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4700 West 77th Street Minneapolis, MN 55435-4803 Phone: 952.832.2600 Fax: 952.832.2601
Engineer’s Report
Nine Mile Creek Restoration Project
Prepared for
Nine Mile Creek Watershed District
August 2015
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Nine Mile Creek Restoration Project
Edina, MN
August 2015
Contents
1.0 Introduction ............................................................................................................................................................................... 1
1.1 Background ................................................................................................................................................................... 1
1.2 Project Location ........................................................................................................................................................... 1
1.3 Summary of Problems ............................................................................................................................................... 1
1.3.1 Stream Stability ............................................................................................................................................ 1
1.4 Project Objectives ....................................................................................................................................................... 2
1.5 Public Participation ..................................................................................................................................................... 2
2.0 Site Characterization............................................................................................................................................................... 3
2.1 Watershed Characteristics ....................................................................................................................................... 3
2.1.1 Land Use ......................................................................................................................................................... 3
2.1.2 Drainage Patterns ....................................................................................................................................... 3
2.1.3 Topography ................................................................................................................................................... 3
2.1.4 Soil Types ....................................................................................................................................................... 3
2.2 Stream Characteristics ............................................................................................................................................... 3
2.2.1 Channel Geometry ..................................................................................................................................... 4
2.2.2 Historical Channel Alignment ................................................................................................................ 5
2.2.3 Stream Profile ............................................................................................................................................... 5
3.0 Site Evaluation .........................................................................................................................................................................13
3.1 Detailed Field Survey ...............................................................................................................................................13
3.2 Hydrologic/Hydraulic Modeling for Creek Modifications .........................................................................13
3.2.1 Nine Mile Creek XP-SWMM Model ...................................................................................................13
3.2.2 Edina Stream Improvements HEC-RAS Models ............................................................................14
3.3 Archeological Investigation...................................................................................................................................14
3.4 Riparian Vegetation Survey ...................................................................................................................................15
4.0 Proposed Improvements ....................................................................................................................................................20
4.1 Stream Stabilization .................................................................................................................................................20
4.1.1 Reach 1 .........................................................................................................................................................20
4.1.1.1 Existing Conditions ..............................................................................................................20
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4.1.1.2 Considerations and Options ............................................................................................20
4.1.1.3 Recommendations ...............................................................................................................21
4.1.2 Reach 2 .........................................................................................................................................................23
4.1.2.1 Existing Conditions ..............................................................................................................23
4.1.2.2 Considerations and Options ............................................................................................23
4.1.2.3 Recommendations ...............................................................................................................23
4.1.3 Reach 3 .........................................................................................................................................................25
4.1.3.1 Existing Conditions ..............................................................................................................25
4.1.3.2 Considerations and Options ............................................................................................25
4.1.3.3 Recommendations ...............................................................................................................26
4.1.4 Reach 4 .........................................................................................................................................................28
4.1.4.1 Existing Conditions ..............................................................................................................28
4.1.4.2 Considerations and Options ............................................................................................28
4.1.4.3 Recommendations ...............................................................................................................29
4.1.5 Reach 5 .........................................................................................................................................................33
4.1.5.1 Existing Conditions ..............................................................................................................33
4.1.5.2 Considerations and Options ............................................................................................33
4.1.5.3 Recommendations ...............................................................................................................34
4.1.6 Reach 6 .........................................................................................................................................................36
4.1.6.1 Existing Conditions ..............................................................................................................36
4.1.6.2 Considerations and Options ............................................................................................36
4.1.6.3 Recommendations ...............................................................................................................36
4.1.7 Reach 7 .........................................................................................................................................................38
4.1.7.1 Existing Conditions ..............................................................................................................38
4.1.7.2 Considerations and Options ............................................................................................38
4.1.7.3 Recommendations ...............................................................................................................39
4.1.8 Reach 8 .........................................................................................................................................................41
4.1.8.1 Existing Conditions ..............................................................................................................41
4.1.8.2 Considerations and Options ............................................................................................41
4.1.8.3 Recommendations ...............................................................................................................41
4.1.9 Reach 9 .........................................................................................................................................................43
4.1.9.1 Existing Conditions ..............................................................................................................43
4.1.9.2 Considerations and Options ............................................................................................43
4.1.9.3 Recommendations ...............................................................................................................43
4.1.10 Reach 10 .......................................................................................................................................................45
4.1.10.1 Existing Conditions ..............................................................................................................45
4.1.10.2 Considerations and Options ............................................................................................45
4.1.10.3 Recommendations ...............................................................................................................45
4.1.11 Reach 11 .......................................................................................................................................................47
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4.1.11.1 Existing Conditions ..............................................................................................................47
4.1.11.2 Considerations and Options ............................................................................................47
4.1.11.3 Recommendations ...............................................................................................................48
4.1.12 Reach 12 .......................................................................................................................................................52
4.1.12.1 Existing Conditions ..............................................................................................................52
4.1.12.2 Considerations and Options ............................................................................................52
4.1.12.3 Recommendations ...............................................................................................................53
4.1.13 Reach 13 .......................................................................................................................................................57
4.1.13.1 Existing Conditions ..............................................................................................................57
4.1.13.2 Considerations and Options ............................................................................................57
4.1.13.3 Recommendations ...............................................................................................................57
4.1.14 Reach 14 .......................................................................................................................................................59
4.1.14.1 Existing Conditions ..............................................................................................................59
4.1.14.2 Considerations and Options ............................................................................................59
4.1.14.3 Recommendations ...............................................................................................................59
4.1.15 Reach 15 .......................................................................................................................................................61
4.1.15.1 Existing Conditions ..............................................................................................................61
4.1.15.2 Considerations and Options ............................................................................................61
4.1.15.3 Recommendations ...............................................................................................................61
4.2 Improved Stormwater Treatment .......................................................................................................................63
4.3 Regional Trail Construction ...................................................................................................................................63
4.4 Preliminary Plan Set .................................................................................................................................................63
5.0 Cost Estimate ...........................................................................................................................................................................64
6.0 Impacts Caused by the Project .........................................................................................................................................65
6.1 Easement Acquisition ..............................................................................................................................................65
6.2 Environmental Review and Permitting .............................................................................................................65
6.3 Other Impacts Caused by the Project ...............................................................................................................65
6.3.1 Wetland Impacts .......................................................................................................................................65
6.3.2 Tree Loss .......................................................................................................................................................66
6.3.3 Soils ................................................................................................................................................................66
6.4 Impacts to Archeological Features .....................................................................................................................66
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List of Tables
Table 5-1 Engineer's opinion of probable cost--Summary of cost estimates by reach ............................64
Table 6-1 ARS Reach and erosion reach correlation ...............................................................................................67
List of Figures
Figure 2-1 Study area watershed ........................................................................................................................................ 6
Figure 2-2 Existing land use .................................................................................................................................................. 7
Figure 2-3 Drainage patterns ............................................................................................................................................... 8
Figure 2-4 Creek crossings .................................................................................................................................................... 9
Figure 2-5 Historical channel locations Reaches 1-9 ................................................................................................10
Figure 2-6 Historical channel locations Reaches 10-15 ...........................................................................................11
Figure 2-7 Channel profile ...................................................................................................................................................12
Figure 3-1 Survey data, Reaches 1-9 ...............................................................................................................................16
Figure 3-2 Survey data, Reaches 10-15 ..........................................................................................................................17
Figure 3-3 Native plant community types .....................................................................................................................18
Figure 3-4 Vegetative community quality .....................................................................................................................19
Figure 4-1 Reach 1 Proposed Work .................................................................................................................................22
Figure 4-2 Reach 2 Proposed Work .................................................................................................................................24
Figure 4-3 Reach 3 Proposed Work .................................................................................................................................27
Figure 4-4A Reach 4 Proposed Work—Option A ..........................................................................................................30
Figure 4-4B Reach 4 Proposed Work—Option B ..........................................................................................................31
Figure 4-4C Reach 4 Proposed Work—Option C ..........................................................................................................32
Figure 4-5 Reach 5 Proposed Work .................................................................................................................................35
Figure 4-6 Reach 6 Proposed Work .................................................................................................................................37
Figure 4-7 Reach 7 Proposed Work .................................................................................................................................40
Figure 4-8 Reach 8 Proposed Work .................................................................................................................................42
Figure 4-9 Reach 9 Proposed Work .................................................................................................................................44
Figure 4-10 Reach 10 Proposed Work ..............................................................................................................................46
Figure 4-11A Reach 11 Proposed Work—Option A .......................................................................................................49
Figure 4 11B Reach 11 Proposed Work—Option B........................................................................................................50
Figure 4 11C Reach 11 Proposed Work—Option C .......................................................................................................51
Figure 4-12A Reach 12 Proposed Work—Option A .......................................................................................................54
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Figure 4-12B Reach 12 Proposed Work—Option B........................................................................................................55
Figure 4-12C Reach 12 Proposed Work—Option C .......................................................................................................56
Figure 4-13 Reach 13 Proposed Work ..............................................................................................................................58
Figure 4-14 Reach 14 Proposed Work ..............................................................................................................................60
Figure 4-15 Reach 15 Proposed Work ..............................................................................................................................62
Figure 6-1 Proposed easement acquisition and affected properties .................................................................68
Figure 6-2 Delineated wetlands and wetland communities...................................................................................69
List of Appendices
Appendix A Project Petition from City of Edina
Appendix B Archeological Investigation
Appendix C Typical Stream Restoration Practices
Appendix D Detailed Cost Estimates by Reach
Appendix E Affected Property Owners
Appendix F Wetland Delineation and Functional Assessment Report
Appendix G Wetland Permit Application (not included with this document)
Appendix H Phase I Environmental Site Assessment (not included with this document)
Appendix I Environmental Assessment Worksheet (EAW) for
Nine Mile Creek Stabilization Project—Edina
Appendix J Preliminary Plan Set
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Certifications
I hereby certify that this Report was prepared by me or under my direct supervision and
that I am a duly Licensed Professional Engineer under the laws of the State of Minnesota.
Bob Obermeyer
BARR ENGINEERING CO.
AUGUST 24, 2015
13303
Date: Reg. No.
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1.0 Introduction
This report summarizes the proposed actions for improving the stability and water quality of the North
Fork of Nine Mile Creek (North Fork) within the City of Edina. It is prepared in accordance with
Section 103D.711 of the Minnesota Watershed Act and Section 103B of the Metropolitan Surface Water
Management Act under the direction of the Board of Managers of the Nine Mile Creek Watershed District.
Although the South Fork of Nine Mile Creek was reviewed, no actions are recommended at this time for
that reach. The petition received from the City of Edina is included in Appendix A.
1.1 Background
The Nine Mile Creek Watershed District (District) was established by the Minnesota Water Resources
Board in 1959. Stormwater management within the urbanizing Nine Mile Creek watershed was guided
initially by the District’s Overall Plan dated March 1961. That plan was revised by the District in April 1973,
as prescribed by the Minnesota Water Board. The 1973 revised Overall Plan guided development in the
District until it was further revised in May 1996 and again in 2006 (Water Management Plan), in
accordance with the Metropolitan Surface Water Management Act and Watershed Law: Minnesota
Statutes Chapters 103B and 103D, respectively.
1.2 Project Location
The proposed improvement projects are located in the City of Edina, Minnesota. The North Fork of Nine
Mile Creek enters the northwestern corner of the City of Edina at its boundary with Hopkins, represented
by US Highway 169. The stream then proceeds in a southeasterly direction, crossing Trunk Highway
(TH) 62 east of Gleason Road and crossing the boundary between Edina and Bloomington just west of
TH 100. The total stream length in the study area is 29,930 feet (5.7 miles), of which 16,982 feet (3.2 miles)
are included in 15 reaches for proposed improvements. The watershed area for this reach is approximately
8,640 acres (13.5 square miles), of which 5,750 acres (9.0 square miles) are within the City of Edina. The
South Fork of Nine Mile Creek, which is located in the southwestern corner of the City of Edina, was
included in the stream evaluation, but no work is proposed on that reach of the creek.
1.3 Summary of Problems
1.3.1 Stream Stability
Channels in urban areas are often lacking many of the features that define stable channels, such as a
defined floodplain and a stable, meandering pattern. Such channels have often been straightened over
the years and their floodplains filled, resulting in higher velocities and shear stress during high flows.
These channels tend to be eroded by fluvial bank erosion, which is exacerbated by higher stresses due to
the confined nature of the channel. The subsequent erosion can be much more severe than for an
equivalent channel in a non-urbanized setting.
Similar to many other urban stream systems, the North Fork of Nine Mile Creek suffers from stream bank
erosion. Based on a detailed site evaluation, the major erosion problems occurring in this portion of creek
may be attributed to the historical realignment of the channel from a meandering shape to a straightened
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channel, combined with increased runoff due to urbanization. Erosion problems tend to develop as the
creek attempts to return to a more stable, meandering pattern. This evolution is occurring via bank
slumping, formation of central bars which direct flow to one bank or the other, and channel widening. In
some areas, the resulting cut banks are very high, likely reflecting some degree of downcutting (channel
incision).
1.4 Project Objectives
The objective of the project is to provide a stable creek channel and correct existing problems of
stormwater discharge points into the creek. The creek has been listed as an “impaired water” by the
Minnesota Pollution Control Agency (MPCA) for turbidity, chlorides, and biotic impairment. Having a
stable stream will reduce internal sediment loading created by bank sloughing, channel downcutting and
meandering, and will provide improved fish habitat.
1.5 Public Participation
The Nine Mile Creek Watershed District has identified the importance of public involvement and seeks
opportunities to incorporate public involvement into District projects. The District will work with
stakeholders to review the project goals and objectives prior to accepting the Feasibility Report and
ordering the Nine Mile Creek Stabilization Project in Edina.
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2.0 Site Characterization
2.1 Watershed Characteristics
The study area includes the North Fork of Nine Mile Creek from east of the US Highway 169 crossing to
the Edina-Bloomington border northwest of the interchange between TH 100 and Interstate Highway 494.
The watershed of the North Fork at its downstream point in Edina is approximately 8,640 acres
(13.5 square miles), and includes area from the cities of Hopkins, Minnetonka, and Edina (Figure 2-1).
Approximately 5,750 acres (9.0 square miles), or two -thirds, of the watershed are within the City of Edina.
2.1.1 Land Use
The contributing watershed to the North Fork has changed over time from a pre-settlement condition to
agricultural land use, and then to urban land use. Currently, the watershed is almost entirely developed;
with primarily commercial, residential, public, and open space/park land uses (see Figure 2-2). Native plant
communities were inventoried in 2004 using the Minnesota Land Cover Classification System (MLCCS) as
part of the Nine Mile Creek Use Attainability Analysis. During the summer of 1999, a wetland inventory
was conducted within the City of Edina. The inventory consisted of field inspecting each wetland in the
city and mapping the approximate wetland boundary in general accordance with the routine
determination method as specified in the U.S. Army Corps of Engineers Wetlands Delineation Manual,
1987. The results of these investigations are discussed in Sections 3.5 and 6.3.
2.1.2 Drainage Patterns
Drainage is primarily conveyed to the creek system through a complex network of storm sewer systems.
Figure 2-3 shows the trunk storm sewer network, with the drainage areas color-coded to identify the areas
that drain to each portion of the creek.
2.1.3 Topography
The topography within the study area is relatively flat, with some rolling hills on the outskirts of the
watershed area. There is an elevation difference of approximately 54 feet from downstream of the
US Highway 169 crossing to the Edina-Bloomington boundary.
2.1.4 Soil Types
The soils within the study area watershed are predominantly hydrologic soil group B (moderate infiltration
capacity); large areas along the creek system and adjacent wetland areas have type D soils (poor
infiltration capacity).
2.2 Stream Characteristics
The North Fork, as it flows through the northern portion of the study area, has features very common to
urbanized streams, such as straightened flow patterns, a narrow corridor, and concentration of flow due to
numerous road crossings (shown in Figure 2-4). The following is a more detailed summary of the channel
geometry, historical channel alignment, and the stream profile
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2.2.1 Channel Geometry
The channel geometry of most streams is influenced by several factors. Channel slope, bed material, bank
material, and riparian vegetation are factors that are directly related to the stream and have significant
influence over channel geometry. Similarly, several hydrologic factors have significant influence as well
since they will control how much water enters the stream. These factors include the amount of rainfall, the
intensity of rainfall, watershed slopes, storage, infiltration capacity, impervious area, and land use within
the watershed. All of these factors can change over time or change along the length of the stream, so the
stream is constantly evolving to achieve equilibrium with these changing influences.
Natural processes of change, such as changing weather patterns or changing vegetation communities,
typically happen at a gradual rate such that the stream geometry has ample time to adjust to influential
factors. Even with these slow processes, however, it is possible for a stream to undergo significant
changes and have correspondingly large erosion problems. This can be caused either by catastrophic
events or by the stream channel and/or valley reaching a point where a major adjustment is necessary.
Man-made processes of change, such as increased development, stream crossings, altering of storage
areas, and changing drainage patterns, tend to happen too quickly for the stream to fully adjust to. Even
though greater measures are being taken to protect streams through the use of detention ponds and
other best management practices within the watershed, streams still undergo a certain amount of
adjustment to achieve equilibrium with their watersheds.
The channel geometry of the North Fork of Nine Mile Creek varies as it flows through Edina, reflecting the
influence of some of the factors listed above. Between TH 62 and Tracy Avenue, the creek has several
sections of modest confinement due to development. In some of these reaches the creek passes through
wetlands; in others it is bordered on one bank or the other by public land, such as a park. Where these
areas border the creek, they are less confining than high development densities on both creek banks, but
there are still constricting features commonly present, such as bridges or mixed-use trails. In these
sections the creek banks tend to vary in height between two and 4 feet, and floodplain access is usually
restricted to the less developed bank, if it exists. A hydraulic model indicated high velocities occur
approximately 150 feet downstream of Gleason Road, where they are greater than 8 ft/sec (feet per
second) in the 100-year return period storm event. Nearby sections have flow velocities ranging between
3.5 and 6 ft/sec for the 100-year return period storm event. These velocities are reduced in Bredesen Park,
where most sections have velocities less than 2 ft/sec.
Downstream of Tracy Avenue, Nine Mile Creek experiences greater confinement due to residential and
commercial development. In these areas, fill has likely been placed adjacent to the creek to accommodate
the development. Thus, the creek is relatively straight with steep, tall banks. Flood flows that would
overtop a more natural stream’s banks are confined by the artificially high banks, leading to high flow
velocities and erosion rates. The highest velocity in the 100-year return period flow event model occurs in
this section. Downstream of the Brook Drive culvert the velocity is modeled at greater than 9.5 ft/sec.
Maximum velocities in this area range from 4 to 6 ft/sec in the 100-year return period flow event. To
accommodate such high velocities, much of the stream bank in these reaches has been armored with rock
in the past. Riprap is still used by some residential and commercial landowners.
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The channel has been straightened between West 70th Street and the Edina-Bloomington boundary,
retaining little of its natural meander pattern. This straightening has also steepened the channel slope,
which, like confinement, tends to increase the velocity of flood flows. The bank vegetation, which is
dominated by reed canary grass, is inadequate to protect the banks in this reach from erosion. Modeled
velocities in this section range from 0.5 to 6 ft/sec, with most sections having velocities ranging between
2 and 4 ft/sec.
2.2.2 Historical Channel Alignment
A qualitative analysis of the historic channel alignment was completed using historic aerial photographs
for entire study area. Aerial photography is available for years 1937, 1947, 1957, 1969, 1979, and 1984, in
addition to the current stream centerline from 2010. The stream alignment was digitized in a Geographical
Information System (GIS) based on these aerial photos. The upstream study reaches (Reaches 1-9) are
shown in Figure 2-5, while the downstream study reaches (Reaches 10-15) are shown in Figure 2-6. The
key findings of the qualitative analysis are detailed below.
The reach between Londonderry Road and Vernon Avenue has been allowed to move naturally across
an existing wetland for the past 70 years. In the 1930s the lower end was ditched for agricultural
purposes, but due to the presence of Walnut Ridge Park some of its meander patterns have been re-
established.
The creek downstream of Vernon Avenue to TH 62 has been confined by the presence of Gleason
Road, houses along Killarney Lane and a mixed-use trail which leads to Bredesen Park. In past years
the creek was somewhat more sinuous in this reach than it is currently. Much of the natural channel
pattern is restored within the park, until the stream is again straightened in order to cross TH 62. The
effects of this artificial straightening extend well downstream of the highway; natural channel patterns
do not appear again until a distance more than 600 feet downstream of TH 62.
From Tracy Avenue to West 70th Street, Nine Mile Creek is very confined on both sides by residential
development. Most of this development occurred between 1957 and 1969. Despite reductions in the
size of the unobstructed floodplain, the stream has been able to maintain a highly sinuous meander
pattern.
The reach with the highest degree of straightening is from West 70th Street to the Edina-Bloomington
boundary. This straightening predates the earliest available aerial photography. This reach had been
partially ditched in the 1947 aerial photos, but certain sections (such as the one extending from the
present day Metro Boulevard almost to Industrial Drive) appear to be almost completely straightened
in the 1937 photos.
2.2.3 Stream Profile
The creek profile is generally mild through the project reach, as shown in Figure 2-7. From Tracy Avenue
to the Edina-Bloomington boundary the average slope is about 0.23 percent. From Vernon Avenue to
TH 62 the slope is steeper, about 0.35 percent. The farthest upstream reach, from US Highway 169 to
Vernon Avenue, has the most gradual slope, averaging 0.16 percent.
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Figure 2-1
STUDY AREA WATERSHEDNine Mile CreekRestoration Project
Edina, MN
Edina
Legend
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WaterWetlandWoodlandErosion reachesNorth Branch Nine Mile Creek
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Pipe Size
Box Culverts
<1 ft
1-2 ft
2-3 ft
3-4 ft
4-5 ft
5-6 ft
>6 ft
Erosion reaches
North Branch Nine Mile Creek
City of Edina Boundary
Nine MileSouth of 70th
§¨¦494
§¨¦494
62
100
456734456728
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SW Ponds
Nine MileSouth of 70th
North Cornelia
Lake Edina
Colonial ponds
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SouthPond
Nine MileSouth of 494
129
1387
14101511
Figure 2-3
DRAINAGE PATTERNS
Nine Mile Creek
Restoration ProjectEdina, MN
!;N
1,200 0 1,200600
Feet
!(
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Gleason Road Culvert - Concrete Arch, 12' Span
Vernon Avenue Culvert - Concrete Arch, 7.25' Span
Highway 62 Culvert - Concrete Box, 6' x 7.66' Span
7
321
56
4
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City of Edina Boundary
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Railroad Culvert - Concrete Ellipse, 7' Span
72nd Street Bridge - Single Span Steel Bridge
Tracy Avenue Culvert - Concrete Arch, 8' Span
Metro Boulevard Culvert - 2 Concrete Arches, 7.25' Span
Industrial Boulevard Culvert - Concrete Box, 8' x 8' Span
Brook Drive Culvert - 2 Concrete Culverts, 4' and 4.5' Diameter
Valley View Road Culverts - Concrete Box, 10' x 7' Span
Highway 100/Industrial Boulevard Ramps Culvert - Concrete Arch, 9' Span
Figure 2-4
CREEK CROSSINGS
Nine Mile Creek
Restoration ProjectEdina, MN
!;N
1,200 0 1,200600
Feet
Barr Footer: ArcGIS 10.0, 2011-11-23 11:48 File: I:\Client\Nmcwd\Workorders\CreekStabilizationWork_2011\Maps\Reports\Edina Engineers Report\Fig08A Historic Channels.mxd User: kac27
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68th St
Indian Hills Rd
W 68th St Dakota Tr Schaefer Rd Mccauley Tr W
Sally
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Grove St Crescent Dr Hillside La Arbour Ave West Tr Walnut Dr Limerick La Washington Ave Olinger Rd Valleyvie
w
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Cahill Rd Tamarac Ave Sun Rd Amy Dr Killarney La Benton Ave Iroquois Tr Nordic Dr Mohawk Tr Chapel Dr
Warden Ave Johnson Dr Gleason Ct
Highland Rd
Biscayne Blvd
W 66th St
Creek Valley Rd Indian Hills Pass Westridge Blvd Countryside Rd
Vernon Ct Scandia Rd W 61st St
Sioux Tr
Arctic Way Wycliffe Rd Susan Ave
Lois La
Parkwood La
Merhold Dr Valley View Rd Colonial Way Cre
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Whiting Ave
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W 64th St
Creek Valley Rd
Limerick L
a Valley View Rd Tracy Ave Grove St
Benton Ave
Biscayne Blvd
Figure 2-5
HISTORIC CHANNEL LOCATIONS
REACHES 1-9Nine Mile CreekRestoration Project
Edina, MN
800 0 800400
Feet
1937 Channel Centerline
1947 Channel Centerline
1957 Channel Centerline
1969 Channel Centerline
1979 Channel Centerline
1984 Channel Centerline
North Branch Nine Mile
Creek (Current Alignment)
City of Edina Boundary
!;N
Barr Footer: ArcGIS 10.0, 2011-11-23 12:02 File: I:\Client\Nmcwd\Workorders\CreekStabilizationWork_2011\Maps\Reports\Fig08B Historic Channels.mxd User: kac2129
13
14101511
100
100
456728
456728
W 70th St
W 66th St Cahill Rd West Shore Dr Metro Blvd Wooddale Ave Brook Dr
Dewy Hill Rd
W 77th St Tracy Ave W 68th St Service Rd Hillside La Hibiscus Ave
Da
n
e
n
s
D
r
O
h
m
s
L
a
Limerick La Dunberry
L
a
Lanham La W Bush Lake Rd Antrim Rd W 78th St
Tifton
D
r
W 74th St
De
l
a
n
e
y
B
l
v
d
Brittany Rd Ridgeview Dr W 76th St Galway
Dr
68th St
Gilford Dr Point Dr Edina Industrial Blvd
M
e
a
d
o
w
R
d
g
Creston Rd Long Brake Tr Aberc
r
o
m
b
i
e
D
r
Valley View Rd Trill
i
u
m
L
a
Upp
e
r
T
e
r
Mcguire Rd Normandale Rd Fleetwood Dr Sou
thc
res
t
D
r
Everett Pl Erin Ter Picture Dr Chapel Dr Larkspur La Fondell
D
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Viking Dr
Kemrich Dr
Du
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Susan Ave Hyde Pa
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Lee Valley Rd
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Kellog Ave Aspasia La Gleason Rd Dunha
m
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Naomi Dr Dewey Hill Rd
W 73rd St Shannon Dr Limerick Dr Shane Dr Poppy La
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ir Warren Ave Village Dr
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W 7
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W 69th St
Figure 2-6
HISTORIC CHANNEL LOCATIONS
REACHES 10-15Nine Mile CreekRestoration Project
Edina, MN
800 0 800400
Feet
1937 Channel Centerline
1947 Channel Centerline
1957 Channel Centerline
1969 Channel Centerline
1979 Channel Centerline
1984 Channel Centerline
North Branch Nine Mile
Creek (Current Alignment)
City of Edina Boundary
!;N
Figure 2-7 Channel Profile
2 year (bankfull), 10 year, and 100 year water surfaces also shown
0 5000 10000 15000 20000 25000 30000780
790
800
810
820
830
840
850
860
870
880
Main Channel Distance (ft)Elevation (ft)Legend
WS 100-yr
WS 10-yr
WS 2-yr
Ground
Reach 15Industrial DriveHwy 100 <-> Industrial Blvd RampsReach 14Metro BoulevardReach 1370th StreetReach 12Railroad CrossingReach 11Reach 10Reach 9Reach 8Valley ViewReach 7Reach 6Hwy 62Reach 5Reach 4GleasonVernon AveReach 3Reach 2Reach 1NineMileCrk North Branch
P:\Mpls\23 MN\27\23271132 Nine Mile Creek Restoration - Edina\WorkFiles\Engineer's Report\Edina_EngrsRpt_Aug-2015.docx 13
3.0 Site Evaluation
3.1 Detailed Field Survey
Detailed field surveys were completed for portions of the study area where bank erosion was noticeable in
order to (1) characterize the channel geometries and slopes of the existing creek; and (2) to evaluate
alternatives for proposed stream improvements. The survey data that was collected in 2011 and 2013 is
summarized in Figures 3-1 and 3-2. Field visits without detailed survey were also completed to evaluate
the stability of each creek segment and identify remedial measures.
3.2 Hydrologic/Hydraulic Modeling for Creek Modifications
Hydrologic and hydraulic models were used to estimate water surface elevations and velocities in the
creek under existing conditions for a range of flows. Most design considerations are based on the 1- to
2-year return period flow event, which are flood frequencies often used to predict ‘bankfull’ flow
conditions. Bankfull flow is also commonly referred to as the “channel forming flow.” The shape, pattern,
and profile of a stream channel are intimately related to the bankfull discharge. When the stream is in
equilibrium with its environment, the shape, pattern and profile are such that the stream can convey the
bankfull discharge without significant change in those parameters. With increased impervious surface area
due to urbanization, the frequency of bankfull discharge increases. It is also important for the design of
stream stabilization improvements to consider the flow regime during events larger than a bankfull event
to gain a complete understanding of the range of flow conditions that may be present in the stream.
The hydrologic and hydraulic models are also used as a tool to design the proposed stream
improvements. The modeling analyses are described in further detail below.
3.2.1 Nine Mile Creek XP-SWMM Model
A hydrologic/hydraulic model was developed by Barr Engineering Company (Barr) for the entire Nine Mile
Creek watershed in 2004-2005 using XP-SWMM. This is a numerical model based on the U.S.
Environmental Protection Agency (USEPA)’s Storm Water Management Model (SWMM). This model allows
simultaneous, continuous (non-steady state) hydraulic and hydrologic modeling, using climate data as
input to generate runoff flows. The XP-SWMM model of Nine Mile Creek covers the entire creek
watershed (approximately 50 square miles) and is subdivided into more than 3,000 subwatersheds.
The XP-SWMM model was used to predict flows in the North Fork for the 2-year frequency, 24-hour
design event. The XP-SWMM model was originally developed to simulate large storm events (10-, 50-,
100-, and 500-year return periods), consistent with the Federal Emergency Management Agency (FEMA)
flood insurance program. Consequently, the level of detail in the existing XP-SWMM model for portions of
the North Fork was insufficient to predict the hydrologic impacts of stream improvements within the
study area. Therefore, the predicted flows for the 2-year frequency, 24-hour event were used as steady-
state flow inputs for the existing conditions Hydrologic Engineering Centers River Analysis System
(HEC-RAS) model. This provides for more detailed hydraulic analysis and was used as a basis for the
design of the proposed channel modifications. In order to study a wider range of flows and velocities, the
P:\Mpls\23 MN\27\23271132 Nine Mile Creek Restoration - Edina\WorkFiles\Engineer's Report\Edina_EngrsRpt_Aug-2015.docx 14
HEC-RAS model also simulated conditions for the four standard FEMA return period flow events (10-year,
50-year, 100-year and 500-year) as calculated by the XP-SWMM model.
3.2.2 Edina Stream Improvements HEC-RAS Models
A steady-state hydraulic model was created for the study area using HEC-RAS, a hydraulic model
developed by the U.S. Army Corps of Engineers (USACE). HEC-RAS pairs unsteady or steady flow data with
channel and floodplain geometry (in the form of two-dimensional (2-D) cross sections) to estimate water
surface elevations, flow velocities, and other hydraulic parameters. The HEC-RAS model for Nine Mile
Creek within the City of Edina modeled the current existing conditions in order to determine which areas
were most at risk of erosion. It contained cross sections from the XP-SWMM model as well as additional
cross sections from the field survey.
As mentioned in Section 3.2.1, flow rates from the XP-SWMM model were used as steady-state inputs for
the HEC-RAS model, the most important of these being the 2-year return period flow event. This was
selected as the best approximation to bankfull, or channel forming conditions. No stormwater inputs or
other flow changes were included in this model. The 2-year, 24-hour storm event was modeled at a rate of
433 cubic feet per second (cfs) for the entire length of the reach.
The existing conditions model indicated that the creek overtops its banks in a 2-year return period flow
event in wetland areas such as Reach 2 (large wetland area just east of US Highway 169), Bredesen Park,
and the wetlands north of the Edina High School near Site 7. Consequently, additional model runs using
standard flood frequencies were performed to examine a wider range of hydraulic conditions that may
occur in this reach, including the 10-year (549 cfs), 50-year (598 cfs), 100-year (659 cfs) and 500-year
(732 cfs) return period flow events. All flow rates for standard flood frequencies were obtained from the
Nine Mile Creek XP-SWMM model.
The recommended channel stabilization measures for this reach were designed based on the 2-year
return period flow event modeling results. The height of channel armoring generally coincides with the
2-year return period flow event elevation. Stream bank stabilization above this elevation will generally
consist of grading and revegetation using native plants.
3.3 Archeological Investigation
During the summer of 2011, Archaeological Research Services (ARS) conducted an archaeological survey
along the City of Edina segment of Nine Mile Creek in Hennepin County, Minnesota. The investigation is
part of this feasibility study. As the implementation of these efforts involve public land and funding as well
as federal permitting of wetland impacts, the project proposers are anticipating that both the State
Historic Preservation Office (SHPO) and the Office of the State Archaeologist (OSA) will request an
archaeological review of the project route. Consequently, a records and literature search and preliminary
field assessment were incorporated into this feasibility study (included as Appendix B).
ARS completed a field inspection during the week of July 25, 2011, following records and literature
searches at SHPO and OSA. Maps of the project location are included in Appendix B.
P:\Mpls\23 MN\27\23271132 Nine Mile Creek Restoration - Edina\WorkFiles\Engineer's Report\Edina_EngrsRpt_Aug-2015.docx 15
Aerial photographs dating back to the 1930s through 1950s show that much of the study area was a rural
patchwork of farmed uplands and extensive wetlands. The photos also indicate that many segments of
the North Fork channel had already been narrowed, straightened and realigned—a process which later
intensified to accommodate residential and industrial development. Older photographs and topographic
maps of the then less urbanized segments of the Nine Mile Creek drainage, indicate a much different
historic appearance, i.e. that of a naturally meandering stream within a wide and often marshy floodplain.
Visual inspection of existing erosion exposure provided enough survey coverage to conclude that none of
the bank segments prioritized for stabilization features any archaeological evidence.
3.4 Riparian Vegetation Survey
Barr conducted an inventory of plant communities and a bird habitat evaluation of the Nine Mile Creek
riparian corridor (‘the corridor’) during the summer of 2003. The objective of the 2003 Minnesota Land
Cover Classification System (MLCCS)-based plant community inventory was to provide a geographical
information system (GIS) map and database of plant community types, location, and quality. The 2003
data were collected in order to compare 2003 results with the previous 1998 inventory, and to update the
classification system to the MLCCS. Another objective was to identify high quality plant communities for
preservation. In the summer of 2011 previous vegetation survey results were reassessed through a
desktop review of the existing land cover mapping from 2003 and with site visits to confirm the relevance
of the prior data.
The 2011 review confirmed that most of the plant community information collected in 2003 remained
valid. In many cases the only change has been an increase in the percent cover and density of the invasive
species present along the corridor. Figures 3-3 and 3-4 provide an overview of the native plant
community types along the stream corridor, and the vegetative community quality based upon the
percent invasive species cover. High invasive species cover is indicative of degraded ecological quality as
invasive species replace the native species cover and thus reduce the habitat quality.
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SURVEY DATA
REACHES 1-9Nine Mile CreekRestoration Project
Edina, MN
800 0 800400
Feet
!(2011 Survey Points
2011 Cross Sections
North Branch Nine Mile Creek
City of Edina Boundary
!;N
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Figure 3-2
SURVEY DATA
REACHES 10-15Nine Mile CreekRestoration Project
Edina, MN
800 0 800400
Feet
!(2011 Survey Points
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North Branch Nine Mile Creek
City of Edina Boundary
!;N
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£¤212
62
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Forest
Box Elder Forest
Shrubland
Wetlands
Open Water
Erosion reaches
North Branch Nine Mile Creek
City of Edina Boundary
§¨¦494
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62
100
456734456728
129
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Figure 3-3
NATIVE PLANT COMMUNITY TYPES
Nine Mile Creek
Restoration ProjectEdina, MN
!;N
1,200 0 1,200600
Feet
£¤169
£¤212
62
4567158
7
321
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4
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0-20% Invasive Species
20-40% Invasive Species
40-60% Invasive Species
60-80% Invasive Species
80-100% Invasive Species
Erosion reaches
North Branch Nine Mile Creek
City of Edina Boundary
§¨¦494
§¨¦494
62
100
456734456728
129
1387
14101511
Figure 3-4
VEGETATIVE COMMUNITY QUALITY
Nine Mile Creek
Restoration ProjectEdina, MN
!;N
1,200 0 1,200600
Feet
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4.0 Proposed Improvements
4.1 Stream Stabilization
Similar to many other urban stream systems, the North Fork of Nine Mile Creek suffers from stream bank
erosion. Based on a detailed site evaluation, the major erosion problems occurring in this portion of creek
may be attributed to the historical realignment of the channel from a meandering pattern to a
straightened channel, combined with increased runoff due to urbanization. Erosion issues tend to develop
as the creek attempts to return to a more stable, meandering pattern. This evolution is occurring via bank
slumping, formation of central bars which direct flow toward one bank or the other, and channel
widening. In some areas, the resulting cut banks are very high, likely reflecting some degree of
downcutting (channel incision).
The proposed stream stabilization improvements for segments of the North Fork within the City of Edina
are summarized in Figures 4-1 to 4-15. Realignment of the channel to a more stable, meandering pattern
is proposed for two reaches of the study area. In most of the remaining reaches- where realignment is not
possible - reshaping of the channel banks to flatter slopes and revegetation of the banks are
recommended. Stabilization of the channel toe and grade control will be necessary in some locations.
Recommendations for one reach consist only of vegetation improvement to improve bank stability,
including the planting of native prairie grasses and removal of existing invasive species. Schematics of
these stream stabilization practices are contained in Appendix C. The recommended improvements for
each reach are summarized below.
4.1.1 Reach 1
4.1.1.1 Existing Conditions
Reach 1 begins at US Highway 169 and extends to approximately 240 feet downstream of Londonderry
Road. This reach generally has stable banks upstream of Dovre Drive and no work is proposed. The reach
has some erosion issues beginning approximately 260 feet downstream from Dovre Drive to
approximately 240 feet downstream of Londonderry Road, for a total erosion reach length of 650 feet.
The existing side slopes of the creek are visibly eroded, suggesting that the erosion reach is downcutting.
A storm sewer outlet invert that is perched approximately 2 feet from the current normal water level also
supports this observation. The bottom width of the channel varies within the reach between
15 and 20 feet. The channel is bordered on the east by residential development and on the west by a
small wooded area and Lincoln Drive. The tree canopy through Reach 1 is dominated by second growth
forest composed of silver maple, elm, green ash, cottonwood, basswood, box elder, and buckthorn. The
closed canopy and dominance of box elder and buckthorn has greatly reduced the ground layer cover,
resulting in large areas of exposed soil. Historical aerial photos show that this channel has essentially
remained in its current location since 1937.
4.1.1.2 Considerations and Options
As previously mentioned, the residential area and the wooded area pose significant limitations on feasible
options to consider at this site. The wooded area on the west side of the stream is along a fairly tall bank
P:\Mpls\23 MN\27\23271132 Nine Mile Creek Restoration - Edina\WorkFiles\Engineer's Report\Edina_EngrsRpt_Aug-2015.docx 21
ranging between 4 to 7 feet high. Grading in that area will require the removal of dozens of trees and a
significant volume of soil. On the east side there are some buildings in the residential area quite close to
the creek’s bank. Also, the low-floor elevations of some residences are similar to the top of bank elevation;
therefore it is important to ensure that any measures within this reach do not raise flood levels and impact
nearby residences.
Since the channel in this reach is incised, the ideal solution would be to reconnect the stream with the
floodplain such that the stream spills out of its banks and onto the floodplain every 1 to 2 years. This
could be done by raising the stream bed with constructed riffles, excavating a new lower floodplain, or a
combination of the two. The proximity of the nearby residences prevents the excavation of a new
floodplain.
Other options for this
reach include measures
that would stabilize the
outside bank and
prevent additional
downcutting. This can be
accomplished by
installing boulder cross-
vanes that will provide
grade control while
directing flow away from
the banks. The outside
bank can be further
stabilized by installing
riprap, rock vanes,
and/or root wads. Rock
vanes and root wads will
require bank disturbance for installation but will result in a more natural appearance. Riprap toe
protection can be installed with or without additional bank grading.
4.1.1.3 Recommendations
Recommendations for addressing erosion problems in Reach 1 include installing riprap toe protection
along the outside bank of the creek meander, installing two cross-vanes to stabilize the stream profile and
prevent downcutting, constructing three root wads for bank protection, and using vegetation
management to remove undesirable and invasive species. Along the east bank, ornamental plants
installed at the nearby residences should be replaced with selected riparian species appropriate for the
setting that provide bank stabilizing root systems and maintain the natural aesthetics. Rock vanes or root
wads are feasible at this site for stabilizing the outside bend, but use of field stone riprap is recommended
at this site to minimize bank disturbance.
Linco
ln
D
r
Vernon Ave Londonderry Rd
1
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
110 0 11055
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Root Wads
Riprap
Bank Grading
4-1
1
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4.1.2 Reach 2
4.1.2.1 Existing Conditions
Reach 2 begins approximately 240 feet downstream of the Londonderry Road crossing of the creek and
extends a distance of approximately 1,500 feet downstream to upstream of the pedestrian bridge at the
end of Tamarac Avenue. This reach meanders through an existing wetland, having a very large floodplain
that is mostly free from surrounding development. However, the reach slope appears to be steepening
over time, as shown by the steep side banks and frequent bank sloughing. The stream is very narrow in
this reach, with a channel width between 5 and 10 feet in most areas. Bank vegetation is dominated by
reed canary grass.
4.1.2.2 Considerations and Options
The channel is incised. As with Reach 1, it would be ideal to reconnect Reach 2 to the floodplain. In
addition to the options that were described in Section 4.1.1.3, the expansive floodplain in this reach would
make it possible to excavate a new, stable channel with appropriate geometry and meander pattern
through the floodplain. The creek could be re-directed into the new channel once vegetation becomes
adequately established. This would direct the stream channel away from two nearby homes. Preliminary
discussions with the homeowners, however, indicated that they prefer to have the creek remain in its
current channel where it is easily visible from their homes.
4.1.2.3 Recommendations
Recommendations for stabilizing the erosion problems in Reach 2 include the installation of six cross-
vanes to stabilize the channel slope and prevent downcutting, as shown in Figure 4-2. Floodplain
excavation may be necessary in order to create a natural floodplain for the stream while maintaining flood
levels that would not increase the flooding risk at the nearby homes. Because this reach is fairly sinuous, a
total of 16 root wads are
recommended for the outside of
stream bends to reduce bank
sloughing.
Londonderry Dr
2
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
160 0 16080
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Root Wads
Bank Grading
4-2
2
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4.1.3 Reach 3
4.1.3.1 Existing Conditions
Reach 3 begins at the pedestrian bridge that crosses Nine Mile Creek at the end of Tamarac Avenue,
extending downstream a distance of approximately 1,600 feet through Walnut Ridge Park and terminating
at Gleason Road. Erosion issues in this reach are mild, mostly limited to minor sloughing and specific
locations of bank erosion. The channel ranges in width from 5 to 10 feet and is bordered on the south and
west sides by residential area. The property located on the west side of the creek and immediately
upstream of Vernon Avenue (6414 Vernon Avenue) is said to have experienced erosion problems in past
years but the creek appears to have achieved a relatively stable condition at this location. There were no
erosion issues observed between Vernon Avenue and Gleason Road.
4.1.3.2 Considerations and Options
The locations with bank erosion can be mitigated with riprap, rock vanes, or root wads. However, riprap is
not recommended because infrastructure is not threatened by the erosion, and other stabilization
methods are considered more beneficial to aquatic life while having a more natural appearance. Rock
vanes are feasible at these locations and would provide bank protection; however, the narrow width of the
stream could make it difficult to design and install the rock vanes in such a manner to function properly
while not causing additional erosion. Root wads would provide bank protection at a scale appropriate to
the channel dimensions (i.e. they would not restrict channel width) and would provide excellent fish
habitat.
The observed areas of bank sloughing are largely caused by poor vegetation management. The
homeowners are maintaining mowed turf grass to the edge of the stream, providing no buffer to the
channel. Turf grass lacks the root
structure to maintain the stream
bank, leaving it vulnerable to
erosion. The sloughing bank is on a
straight stretch of the stream, so
additional bank or toe protection is
not necessary. Establishing a 10 to
15 foot buffer with native vegetation
(only grasses or a mix of grasses and
shrubs) would provide the root
structure needed for long term
stability. The bank could also be
graded to a more gradual slope to
facilitate vegetation establishment
at the toe of the bank.
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4.1.3.3 Recommendations
Proposed improvements to this reach are shown in Figure 4-3. Installation of six root wads is
recommended for the areas of bank erosion at meander bends. Other recommendations for Reach 3 are
limited to bank grading combined with vegetation management within Walnut Ridge Park and on the
properties with mowed turf grass to the edge of the stream. It is also recommended that educational
materials be supplied to homeowners with properties bordering the creek to the east. Combining these
efforts should stabilize the channel and protect both public and private properties.
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
160 0 16080
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Root Wads
Bank Grading
4-3
3
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4.1.4 Reach 4
4.1.4.1 Existing Conditions
Reach 4 begins downstream of Gleason Road and extends for a distance of approximately 940 feet to an
existing pedestrian bridge in Bredesen Park. The creek banks in this reach are eroded and require
stabilization in order to protect the existing mixed-use bituminous trail along the east bank of the creek
leading to the park. Along the west bank of the creek is a forested buffer and turf grass right-of-way
along Gleason Avenue. The stream is currently very straight and averages about 10 feet in width. A grove
of walnut trees within this reach requires protection during construction, as well the burr oaks and large
cottonwood trees that are present.
4.1.4.2 Considerations and Options
Given the proximity of the mixed-use bituminous trail and residential streets on the east side of the
stream, riprap may be necessary to stabilize the eroding banks. Even with riprap it may be necessary to
grade the top of the bank to a stable slope without disturbing the trail. It would also be possible to
stabilize the creek bank with a bioengineering approach by using vegetated reinforced soil slopes (VRSS).
VRSS often uses willow cuttings that require a lot of sunlight. Providing full sun to these cuttings would
require thinning of the vegetation on the opposite bank. It would also be possible to plant more shade
tolerant shrubs instead of willow cuttings, but these would still require some thinning of the vegetation on
the opposite bank. The shade tolerate shrubs are also more expensive than willow cuttings. With riprap or
VRSS, it would be difficult to grade the top of the bank to a stable slope without disturbing the trail.
Alternatively, it would be possible to push the toe of the east bank out into the stream to create room for
a stable bank slope, but such action should be accompanied with equivalent excavation on the west bank
to maintain the channel geometry and flow
area.
The stream was obviously straightened in the
past. The stream is now attempting to
recreate meanders, alternating locations of
bank erosion as the flow pattern moves back
and forth through the channel. Therefore,
another alternative would be to restore
meanders to this reach. The corridor between
Gleason Avenue, residential streets, and the
trail system is narrow in some places, but it
would be possible to re-establish meanders
through Reach 4.
Option A- Stabilize in Place
The existing erosion problems within this reach can be addressed with the installation of five cross-vanes
for grade control and placing riprap along the east bank of the creek to protect the trail as shown in
Figure 4-4A. However, the use of riprap is generally not considered natural and aesthetically pleasing. The
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bank grading followed by riprap placement would require the removal of many trees from the east bank.
Because the existing trees are well-established and currently acting as erosion protection for the trail,
bank grading and riprap are not the preferred option in Reach 4.
Option B- Remeander Away From Trail
Figure 4-4B shows the proposed re-establishment of a meander pattern. Option B would move the creek
farther away from the residential properties and the trail, but has larger and more gradual meanders. This
option includes the use of two cross vanes to maintain the grade established in the new channel, and
prevent downcutting from causing future problems along the stretch. This option also includes eleven
root wads and six boulder vanes for bank protection. This option would increase the creek length to
approximately 900 feet.
Option C- Remeander in Current Corridor
If trail users or residents object to Option B, Option C introduces a smaller meander pattern and keeps the
stream closer to its original location. Both designs are the same for the final 620 feet of the re-
establishment of a meander pattern in this reach. This option includes four cross vanes to maintain the
established grade in the new channel. This option also includes eleven root wads and six rock vanes for
bank protection. This option would increase the creek length to approximately 1,100 feet.
4.1.4.3 Recommendations
The preferred recommendation for the erosion issues in Reach 4 is to re-establish a meandering pattern
to the channel, which will decrease the slope of the affected reach and help decelerate bank erosion.
Option B will provide maximum trail protection, but Option C will require less grading while still providing
good protection to the trail and maintaining aesthetic value to trail users.
4567158 View La Killarney La Gl
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a
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o
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Glacier Pl
4
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Figure 4-4A
REACH 4 PROPOSED WORK -
OPTION A
Nine Mile Creek
Restoration ProjectEdina, MN
100 0 10050
Feet
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Root Wads
Riprap
NMCWD Parcels
Bank Grading
4567158 View La Gleason Rd Killarney La Glac
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P
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Arct
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Schaefer Rd
Gleaso
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Figure 4-4B
REACH 4 PROPOSED WORK -
OPTION B
Nine Mile Creek
Restoration ProjectEdina, MN
150 0 15075
Feet
Cross Vanes
North Branch Nine
Mile Creek
Remeander Option 1
Vanes
Root Wads
NMCWD Parcels
4567158 View La Gleason Rd Killarney La Glac
ie
r
P
l
Arct
i
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W
a
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Schaefer Rd
Gleaso
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C
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Figure 4-4C
REACH 4 PROPOSED WORK -
OPTION C
Nine Mile Creek
Restoration ProjectEdina, MN
150 0 15075
Feet
North Branch NineMile Creek
Remeander Option 2
Cross Vanes
Vanes
Root Wads
NMCWD Parcels
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4.1.5 Reach 5
4.1.5.1 Existing Conditions
Reach 5 begins at a pedestrian bridge within Bredesen Park and continues a distance of approximately
1,250 feet downstream to TH 62. The upper portion of this reach is highly sinuous and winds through a
forested wetland area. The creek banks are low but quite steep, indicating that the stream may be in the
process of downcutting. Sloughing of the channel banks is common. The reach becomes less sinuous as it
continues south towards TH 62, but downcutting continues and a large scarp is forming near the highway
that requires stabilization. Along this reach the creek ranges in width from 8 to15 feet.
4.1.5.2 Considerations and Options
The bank sloughing in this reach is likely caused by poor riparian vegetation. The grassy areas are
dominated by reed canary grass, which is an aggressive, invasive species that is very difficult to control.
Reed canary grass has a shallow root system, so it does a poor job of stabilizing stream banks. A feasible
option for the observed sloughing banks is to regrade the banks to a shallower, stable slope and plant
native riparian grasses and shrubs (dogwoood, willow, etc). Given the large areas dominated by reed
canary grass that are adjacent to the erosion sites, maintenance efforts should be provided for the first
three years to ensure the native plants become established. The shrubs will be better able to out-compete
the reed canary grass as it attempts to invade the site again.
Similar to Reachs 2 and 4, fieldstone riprap, rock
vanes, and root wads could also provide
adequate bank protection for the outside banks
at meanders. All three have similar pros and cons
as they did for the other reaches, and, once again,
root wads appear to be the most feasible option
for stabilizing the outside banks through the
grassy area of this reach.
The downcutting occurring within this reach can
be mitigated by raising the stream bed,
excavating a new floodplain, or a combination of
the two. Since there are no nearby properties, raising the stream bed with constructed riffles (made of
either rock or woody debris) is the most feasible option. This would reconnect the stream with its wide,
natural floodplain and minimize floodplain disturbance. The hydraulic modeling indicates (on a
preliminary basis) that this can be accomplished without a rise in flood levels.
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The lower section of the reach is more wooded and
the stream is slightly wider; thereby making rock
vanes a more feasible option for bank protection
than for the upper portion of this reach. Root wads
are again preferred due to their natural appearance
in the park setting and due to the fish habitat that
would be created.
4.1.5.3 Recommendations
Recommendations for correcting erosion problems
within Reach 5 include the installation of four cross-
vanes, which will serve to raise the stream bed by
encouraging deposition between the vanes, and approximately 22 root wads for bank stabilization. The
stream banks in the lower section of this reach should also be graded to a stable slope. The failing fence
that crosses the existing scarp immediately upstream of TH 62 (seen in the photo above) should be
removed. Fieldstone riprap should be added for additional bank protection in the downstream section as
the stream enters the TH 62 right-of-way. Buckthorn control throughout the reach will be critical for the
establishment of native cover. All buckthorn removal will require stump treatment with herbicide and
followup control for three years. Control of reed canary grass is also required for native plants to become
established.
62
62
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
160 0 16080
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Root Wads
Riprap
Bank Grading
4-5
5
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4.1.6 Reach 6
4.1.6.1 Existing Conditions
Reach 6 begins at the TH 62 crossing of
the creek and continues for a distance of
approximately 600 feet downstream. This
reach is northwest of the Edina High
School athletic fields and has a forested
buffer corridor along both banks. Erosion
issues are mild within this reach and
generally consist of bare or eroding
stream banks. This reach has a fairly
consistent width of around 15 feet.
Buckthorn coverage in this reach exceeds 60 percent along both sides of the creek with box elder being
the other major tree species present. Buckthorn control will be critical to the establishment of native
cover; thus all buckthorn removal will require stump treatment with herbicide and followup control for
three years.
4.1.6.2 Considerations and Options
Once again, fieldstone riprap, rock vanes, and root wads are all options that would stabilize the eroding
banks. Additional systemic issues do not appear to be present in this reach.
4.1.6.3 Recommendations
With the erosion issues in Reach 6 being relatively mild in comparison with other reaches, the proposed
solutions are grading of stream banks and installation of four rock vanes to reduce velocity near the
banks, particularly during high flow scenarios.
Native prairie vegetation should be planted along the south bank of the creek channel to blend with the
adjoining prairie restoration areas. Control of buckthorn and reed canary grass will be required during the
five-year establishment period.
62
62
6
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
130 0 13065
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Vanes
Bank Grading
4-6
6
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4.1.7 Reach 7
4.1.7.1 Existing Conditions
Reach 7 begins at the northeastern corner of the existing soccer fields, and continues downstream for a
distance of approximately 4,300 feet to Valley View Road. The majority of this reach of the creek winds
through an existing wetland area. Erosion issues are minor, and include moderate sloughing and bank
erosion. The creek width is highly variable within this reach, ranging from 6 8 feet in the upstream part to
more than 15 feet where it enters a small excavated pond located approximately 900 feet upstream of
Valley View Road.
4.1.7.2 Considerations and Options
Since this reach is in an existing
wetland, there is no need to restrain
the creek from meandering back and
forth across the landscape, as it has
historically done (see Figure 2-5).
Issues of bank sloughing and bank
stabilization in this area can be
addressed by improving and
managing the vegetation. The current
land cover consists mostly of reed
canary grass, but the planting of native
species, including more shrub-type
plants such as willows, would increase
soil strength and improve the diversity
of the floodplain plant species.
Removal of buckthorn in the forested areas could also be accomplished at this time.
This reach is located near Edina High School and Creek Valley Elementary School, providing an
opportunity to partner with one or both of schools to create educational features. The District has been
working with the Edina High School science department in testing the water quality of Nine Mile Creek.
Potential project components and educational opportunities include but are not limited to the following:
1) Invasive species control;
2) Creating oxbow “lakes” in historic meander patterns and studying how they change over time.
3) Installing demonstration features (root wads, rock vanes, riprap, etc.) so the students can observe
differences in how they work to stabilize banks.
4) Creating specific habitat features (shallow riffles, deep pools, woody debris) and studying the
different aquatic organisms in each habitat.
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5) Native prairie vegetation should be planted on the south bank of the creek channel to blend with
the adjoining prairie restoration areas. Control of buckthorn and reed canary grass will be
required during the five-year establishment period.
6) Buckthorn control will be critical to the establishment of native cover; thus all buckthorn removals
will require stump treatment with herbicide and follow-up control for three years.
4.1.7.3 Recommendations
No work to stabilize stream banks in this reach is recommended, and no other measures are
recommended within this reach at this time. Future possibilities include the vegetation management
described above, and educational opportunities could be explored by contacting the nearby schools and
determining an appropriate scale and cost for educational features.
62
62
Creek Valley
Rd
7
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
330 0 330165
Feet
Figure
North Branch NineMile Creek
Erosion reaches
NMCWD Parcels
4-7
7
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4.1.8 Reach 8
4.1.8.1 Existing Conditions
Reach 8 begins downstream of Valley View Road and continues downstream for a distance of
approximately 2,125 feet to the corner of Cahill Road and West 66th Street. This reach is in a residential
neighborhood with a small forested riparian buffer on both sides of the creek. The first 550 feet
downstream of Valley View Road has some erosion issues, but the remainder of the reach appears stable.
The creek banks are fairly steep and moderately eroded, and the slope is mild. Riprap is currently in
limited use to protect creek banks which are eroding private properties.
4.1.8.2 Considerations and Options
Systemic issues do not appear to be present
at this reach and the bank erosion is limited
to isolated sites.
One bank erosion site is at the base of a
long, tall slope. Installing root wads or rock
vanes on this slope would create too much
disturbance and are not practical options.
Fieldstone riprap is a more feasible option
for this site.
Mowed turf grass to the stream’s edge is also contributing to bank erosion. Educating homeowners and
establishing a buffer of native vegetation would serve to better protect the stream banks.
4.1.8.3 Recommendations
Recommendations for Reach 8 involve the installation of fieldstone riprap along a section of eroding
stream bank and installation of 6 root wads along selected meander bends to protect the existing stream
banks from erosion. Educational materials about stream bank preservation and maintenance should be
provided to homeowners along the creek.
62
62
Valley La Tracy Ave Valley View Rd Hillside Ct Limerick L
a
W 64th St Doron La Dor
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
220 0 220110
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Root Wads
Riprap
NMCWD Parcels
Bank Grading
4-8
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4.1.9 Reach 9
4.1.9.1 Existing Conditions
Reach 9 is one of the most sinuous reaches of Nine Mile Creek in the project study area. The reach begins
just south of the intersection of West 66th Street and Cahill Road and continues downstream for a distance
of approximately 1,550 feet. There are many trees along the creek, but the channel itself is fairly confined
by residential development on both sides. The creek within Reach 9 is fairly narrow, ranging from
5 to 10 feet in most locations, and has many extremely sharp bends. In one location the stream has
straightened itself by cutting off a former meander. In another location it has extended outward from a
former meander, more than doubling its length when compared to the previous state. These features,
along with steep and actively eroding banks, suggest that the stream in this area has a steepening slope,
resulting in more erosion, active downcutting, and increased stream power. Several homeowners along
the channel have installed riprap to protect their yards and gardens from erosion.
4.1.9.2 Considerations and Options
Existing land use prevents significant realignment
of Nine Mile Creek within this stream segment. The
active meanders do not threaten existing
infrastructure but may pose problems for
anticipated future pedestrian uses.
Grade control measures such as cross-vanes can be
implemented to reduce channel steepening.
Vegetative management, including removal of
invasive species and establishment of a native
vegetation buffer, would help to protect the stream
channel and the adjacent properties from further
erosion.
4.1.9.3 Recommendations
Proposed solutions to erosion problems within Reach 9 are limited to grade control and bank stabilization
measures. Grade control will be established by the installation of three cross-vanes and ten vanes, spaced
along the entire length of the reach. Nineteen root wads, placed along the outside of selected meander
bends, will protect existing stream banks and increase roughness in these areas, helping to dissipate
excess stream power.
Cahill Rd Limerick Dr Cahil
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Nine Mile CreekRestoration Project
Edina, MN
130 0 13065
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Vanes
Root Wads
NMCWD Parcels
Bank Grading
4-9
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4.1.10 Reach 10
4.1.10.1 Existing Conditions
Reach 10 begins 100 feet upstream of the
intersection of W. 68th Street and Cahill Road and
continues downstream for a distance of
approximately 975 feet to Brook Drive. It is
bordered on both sides by residential
development. The eroding portion of this reach is
approximately 500-feet long, with eroded banks
and noticeable downcutting resulting in large
amounts of woody debris deposition. Scarp
development is present but fairly limited. The
creek in this reach averages 12- to 15-feet in
width.
4.1.10.2 Considerations and Options
Two single-family homes are located near the two stream meanders within this reach; thereby making
grading and access to the sites somewhat difficult. Due to the immediate proximity of one of the homes
and other infrastructure, fieldstone riprap is a preferred option for the most severe scarp development;
however, sufficient space is available to install vanes and root wads on the other banks. Vegetative
Reinforced Slope Stabilization (VRSS) is also an option for the less eroded meander, but will require
thinning of surrounding vegetation. It is assumed that the homeowners would prefer to maintain as much
of the existing vegetation as possible. The homeowners will be contacted prior to final design to
determine if vegetation thinning and VRSS would be an acceptable alternative.
4.1.10.3 Recommendations
Recommendations for Reach 10 include the installation of one cross-vane to prevent further downcutting
and stabilize the reach slope; and installation of three root wads, two rock vanes and grading of stream
banks is recommended in order to prevent further erosion on banks that are not an immediate threat to
homes. Riprap should be installed on the slope where the existing scarp has developed. Educating
homeowners about bank stabilization practices is also recommended.
Brook Dr Cahill Rd 10
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Nine Mile CreekRestoration Project
Edina, MN
110 0 11055
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Vanes
Root Wads
Riprap
NMCWD Parcels
Bank Grading
4-10
10
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4.1.11 Reach 11
4.1.11.1 Existing Conditions
Reach 11, approximately 1,300 feet
from Brook Drive to the Soo Line
Railroad, is bordered by residential
properties to the south and a wetland
to the north. The most actively eroding
area is a highly sinuous reach bordering
two private properties along Creekview
Lane. Downstream of this area, a
second reach that is approximately
400-feet long, contains debris jams
which have caused the creek to form a
network of multiple channels through
the wetland. The original channel has a
fairly healthy meander pattern through this reach with low bank heights, and erosion issues are minor.
The channel width in this reach ranges from 5 to 8 feet.
4.1.11.2 Considerations and Options
The main issue in this reach is the proximity of the creek to two single-family homes. The creek within
Reach 11 currently crosses four private lots and is within 50 feet of the homes on these properties. In
order to minimize future erosion risks, the options would be to stabilize the existing channel or excavate a
stable channel along one of two new routes. The multiple channel formation can be addressed by clearing
the debris jams during stabilization.
Option A- Stabilize in Place
The first option for stabilization on Reach 11 is to grade back the banks and use cross vanes to prevent
downcutting as the reach enters the wetland area. Placing rock vanes at outer bends which are moving
towards existing homes would help direct flow to the channel centerline and slow erosion at these
locations. Riprap would also protect the banks that are closest to existing homes.
Option B- Remeander for Riparian Habitat Connection
This option for channel reconstruction would redirect the channel into the existing wetland, providing
space for the channel to naturally migrate as well as maintain a more natural riparian habitat with less
influence from lawn management. This option would include four cross vanes to maintain the existing
grade and fifteen root wads and eight rock vanes to stabilize the outside banks of the new meanders.
Option C- Remeander for Homeowner Protection
A smaller remeander, other than the one proposed in Option B, would move the main channel away from
homes closest to the creek in order to provide additional protection of the homes from flooding. This
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option would utilize five cross vanes for grade control. Three rock vanes and six root wads would stabilize
the new outer banks of the new channel.
4.1.11.3 Recommendations
Erosion on Nine Mile Creek in Reach 11 is posing a risk to existing homes. Because of the proximity of an
existing wetland owned by the City, the best option would be to create a new channel for the creek where
it can maintain a stable pattern and have access to its floodplain. Option B would provide the most
protection to homeowners over the long term, but Option C is viable in case homeowners object to
moving the creek so far from their homes.
Brook Dr
Creek View La
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North Branch NineMile Creek
Erosion reaches
Cross Vanes
Vanes
Root Wads
Riprap
NMCWD Parcels
Bank Grading
Figure 4-11A
REACH 11 PROPOSED WORK -
OPTION A
Nine Mile Creek
Restoration ProjectEdina, MN
Brook Dr Creek View La Barr Footer: ArcGIS 10.2.2, 2014-12-16 10:11 File: I:\Client\Nmcwd\Workorders\2011\CreekStabilizationWork_2011\Maps\Reports\Edina Engineers Report 2014 Update\Figure 4-11B Reach 11 Proposed Work - Option B.mxd User: jrv!;N
100 0 10050
Feet
North Branch NineMile Creek
Remeander Option 1
Cross Vanes
Vanes
Root Wads
NMCWD Parcels
Figure 4-11B
REACH 11 PROPOSED WORK -
OPTION B
Nine Mile Creek
Restoration ProjectEdina, MN
Brook Dr
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North Branch NineMile Creek
Remeander Option 2
Cross Vanes
Vanes
Root Wads
NMCWD Parcels
Figure 4-11C
REACH 11 PROPOSED WORK -
OPTION C
Nine Mile Creek
Restoration ProjectEdina, MN
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4.1.12 Reach 12
4.1.12.1 Existing Conditions
Reach 12 extends downstream from the Soo Line Railroad to the culvert crossing at West 70th Street. The
creek is bordered to the south by residential development and to the north by forested wetland and
residential development. The stream maintains most of its historical meander pattern, but has noticeable
downcutting, particularly in the upper portion of the reach. The stream banks also display moderate
erosion. The stream has an average width
through this reach of 10 feet. This reach
crosses from City property onto three
private lots. One lot is relatively large
(approximately 1 acre) near the railroad
crossing, which is currently bisected by
the creek. The other two lots are smaller
(approximately 1/3 acre each), and are
the last two parcels on the south bank
before the creek crosses West 70th Street.
One property is essentially bordered by
the creek while the other parcel is divided
by the creek, creating an area comprising
approximately a 25 to 75 percent split of
its total lot area.
4.1.12.2 Considerations and Options
At locations where the creek is on or very near private property, bank erosion is at least partially caused
by poor vegetation management adjacent to the stream bank (i.e., mowed turf grass to the top of the
bank). An educational component would be useful to help the adjacent homeowners understand the
benefits of maintaining healthy bank vegetation.
Near West 70th Street, stream meanders are migrating toward the road and pose a long term threat to the
stability of the road embankment. Upstream of this location, the stream crosses two private properties as
previously mentioned.
Option A- Stabilize in Place
It would be possible to stabilize all of the banks in place with a combination of fieldstone riprap, VRSS,
vanes, root wads, and vegetation management. This option would include two cross vanes, fourteen rock
vanes, and seven root wads, which would stabilize the channel in its current location and reduce the risk
of the creek moving farther onto private property. The stabilized creek length would be approximately
1,600 feet.
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Option B- Remeander for Riparian Habitat Connection
An alternative to in-place bank stabilization is to establish a new meander pattern completely within the
City-owned property. The first remeander option would move a longer length of stream to the north,
moving it onto City property that is now being used by nearby residents for various purposes, including as
a soccer field. This alternative would restore full access to the private properties along the reach, remove
dependence on homeowners for proper vegetation management, move the stream meanders away from
West 70th St, and establish stable channel geometry. This option would include two cross vanes, thirteen
rock vanes, and twenty-four root wads. The meanders would preserve and not result in an increase in
creek length.
Option C- Remeander for Homeowner Protection
If surrounding homeowners object to moving the creek back on to City-owned property, the second
option would move only one meander of the stream, diverting it to the north instead of to the south,
achieving the goal of moving of the creek from private to public property. Both remeander options would
involve bank grading along the existing channel centerline. The meanders would preserve and not result
in an increase in creek length.
4.1.12.3 Recommendations
The primary recommendation for Reach 12 is to re-establish meanders within the lower portion of the
reach, moving the creek from private to public property and providing a better transition to the
West 70th Street culvert. Option B would provide better protection to homes along West 70th Street, but
Option C would be sufficient to protect existing infrastructure while maintaining the current creek
centerline.
W 70th St
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Feet
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Vanes
VRSS
Root Wads
Riprap
NMCWD Parcels
Bank Grading
Figure 4-12A
REACH 12 PROPOSED WORK -
OPTION A
Nine Mile Creek
Restoration ProjectEdina, MN
W 70th St
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North Branch NineMile Creek
Remeander Option 1
Cross Vanes
Vanes
Root Wads
Riprap
NMCWD Parcels
Figure 4-12B
REACH 12 PROPOSED WORK -
OPTION B
Nine Mile Creek
Restoration ProjectEdina, MN
W 70th St
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Feet
North Branch NineMile Creek
Remeander Option 2
Cross Vanes
Vanes
Root Wads
Riprap
NMCWD Parcels
Figure 4-12C
REACH 12 PROPOSED WORK -
OPTION C
Nine Mile Creek
Restoration ProjectEdina, MN
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4.1.13 Reach 13
4.1.13.1 Existing Conditions
Reach 13 begins downstream of West 70th Street
and continues for a distance of approximately
1,750 feet, crossing West 72nd Street and ending
200 feet upstream of the culvert at Metro
Boulevard. This reach is confined by residential
and commercial development on both sides, and
has been straightened to align with the West 72nd
Street culvert and the Metro Boulevard crossing. A
large amount of riprap was used to stabilize the
channel upstream of the West 72nd Street
crossing. Bank erosion is moderate, but
downcutting is very evident with storm sewers
perched above the existing streambed. The stream
width ranges from 10 to 15 feet and there are
significant amounts of large woody debris, both
naturally occurring and likely abandoned by past
construction projects in the area.
4.1.13.2 Considerations and Options
This reach is located on a narrow strip of City-
owned property and any option considering
establishing new meanders would require an
easement(s). The property on the east side of the
channel has detention ponds and buildings too close to the stream to establish meanders in that
direction. Buildings and property infrastructure on the west side of the channel just upstream from
West 72nd Street are also located too close to the stream for a new meander. Sufficient area on the
property on the west side of the channel immediately downstream from West 70th Street for a new
meander is available, but the relatively short channel length available would minimize the effectiveness of
a new meander.
The stream banks can be stabilized while remaining on City-owned property by using a combination of
vanes, cross vanes, root wads, and vegetation management.
4.1.13.3 Recommendations
Recommendations for this reach include the installation of four cross-vanes and three rock vanes to
reduce downcutting and bank erosion, and eight root wads on the meander bends near West 70th Street
and along Metro Boulevard to protect the roadway.
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200 0 200100
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
Vanes
Root Wads
NMCWD Parcels
Bank Grading
4-13
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4.1.14 Reach 14
4.1.14.1 Existing Conditions
Reach 14 begins downstream of the Metro Boulevard crossing of the creek and extends a distance of
approximately 2,350 feet to the creek crossing underneath the entrance and exit ramp connecting
Industrial Drive and TH 100. The stream ranges in width from 10 to 15 feet in its non-braided sections.
Most of this reach is a straightened channel on private industrial property or within the Mn/DOT right-of-
way. Immediately upstream of the entrance/exit ramp, the stream has maintained a natural meander
pattern. This section has mild to moderate bank erosion, with moderate bank sloughing and downcutting
for approximately 800 feet upstream of the ramps. The channel is also beginning to braid around a large
island. Finally, a fence which was initially erected to protect TH 100 is failing and falling into the creek.
4.1.14.2 Considerations and Options
Due to nearby infrastructure and buildings, it is not possible to alter the stream path through this reach.
The primary options require stabilizing
the stream banks in place.
Riprap stabilization is an option, but it is
not recommended because the velocities
in this reach are not excessive and the
nearby infrastructure is not immediately
threatened. The existing banks can be
stabilized with a combination of cross
vanes, single vanes, and root wads.
4.1.14.3 Recommendations
Recommendations for Reach 14 include
installing seven single vanes and nine
root wads to protect the creek banks on the outside edges of the larger bends. It is also recommended
that the existing failing fence be removed and a new one installed away from the channel bank.
100
100
Edina Industrial Blvd Metro Blvd W 77th St
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
200 0 200100
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Vanes
Root Wads
NMCWD Parcels
Bank Grading
4-14
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4.1.15 Reach 15
4.1.15.1 Existing Conditions
Reach 15 begins downstream of Industrial
Boulevard and continues downstream for a
distance of approximately 725 feet to the city
limits. The average creek width in this stretch is
12 feet. The creek has been straightened through
this stretch and is confined by TH 100 to the east
and the TH 100 frontage road to the west.
Sedimentation is a major problem, particularly in
the box culverts crossing Industrial Boulevard.
Bank erosion issues are minimal.
4.1.15.2 Considerations and Options
This reach is located entirely within the Mn/DOT right-of-way and nearby infrastructure eliminates any
options for new meanders. The main options for this reach include methods to stabilize the existing
erosion and establish measures to reduce the potential for future erosion.
4.1.15.3 Recommendations
Since this reach is extremely confined, the recommended method to address headcutting is to install two
cross-vanes within a 400-foot segment of the reach. Removing sediment from the existing box culverts is
also recommended to reduce the likelihood of upstream pooling.
100
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REACH PROPOSED WORK
Nine Mile CreekRestoration Project
Edina, MN
200 0 200100
Feet
Figure
North Branch NineMile Creek
Erosion reaches
Cross Vanes
NMCWD Parcels
Bank Grading
4-15
15
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4.2 Improved Stormwater Treatment
The project will provide in-stream water quality improvement through creek bank stabilization and
channel grade control to minimize the downcutting and continued degradation. The creek has been
classified as an Impaired Water by the Minnesota Pollution Control Agency for chlorides, turbidity, and
biotic integrity. The creek has since been delisted for turbidity, however the project will continue to
maintain and further improve the water quality of the creek for the impairments.
4.3 Regional Trail Construction
Construction of a multi-use trail with sections to be located adjacent to the North Fork is proposed as a
separate project by Three Rivers Park District. The proposed trail would continue from the City of Hopkins,
crossing TH 169 just south of where the North Fork of Nine Mile Creek crosses. The trail alignment would
generally follow the creek corridor before crossing TH 100 approximately 1,500 feet north of
West 77th Street via a new, proposed bridge crossing. The trail would then continue east through Edina.
The proposed trail constructed by Three Rivers Park District will be a continuation of the Three Rivers Park
District regional trail system that will run through Hopkins, Edina, and Richfield to Cedar Avenue in
Richfield. The channel improvements that are proposed by the District will be coordinated with the trail
location and future construction as much as possible.
4.4 Preliminary Plan Set
A set of the preliminary construction plans is included for reference in Appendix J.
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5.0 Cost Estimate
Table 5-1 shows the total estimated construction costs for the recommended option for each reach and
the total project cost. Detailed cost tables for each reach are contained in Appendix D.
Table 5-1 Engineer's opinion of probable cost--Summary of cost estimates by reach
Reach Estimated Construction Costs
Reach 1 $173,000
Reach 2 $264,600
Reach 3 $50,400
Reach 4 $333,100
Reach 5 $240,500
Reach 6 $86,000
Reach 7 $0
Reach 8 $97,900
Reach 9 $315,600
Reach 10 $104,400
Reach 11 $219,700
Reach 12 $258,100
Reach 13 $318,400
Reach 14 $137,300
Reach 15 $52,600
Construction Costs Subtotal $2,651,600
Contingency 15% $397,800
Engineering, Legal, and Administrative (30%) $914,900
Total* $3,964,300
*Difference between the total shown and the cumulative totals on Tables D-1 through D-15 in Appendix D
is the result of rounding.
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6.0 Impacts Caused by the Project
6.1 Easement Acquisition
Public ownership of the corridor area adjacent to the North Fork of Nine Mile Creek is recommended.
Currently, the majority of the creek corridor is either publicly owned or lies within public easements.
However, a few reaches of the creek have migrated onto private property. As part of this project, it is
recommended that Reaches 11 and 12 be re-aligned such that the channel will once again be on public
property. Figure 6-1 shows the areas for proposed easement acquisition and affected properties. A list of
the affected property owners is identified in Appendix E.
6.2 Environmental Review and Permitting
The Environmental Assessment Worksheet (EAW) for the proposed project is included in Appendix I. This
process requires approximately 1 month for agency review and public comment and is used to determine
whether a more detailed Environmental Impact Statement (EIS) is warranted. An EIS is not anticipated to
be required for the proposed project.
The following permits will likely be necessary in order to perform the recommended project
improvements:
City of Edina, Conditional Use Permit
Nine Mile Creek Watershed District, Grading and Land Alteration Permit
Nine Mile Creek Watershed District, Wetland Conservation Act Permit
Minnesota Department of Natural Resources, Work in Public Waters Permit
Army Corps of Engineers, Section 404 Permit
Minnesota Pollution Control Agency, N.P.D.E.S. Construction Permit
6.3 Other Impacts Caused by the Project
No long-term adverse impacts to natural resources are expected to result from implementation of the
recommended improvements. Some temporary construction-related impacts will occur to riparian
wetlands, and mitigation may be required, but impacts are generally expected to be minor. There are no
new impervious surfaces created by the project.
6.3.1 Wetland Impacts
The existing wetlands within the project area were inventoried in accordance with the U.S. Army Corps of
Engineers Wetlands Delineation Manual, 1987. (“1987 Manual”, USACE, 1987), the Regional Supplement to
the Corps of Engineers Wetland Delineation Manual: Midwest Region (USACE, 2010) and the requirements
of the Minnesota Wetland Conservation Act (WCA) of 1991. A wetland functional assessment (MnRAM)
has also been completed. Appendix F contains the Wetland Delineation and Functional Assessment
Report of May 2014 that was completed for the project.
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The Nine Mile Creek Watershed District, being the Local Government Unit (LGU) administering the
requirements of the WCA, at the May 21, 2014 meeting of the Board of Managers approved the wetland
type and boundary determination completed for the project.
The recommended stream stabilization improvements are not expected to cause any long term adverse
impacts to the creek system, but will result in a more stable, healthy system. The most anticipated impact
to existing wetlands is the proposed realignment of the creek in Reaches 4, 11 and 12, in which the
channel will have meanders re-established and, for Reaches 11 and 12, relocated away from private
property onto public easement. A copy of the Wetland Permit Application is included in Appendix G.
6.3.2 Tree Loss
Much of the creek corridor is forested, with varying degrees of quality. Reasonable effort will be made to
avoid or minimize tree loss in connection with various aspects of the recommended projects. Trees that
are unavoidably lost will be replaced, as deemed necessary and in coordination with current property
owners and the City of Edina. Native species will be planted whenever tree replacement is needed. In a
number of reaches, existing high value species will be designated for protection during construction.
Buckthorn control will be critical to the establishment of native trees; thus all buckthorn removal will
require stump treatment with herbicide and followup control for a minimum of three years.
6.3.3 Soils
A Phase I Environmental Site Assessment (ESA) was prepared for the proposed project area in March,
2014. A copy of the Phase I assessment is included in Appendix H. The ESA identified one recognized
environmental condition in connection with the project. The potential presence of dump material from an
unpermitted dump property adjacent to the project will be addressed in the construction documents
prepared for the project. In general, should unsuitable material be encountered, work in the area would
stop, the situation would be assessed, and work would proceed only after consultation with the MPCA.
6.4 Impacts to Archeological Features
Archaeological Research Services (ARS) concluded, based on visual inspection of existing erosion
exposure, that none of the bank segments prioritized for stabilization feature any archaeological evidence.
Should final design of stabilization measures for the sites investigated for this report change, the initial
archeological inspection will need to be supplemented with further survey in the following areas:
In ARS 1, the last approximately 100’ before the creek enters a large wetland and is flanked by
fairly level terraces that appear to have some archaeological potential.
In segments ARS 2, 3, 4, 7, and 8 only along any areas that would be affected if the current
channel is altered enough to impact surrounding uplands.
As mentioned in Section 3.0 of the Archeological Investigation (Appendix B), any such additional survey
would need to follow federal and state guidelines.
P:\Mpls\23 MN\27\23271132 Nine Mile Creek Restoration - Edina\WorkFiles\Engineer's Report\Edina_EngrsRpt_Aug-2015.docx 67
Table 6-1 shows the correlation between ARS reaches (numbered 1-16) and Reaches 1-15 designated by
the project as needing stabilization measures. This information is also presented in map form in
Appendix B, Figures B-1 through B-7.
Table 6-1 ARS Reach and erosion reach correlation
Archaeology Reach Corresponding Erosion Reach
ARS 1 Reach 1 - Entire
ARS 2 Reach 2 - Upstream
ARS 3 Reach 2 - Middle
ARS 4 Reach 2 - Downstream
ARS 5 Reach 4 - Upstream
ARS 6 Reach 4 - Downstream
ARS 7 Reach 5 - Upstream
ARS 8 Reach 5 - Downstream
ARS 9 Reach 6 - Entire
ARS 10 Reach 8 - Entire
ARS 11 Reach 9 - Entire
ARS 12 Reach 10 - Entire
ARS 13 Reach 11 - Entire
ARS 14 Reach 12 - Entire
ARS 15 Reach 13 - Upstream
ARS 16 Reach 14 – Upstream
£¤169
£¤212
62
4567158
£¤169
17
18
114
216
124
0
124
19
2068
86
16
152
35
50
31
21
3
7
23
6 4
9
5
25
34
8
1
12
11
28
32
33
30
10
16
2
29
13
43
51
3
7
1
56
4
542
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North Branch Nine Mile Creek
Creek Adjacent Parcels
178
163
175
164
165
139
141
205
113
10895
199
144146
220214
213221106
202
173179
228231174170
119123131
107
103104
100
129
1
38
1511
1410233
198
129
143
201
136
224
197
135
235
185
116
194
162
97
227 177
133
204
130
155192
147 111
232
234
145
196
128
109
153
203
127
212
218101
217
207
102
110
138
193
195
93
92
91
118
229
98
94
189
105
120
99
188
151
225
100
174
121
191
230
115134
96
219
226
190184
117
222
122
142
215
150
159
112
125
206
172
137
208
169
209
140
171
161
176
160167
156
182
Figure 6-1
PROPOSED EASEMENT ACQUISITION
AND AFFECTED PROPERTIES
Nine Mile Creek
Restoration ProjectEdina, MN
!;N
1,200 0 1,200600
Feet
24 26
14
2722
54
67
66
52
69
15
70
53
49
1
£¤169
£¤212
62
4567158
7
321
56
4
54
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Erosion reaches
North Branch Nine Mile Creek
City of Edina Boundary
§¨¦494
§¨¦494
62
100
456734456728
129
1387
14101511
Figure 6-2
DELINEATED WETLANDS
AND WETLAND COMMUNITIES
Nine Mile CreekRestoration Project
Edina, MN
!;N
1,200 0 1,200600
Feet
Appendices
“Stand-alone” file(s) due to file size
Appendix A Project Petition from City of Edina
Appendix B Archeological Investigation
Appendix C Typical Stream Restoration Practices
Appendix D Detailed Cost Estimates by Reach
Appendix E Affected Property Owners
Appendix F Wetland Delineation and Functional Assessment Report
Appendix G Wetland Permit Application (not included with this document)
Appendix H Phase I Environmental Site Assessment (not included with this document)
Appendix I Environmental Assessment Worksheet (EAW) for
Nine Mile Creek Stabilization Project—Edina
Appendix J Preliminary Plan Set