies and abuldant food chain: insects bait fish turtles frogs
We enjoy the peace and quiet and serenity of the lake.
Connection to nature and lake in suburban setting
1) the view 2) option for boating activities 3) option to fish
just its presence
The quiet, the view, wildlife and the neighborhood
It is regarded to be an environmental lake and that is why I treasure it; the vegetation, the
trees!, fish, etc. the beauty of it.
It attracts wildlife- particularly birds like herons, eagles, egrets, hawks. They are probably drawn
to the fish- The fish depend on the aerators. Natural shorelines, for the most part. Trees.
The natural beauty. Lights reflecting off the lake at night. The movement of the water. The
attraction of the animals. The quiet of the neighborhood that surrounds the lake. Sitting on my
dock- peaceful.
Wildlife. Mature trees forest around perimeter of lake and resident landscaping. Fish plentiful in
lake.
6
6.What specific features of the lake do you like?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
quiet, good fishing
The shape. The way the trees make it feel like you are up north
fishing, nature, wildlife
secluded ability to fish clear ability to swim
Scenic views fish population
We enjoy the peace and quiet and serenity of the lake.
The view lack of nearby neighbors
we use it for irrigation and for our decorative waterfall
It is regarded to be an environmental lake and that is why I treasure it; the vegetation, the
trees!, fish, etc. the beauty of it.
Size, no powers boats, tranquility, fish, birds, trees
The neighbor kids can fish. The privacy. Seeing neighbors canoe. I love the way the water
reflects light and the sun. Its very special to live by a lake.
Calmness of water. Minimal weeds in lake.
21
22
7.What are some issues or concerns that you have regarding the lake?
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
fishing
trees down in the north lagoon
The cattails seem to be taking over the lake I’m fortunate that they are not growing in front of
our house but they seem to be spreading
Of course weed coverage
encroachment of cattails water quality water levels - maintaining constant levels runoff
upgrading aeration system
clarity without sacrificing aquatic life
Raising water level algae blooms
overgrowth of cattails
Lake level - too many cattails, shrinking of shore - lake level cleanliness of lake due to run off
fertilizers
floating algae sometimes
water levels
The growth of cattails on the south east section. Aren’t these invasive to begin with? Periodic
water rise which threatens trees. Toxic run off from the surrounding neighborhood streets?
Algae in mid-late summer.
Is it safe- does it get tested- by whom- how do we know the results. My grandchildren use the
paddleboat- are they going to get sick if they fall in the lake. Does the lake have e.coli or other
bacteria that causes infection. The changing levels of the water- sometimes it’s too high. RIght
now it’s very low.
Certainly wish for more clarity of water. Managing water level
23
7. What activities do you participate in to improve the water quality of the lake?
Of the 17 respondents, 1 (5.9%) did not do any activities listed to improve the water quality of Indianhead Lake. 8
(47.1%) restored shoreline with native plants to improve the water quality of Indianhead Lake, 5 (29.4%) replaced turf
grass with native plants to improve the water quality of Indianhead Lake, 1 (5.9%) installed a rain garden to improve
the water quality of Indianhead Lake, 13 (76.5%) limited salt use in winter to improve the water quality of Indianhead
Lake, 12 (70.6%) limited fertilizer application to improve the water quality of Indianhead Lake, 13 (76.5%) directed
downspouts to lawns to improve the water quality of Indianhead Lake, 5 (29.4%) adopted a drain to improve the
water quality of Indianhead Lake, and 16 (94.1%) keep leaves and grass off sidewalks and roads to improve the water
quality of Indianhead Lake.
9.What activities are you willing to participate in to improve the water quality of the lake?
Of the 17 respondents, 1 (5.9%) will not do any of the listed activities to improve the health of Indianhead Lake.
6 (35.3%) will apply for a cost share grant to improve the water quality of Indianhead Lake, 9 (52.9%) will restore
shoreline with native plants to improve the water quality of Indianhead Lake, 9 (52.9%) will replace turf grass with
native plants to improve the water quality of Indianhead Lake, 5 (29.4%) will install a rain garden to improve the water
quality of Indianhead Lake, 11 (64.7%) will limit salt use in winter to improve the water quality of Indianhead Lake, 12
(70.6%) will limit fertilizer application to improve water quality in Indianhead Lake, 11 (64.7%) will direct downspouts
to lawns to improve the water quality of Indianhead Lake, 10 (58.8%) will adopt a drain to improve the water quality
of Indianhead Lake, and 13 (76.5%) will keep leaves and grass clippings off sidewalks and roads to improve the water
quality of Indianhead Lake.
16 (94.1%)
5 (29.4%)
13 (76.5%)
12 (70.6%)
13 (76.5%)
1 (5.9%)
5 (29.4%)
8 (47.1%)
1 (5.9%)
Keeping leaves and grass clippings off sidewalks and roads
Adopting a storm drain and keeping it clear of debris
Directing downspouts to lawns instead of sidewalks/driveways
Limiting fertilizer application
Limiting salt use in winter
Installing a rain garden
Replacing turfgrass with native plants
Restoring shoreline with native plants
None
13 (76.5%)
10 (58.8%)
11 (64.7%)
12 (70.6%)
11 (64.7%)
5 (29.4%)
9 (52.9%)
9 (52.9%)
6 (35.3%)
1 (5.9%)
Keeping leaves and grass clippings off sidewalks and roads
Adopting a storm drain (grated drain along street curb) and…
Directing downspouts to lawns instead of sidewalks/driveways
Limiting fertilizer application
Limiting salt use in winter
Installing a rain garden
Replacing turfgrass with native plants
Restoring shoreline with native plants
Applying for a cost share grant
None
24
10. Do you fertilize your lawn?
Of the 17 respondents, 9 (52.9%) do not fertilize their lawn or hire someone to fertilize their lawn, 6 (35.3%) hire a
contractor to fertilize their lawn, and 2 (11.8%) fertilize their lawn themselves.
11.What time(s) of year do you fertilize your lawn?
Of the 17 respondents, 9 (52.9%) do not fertilize their lawn, 2 (11.8%) are unsure when they fertilize their lawn, 0 (0%)
fertiilize their lawn in October, 3 (17.6%) fertilize their lawn in September, 1 (5.9%) fertilize their lawn in August, 2
(11.8%) fertilize their lawn in July, 2 (11.8%) fertilize their lawn in June, 4 (23.5%) fertilize their lawn in May. Of the 6
respondents that fertilized their lawn and knew when they fertilized their lawn, 2 fertilized their lawn once a year, 2
fertilized their lawn twice a year, and 2 fertilized their lawn 3 times a year.
2 (11.8%)
6 (35.3%)
9 (52.9%)
Yes, I fertilize my lawn or someone in
my household fertilizes the lawn
Yes, I hire a contractor to fertilize my
lawn
No, I do not fertilize my lawn or hire
someone to fertilize my lawn
9 (52.9%)
2 (11.8%)
0 (0%)
3 (17.6%)
1 (5.9%)
2 (11.8%)
2 (11.8%)
4 (23.5%)
NA
Unsure
October
September
August
July
June
May
25
12. Do you use phosphorus-free fertilizer (noted by the zero in the middle number describing
the fertilizer blend)?
Of the 17 respondents, 9 (52.9%) did not fertilize their lawn, 2 (11.8%) were unsure if they use phosphorous-free
fertilizer on their lawn, 1 (5.9%) did not use phosphorous-free fertilizer on their lawn, 5 (29.4%) use phosphorous-free
fertilizer on their lawn.
13.Would you be interested to participate in a free soil sampling program to confirm optimal
fertilization needs for your lawn?
Of the 17 respondents, 2 (14.3%) were unsure if they would be willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn, 9 (52.9%) were not willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn, and 6 (35.3%) were willing to participate in a free soil sampling to confirm
optimal fertilization needs for their lawn.
5 (29.4%)
1 (5.9%)
2 (11.8%)
9 (52.9%)
Yes
No
Unsure
NA
6 (35.3%)
9 (52.9%)
2 (14.3%)
Yes
No
Unsure
26
14. How would you prefer to receive information about the water quality study and future
projects?
Of the 17 respondents, 1 (5.9%) preferred to receive information about the water quality study and future projects
from the city of Edina webpage, 6 (35.3%) preferred to receive information about the water quality study and future
projects from the city of Edina e-newsletter, 3 (17.6%) preferred to receive information about the water quality
study and future projects from an in-person meeting, 4 (23.5%) preferred to receive information about the water
quality study and future projects from a virtual meeting, 1 (5.9%) preferred to receive information about the water
quality study and future projects from the Nine Mile Creek Watershed District Webpage, 1 (5.9%) preferred to
receive information about the water quality study and future projects from the Nine Mile Creek Watershed District
e-newsletter, 12 (70.6%) preferred to receive information about the water quality study and future projects from a
mailing, 2 (11.8%) preferred to receive information about the water quality study and future projects from neighbors/
word of mouth, 0 (0%) did not want to receive information on the water quality study or future projects, and 3 (17.6%)
preferred to receive information about the water quality study and future projects from an unlisted option. Other
options included, “email”, “email info”, and “Lake Association”.
1 (5.9%)
6 (35.3%)
3 (17.6%)
4 (23.5%)
1 (5.9%)
1 (5.9%)
12 (70.6%)
2 (11.8%)
0 (0%)
3 (17.6%)
City of Edina Webpage
City of Edina e-newsletter
In-Person Meeting
Virtual Meeting
Nine Mile Creek Watershed District Webpage
Nine Mile Creek Watershed District e-newsletter
Mailing
From Neighbors/Word of Mouth
I do not want to receive information on this topic
Other
27
15. How long have you lived at your current residence?
Of the 17 respondents, 2 (11.8%) have lived in their current residence for 0-4 years, 2 (11.8%) have lived in their current
residence for 5-10 years, 1 (5.9%) have lived in their current residence for 11-15 years, 2 (11.8%) have lived in their
current residence for 16-20 years, 2 (11.8%) have lived in their current residence for 21-25 years, 1 (5.9%) have lived in
their current residence for 26-30 years, 3 (17.6%) have lived in their current residence for 31-35 years, 0 (0%) have lived
in their current residence for 35-40 years, and 4 (23.5%) have lived in their current residence for 40+ years.
4 (23.5%)
0 (0%)
3 (17.6%)
1 (5.9%)
2 (11.8%)
2 (11.8%)
1 (5.9%)
2 (11.8%)
2 (11.8%)
41+ years
36-40 years
31-35 years
26-30 years
21-25 years
16-20 years
11-15 years
5-10 years
0-4 years
28
16. Do you have any additional comments, information, or stories about Indianhead Lake
that you would like to add? You may also share a photo on the next question. Please describe
the photo here, if sharing one.
This question was open ended and gathered no statistical data. Spelling and grammar mistakes were not corrected,
see responses below:
City of Edina has an access area. -well and aeration equipment. Needs to be cleaned up
improvements needed need to have an alarm or monitoring system. If the system fails the fish
die Need alert to correct/fix It has happened in the winter complete fish kill - piles of fish on
the shore restocking takes years water level management needs to have permanent solutions.
Runoff should go to a retention pond (north lagoon) possibility of alum treatments
We have absolutely no lawn. All natural, will never change that.
The lake level is a challenge. It killed one of my large trees which cost $4k to remove. It could
happen again. Great job on the curly-leaf pondweed, but algae in the summer is still a problem.
The north end around the aerators is a MESS and the shed is falling apart. Some thoughtful
environmental engineering there might convert this area to a “rain garden” of sorts for the
entire lake. There is no long term strategy- we are just responding piecemeal to problems when
they arise. There are no sidewalks here- we LOVE that. The last thing we need anywhere near
this lake are more hard surfaces for runoff. Setting aside the aesthetic concerns about sidewalk
installs, it’s a bad idea for this unique environment. The planning department seems impervious
to this issue. The lake lost some major trees on perimeter of lake 2 years ago during high water
level periods. We pumped the lake level down 3 times in past 2 years but now it is in need of
adding water hopefully this autumn. Cattails continue to invade the lake and needs to be
managed.
17.Would you like to share a photo of the lake? (separate question for online survey to
provide place to upload photos)
Respondents had the opportunity to send in pictures through the online survey and the paper survey. None were
submitted in the Indianhead Lake survey.
Appendix E
In-lake Water Quality Proposed Best Management Plots
E-1
Figure E-1 Proposed BMP impacts to in-lake total phosphorus concentrations – maintaining
copper sulfate treatments in Arrowhead Lake
Figure E-2 Proposed BMP impacts to in-lake total phosphorus concentrations – stopping
copper sulfate treatments in Arrowhead Lake
E-2
Figure E-3 Proposed BMP impacts to in-lake total nitrogen concentrations – maintaining
copper sulfate treatments in Arrowhead Lake
Figure E-4 Proposed BMP impacts to in-lake total nitrogen concentrations – stopping copper
sulfate treatments in Arrowhead Lake
E-3
Figure E-5 Proposed BMP impacts to in-lake chlorophyll-a concentrations – maintaining
copper sulfate treatments in Arrowhead Lake
Figure E-6 Proposed BMP impacts to in-lake chlorophyll-a concentrations – stopping copper
sulfate treatments in Arrowhead Lake
E-4
Figure E-7 Proposed BMP impacts to in-lake total phosphorus concentrations – maintaining
copper sulfate treatments in Indianhead Lake
Figure E-8 Proposed BMP impacts to in-lake total phosphorus concentrations – stopping
copper sulfate treatments in Indianhead Lake
E-5
Figure E-9 Proposed BMP impacts to in-lake total nitrogen concentrations – maintaining
copper sulfate treatments in Indianhead Lake
Figure E-10 Proposed BMP impacts to in-lake total nitrogen concentrations – stopping copper
sulfate treatments in Indianhead Lake
E-6
Figure E-11 Proposed BMP impacts to in-lake chlorophyll-a concentrations – maintaining
copper sulfate treatments in Indianhead Lake
Figure E-12 Proposed BMP impacts to in-lake chlorophyll-a concentrations – stopping copper
sulfate treatments in Indianhead Lake
Appendix F
Opinions of Probable Cost
ITEM DESCRIPTION UNIT
ESTIMATED
QUANTITY UNIT COST COST
Mobilization/Demobilzation LS 1 $ 15,000.00 $ 15,000.00
Alum Sediment Treatment LS 1 $ 32,000.00 $ 32,000.00
Iron Sediment Treatment LS 1 $ 18,500.00 $ 18,500.00
Aerator Optimization LS 1 $ 25,000.00 $ 25,000.00
Dissolved Oxygen Monitoring HRS 30 $ 150.00 $ 4,500.00
Engineer Data Review/Field Observation HRS 50 $ 130.00 $ 6,500.00
Project Planning/Design HRS 70 $ 150.00 $ 10,500.00
$ 112,000.00
$ 11,200.00
$ 124,000.00
$ 87,000.00
$ 186,000.00
Assumptions
- 3,954 gallons of alum
- 1,977 gallons sodium aluminate
- 4,300 gallons of ferric chloride
- Addition of 1 aerator
- Engineering assistance with bid administration and contract documents
- Two engineering staff members to observe alum application and perform pH monitoring.
- Estimated total cost is reported to the nearest thousand dollars
-30%
+50%
2021 Water Quality Study for Arrowhead Lake and Indianhead Lake
ENGINEERS OPINION OF COST
ARROWHEAD LAKE SEDIMENT TREATMENT
Subtotal =
Contingency (10%)
Total
ITEM DESCRIPTION UNIT
ESTIMATED
QUANTITY UNIT COST COST
Mobilization/Demobilzation LS 1 $ 15,000.00 $ 15,000.00
Alum Sediment Treatment LS 1 $ 34,000.00 $ 34,000.00
Iron Sediment Treatment LS 1 $ 14,400.00 $ 14,400.00
Aerator Optimization LS 1 $ 25,000.00 $ 25,000.00
Dissolved Oxygen Monitoring HRS 30 $ 150.00 $ 4,500.00
Engineer Data Review/Field Observation HRS 50 $ 130.00 $ 6,500.00
Project Planning/Design HRS 70 $ 150.00 $ 10,500.00
$ 110,000.00
$ 11,000.00
$ 121,000.00
$ 85,000.00
$ 182,000.00
Assumptions
- 4,273 gallons of alum
- 2,136 gallons sodium aluminate
- 5,580 gallons of ferric chloride
- Addition of 1 aerator
- Engineering assistance with bid administration and contract documents
- Two engineering staff members to observe alum application and perform pH monitoring.
- Estimated total cost is reported to the nearest thousand dollars
-30%
+50%
2021 Water Quality Study for Arrowhead Lake and Indianhead Lake
ENGINEERS OPINION OF COST
INDIANHEAD LAKE SEDIMENT TREATMENT
Subtotal =
Contingency (10%)
Total
ITEM DESCRIPTION UNIT
ESTIMATED
QUANTITY UNIT COST COST
Crosswind 4 Wheel Regenerative Air Sweeper EA 1 $ 210,000.00 $ 210,000.00
Annual Vehicle Maintenance EA 1 $ 4,800.00 $ 4,800.00
Annual Labor (10 sweeping sessions) HRS 170 $ 75.00 $ 12,750.00
Annual Fuel (10 sweeping sessions) GAL 60 $ 3.50 $ 210.00
$ 228,000.00
$ 22,800.00
$ 251,000.00
$ 176,000.00
$ 377,000.00
Assumptions
- New street sweeper must be purchased to handle additional sweeping miles
- Sweepable public street curb miles in Arrowhead/Indianhead Lake watersheds = 9.6 miles
- Sweeper operation speed = 4.5 mph
- 1.5 hours of labor needed for every 4 hours of sweeping time
- Total transit (brush off) are about 3 times total swept miles
- Average fuel consumption is 5 mpg
- Sufficient staffing
- 10 Sweeping Sessions per year (May through November)
- Maximum number of hours worked in one week by one worker = 40 hours
- Assuming Class 5 opinion of cost with accuracy range of -30% to +50% standards established by the Association
for the Advancement of Cost Engineering (AACE).
- Estimated total cost is reported to the nearest thousand dollars
-30%
+50%
2021 Water Quality Study for Arrowhead Lake and Indianhead Lake
ENGINEERS OPINION OF COST
STREET SWEEPING (WATERSHED-WIDE)
Subtotal =
Contingency (10%)
Total
ITEM DESCRIPTION UNIT
ESTIMATED
QUANTITY UNIT COST COST
University of Minnesota Soil Testing EA 34 $ 17.00 $ 578.00
Resident Correspondence/Coordination HRS 102 $ 100.00 $ 10,200.00
Soil Sample Collection HRS 34 $ 100.00 $ 3,400.00
Engineer Data Review HRS 8 $ 130.00 $ 1,040.00
Project Planning HRS 16 $ 120.00 $ 1,920.00
$ 18,000.00
$ 1,800.00
$ 20,000.00
$ 14,000.00
$ 30,000.00
Assumptions
- 50% resident participation (68 residences on Arrowhead and Indianhead Lake)
- 3 hours of communication per resident for project background, soil sampling coordination and results summary
- 8 hours of data review by project engineer to assess results of soil sampling on project-wide basis
- Assuming Class 5 opinion of cost with accuracy range of -30% to +50% standards established by the Association
for the Advancement of Cost Engineering (AACE).
- Estimated total cost is reported to the nearest thousand dollars
-30%
+50%
2021 Water Quality Study for Arrowhead Lake and Indianhead Lake
ENGINEERS OPINION OF COST
NITROGEN SOIL TESTING
Subtotal =
Contingency (10%)
Total