HomeMy Public PortalAbout04.19.2016 City Council Special Meeting PacketMEDINA
SPECIAL MEETING AGENDA
MEDINA CITY COUNCIL
Tuesday, April 19, 2016
6:00 P.M.
Medina City Hall
2052 County Road 24
I. Call to Order
II. Ardmore Area Subwatershed Stormwater Retrofit Assessment
III. Adjourn
Posted 4/15/2016
MEMORANDUM
TO: Medina City Council
FROM: Scott Johnson, City Administrator
DATE OF REPORT: April 13, 2016
DATE OF MEETING: April 19, 2016
SUBJECT: April 19, 2016 Work Session — 6:00 PM
Work Session 6:00 PM
Ardmore Area Subwatershed Stormwater Retrofit Assessment (60 Minutes)
Attached is a draft copy of the report for City Council review. Jim Kujawa from the Hennepin
County Department of Environment and Energy and Hakanson Anderson will be at the work
session meeting to present on the findings from the report. Staff is requesting City Council
discussion and input on the draft report.
Ardmore Area Subwatershed
Stormwater Retrofit Assessment
Hennepin County
Public Works
Environment and Energy
Halcanson
Anderson
Prepared by Hakanson Anderson and Hennepin
County Department of Environment and Energy with
assistance from the Metro Conservation Districts
March 2016
Table of Contents
Executive summary 3
Document organization 6
Selection of the subwatershed 6
Analytical process and elements 6
Subwatershed assessment steps 6
Target elements 7
Urbanized Ardmore subwatershed assessment 8
Urbanized subwatershed project rankings 12
Urbanized subwatershed project profiles 13
Urbanized subwatershed summary 33
Rural Ardmore subwatershed assessment 34
Rural subwatershed basic conclusions 36
Rural subwatershed document organization 36
Rural subwatershed project rankings 37
Rural subwatershed project profiles 42
Appendix 69
References 80
Ardmore Area Subwatershed Stormwater Retrofit Analysis 2
Executive Summary
This report details urban and rural stormwater assessment studies and Best Management Practices
(BMPs) recommendations within the City of Medina to reduce phosphorus loads flowing into Lake
Independence and Lake Ardmore. Since different types of BMPs must be utilized in order to be
effective for the urban and rural portions of the watershed, the report is organized in two explicit
sections. The first section analyzes the residential urban area that it situated between Lake
Independence and Lake Ardmore and drains to both basins. The second section analyzes the rural
subwatershed that drains to Lake Ardmore and ultimately to Lake Independence.
The rural portion of this assessment (Figure 1A) is approximately 472 acres in size. Four hundred and
twenty three acres of that watershed are in Medina and 49 acres are in the City of Independence. The
developed community studied for this assessment is 113 acres and located in Medina between Lake
Independence and Lake Ardmore (Figure 2A).
The purpose of this report is to assist the City of Medina in its decisions and processes to provide cost
effective methods to help reduce phosphorus loads into Lake Ardmore and Lake Independence from
these two subwatersheds.
In 2002, Lake Independence was listed as impaired under Section 303(d) of the Clean Water Act due to
excessive nutrients affecting aquatic recreation. The Pioneer -Sarah Creek Watershed Commission and
Three Rivers Park District prepared a phosphorus Total Maximum Daily Load (TMDL) study to
determine the phosphorus reductions needed for Lake Independence to achieve the 40 µg/L water
quality standard for Class 2 recreational waters. Each municipality contributing to the Lake
Independence (Medina, Independence, and Loretto) watershed has been designated a load reduction
proportionate to their existing phosphorous export. The City of Medina must achieve a phosphorus
reduction of 284 lbs. per year.
Lake Ardmore is proposed by the Minnesota Pollution Control Agency to be listed as an impaired lake
in 2016 for aquatic recreation. Three Rivers Park District, in cooperation with the Pioneer -Sarah Creek
Watershed Management Commission, is undertaking a TMDL study to determine the extent of the
impairment, provide nutrient budgets and possible solutions to achieve a non -impaired status for the
lake. Preliminary numbers from their model indicates that a phosphorus load of 269 pounds per year
enters the lake from its contributing watershed.
This study models various stormwater treatment BMPs within the two subwatersheds. These BMPs are
analyzed to determine their effectiveness in reducing nutrient loads into Lake Ardmore and Lake
Independence. These practices will be rated from the most cost effective project per pound of
phosphorus reduction to the least cost effective. To provide a better understanding of each BMP and
the approach for implementation, conceptual drawings and/or photos are incorporated within this
report. Prior to implementation, more detailed, site -specific designs will need to be prepared for each
BMP selected. Most will require additional study and/or engineered plans. For all the recommended
projects, partnerships with committed and willing landowners are essential.
The process used to select recommended BMPs was based primarily on a combination of the target
pollutant (phosphorus), the project type and their cost/benefit analysis and the location of the project
in the watershed. Additional factors should be considered before prioritizing recommended BMPs
(e.g., project costs, available funding, economies of scale, landowner willingness, short and long-term
Ardmore Area Subwatershed Stormwater Retrofit Analysis 3
impacts on property values and the public infrastructure). As presented in Table 2U on page 12, a total
of 10 projects areas were identified for the urbanized Ardmore subwatershed with a combined phos-
phorus removal of 15.9 pounds per year. The rural Ardmore subwatershed identified 26 projects with
a combined phosphorus removal of 99.3 pounds per year as shown in Table 1R on page 37.
Figure 1A: Lake Ardmore Watershed Outline
Ardmore Watershed
Hennepin County, Minnesota
QArdmore Watershed Boundary
EIM 2015 Aerial Imagery
Hennepin
0 500 1.000
5
2000 3000
Feet
Ardmore Area Subwatershed Stormwater Retrofit Analysis 4
Figure 2A: Urban area of Ardmore Subwatershed Assessment
Existing Rain Garden -••-••---'11F.-
Ardmore Area Subwatershed Stormwater Retrofit Analysis
5
Document Organization
This document is organized into two separate sections: rural and urban. Both present a brief overview
of the processes involved to yield the project rankings and selections. The technical aspect of the
subwatershed assessment process and supporting model results are presented throughout the report
and in the appendices. The majority of the report focuses on the projects themselves: their rankings in
cost per pound of nutrient reduction and the profile of the project.
Selection of the Subwatershed
The TMDL for Lake Independence completed in 2007 determined that the Lake Ardmore Subwatershed
contributed 6% of the external phosphorus loads to Lake Independence per year. It further identified
direct surface flows (including the developed areas in the SE corner of the lake) as contributing 8% of
the phosphorus loads to the lake. Based on these contributions and in anticipation of the Lake
Ardmore study, these subwatersheds were chosen for additional analysis through cooperative efforts
of the City of Medina, the Hennepin County Environment and Energy Department (HCEED), Hakanson
Anderson and the Metropolitan Association of Conservation Districts (MCD).
Analytical Process and Elements
The purpose of subwatershed assessments through stormwater retrofit analysis is to improve water
quality, increase groundwater recharge and reduce stormwater runoff volumes by identifying
opportunities and developing conceptual designs for BMPs that are contributing the largest pollutant
loads to the receiving water body. The following are the steps taken in this assessment process:
Subwatershed Assessment Steps
1. Identify and prioritize subwatersheds that contribute the greatest to water quality degradation
of high priority water resources.
2. Map BMP retrofit potential within neighborhoods of the highest priority subwatersheds utilizing
the "Urban Stormwater Retrofit Practices" manual (August 2007).
3. Design retrofits primarily involving ponds, wetland restoration, vegetated buffers, water flow
controls, vegetative swales and management techniques for rural residential runoff, livestock and
tillable land.
4. Calculate pollutant removal utilizing Soil and Water Assessment Tool (SWAT), Source Loading
and Management Model for Windows (WinSLAMM), Board of Water and Soil Resources Pollution
Reduction Model, Revised Universal Soil Loss Equation Version 2(RUSLE2), P8 Urban Catchment
Model (Program for Predicting Polluting Particle Passage thru Pits, Puddles, & Ponds), and Minimal
Impact Design Standards (MIDS) calculator from the Minnesota Stormwater Manual, Elm Creek
Watershed Management Commission land use phosphorus export loading and Minnesota Feedlot
Assessment Runoff model (MinnFARM). See appendix for detailed modeling parameters.
5. Manage installation based on landowner's willingness and funding availability.The subwatershed
retrofit analysis process is a tool to help identify and prioritize BMPs by performance and cost/
benefit analysis.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 6
The process for the Lake Ardmore Subwatershed Analysis was as follows;
• Scoping
• Desktop analysis
• Field Investigation
• Modeling
• Cost estimating
• Project Ranking and Selection
Target Elements
The main element considered for this analysis was the target pollutant of phosphorus for Lakes
Ardmore and Independence. Volume and total suspended solid controls were also considered, but it
was determined that these two components were so interrelated to the main target of phosphorus
that ultimately, the reduction in phosphorus related directly or indirectly to their controls. Therefore,
this report focuses primarily on Lake Independence and Lake Ardmore impairments and phosphorus
load reductions to ultimately achieve the goal of 40 µg/L water quality standard for Class 2 recreational
waters.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 7
Urbanized Ardmore Subwatershed
This section focuses on Total Phosphorus (TP) reduction within the developed community located in
Medina between Lake Independence and the smaller Lake Ardmore (Figure 2A). Developed areas have
increased impervious surfaces, such as rooftops, roads, and sidewalks. Impervious surfaces contribute
to greater runoff volume by preventing water infiltration into the soil, and they also cause increased
rates of stormwater runoff due to lack of obstruction from the minimal vegetation. Increased rates of
stormwater runoff are concerning as it increases the ability to pick up and transport sediment and
other pollutants to Lake Independence.
Phosphorus commonly binds with minerals in sediment, so events that transport sediment, in effect,
also transport phosphorus. The higher flows from the impervious surfaces are able to transport
sediment, and the phosphorus that is bound to it, to other water bodies. Thus, managing stormwater
runoff to Lake Independence is critical to reducing the phosphorous load and complying with the
TMDL.
Since much of the phosphorus is in the particulate form, load reduction projects in this area will
emphasize limiting the amount of Total Suspended Solids (TSS) within the runoff. TSS is mainly
sediment but can also include other non -dissolved floatables such as leaves, sticks, and trash. The
projects include shoreline restoration, gully and stream stabilization, pond excavations, and rain
gardens, as well as alternative higher efficiency options such as a manufactured filtering device and an
iron enhanced sand filter. These projects are discussed in further detail in later sections.
Analysis
This urban area of the Ardmore watershed was delineated to determine the sub -watershed
boundaries. Drainage patterns were determined using available LiDAR two -foot contours, aerial
photos, and visual observations. The sub -watershed drainage areas are depicted in Figure 1U.
The proposed ponds were sized according to Natural Urban Runoff Program (NURP) standards, which
requires ponds to retain the runoff generated from 2.5 inches of precipitation within the drainage
area. The delineated drainage areas mentioned above were input into HydroCAD Stormwater
Modeling software to determine the stormwater runoff volume generated from a 2.5 inch
precipitation event. The ponds were then sized to retain the entire runoff volume from the 2.5 inch
event below the normal water level. Depth was maximized in order to provide the same amount of
volume in a smaller surface area. However, depths were limited to eight -feet as deeper ponds may
cause hypoxic conditions. Hypoxia, or low oxygen levels, is a concern for phosphorus reduction as it
can have the counter effect of releasing the phosphorus within the sediment. The sizes of the rain
gardens were more restricted by their proximity to housing and the surrounding landscape.
A P8 Urban Catchment Model and the Minimal Impact Design Standards (MIDS) calculator from the
Minnesota Stormwater Manual were utilized to approximate phosphorus loading and possible
reductions. The P8 Urban Catchment Model is a useful tool in determining phosphorous reductions
associated with pond excavation projects. Since the P8 model does not have a structure that
accurately represents rain gardens with an underdrain, the MIDS calculator was used. As the MIDS
Ardmore Area Subwatershed Stormwater Retrofit Analysis 8
calculator can also model ponds, it was used to compare the P8 model outputs. The MIDS estimates
were more conservative than the P8 model, so this report used the MIDS results.
The phosphorus loads from the gully and stream stabilization and shoreline restoration are based on
the amount of erosion occurring. The dimensions of the erosion was measured in the field and entered
into the Board of Water and Soil Resources (BWSR) Pollution Reduction Estimator worksheets.
For the two alternative higher efficiency options, neither the P8 model nor MIDS calculator were used
directly. The iron enhanced sand filter used calculations found in the Minnesota Stormwater Manual to
estimate phosphorus reductions. The enhanced filtering device has a seventy -percent reduction of the
phosphorus input load as stated by the manufacture.
Cost Estimates
Determining probable costs of any given BMP is necessary in order to rank projects and determine
overall effectiveness. For nearly all projects, there is a capital cost of initially installing or constructing
the BMP as well as the maintenance cost for maintaining the device over its life span. Cost estimates
for design and easement acquisition were also estimated, if applicable. Most projects are proposed to
be within City or County owned property, as seen in Figure 2U. For this analysis, the lifespan of a given
BMP was assumed to be 20 to 50 years. Therefore, the cost of the installation and maintenance can be
divided by the BMP lifespan and phosphorous reduction in order to achieve a cost per pound. The cost
per pound is specific to the project and is therefore included in each of the BMP Summary Tables for
each project. The following costs were assumed for this report:
Table 1U: Best Management Practices Summary
BMP Type
Promo /
Admin
(hrs)
Residential Rain Garden 35
Shoreline Restoration
35
Stream Stabilization
Gulley Stabilization
20
10
Pond Excavation
35
Enhanced Filtering Device
Iron Enhanced Sand Filter
10
35
Design
($)
$4,500
$1,500
$4,000
$4,000
$12,500
$20,000
$15,000
Easement
Acquisition
$20,000/ac
Construction
Cost ($)
$15/sq ft
$100 /lin ft
$75 /sq ft
$20/sq ft
$6/sq ft
$200,000/Ea
$20/sq ft
Annual Mainte-
nance
$100
$1.50
$0.50 / sq ft
$0.25 / sq ft
$250
$1,500
$500
Ardmore Area Subwatershed Stormwater Retrofit Analysis 9
Figure 1U: Proposed BMP exhibit within drainage areas
Ardmore Area Subwatershed Stormwater Retrofit Analysis
10
Figure 2U: Proposed BMP exhibit within parcels
Lake independence
Parcels owned by the City of Medina
or Hennepin forfeited land
Ardmore Area Subwatershed Stormwater Retrofit Analysis
11
Project Ranking
The information within this report will be provided to City and Watershed officials in order to
determine the feasibility of certain projects within the urban portion of the Ardmore watershed. One
important factor in prioritizing projects is the cost of the project divided by the total pounds of
phosphorous removed.
Table 2U. Project Ranking
BMP ID
GS1
TP Decrease
(Ibs/yr)
SR1
Project Life
(Years)
Project Cost
Cost -Benefit ($/
Ibs TP)
3.4 20 $18,850 $277
2.0 20
PD2
1.8
30
$22,000
$47,650
$550
$882
ISF1
3.1
30
$87,500 $941
RG1
1.1
20
$21,400 $973
PD4
1.2
30
PD1
PDS*
RG2
1.8
1.0
0.6
30
30
20
$47,350
$76,350
$1,315
$1,414
PD3 1.1
30
SS1
EFD1t
Totals*
0.2
1.4
14.2 / 15.9
20
$43,750 $1,458
$18,400 $1,533
$1,562
$13,200 $3,300
$51,550
50
$318,000
$360,500 / $674,600
$4,542
*PD2 and ISF1 are in the same location. tPDS and EFD1 are in the same location. tNumbers to the left
include PD2 and PD5 and not ISF1 and EFD1, and numbers to the right include ISF1 and EFD1 and not PD2
and PD5.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 12
Projects
The majority of TP in urban runoff is in the particulate form present in sediment (Maestre and Pitt,
2005). Stormwater runoff carries sediment, a main component of TSS, and deposits it into Lake
Independence. Treating stormwater to reduce its TSS, and therefore phosphorus, load is essential in
order to meet Medina's phosphorus reduction goals. Several projects are proposed to help in reducing
TP in this area and are outlined in Table 3U below.
Table 3U: Proposed Projects
Project Type
1 Rain Garden
2 Rain Garden
3 Stream Stabilization
4 Gully Stabilization
Label
RG1
Drainage Area
(ac)
RG2
SS1
GS1
5 Shoreline Restoration
6 Pond Excavation
7 Pond Excavation /
Iron Enhanced Sand Filter
8 Pond Excavation
9 Pond Excavation
SR1
PD1
PD2
ISF1
PD3
PD4
10 Pond Excavation / Enhanced PD5
Filtering Device EFD1
4
3.3
2.0
N/A
N/A
N/A
2.9
4.1
4.1
8.0
2.7
1.6
1.6
P Reduction (Ibs/yr)
Total
1.1
0.6
0.2
3.4
2.0
1.8
1.8
3.1
1.1
1.2
1.0
1.4
14.2 / 15.9
Rain Gardens
Rain gardens are a practical treatment device for treating runoff and improving water quality for
relatively small drainage areas. Rain gardens are small depressions with flood -tolerant vegetation
positioned in areas that intercept stormwater runoff from impervious surfaces. During a storm event,
stormwater pools in the rain garden, which allows the TSS to settle out of the pooled runoff. This
decreases the phosphorus load within the water since the majority of the phosphorus is attached to the
sediment.
There are two types of rain gardens that have varying levels of phosphorous removal efficiency. Rain
gardens that are situated in areas that have favorable infiltration rates, predominately sandy soils,
infiltrate the entire design volume and do not require an underdrain. Since the entire volume stored
within the rain garden is infiltrated into the ground, essentially all pollutants are captured within the
basin and are not transported downstream for the design rain event. Typically rain gardens are
designed to capture 1" of runoff from the impervious surfaces, which represents approximately 90% of
the storm events. Therefore, the first type of rain garden has a very high removal rate for
approximately 90% of storm events. Rain events larger than 1" result in downstream discharge with
little or no treatment. However, sizing a rain garden to treat all storm events as opposed to the 1"
event would require an extremely large footprint and would not be practical in most cases.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 13
The second type of rain garden requires an underdrain and is suitable for clay soils or soils that have a
relatively low infiltration rate. This type, referred to as biofiltration, is rather efficient at removing the
particulate portion of the phosphorous load, but is not as efficient in removing the dissolved portion.
During a storm event, the water quality volume is pooled in the rain garden allowing the TSS and the
particulate form of phosphorous that is attached to it to settle out. The stormwater is then filtered
through the engineered media and discharged downstream via the perforated underdrain. Although
the rain water is filtered through the media, it does not remove the dissolved portion of the
phosphorous. A relatively small volume that is captured below the underdrain may be infiltrated into
the soil, which slightly decreases runoff volume but is more or less negligible. Therefore, given the
design rain event, a biofiltration rain garden is efficient at removing the particulate phosphorous, which
represents approximately 55% of the phosphorous load, and essentially passes all of the dissolved
portion downstream, which represents approximately 45% of the load (MPCA, 2016). Similar to the
first type of rain garden, rain events that are larger than the design event (typically 1") receive
considerably less treatment and are discharged downstream.
Rain gardens are a practical and relatively low cost BMP that may be implemented in priority
subwatersheds that offer treatment benefits prior to discharge into a surface water. In many instances,
rain gardens can be implemented in areas where stormwater would otherwise enter the surface water
untreated.
Figure 3U: Rain Garden Schematic
RANT IAATPRIAL TOLER8NT aF
NUNDATIDN AND DRCIJGNT.
NATIVE PLANTS RMEOOMMiE+CIED.
ELEVATION OF PL ANTP10 AREA
TO BE 1 d' BELOW EXISTING
CULVERT ELEVATION
PAVEMENT
4_I
GRASS PRE-TREATMENT STRIP
LIINDISTURSED. U
INSrIU SOL - If1FILTRATXN
ram GREATER THAN l'/HOOR
7 SHREDDED 9lrCXXII.
(i1nOOT TYPE d)-
I
PLANTING MEDIUM MIN. DEPTH 30'
WITH A WELL BLENDED MIATURE (DY VOLUME):
5EF40M4 HOMOGENOUS CONSTRUCTION SAND
20-3r1% ORGANIC LEAP COMPOST
NATIVE TOPSOIL
4" PERF, SCM 40 PVC
Wit MEMO SOCK
Ardmore Area Subwatershed Stormwater Retrofit Analysis
14
RG1
Two rain garden projects were chosen for this analysis. The first rain garden (RG1) is located on Walnut
Street across from Walnut Park. It appears that a rain garden may have been previously attempted for
this site; however, it does not appear to be functioning well and enhancements are proposed. There is
an existing curb cut leading directly to the rain garden site, which can be seen in Figure 4U. In order to
be effective, the rain garden must be over -excavated, filled with engineered media, and an underdrain
installed. The final surface of the rain garden should be approximately 1.5' below the adjacent culvert
to provide ponding during rain events. The phosphorus removal rate was estimated using the MIDS
calculator. The projected phosphorus removal for RG1 is 1.1 Ibs per year.
Table 4U: Site Summary
— RG1
MIDS
Model Used
Drainage Area
3.3 ac
Rain Garden Size
1,000 sq ft
Estimated TP removal
1.1 Ibs/yr
Installation Cost
$15,000
Design/Admin
$4,500
Maintenance / yr
$100
Total 20 Year Cost
$21,400
$/Ib-TP removal/yr
$973
Figure 4U: Site photographs at
proposed RG1
Figure 5U: Drainage area and locational map. Orange lines
indicate existing drainage pipes
Ardmore Area Subwatershed Stormwater Retrofit Analysis 15
RG2
The second proposed rain garden (RG2) is on Lakeshore Avenue across from Brooke Street. There is
already a rain garden on the east side of Lakeshore Avenue, but on the west side, the water is
directed towards a curb cut that leads straight to Lake Independence (Figure 6U). A rain garden at this
location could filter the runoff and decrease the phosphorus load before it enters the lake. The
existing storm sewer pipe would be modified, with the rain garden intercepting and filtering the
stormwater runoff. Suspended solids and particulate phosphorous would be trapped in the rain
garden basin.
Table 5U: Site Summary
— RMIM
Model Used
MIDS
Drainage Area
1.6 ac
Rain Garden Size
800 sq ft
Estimated TP removal
0.6 Ibs/yr
Installation Cost
$12,000
Design/Admin
$4,500
Maintenance Cost/yr
$100
Total 20 Year Cost
$18,400
$/Ib-TP removal/yr
$1,533
Figure 6U: Looking west to Lake
Independence. The blue circle
shows proposed location for RG2.
Figure 7U: Drainage area and location map
Independence
Ardmore Area Subwatershed Stormwater Retrofit Analysis 16
Stream Stabilization
Erosion from streams releases sediment and transports it directly into the lake. Since particulate
phosphorous is adhered to the soil particles, this results in direct phosphorus loading as well as a
reduction of water clarity. The stream on the south side of Lake Ardmore that flows into Lake
Independence is experiencing moderate erosion in the area between Ardmore Avenue and Lakeshore
Avenue. The moderate erosion is occurring at a sharp natural meander point in the stream. Sharp
curves encourage erosion because water on the outside of the curve has to move faster than the
water on the inside of the curve to cover more distance in the same amount of time. The force of the
accelerated stormwater along the stream bank is greater than the cohesive force of the soil. It is
recommended that moderate stream bank erosion is corrected sooner rather than later; as left
unrepaired, it will continue to erode the bank and deposit phosphorous rich sediment into the lake.
We measured the volume of the moderate erosion to be approximately 40 cubic feet. The BWSR
Pollution Reduction Estimator estimated 0.2 Ibs/yr of phosphorus export from this area. Repairing
the stream bank erosion would cease its TP loading. Repair and stabilization of this area may be
accomplished by placement of toe boulders, brush bundles, or geo-synthetic mats. Native vegetation
with deep root systems also helps stabilize these areas but may be difficult to establish in this
location due to the extensive tree cover.
Although the remaining portions of the channel are un-vegetated and may be susceptible to erosion,
BMPs are not proposed at this time. Active erosion was not observed during field reconnaissance,
and similar to the area above, stabilization by establishing a vegetated stream bottom would be
extremely difficult due to the extensive tree cover. If observations at a later date determine stream
bed erosion to be a concern, this segment should be re-evaluated.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 17
SS1
Table 6U. Site 9ummary
— SS1
Model Used
BWSR
Calculator
Erosion Length
70 ft
Erosion Area
110 sq ft
Estimated TP
Removal
0.2 Ibs/yr
Installation Cost
$8,250
Design/Admin
$4,000
Maintenance
Cost / yr
$50
Total 20 Year
Cost
$13,200
$/Ib-TP
removal /yr
$3,300
Figure 8U: Erosion seen looking southeast
Figure 9U: Drainage area and location map
Ardmore Area Subwatershed Stormwater Retrofit Analysis
18
Gully Stabilization
Gullies are created by concentrated stormwater cutting into the landscape and eroding away the soil.
This occurs when the erosive force of the water flow is greater than the cohesive force of the soil.
Over time the gulley cuts deeper into the soil, creating unstable side slopes. The near vertical side
slopes of the gully then slough in and are transported downstream into the receiving water. Since
particulate phosphorous is attached to the sediment, this directly contributes to the phosphorous
loading into the receiving water. If not repaired, gullies continue to cut and become larger and
contribute to the phosphorous load.
Gullies can be stabilized by using rip rap, boulders, natural vegetation, and manufactured synthetic
products. Stabilization of a gully is a similar process to stabilizing a stream. Riprap can often be
positioned at strategic locations to dissipate the flow and reduce scouring. Vegetation and synthetic
products can also be used to create greater cohesion and resistance to scouring, as well as slowing
down the velocity of water flow.
Figure 10U: Stabilization using manufactured synthetic
products; Source: Contech Engineered Solutions
GS1
The gully north of Fern Street receives concentrated flow via a storm sewer pipe. Field
measurements showed that the gully is approximately 120 feet long. The largest width
measurement was recorded as five -feet, and the largest depth measurement was recorded as four -
feet. In total, it is estimated that 1,390 cubic feet or 50 tons of sediment has been eroded to date.
The BWSR Pollution Reduction Estimator worksheet was utilized to estimate the phosphorous load
that the gully is producing. Stabilizing the gully could reduce the TP load by 100%.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 19
Table 7U. Site
Summary — GS1
Model Used
BWSR worksheet
Erosion Length
120 ft
Erosion Area
600 sq ft
Estimated TP
Removal
3.4 Ibs/yr
Installation Cost
$12,000
Design/Admin
$4,000
Maintenance
Cost
$150
Total 20 Year
Cost
$18,850
$/Ib-TP remov-
al /yr
$277
Figure 11U: Left— Erosion to the
eastern side of the gully. Right -
West side of the gully, eventually
flowing into wetland connected to
Lake Independence.
Figure 12U: Drainage area and location map
Gully Stabilization
I
Ardmore Area Subwatershed Stormwater Retrofit Analysis 20
Shoreline Restoration
Shoreline erosion is also a source of phosphorus. All of the sediment created by shoreline erosion is
directly deposited into the lake with no chance for treatment. Visual observations revealed that
shoreline erosion is occurring near Lakeshore Park on either side of the boat ramp. The erosion is
approximately 160 ft. long and is estimated to contribute 2 Ibs/yr of phosphorus to Lake
Independence. This phosphorus load could be greatly reduced by stopping the erosion and restoring
the shoreline.
Shoreline restoration is not much different than gully and stream stabilization. Shoreline restoration
may include the use of rip rap boulders near the water surface to armor the shore against the wave
action. Vegetation can be re-established above the hard armor, which will penetrate deep into the
underlying soil to prevent erosion and reduce the velocity of the stormwater that flows down the
bank.
Figure 13U: Photo of shoreline stabilization; Source: MN DNR
Ardmore Area Subwatershed Stormwater Retrofit Analysis 21
SR1
able 8U. Site Summary
- SR1
Model Used
BWSR worksheet
Eroding Shoreline
160 ft
Estimated TP Removal
2.0 Ibs/yr
Installation Cost
$16,000
Design/Admin
$1,500
Maintenance Cost / yr
$240
Total 20 Year Cost
$22,000
$/Ib-TP removal /yr
$550
Figure 14U: Close up of the
shoreline erosion
Figure 1511: The erosion exists on both sides of the boat launch. It extends
approximately 120 ft. to the right of the launch and 40 ft. to the left.
Fi ure 16U: Drainage area and location ma
1
7I
A
Ardmore Area Subwatershed Stormwater Retrofit Analysis 22
Pond Excavation
Traditional stormwater ponds can reduce phosphorus loads in urban runoff by allowing for
sedimentation to occur. Once the water reaches the pond the velocity is greatly reduced, and thus
allowing the suspended solids to settle out. This traps the phosphorous rich sediment in the bottom
of the pond and prevents it from entering downstream surface waters. Ponds are a good way to treat
large areas, and the larger the pond, the greater the efficiency.
Five pond excavation projects are proposed. Two of the projects already have existing ponds and are
proposed to be expanded to NURP standards. The other three pond excavation projects are new
ponds in locations that could benefit from the water quality treatment.
The first proposed pond to be excavated (PD1) is an already existing pond in Walnut Park. The
current pond is estimated to have a surface area of 620 square feet and has a drainage area of 2.9
acres. This pond is severely undersized and is providing little treatment in the existing condition. To
meet NURP standards, the pond must be enlarged considerably. It is noted that a rain garden is also
proposed within this sub -watershed, which would remove a fraction of the suspended solids before
entering the pond. Routing stormwater through multiple BMPs is often referred to as a treatment
train and can have increased water quality benefits. The phosphorous reduction reported in Table 9U
takes into account the minimal treatment that is occurring in the existing condition in the undersized
pond.
The second proposed pond (PD2) would be located at the receiving end of the eroding gully, north of
Fern Street. This is a new proposed pond that would be approximately 2,900 square feet in surface
area. This pond would have water quality benefits as it would intercept particulate phosphorous
prior to discharging into the large downstream wetland, which is directly connected to Lake
Independence. It should be noted that a gully stabilization project is proposed upstream of PD2, and
it would be critical that the gulley stabilization project be completed prior to implementing PD2.
The third pond (PD3) would be an expansion of an existing pond east of Aspen Avenue and south of
Maple Street. Visual observations have determined that this pond requires maintenance to remove
sediment. Removal of sediment and expansion of the pond is proposed to increase pollutant removal
efficiency. The pond is proposed to be expanded westward as to not impact surrounding wetlands.
The fourth pond (PD4) would be a new pond west of the stream erosion. In the current condition, the
storm sewer from Lakeshore Avenue directs stormwater into the vicinity of the proposed PD4, and it
enters the stream untreated. A stormwater pond in this location would treat the stormwater and
remove pollutants before discharging it into the stream and ultimately Lake Independence.
The fifth pond (PD5) would be excavated north of Pine Street near Lakeshore Avenue. The new 4,000
square -foot pond would treat street runoff that would otherwise flow into the lakes.
Figure 17U: Stormwater treatment basin
a
Q
TOP OF
BERM
10` MIN
1
CUTLET
STRUCTURE
W5
41 100 YEAR
re
STORM EVENT
PEAK ELEVATION
12" MIN
EXCAVATE TO INVERT
NORMAL WATER LEVEL
TRAPPED
SEDIMENT
10'
Ardmore Area Subwatershed Stormwater Retrofit Analysis 23
PD1
i Table 9U. Site Summary — PD1
Model Used
MIDS
Drainage Area
6.2 ac
Existing Pond Area
620 sq fit
Proposed Pond Area
9,445 sq ft
Estimated TP removal
1.8 Ibs/yr
Installation Cost
$56,600
Design/Admin
$12,500
Maintenance Cost
$250
Total 30 Year Cost
$76,350
$/Ib-TP removal /yr
$1,414
Figure 18U: Top- The existing
pond. Bottom- The purple line
shows location of proposed pond.
Figure 19U: Drainage area and location map
Ardmore Area Subwatershed Stormwater Retrofit Analysis 24
PD2
Table 10U. Site Summary
— PD2
Model Used
MIDS
Drainage Area
4.1 ac
Proposed Pond Area
5,400 sq ft
Estimated TP removal
1.8 Ibs/yr
Installation Cost
$32,400
Design/Admin
$8,000
Maintenance Cost / yr
$250
Total 30 Year Cost
$47,650
$/Ib-TP removal /yr
$882
Figure 2OU: Purple outline below
shows proposed location of PD2.
Figure 21U: Drainage area and location map
Excavate Pond
Ardmore Area Subwatershed Stormwater Retrofit Analysis
25
PD3
Table 11U. Site Summary
— PD3
Model Used
MIDS
Drainage Area
8.0 ac
Existing Pond Area
8,700 sq ft
Proposed Pond Area
14,000 sq ft
Estimated TP removal
1.1 Ibs/yr
Installation Cost
$31,800
Design/Admin
$12,500
Maintenance Cost/yr
$250
Total 30 Year Cost
$51,550
$/Ib-TP removal /yr
$1,562
Figure 22U: Purple outline shows
proposed enlarged pond for PD3.
Above- view looking south. Below -
view looking west.
Figure 23U: Drainage area and location map
Maple St
Excavate
Pre-existing Pond
5 D CD
actratmoD
Ardmore Area Subwatershed Stormwater Retrofit Analysis 26
PD4
Table 12U. Site Summary
— PD4
Model Used
MIDS
Drainage Area
2.7 ac
Proposed Pond Area
4,600 sq ft
Estimated TP removal
1.2 Ibs/yr
Installation Cost
$27,600
Design/Admin
$12,500
Maintenance Cost/yr
$250
Total 30 Year Cost
$47,350
$/Ib-TP removal /yr
$1,315
Figure 24U: Purple outline shows the
proposed location of PD4. View is
looking southwest.
Figure 25U: Drainage area and location map
Ardmore Area Subwatershed Stormwater Retrofit Analysis
27
PD5
Table 13U. Site Summary
— PD5
Model Used
MIDS
Drainage Area
1.6 ac
Proposed Pond Area
4,000 sq ft
Estimated TP removal
1.0 Ibs/yr
Installation Cost
$24,000
Design/Admin
$12,500
Maintenance Cost/yr
$250
Total 30 Year Cost
$43,750
$/Ib-TP removal /yr
$1,458
Figure 26U: Purple outline shows
location of proposed PD5
Figure 27U: Drainage area and location map
Ardmore Area Subwatershed Stormwater Retrofit Analysis
28
Alternative Higher Efficiency BMPs
Enhanced Filtering Device
Although the rain gardens and ponds as previously discussed are rather effective in removing the
particulate phosphorous contained in stormwater, they are not very effective in removing the
dissolved portion of the phosphorous. Since it is estimated the dissolved portion is 45% of the total
phosphorous, utilizing treatment methods that do not target dissolved phosphorous can result in lost
opportunity.
The dissolved phosphorous is the most difficult portion of the phosphorous load to capture.
Traditional settling and even filtering methods have not proven to be effective in removing dissolved
phosphorous. However, certain methods such as introducing aluminum or iron in a filter media
cause the dissolved portion of the phosphorous to bind to the media, and thereby removing it from
the stormwater.
The schematic shown in Figure 28U below is a proprietary device developed by Contech Engineered
Solutions. The device filters the stormwater through an aluminum enhanced media contained within
the internal cartridges. The dissolved phosphorous binds to the internal media, allowing the filters to
pass clean stormwater. The clean stormwater exits the internal cartridges through the bottom into a
trench within the false floor, which leads to the outlet. Pre-treatment of stormwater is
recommended prior to entering the device; however, remaining suspended solids will also settle out
in the bottom of the structure.
Figure 28U: Enhanced filtering device; Source: Contech Engineered
Solutions
iNtF T f N1RGY OiSUPAi t .
I�A1 ITV[
CN4 R tOW Mk lit AND 04000
OF
Ardmore Area Subwatershed Stormwater Retrofit Analysis 29
Large filtering devices require periodic maintenance and must be easily accessible by a
vacuum truck. Therefore, they must be located within or in close proximity to a driving
surface. The site previously mentioned for PD5 would be ideal for an enhanced filtering
device (EFD1). EFD1 is an alternative BMP to PD5, so if the enhanced filtering device were to
be installed in this location, the pond would not be excavated.
EFD1
Table 14U. Site Summary
— EFD 1
Model Used
N/A
Drainage Area
1.6 ac
Estimated TP removal
1.4 Ibs/yr
Installation Cost
$200,000
Design/Admin
$20,000
Maintenance Cost
$2,000
Total 50 Year Cost
$318,000
$/Ib-TP removal /yr
$4,543
Figure 29U: Possible location of
underground enhanced filtering
device
Figure 30U: Drainage area and location map
Enhanced Filt
Ardmore Area Subwatershed Stormwater Retrofit Analysis 30
Iron Enhanced Sand Filters (MN Filter)
Similar to enhanced filtering devices, iron enhanced sand filters are efficient in reducing the dissolved
portion of the phosphorous. Iron enhanced filters utilize iron filings within the filter media. As the
stormwater passes through the media, the dissolved phosphorous attaches to the iron filings within
the media, effectively treating the stormwater. A pre-treatment settling basin is utilized upstream of
the iron enhanced filter to settle out the sediment. Any sediment that passes through the pre-
treatment will still have an opportunity to settle out in the iron enhanced filter; however, over time,
sediment may plug the iron enhanced filter and reduce overall effectiveness.
In order for iron enhanced sand filters to be effective, they must be designed to drain after a storm
event in order to prevent hypoxic conditions.
Figure 31U: Schematic of iron enhanced sand filter
IRON ENHANCED FILTER MEDIA
PVC UNDERDRAIN
There is one iron enhanced sand filter (ISF1) proposed in this watershed, which is in the same
location as PD2. Only one BMP should be considered at this site; therefore, if an iron enhanced sand
filter is utilized, pond PD2 would not be constructed.
Figure 32U: Iron enhanced sand filter; Source: BWSR
Ardmore Area Subwatershed Stormwater Retrofit Analysis 31
ISF1
Figure 33U: Location of the proposed ISF1
Table 15U. Site Summary
—ISF1
Model Used
N/A
Drainage Area
4.1 ac
Proposed Pond Area
5,400 sq ft
Estimated TP removal
3.1 Ibs/yr
Installation Cost
$58,000
Design/Admin
$15,000
Maintenance Cost / yr
$500
Total 30 Year Cost
$87,500
$/Ib-TP removal /yr
$941
Figure 34U: Drainage area and location map
CD Est
Ardmore Area Subwatershed Stormwater Retrofit Analysis 32
Urbanized Ardmore Subwatershed Summary
Twelve projects in ten areas have been identified that will reduce the phosphorus load up to a
combined 15.9 pounds per year to Lake Independence from the urban area of the Ardmore
subwatershed. The data included within this report should be utilized for determining feasibility and
prioritizing projects. Before any project is advanced, preliminary design should be completed to
confirm the results included herein. Prior to construction of any of the proposed projects, detailed
plans and specifications should be prepared by a professional engineer.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 33
Lake Ardmore
Rural Subwatershed Assessment
Ardmore Watershed
Hennepin County, Minnesota
Hennepin
QArdmore Watershed Boundary
I�
2015 Aerial Imagery
500 11.000
Watershed Location Map
2.000 3.000
Feet
Figure 1R: Lake Ardmore Rural Watershed Outline
Ardmore Area Subwatershed Stormwater Retrofit Analysis
34
Introduction
This report details a stormwater assessment with BMP recommendations within the Lake Ardmore rural watershed. Its
purpose is to assist the City of Medina in its decisions and processes to provide cost effective methods to help reduce
phosphorus loads into Lake Ardmore and ultimately into Lake Independence.
Because of excessive nutrients, Lake Ardmore is proposed by the Minnesota Pollution Control Agency to be listed as an
impaired lake in 2016 for aquatic recreation. Three Rivers Park District, in cooperation with the Pioneer -Sarah Creek
Watershed Management Commission, is undertaking a TMDL study to see the extent of the impairment, provide nutri-
ent budgets and possible solutions to achieve a non -impaired status for the lake. Preliminary numbers from their mod-
el show 269 pounds per year phosphorous loads from its contributing watershed. This report will focus specifically on
the nutrient loads from the rural section of the watershed located north of Maple Street that drains into Lake Ardmore.
The Lake Ardmore watershed is approximately 537 acres in size. The primary land uses that make up this watershed
are wetlands (158 acres), woodlands (143 acres), farmsteads/residential/hobby farms (119 acres) cropland (95 acres)
grassland (7 acres), and roads and right of ways (14 acres). The focus of this analysis is the rural section of the water-
shed north of Maple Street which encompasses 472 acres. Four hundred and twenty three acres are in Medina, and 49
acres are in Independence.
Lake Ardmore outlets into a channel that flows approximately 1,000 feet before entering Lake Independence. In 2002
the Minnesota Pollution Control Agency listed Lake Independence as impaired for aquatic recreation under Section 303
(d) of the Clean Water Act. The Lake Ardmore subwatershed is one of the 6 primary subwatersheds that drain to Lake
Independence. The Lake Independence TMDL study idenfified the Ardmore Lake watershed as contributing 6% (96 lbs.)
of the external load running into Lake Independence, causing its impairment.
This stormwater assessment will model various stormwater treatment BMPs within the 472 acres of rural watershed
that drains into Lake Ardmore. These BMPs are analyzed to determine their effectiveness in reducing nutrient loads
into the lake. These practices will be rated from the most cost effective project per pound of phosphorus reduction to
the least effective. To provide a better understanding of each BMP and approach for implementation, conceptual
drawings and/or photos are incorporated within this report. Prior to implementation, more detailed, site -specific de-
signs will need to be prepared for each BMP selected. Most will require additional study and/or engineered plans. For
all the recommended projects, partnerships with committed and willing landowners are essential.
The process used to select recommended BMPs was based primarily on a combination of the target pollutant
(phosphorus), the project type and their cost/benefit analysis, and the location of the project in the watershed. Addi-
tional factors should be considered prior to the prioritization of recommended BMP (e.g., project costs, available fund-
ing, economies of scale, landowner willingness, short- and long-term impacts on property values and the public infra-
structure).
Ardmore Area Subwatershed Stormwater Retrofit Analysis 35
Basic conclusions
This study, using site specific observations and measurements; new topographic data (2 foot contour LiDAR data); land
use; and modeling processes, supports the findings from previous studies, which show a direct correlation between
land use, land management and phosphorus transport to the amount of pollutants in the Lake Ardmore watershed.
The implementation of any land practices that helps rainfall stay on the land, keeps it from running off and prevents
nutrients (attached to soil and dissolved in the runoff water) from reaching the drainage system and benefits the water
quality of Lake Ardmore and ultimately Lake Independence.
The cost/benefit relationship of putting these BMPs into place is highly dependent upon how severe the land disturb-
ance is and how close the practice is to Lake Ardmore.
Table 1R shows the reductions of phosphorus at the source of a BMP and at Lake Ardmore. It breaks down what the
total project cost is estimated at and cost per pound of total phosphorus (TP) removed from the lake.
As part of this process, the cost effectiveness and nutrient reductions for some conceptual practices were generalized.
For example, livestock facilities were not modeled due to the specific site and management techniques each facility
uses. However, the concept of on -site nutrient management systems that would adequately store, manage and apply
manure and nutrients to cropland along with adequate pasture management techniques were evaluated, and a deliv-
ery ratio of nutrients to Lake Ardmore was determined based on distance to the drainage systems and lake. A general-
ized load reduction and cost/benefit analysis can be estimated to locate livestock BMPs that warrant additional study.
If the landowner is interested in such a study, the exact nutrient reductions must be analyzed on a site by site basis.
Rural watershed assessment: document organization
This rural section of the document is organized to present a brief overview of the processes involved to get to the pro-
ject rankings and selections. The technical aspect of the Subwatershed assessment process and supporting model re-
sults are presented in the appendices. The majority of the report focuses on the projects themselves: their rankings in
cost per pound of nutrient reduction and the profile of the project.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 36
Recommended projects
Table 1R: Ardmore Lake retrofit projects and rankings
Project
rank
Retrofit type
(refer to catchment
profile pages for
additional detail)
Project
identified
Total
phosphorus
reduction
(Ib/yr)
Phorphorus
delivery ratio
to Lake
Ardmore
Phosphorus
reduction to
Lake Ardmore
(Ib/yr)
Total project
cost
(includes 10-yr
maintenance )
Estimated
cost
(lb-TP/year for
10 years)
1
Nutrient Management
System
Lvst D
8.8
0.5
4.4
$4,200
$96
2
Field Buffer
FB-4
10.3
0.9
9.2
$12,760
$139
3
Pasture & Paddock
Management
Lvst A
2.5
1.0
2.5
$4,750
$190
4
Field Buffer
FB-5 (Ivst A)
6.3
1.0
6.3
$12,098
$192
5
Gully Stabilization
G-1 (Ivst C)
22.1
0.4
6.7
$19,165
$218
6
Field Buffer
FB-3 (Ivst D)
12.7
0.4
5.1
$12,169
$239
7
Exclusion Fencing
EsFn D-1
(lust D)
4.6
0.5
2.3
$5,875
$255
8
Field Buffer
FB-2E
13.1
0.4
5.2
$14,450
$278
9
Exclusion Fencing
ExFn A-1
(Ivst A)
2.0
1.0
2.0
$5,775
$289
10
Field Buffer
FB-2W
26.0
0.3
7.8
$27,970
$359
11
Field Buffer
FB-1
11.0
0.2
2.2
$7,960
$362
12
Field Buffer
FB-2S
4.0
0.6
2.4
$8,704
$363
13
Wetland Restoration 3
WR-3
48.0
1.0
48.0
$386,000
$402
14
Gully Stabilization
G-2 (Ivst A)
12.8
0.7
8.9
$36,200
$407
15
Exclusion Fencing
ExFn A-2
(lust A)
1.8
1.0
1.8
$7,875
$438
16
Grass Waterway
(lust
GW-A)
1.8
1.0
1.8
$9,180
$510
17
Manure Storage
System
Lvst C
6.0
0.4
2.4
$14,375
$599
18
Manure Storage
System
Lvst B
2.0
0.5
1.0
$7,875
$788
19
Wetland Restoration
2E
WR-2E
30.8
0.4
12.3
$204,375
(20 year cost)
$831
(20 year cost)
20
Regional Pond 1
RP-1
30.9
0.4
12.4
$208,125
(20 year cost)
$846
(20 year cost)
21
Wetland Restoration
2W
WR-2W
5.0
0.4
2.0
$226,500
(20 year cost)
$5,663
(20 year cost)
22
Gully Stabilization
G-3
0.4
0.7
0.3
$19,500
$6,500
Ardmore Area Subwatershed Stormwater Retrofit Analysis
37
Table 1R: Ardmore Lake retrofit projects and rankings (continued)
Total
phosphoru
Retrofit type s Phorphorus
Project (refer to catchment Project reduction delivery
rank profile pages for identified ratio to Lake
additional detail) Ardmore
(Ib/yr)
Phosphorus
reduction to
Lake Ardmore
(Ib/yr)
Total Estimated
project cost cost
(includes 10
-yr (Ib-TP/year
maintenanc for 10 years)
e)
23
Wetland Restoration 1
W R-1
3.2
0.1
0.3
$43,750
(20 year
cost)
$6,836
(20 year
cost)
24
Manure Storage System
Lvst A
$66,200
N/A
25
Clean Water Diversion
Lvst A
$7,325
N/A
26
Clean Water Diversion
(roof gutters)
Lvst C
$4,000
N/A
27
Manure Storage System
Lvst D
$35,400
N/A
Figure 2R: Ardmore watershed projects and best management practices map
Watershed Projects & Best Management Practices
Ardmore Watershed - Hennepin County, Minnesota
Hennepin
Ardmore Watershed Projects
Ardmore Watershed Boundary
2015 Aerial Imagery
Watershed Location Map
Anoka
Ardmore Area Subwatershed Stormwater Retrofit Analysis
38
Figure 3R: Ardmore watershed
49 rural acres r
in Independence
'�— -- Independen*Ina
423 rural acres in Medina
Ardmore Residential Area
Urban area = 113 acres
Ardmore Area Subwatershed Stormwater Retrofit Analysis
39
Table 2R: Priority elements analyzed in Lake Ardmore subwatershed assessment
Priority elements Description
analyzed
Total phosphorous
Phosphorus is an essential nutrient for plants, animals and humans. Under
natural conditions, phosphorus (P) is typically scarce in water. However,
changes in pre -settlement land use activities have resulted in excessive loading
of phosphorus into many freshwater systems. This can cause water pollution
by promoting excessive algae growth, particularly in lakes. Total Phosphorus is
a combination of particulate phosphorus, which is bound to sediment and
organic materials, and dissolved phosphorus, which is phosphorus in solution
available for plant growth.
Total Suspended Solids (TSS) are particles remaining dispersed in a liquid due
to turbulent mixing that can create turbid or cloudy conditions. Reducing TSS
will reduce particulate phosphorus loads to Lake Ardmore.
Volume of water: Higher runoff volumes and velocities can carry greater
amounts of TSS and dissolved phosphorus to Lake Ardmore. Reductions in
volume will reduce total phosphorus loads to Lake Ardmore.
Cost
Each retrofit practice has been analyzed for the annual cost per pound of
phosphorous load reduction into Lake Ardmore. Cost includes installation,
annual maintenance, life expectancy, design and project oversight.
Watershed location
All projects are analyzed by determining their phosphorus load reductions
entering Lake Ardmore. Our methods of modeling takes into account the
modeled, edge of field phosphorus load reductions multiplied by a pollutant
delivery ratio to estimate what actually gets into the lake. The pollutant
delivery ratio was arrived at by the report authors and other natural resource
professionals utilizing maps showing the project location in the watershed,
distance to Lake , aerial photographs, topography, type of phosphorus (soluble
vs. particulate) and flow paths. Each project was assigned a number from 0.1
to 1.0 with 0.1 having a lower nutrient reduction benefit that 1.0.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 40
Potential project types
The retrofit analysis considered various stormwater and erosion/sediment control BMPs. Table 3R describes these
BMPs and how their benefits were analyzed.
Table 3R: Potential project types for Ardmore Lake subwatershed
assessment
Project type
Description
A strip or area of herbaceous vegetation situated
between cropland, grazing land or disturbed land
and environmentally sensitive areas.
Modeling methods
RUSLE 2/ BWSR Pollution
Reduction Estimator
Vegetated buffer strip
Grassed waterway
A natural or constructed channel that is shaped
or graded to required dimensions and
established with suitable vegetation for the
stable conveyance of runoff.
BWSR Pollution Reduction
Estimator
Gully stabilization
Corrective actions on active gully erosion with
rock rip rap, check dams or other stabilization
measures and vegetation for the stable
conveyance of channelized flows.
BWSR Pollution Reduction
Estimator
Livestock best
management practices
Restricting livestock access to critical or sensitive
areas through the use of fencing or other
restrictive forms of animal exclusion. Analyzing
manure storage needs for livestock facilities.
Analyzing the potential use of compost, stacking
slabs, storage facilities, and pasture and nutrient
management.
MinnFARM/RUSLE2/Elm
Creek and U of WI loading
estimates
Wetland restoration
Restoring hydrology to cropland areas that have
been partially or completely drained.
SWAT
Ponding
Creating new regional or local ponds to capture
and treat runoff.
SWAT/NURP
Ardmore Area Subwatershed Stormwater Retrofit Analysis 41
Project profiles
Ardmore Area Subwatershed Stormwater Retrofit Analysis 42
Buffer strips
Buffer strips are land areas of vegetation, situated
between a potential, pollutant -source area and a surface- strips
water body that receives runoff (Figure 4R). The term
'buffer strip' is sometimes used interchangeably with
filter strip. Runoff may carry sediment and organic
matter and plant nutrients and pesticides that are
either bound to the sediment or dissolved in the
water. A properly designed and operating buffer strip
provides water -quality protection by reducing the
amount of sediment, organic matter, and some
nutrients and pesticides in the runoff at the edge of
the field and before the runoff enters the surface -
water body. Buffer strips also provide localized erosion
protection since the vegetation covers an area of soil
that otherwise might have a high erosion potential.
Figure 4R: Examples of vegetative buffer
Often constructed along stream, lake, pond or wetland boundaries, buffer strips installed on cropland not only help
remove pollutants from runoff, but also serve as habitat for wildlife and provide an area for field turn rows and
haymaking. In some instances, a buffer strip could be used as pasture in a controlled -grazing, livestock management
system if livestock are kept fenced out of the stream or lake.
Buffer strips are an edge -of -the -field BMP. They often are used in conjunction with other sound agricultural and land
management practices, such as contour plowing, pest scouting, conservation tillage, crop rotations, strip cropping, soil
testing, and proper nutrient and pest management. Because of their potential environmental benefits, buffer strips are
a recommended urban and agricultural BMP.
Most field research supports the use of buffer widths in the range of 10 to 40 feet depending on the receiving water
and amount of flows it is designed to intercept. This report uses a 35 foot strip in its analysis for pollutant reductions
and cost/benefits.
Buffer strips are proposed in areas where active agricultural activities are occurring near a water course or wetland.
The benefits of the buffer strip will vary greatly depending on many variables, including: whether the water flowing
over it is in a channelized or sheet type of flow, the slope of the land, type of vegetation in the strip, width of the strip,
distance to the stream or wetland and distance to Lake Ardmore to name a few.
The cost/benefits of buffer strips are estimated based on the pollutant reductions, which is determined by the width of
the filter strip, pollutant reduction, life span, crop loss, design and promotion costs and maintenance costs.
The expected life span of a buffer strip is 10 years. It is highly determined by the amount of soil/sediment that the
grass in the filter strip traps. Eventually the cropland at the edge of the grass will build up with sediment causing the
water to back up at the edge of the filter creating wetness issues in the cropland. This edge between the filter strip
and cropland will need to be re-established to allow for the water to flow into and through it as intended. If upland
erosion is not controlled, the lifespan of the filter strip is greatly reduced.
To help remove nutrients during the lifespan of the buffer strip, we encourage harvesting the hay at least once a year
(after August for nesting bird protection).
Ardmore Area Subwatershed Stormwater Retrofit Analysis 43
Lake Ardmore vegetated buffer analysis parameters
Buffer width
The standard vegetated buffer width used in this report is 35 feet wide, which provides the necessary benefits with
good representative costs.
Buffer length and area
Buffer lengths are established based on the sensitivity of the water resources being protected. Buffer area is
determined by multiplying the buffer length by 35 feet (the standard buffer width) and converted to acres.
Phosphorus reductions
The phosphorus reduction that will be provided by a buffer strip is estimated by using the Board of Water and Soil
Resources (BWSR) Pollution Reductions Calculator for Filter Strips (www.bwsr.state.mn.us/outreach/eLINK/
index.html), and is calculated in pounds and measured at the edge of the field using the following input parameters:
• Soil type: Silt was used for all sites
• Area: Measured in acres draining into and through the buffer
• Average soil loss: Measured in tons per acre of the contributing area
• Average field soil loss: Determined for each site using the USDA, NRCS Revised Universal Soil Loss Equation
(RUSLE2). RUSLE2 uses the following input parameters:
Specific slope length: Measured from top of slope to where the water channelizes (LS factor)
Specific slope steepness: Measured from 2-foot topographic maps of Hennepin County LiDAR
information (LS factor)
Site -specific soil: From the Hennepin County Soil Survey (k factor)
Crop rotation and tillage history: Based on review of aerial photos from 2006, 2008, 2011 and 2012
(c factor)
Existing conservation practice: Based on aerial photographic reviews (p factor)
Regional climate conditions for Hennepin County
Phosphorus delivery ratio
Depending on the distance between the buffer strip and the protected target resource, some of the phosphorus
reduction benefit may be diminished. All the vegetated buffers were further analyzed to determine the reduction of
phosphorus that would reach Lake Ardmore. This reduction is the Phosphorus Delivery Ratio (PDR) of the vegetated
buffer strip. Therefore, the phosphorus load that actually reaches Lake Ardmore was estimated by multiplying
phosphorus reduction at the field edge and PDR. The PDR was estimated for each site by considering the location and
distance of the buffer strip with respect to Lake Ardmore, flow restrictions, aerial photographs, topography and the
type of nutrient available for transport (soluble versus particulate). Each buffer site was assigned a PDR from 0.1 to
1.0, with 0.1 having a lowest delivery ratio (10% from the field edge), and 1.0 having the highest delivery ratio (100%
from the field edge) to Lake Ardmore.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 44
Cost basis for vegetated buffers
Construction costs are estimated at $350 per acre of buffer area and include seedbed preparation, fertilizer and
planting.
Maintenance costs are estimated at $100 per acre of buffer area and are figured for the complete lifespans of the
practice (10 years). Maintenance costs cover weed suppression and reseeding where needed.
Crop production losses are estimated at $800 per acre of buffer area. The largest cost associated with vegetated
buffers is the losses incurred from taking cropland out of production. Although this will vary based on type of crop,
land productivity and crop pricing, this report uses a standard of $800 in crop production losses per acre per year,
totaling $8,000 per acre over 10 years.
Design, easement and oversight costs are estimated as a lump sum of $6,000 per buffer and is largely for easement
development and recording.
Lake Ardmore specific buffer assumptions
• Buffer width = 35 feet
• Buffer length = varies
• Project lifespan = 10 years
• Cost (estimated by the Metropolitan Association of Conservation Districts' BMP Cost Estimator):
Construction cost = $350/acre
10-year maintenance cost = $100/acre
1-year production cost lost = $800/acre
Design, easement and oversight costs = $6,000 lump sum
• Nutrient and sediment reductions: Estimated by BWSR Pollution Reductions Calculator for Filter Strips
• Soil: Assumed as silt with average bulk density of 85 lbs./cu. ft.
Table 4R shows the estimated phosphorus reduction entering Lake Ardmore from the fields analyzed and the
associated cost for the life span of the project due to the implementation of buffer strips.
Buffer 1 is in the far west portion of the Lake Ardmore watershed. It is the south field boundary above an existing,
drained wetland basin.
Buffer 2W would be around the large wetland basin in field 2
Buffer 2E would be around the small wetland basin near CSAH 19 in field 2
Buffer 2S would be along the southwest field boundary in field 2
Buffer 3 is located between the wetland and pasture in livestock area D
Buffer 4 is located along the west field boundary in field 4.
Buffer 5 is located along the horse pasture on livestock site A
Ardmore Area Subwatershed Stormwater Retrofit Analysis 45
Table 4R: Phosphorous reduction to Lake Ardmore and associated costs of
proposed buffer strips
Field
buffer
ID
Buffer
Length
(ft)
Area
(acres)
Area up -
stream of
buffer
(acres)
Total 10-
year cost
($)
Average soil
loss from
contributing
field
(tons/acre)
p reduction
(Ibs/year)
pDR
Phosphorus
reduced to
Lake
Ardmore
(Ibs/year)
Cost of P reduction
to Lake Ardmore
for lifespan of
practice
($/Ibs)
FB-4
1000
0.8
4.2
12,760
6.4
10.3
09
9.2
$139
FB-5
900
0.72
5.6
12,098
2.3
6.3
1.0
6.3
$192
FB-3
910
0.73
8.4
12,169
3.6
12.7
0.4
5.1
$239
FB-2E
1165
1.0
9.0
14,450
3.4
13.1
0.4
5.2
$278
FB-2W
3200
2.6
21.7
27,970
6.5
26.0*
0.3
7.8
$359
FB-1
275
0.22
3.1
7,960
11.1
11.0
0.2
2.2
$362
FB-2S
400
0.3
1.4
8,704
7.8
4.0
0.6
2.4
$363
*P reductions is 50% of modeled reduction due to variables associated with a large contributing watershed
Figure 5R: Location of proposed buffer strips
Field Buffer Projects
Ardmore Watershed - Hennepin County, Minnesota
Hennepin
�r
Field Buffer Projects
OArdmore Watershed Boundary
2015 Aerial Imagery
Watershed Location Map
Anoka
Hennepin .� J �JRamsey
,1-9
i _1l)
Dakota
N
0 500 1.000 2,000 3,000
E I Feel
s
Ardmore Area Subwatershed Stormwater Retrofit Analysis
46
Grassed waterways
Grassed waterways are constructed graded channels that
are seeded to grass or other suitable vegetation. The
vegetation slows the water, and the grassed waterway
conveys the water to a stable outlet at a non -erosive
velocity. Grass or permanent vegetation established in
waterways protects the soil from concentrated flows.
Grassed waterways significantly reduce gully erosion.
A natural drainage way is graded and shaped to form a
smooth, bowl -shaped channel. This area is seeded to sod -
forming grasses. Runoff water that flows down the drainage
way flows across the grass rather than tearing away soil and
forming a larger gully. An outlet is often installed at the
base of the drainage way to stabilize the waterway and
prevent a new gully from forming.
Figure 6R: Photo of well -functioning
grassed waterway
Grass cover protects the drainage way from gully erosion. Vegetation may act as a filter, absorbing some of the
chemicals and nutrients in runoff water. Vegetation provides cover for small birds and animals.
The expected life span of a waterway is 10 years. It is highly determined by the amount of sediment that the grass in
the waterway traps. Eventually the cropland at the edge of the grass and the waterway itself will need to be re -
excavated to allow for the water to flow into and down the waterway. If upland erosion is not controlled, the lifespan
of the waterway is greatly reduced.
Lake Ardmore grassed waterway analysis parameters
Grassed waterway siting
The Lake Ardmore rural watershed was analyzed for sites that would benefit from waterway construction. The sites
were determined by in -field site observations, topographic information (LiDAR) and aerial photographic desktop
analysis.
Visual evidence was gathered by observations of the sites during various times throughout 2015
Topographic evidence was based on LiDAR indicators, including incised topographic settings and well-defined drainage
areas leading to water collection flowage areas.
Aerial photographs were also used to site waterway projects. In areas we could not observe during our field
reconnaissance, photographic evidence of erosion coupled with the LiDAR indicators mentioned above were utilized.
Phosphorus reductions
At this time, only one site where a waterway could be beneficial was determined within this watershed. The site is in a
pasture area located in Livestock Site A. Utilizing an erosion equation such as the BWSR pollution reduction calculator
for gullies and waterways was not feasible on this site because soil erosion itself is not a significant contributor to
phosphorus transport in this area. Although erosion isn't a significant factor in this pasture area, the concentrated
flows in this channel create the opportunity to transport a high volume of any waste material located within the flow
path of the water during runoff events. The amount will vary on how concentrated the animals are in the vicinity of
the waterway. The phosphorus reductions were estimated based on an average mean phosphorus load as cited in
various University of Wisconsin Discovery Farm, Iowa State University and other studies in pasture situations. These
studies have determined loads from a pasture can vary from 0.20 lbs. per acre to 12.0 lbs. per acre. Because of the
channelized nature of the water running through a pasture area, this study chose the middle of the loads/reductions,
or the 6 lbs./acre of load from the area of the waterway.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 47
Phosphorus delivery ratio
The phosphorus delivery ratio for the one waterway analyzed was considered at 100% because of its proximity to Lake
Ardmore.
Cost basis for grassed waterways
Construction costs were estimated at $10.00 per foot for the waterway and drain file associated with it on this site.
This includes 600 feet of 4" drain tile, excavation and distribution of the material on site, seeding and mulching. Drain
tile was a component of this waterway because the slope of the waterway appear to be at +1% near the upper reaches
of it. Drain tile will assist in removing excess water in the vicinity of the waterway to minimize damage to the grass
areas from the horses when they are near the waterway.
Maintenance costs were estimated at $0.25 per year per foot for the water and tile system over a 10 year period.
Design and oversight costs were estimated as a lump sum of $1,680 per project site. This includes surveying, design,
staking and construction inspection.
Table 5R: Phosphorous reduction to Lake Ardmore and associated
costs of proposed grassed waterways
Field ID
Cost of P
Total Distance to Phosphorus reduction to
Total 10- reduced to Lake Ardmore
length of P reduction surface water
waterways Year cost (ditch system) Lake for the life
Ardmore span of the
practice
(ft) ($) (Ibs/year) (ft) (Ibs/year) ($/Ibs)
GW-A1 I 600 I 9,180 I 1.8
0 I 1.8 I $510
Figure 7R: Location of proposed grassed waterway projects
Grassed Waterway Projects
Ardmore Watershed - Hennepin County, Minnesota
= Grassed Waterway Projects
QArdmore Watershed Boundary
� o' 1 2015 Aerial Imagery
Hi
Ardmore Area Subwatershed Stormwater Retrofit Analysis 48
Gully stabilization
Gullies are a specific form of severe erosion typically caused by
concentrated water flow on erosive soils. Concentrated water flow
may begin as minor sheet flow that produces rills and eventually
results in major gully formation. Gullies can have major impacts on
an area by taking land out of production, lowering the
groundwater table and acting as a major source of sediment. Once
formed, gullies typically get deeper and wider until they reach a
resistant material. Gullies often form at the outlet of culverts due
to the concentrated flows and relatively fast water velocities.
Stabilization of gullies typically requires reducing the volume and
the velocity of water flowing through the gully. This can be
achieved by refilling the gully and building dikes or small check dams at specific intervals along the gully. Reshaping and
stabilizing long and steep banks may also be needed. Typical gully stabilization structures are constructed of rock,
gabions or vegetative barriers. Biotechnical methods offer a combination of physical structures along with vegetative.
Figure 8R: Photo of unstable
Lake Ardmore gully analysis parameters
Gully locations
streambank in Baker Park Reserve
Gully erosion sites in the Lake Ardmore watershed were located through in -field identification, aerial photograph and
LiDAR desk top analysis. Areas that would benefit from a gully project were determined by in -field site observations,
topographic information (LiDAR) and aerial photographic desktop analysis.
Visual evidence was gathered by observations of the sites at various times in 2015 and previous site visits.
Topographic evidence was based on LiDAR indicators, including incised topographic settings and well-defined drainage
areas leading to water collection flowage areas.
Aerial photographs were also used to site gullies. In areas we could not observe during our field reconnaissance, pho-
tographic evidence of erosion scars, sediment fans and the LiDAR indicators mentioned above were utilized.
Phosphorus reductions
The phosphorus reduction that would be achieved through gully stabilization projects is estimated using the BWSR Pol-
lution Reductions Calculator for Gully Stabilization (www.bwsr.state.mn.us/outreach/eLINK/index.html), and is calcu-
lated in pounds and measured at the bottom of the gully using the following input parameters:
• Soil type: Silt with an average bulk density of 85 lbs./cubic foot was used for all sites
• Soil volume voided per year (cubic feet): Based on the severity of erosion occurring within the specific gul-
ly. These were based on the Rapid Assessment Point Method (Inventory and Evaluation of Erosion and Sed-
iment for Illinois by R.D. Windhorn, December, 2000.)
The two gully areas (G1 and G2) observed within the watershed are described as a moderate yearly recession
rate. This is generally a gully with predominantly bare banks with some rills and vegetative overhang and some
exposed tree roots. A moderate recession rate used for the Ardmore analysis was 4 inches per year along the
length and width of the gully. One gully (G3) was described as a slight recession rate because of stabilization
efforts done in the past. This gully was generally stable with approximately 6 areas where some additional
bank and in -stream stabilization could benefit areas of slope instability. (continued)
Ardmore Area Subwatershed Stormwater Retrofit Analysis 49
Phosphorus reductions (continued)
• For the BWSR pollution reduction calculator, gully conditions were assumed to be channelized with no
filter/buffer strips upstream. Gullies 1 and 3 were measured from aerial photographs at 525 feet and 750
feet long respectively. Gully 2 is actually a compilation of a series of gullies that have formed over time
along the north and easterly slopes adjacent to the farmstead area where they are located. For the
purpose of this analysis we summarized Gully 2 assuming two gullies, both 90 feet long by 5 foot wide. The
actual area of Gully Site 2 will need to have a more thorough, on site survey conducted for the costs and
benefits derived from this practice
• For Gully Sites 1 and 3, the wetted perimeter of the gully was assumed to be 3 feet. For Gully Site 2 it was
assumed as 5 feet wide.
Phosphorus delivery ratio (PDR)
Depending on the distance between the gully and Lake Ardmore, some of the phosphorus reduction benefits will be
diminished. All the gullies were analyzed to determine the reduction of phosphorus that would reach to Lake
Ardmore. Therefore, the phosphorus load that actually reaches Lake Ardmore was estimated by multiplying
phosphorus reduction at the bottom of the gully and the phosphorus delivery ratio (PDR). The PDR was estimated for
each site by considering the location and distance of the gully with respect to Lake Ardmore, flow restrictions, flow
route, topography and the type of nutrient available for transport (particulate in the case of sediment from gully
erosion). Each gully was assigned a PDR between 0.1 to 1.0, with 0.1 having a lowest delivery ratio and 1.0 having the
highest delivery ratio to Lake Ardmore.
Cost basis for gully stabilization
Construction costs were estimated at $90 per linear foot
for Gully 2 based on access and material disposal
limitations. Costs for Gully 1 were estimated at $45 per
linear foot because of ease of access and material
disposal. Gully 3 would be estimated at $120 per linear
foot of repair due to intermittent repair needs and
difficulty of access. Moderate recession rate projects
would generally consist of clearing and grubbing, shaping,
rip rap lined channels, check dams and restoration work.
Projects with slight recession rate gullies usually involve
check dams, minimal rip rap work with more vegetation
restoration.
Design and oversight costs were estimated at a $5,000 Figure 9R' Photo of rip -rap lined gully
lump sum per gully site and include scoping work, survey, stabilization BMP
staking, design and construction inspection.
Maintenance costs were assumed to be a $250 lump sum per year per gully site and include repair work, restoration
work and other erosion and vegetation control.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 50
Table 6R: Phosphorous reduction to Lake Sarah and associated costs of proposed
gully stabilization projects
Total length
Gully site of gully
ID
(ft.)
Recession rate P reduction
(ft3/year)
(Ibs./yr.)
Total
10-year cost
($)
PDR
P reduced to Cost of P
Lake reduction to Lake Ardmore
Ardmore for the practice lifespan
(Ibs./yr.)
($/Ibs.)
G-1
525
moderate
22.1
19,167
0.4
6.7
$218
G-2*
180
moderate
12.75
36,200
0.7
8.9
$407
G-3
750
Slight
0.4
19,500
0.7
0.3
$6,500
*Gully 2 design and maintenance costs were doubled due to multiple gullies anticipated on site.
Figure 10R: Location of proposed gully stabilization projects
Gully Projects
Ardmore Watershed - Hennepin County, Minnesota
Gully Projects
QArdmore Watershed Boundary
2015Aerial Imagery
Hennepin
Ardmore Area Subwatershed Stormwater Retrofit Analysis
51
Figure 11R: Photo of Baker Park Reserve Gully East of CSAH 19
Ardmore Area Subwatershed Stormwater Retrofit Analysis
52
Livestock best management practices
The subwatershed to Lake Ardmore has four (4) known livestock facilities. Three are horse facilities, and one is beef.
The total estimated animal units in the subwatershed is 40.5 at the time of this analysis.
This report is primarily concerned about the protections necessary to prevent nutrients from entering the stream
system leading into Lake Ardmore. Because each livestock facility is unique and analysis of the requirements, needs
and desires of each producer or landowner cannot begin to be examined without a complete and detailed facility study
with the owner, this study generalizes many aspects of the individual sites identified as livestock production sites in the
report. On site investigations are necessary before specific projects can move forward. Individual management and
structural practices observed by site observations and aerial photo reviews are used in the report analysis and
assumptions. Final analysis must be done in cooperation with the producer. Various models are used in our study to
determine the Watershed and Lake Ardmore nutrient loads. Elm Creek Watershed Management Commission
phosphorus loads based on land use, RUSLE2, and BWSR water pollution calculator are used in this report for livestock
facilities, depending on the site, individual observations, topography and aerial photo analysis.
This report assumes non -production livestock facilities (i.e. horses) do not have a managed manure storage or disposal
system, which may not be the case in some instances. Storage is primarily stacking onsite on the ground with no
protections. Disposal is on an opportunity, not organized/planned type of basis. This report further assumes the one
beef production facility has a managed, short term (1 or 2 month) storage and disposal system. It further assumes
manure, crop and land nutrient needs are analyzed infrequently (every 4 or more years). Again, these assumptions
may not be accurate in this instance.
Phosphorus reductions practices used to evaluate and rank cost/benefits for livestock and horse facilities within the
Ardmore Watershed are as follows:
• Exclusion Fencings
• Manure Storage Facilities
• Pasture Management
• Channel and Gully Erosion Controls (see waterway and gully sections)
• Nutrient Management Plans
Phosphorus Delivery Ratio
Depending on the distance between the buffer strip and the protected target resource, some of the phosphorus
reduction benefit may be diminished. All the vegetated buffers were further analyzed to determine the reduction of
phosphorus that would reach Lake Ardmore. This reduction is the Phosphorus Delivery Ratio (PDR) of the vegetated
buffer strip. Therefore, the phosphorus load that actually reaches Lake Ardmore was estimated by multiplying
phosphorus reduction at the field edge and PDR. The PDR was estimated for each site by considering the location and
distance of the buffer strip with respect to Lake Ardmore, flow restrictions, aerial photographs, topography and the
type of nutrient available for transport (soluble versus particulate). Each buffer site was assigned a PDR from 0.1 to
1.0, with 0.1 having a lowest delivery ratio (10% from the field edge) and 1.0 having the highest delivery ratio (100%
from the field edge) to Lake Ardmore.
A brief description of the livestock practices used in this report are as follows;
Livestock Exclusion (or access control): The temporary or permanent exclusion of livestock from a designated area —
often to protect streambanks, wetlands, woods, cropland, wildlife habitat or conservation buffers. (continued)
Ardmore Area Subwatershed Stormwater Retrofit Analysis 53
In this analysis, livestock exclusion is closely associated with wetland and
stream corridor protection from the water quality impacts related to the
waste produced by the animal. Eliminating that waste source by exclusion
fencing will eliminate the transport of that source into the Lake Ardmore
system.
Livestock exclusion can be a component of many conservation practices,
especially wetland and streambank protection, stream habitat improvement,
rotational grazing, and riparian buffers including grass filter strips and
forested riparian buffers.
Figure 12R: Photo of
livestock exclusion
Phosphorus reductions
This report assumes a standard phosphorus coefficient load of 2 lbs. per acre per year from pasture areas. This is
based on standard export models for phosphorus loads from uncontrolled pasture areas.
Costs of exclusion fencing
Instillation costs for fencing was assumed at $3.00 per linear foot (adjusted from 2012 MN Dept. of Ag BMP
Handbook). Maintenance costs were assumed at $0.30 per foot per year. Design and oversight was assumed at $75
per hour.
Manure storage facilities
Manure storage is any properly designed and installed pit, lagoon or above -ground structure that safely holds
manure from livestock production. Manure storage is a key component of manure management, nutrient
management and feedlot runoff management. For barns housing 15 or more animal units (1000 lbs. livestock weight
= 1 animal unit) manure volume increases substantially. Facility design and construction costs can be significant, but
can save labor and costs in the long term. The principles are similar to smaller facilities, but access to larger
equipment, sturdier designs and impervious footings are critical.
For the two larger facilities in the watershed, the storage facilities used in this analysis were above ground concrete
containment systems. They take into account:
• 6 months (or more) of storage
• Easy equipment access
• Ease of collection
• Prevent surface water, spring melt and storm water from running into the pile
• Durable floor material
• Convenient location from the barn
For the two smaller facilities this report used composting as the primary practice to store and dispose of the horse
waste and bedding. Livestock site B was designed as a smaller compost storage facility (2 bins 8'x8'x3' for 2 horses).
Livestock site C was designed with a larger compost facility (4 bins 8'x8'x3' for 6 horses).
Figure 13R: Photo
of aboveground
concrete storage
system for horse
waste
Ardmore Area Subwatershed Stormwater Retrofit Analysis 54
Phosphorus reductions from manure storage facilities
As a component of a properly designed nutrient and storage management plan and system where the manure was
utilized on cropland this report used an average savings of 0.25 lbs./yr./ac of phosphorus reduction. These rates were
based on average mean phosphorus reduction results cited from the University of Wisconsin Discover Farm Program in
cooperation with the Department of Interior USGS. These reductions can vary from 0.20 lbs. per acre to 6.0 lbs. per
acre. Where compost bins were analyzed, a savings of 1 lbs. of phosphorus per horse was assumed based on the same
studies.
Costs used for manure storage facilities
Construction of an above ground concrete facility was assumed at $7.50 per cubic foot of storage. Maintenance for
the facility was assumed at $0.01 per year per cubic foot of storage. Design and oversight was assumed at a set cost of
$5,000 per facility. Cost assumptions for compost storage facility:
Compost bin material and construction costs $5,000
Yearly compost bin maintenance cost ($250) $2,500
Design and oversight = 5 hours at $75/hour $ 375
Total $7,875
Pasture management
Pasture management, also called rotational grazing, prescribed or managed
grazing, is a management -intensive system of raising livestock on
subdivided pastures called paddocks. Livestock are regularly rotated to
fresh paddocks at the right time to prevent overgrazing and optimize grass
growth. A rotational grazing system is an alternative to continuous grazing
in which a one -pasture system is used that allows livestock unrestricted
access to the entire pasture throughout the grazing season.
Animal rotations can vary from a simple rotational grazing system in which Figure 14R: Photo of mixed
animals move or rotate to a fresh paddock every 3 to 6 days, to an pasture seeding of red clover and
intensive rotational grazing system in which animals are moved to a fresh grass
paddock as frequently as every 12 hours. Grazing is started when forage is
about 8 inches tall and stopped once it is grazed down to about 4 inches
tall (depending on vegetation type). This means less need to feed hay, silage or grain. The primary benefit of rotational
grazing to the producer is a more efficient and productive pasture allowing for increased carrying capacity, longer stays
on pasture, resulting in less need to feed hay, silage or grain.
Phosphorus reductions from pasture management.
Pasture management doubles as a system of perennial grassland management, providing exceptional erosion and
runoff control on uplands as well as stream corridors. It offers a productive alternative for marginal, erosion -prone or
flood -prone cropland and other environmentally sensitive land, including overgrazed pastures. Rotational grazing also
provides built-in manure management. Manure on healthy, well -managed grassland decomposes into the soil rather
than running off. Rotating livestock from paddock to paddock allows time for manure to be incorporated into the soil.
The manure helps maintain soil fertility for new grass growth, eliminating the need to store, process, haul or spread
manure as a nutrient. As with other pasture and nutrient management practices, phosphorus reduction for proper
pasture and paddock management is assumed to be 0.25 lbs/year/acre. This is based on average mean phosphorus
reduction results cited from the University of Wisconsin Discover Farm Program in cooperation with the Department of
Interior USGS. These reductions can vary from 0.20 lbs. per acre to 6.0 lbs. per acre.
Costs of pasture management
Rotational grazing costs are low in comparison to other agricultural production practices. Pasture management costs
do not typically entail taking land out of production. Costs for fencing and water systems can be higher than with
continuous grazing and tend to increase with increased intensity of the grazing system. For this report we used a cost
of $200 per acre to design and establish the system. This assumed minimal fence and equipment needs.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 55
Nutrient management
Nutrient management is the management of the amount, method, and timing of applications of fertilizers, ma-
nure, and other soil amendments. The nutrients that have the greatest impact on water quality are nitrogen
(N) and phosphorus (P). Among all BMPs, nutrient management BMPs are one of the most effective ways to
improve water quality because of the extent of nutrient related water quality issue. Nutrient management can
be divided into three management areas: amount, method and timing.
Phosphorus reductions from nutrient management
As part of a nutrient management system, proper manure application annually or less frequently is known to
reduce soil erosion and amount of runoff from the field. At several locations in Minnesota, Iowa, and Wiscon-
sin where manure was applied annually on agricultural fields, runoff was reduced 2% to 62%, and soil erosion
was decreased 15% to 65 % compared to the sites without manure application. Again, this report assumed
proper nutrient management reduces phosphorus loads 0.25 lbs./year/acre. This is based on average mean
phosphorus reduction results cited from the University of Wisconsin Discover Farm Program in cooperation
with the Department of Interior USGS. These reductions can vary from 0.20 lbs. per acre to 6.0 lbs. per acre.
Cost for nutrient management
The cost of nutrient management consists of soil sampling and testing for nutrient availability, as well as calcu-
lation of fertilizer and/or manure need based on information such as soil productivity, crop nutrient budgeting,
and recent proven yields. This report assumed the cost of a crop consultant would be $20/acre per year for
the first two years to get the plan established, and $10/ac reper year thereafter to operate and maintain the
plan. The total cost per acre for a 10 year period would be $120.
Individual Lake Ardmore Watershed Livestock Site analysis
and nutrient export assumptions
Horse Facility A
This livestock facility is unique, and analysis of the requirements, needs and desires of this site cannot begin to
be examined without a complete and detailed facility study with the owner. The following analysis generalizes
many aspects of this site. A final analysis must be done in cooperation with the producer to better understand
the existing conditions and needs of this facility.
Site A existing conditions
This site appears to have approximately 25 horses (25 animal units) with 16 moderately vegetated pasture/
paddock areas on 10 acres. Various sparsely vegetated small paddocks and the outdoor arena on this facility
cover about 1.5 acres of the site. Manure appears to be stored northwest of the outdoor arena near a barn in
a fenced in, open air location approximately 35'x 25'x 3.5' high open on the north end. Based on aerial photos,
the bedding/manure storage area appears somewhat contained. It is unknown how the material is disposed
from this storage area.
The barn, arena and paddock areas do not appear to have adequate runoff control measures to prevent water
from running uncontrolled over the steeper slope north and east of the buildings. The lack of water controls,
channelization of the water and the steepness of the slope are the primary reasons for the gullying issues on
this slope area. The pasture and paddock areas appear to be somewhat overgrazed, creating the opportunity
for excess runoff on these areas. One channelized area runs uncontrolled through portions of four paddocks.
Approximately 1.0 acre of the three easterly most paddocks are located in the wetland basin that flows into
Lake Ardmore.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 56
Site A proposed conditions
• Roof gutters to control and redirect clean water away from contamination sources (un-vegetated surfaces and
areas where horses or manure are located).
• A waterway with exclusion fencing is proposed through the southerly area of the paddock to channelize the water
in a controlled manner creating the opportunity for it to be filtered in the grass waterway
• Stabilizing the steep gully and washing areas on the slopes below the farmstead area was addressed in the gully
section for site G2
• Exclusion fencing to prevent the horses from entering the wetland and buffer area along the easterly paddocks.
• A 35 foot buffer area above the wetland on the easterly paddocks
• Pasture and paddock management plans to maximize the pasture potential for grazing and minimizing runoff
potential
• Manure storage and disposal
Site A exclusion fencing
Two primary areas of livestock exclusion fencing are proposed on this site.
• Wetland/Buffer exclusion along the easterly paddock area (900 feet of fence)
• Waterway exclusion for the channel that runs from west to east through the southerly paddocks (1250 feet of
fence)
Construcfion costs for fencing
ExFn A-1 $3.00/ft. wetland/buffer fence (900 feet) $2,700
ExFn A-2 $3.00/ft. waterway fence (1250 feet) $3,750
Maintenance costs
ExFn A-1= $0.30/ft./yr. (900 ft.) over 10 years. $2,700
ExFn A-2=$0.30/ft./yr. (1250 ft.) over 10 years $3,750
Design and oversight
ExFn A-1= 5 hours at $75/hr. $375
ExFn A-2= 5 hours at $75/hr. $375
Total cost
ExFn A-1 = $5,775
ExFn A-2 = $7,875
Phosphorus reductions for exclusion fencing
Assume a standard phosphorus coefficient load of 2 lbs. per acre per year export in the wetland area, 6 lbs. per acre in
the waterway area, and a 100% delivery ratio for this site.
• Site ExFn A-1= 1.0 acre of wetland is proposed for exclusion. = 2.0 lbs. of phosphorus.
• Site ExFn A-2=0.3 acres of waterway exclusion = 1.8 lbs./year
With a 100% delivery ratio the amount of phosphorus reduction to Lake Ardmore would be:
• 2.0 lbs./yr. for site ExFn A-1
• 1.8 lbs./yr. for site ExFn A-2
Cost per lb. of reduction for exclusion fencing is:
• Site ExFn A-1 = $5,775/20 = $289/Ib.
• Site ExFn A-2 = $7,875/18 = $438/Ib.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 57
Site A wetland buffer
Specifics for the costs and phosphorus reductions from the wetland buffer for this site (see buffer #5 on page 14) are
described in the buffer section. It is proposed to be 0.72 acres in size and filter out approximately 6.3 lbs./year phos-
phorus from the contributing watershed area (5.6 acres) for a cost of $192/Ib. over a 10 year period.
Site A pasture and paddock management
600 feet of waterway with drain file to control and filter the channelized water through the site (this was evaluated
as project GW A-1 and ExFn A-1)
10 acres of pasture and paddock management plan.
Construction costs for pasture and paddock management
$200/ac for pasture/paddock management plan $2,000
$20/ac per year for maintenance $2,000
Design and oversight, pasture mgmt.10 hr.@ $75/hr. $750
Total Cost = $4,750
Phosphorus reduction for proper pasture and paddock management is assumed to be 0.25 lbs./year/acre. This is
based on average mean phosphorus reduction results cited from the University of Wisconsin Discover Farm Program
in cooperation with the Department of Interior USGS. These reductions can vary from 0.20 lbs. per acre to 6.0 lbs.
per acre. With this site assumed to be 100% delivery to Lake Ardmore, the total phosphorus reduction would be 2.5
lbs./year.
The costs/benefits for phosphorus reductions from the waterway/tile system were determined in the exclusion fenc-
ing section of this site analysis. Cost per pound for pasture management with a constructed waterway and drain file
would be $4,750/25= $190/Ib. of phosphorus reduction.
Site A grassed waterway
Specifics for the costs from the grassed waterway for this site (see waterway GW-A1 on page 45) are described in the
waterway section. The waterway is proposed to be 600 feet long by approximately 25 feet wide. A specific cost per
pound of phosphorus reduced was not analyzed for the waterway. This was based on the fact if exclusion fencing as
described for Ex Fn A-2 was established, and this fencing contained the waterway flows, the phosphorus reduction
could be achieved without a waterway constructed. A waterway was provided as a BMP for this site because a con-
structed waterway would better contain the flows, and the instillation of drain file would assist in drying the saturat-
ed surfaces adjacent to the waterway establishing a better pasture/paddock environment for the horses and general
maintenance in the vicinity.
Site A manure storage and disposal
A designed manure and disposal system for a 6 month period will be analyzed for this site. Twenty five horses with
bedding material stored for 6 months will be approximately 6,000 cubic feet of storage. Construction costs for stor-
age system are as follows:
6000 cubic foot concrete storage facility $45,000
10 year maintenance at $0.01 c.f. $600
Design and oversight $5,000
Total Cost $50,600
Phosphorus reductions for proper manure storage and disposal was not calculated for this facility. Too many varia-
bles are associated with this site to make a determination. If the current facility currently hauls the manure off site,
the phosphorus advantage would be negligible. If not, it could be significant.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 58
Site A clean water diversion
Based on past site visits from other resource experts, various areas of the farmstead were reported to have flows from
roof and high traffic areas creating erosive and uncontrolled flows into the steeper slopes along the east and north
sides of the farmstead. This in turn has helped exasperate the gully conditions addressed on page 47 (Gully G2).
Additional costs associated with diverting and controlling this water should be mentioned as part of the overall costs
on this facility to adhere to good housekeeping BMPs and water controls over the long run. Phosphorus reductions will
not be a component of this BMP. It is addressed in a compilation of all the other BMPs on this site. Costs for a clean
water diversion were estimated taking into account roof gutters for the buildings near the slope, manure storage area
and a berm/diversion to direct water from the farmstead area to the gully. The roof gutters would total approximately
270 feet. The berm/diversion would also be approximately 270 feet.
Costs for clean water diversions:
Roof Gutters (270 feet)
$10/ft. for gutter and downspouts $2,700
Oversight/maintenance (lump sum)= $500
Berm/diversion (270 feet)
$10/ft construction $2,700
Oversight and design (10 hrs. @ $75/hr.) $ 750
Maintenance $0.25/ft./yr. $675
Total Clean Water Diversion Costs = $7,325
Horse Facility B
This site appears to have 2 horses with two pasture areas approximately 2 acres in size and a small outdoor horse
arena approximately 0.2 acres in size. Paddock and pasture areas appear well vegetated, outside of wetland areas
with no excessive erosion or uncontrolled runoff issues. Based on previous site visits, this site is well maintained.
Wetland areas appear to be fenced off adequately. Some minor benefits from manure storage and disposal could
occur. This analysis made a general assumption of 2.0 Ibs/year reduction of phosphorus to Lake Ardmore if proper
storage and disposal of manure and good housekeeping practices were followed. To achieve that assumption, a
manure compost facility was analyzed for the cost/benefit. The phosphorus delivery ratio to Lake Ardmore was
estimated at 50% from this site
Please remember, this livestock facility is unique, and analysis of the requirements, needs and desires of this site
cannot begin to be examined without a complete and detailed facility study with the owner. The following analysis
generalizes many aspects of this site. A final analysis must be done in cooperation with the producer to better
understand the existing conditions and needs of this facility.
Site B manure storage and disposal
A manure compost facility was analyzed for this site because there is less than 3 horses located here.
Construction Costs
Compost bin material and construction costs = $5,000
Yearly compost bin maintenance cost ($250) $2,500
Design and oversight costs (5 hours @ $75/hr.) $375
Total = $7,875
Phosphorus reductions from this storage facility were assumed at 2.0 Ibs./year based on proper storage and disposal of
the manure/compost. The site was estimated to have a phosphorus delivery ratio to Lake Ardmore of 0.5.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 59
Horse Facility C
This site appears to have 6 horses with two pasture areas approximately 9 acres is size. The pasture appears to be well
vegetated. Wetland areas appear to be fenced off adequately. Runoff has created an erosion problem through the
main paddock/feedlot section of the facility. This was addressed in the gully section of the report. Additional storage
and disposal alternatives were explored on this site and analyzed in this section. Some clean water diversion of roof
water was analyzed for this site. Removing this water from the feedlot area will eliminate runoff from the high use ar-
ea and decrease mud issues.
Again remember, this livestock facility is unique, and analysis of the requirements, needs and desires of this site cannot
begin to be examined without a complete and detailed facility study with the owner. The following analysis generalizes
many aspects of this site. A final analysis must be done in cooperation with the producer to better understand the ex-
isting conditions and needs of this facility
Site C manure storage and disposal
A larger manure compost facility was analyzed for this facility because there is 6 horses on this site.
Construction costs
Compost bin material and construction $10,000
Yearly compost bin maintenance ($400) $4,000
Design and oversight (5 hours @ $75/hr.) $375
Total = $14,375
Phosphorus reductions were based on standard models for uncontrolled vs controlled storage and disposal techniques
for livestock systems. For 6 horses, assume 6 lbs. less phosphorus entering the Lake Ardmore drainage system. This
site has an estimated phosphorus delivery ratio of 0.4.
Site C grassed diversion/waterway/clean water diversion livestock
These items are all a component of controlling water from running through the high use area on this site. Barn roof
gutters and a grassed diversion/waterway to route clean water away from and around the feedlot area will reduce sed-
iment and phosphorus loads from entering the Lake Ardmore drainage system. The grassed diversion and waterway
was analyzed under the gully section of this report (see Gully Stabilization G-1).
The diversion/waterway was measured at 525 feet and would cost approximately $19,167. With a phosphorus delivery
ratio of 0.4 this conservation system would reduce nutrient load to Lake Ardmore by 6.7 lbs./year. Costs for roof
gutters for the buildings near the high use feedlot area were also analyzed as part of the overall best management
practices recommended for the site. These gutters would direct clean water away from the high use areas, keeping the
roof water relatively clean and uncontaminated with the soil and manure in the feedlot. The roof gutters would total
approximately 350 feet.
Costs for 350 ft. of roof gutters (clean water diversion)
$10/ft. for gutter and downspouts $3,500
Oversight and maintenance (lump sum) $ 500
Total = $4,000
Ardmore Area Subwatershed Stormwater Retrofit Analysis 60
Livestock Facility D
This livestock facility is unique, and analysis of the requirements, needs and desires of this site cannot begin to be ex-
amined without a complete and detailed facility study with the owner. The following analysis generalizes many aspects
of this site. A final analysis must be done in cooperation with the producer to better understand the existing conditions
and needs of this facility.
Site D existing conditions
This facility has approximately 15 beef cattle. The feedlot (denuded of vegetation) area is 0.25 acre in size. An area of
'high use' pasture with poor vegetation establishment is 1.5 acres. There is approximately 3 acres of lower use, moder-
ately vegetated pasture on site. This moderately used pasture has about 1.5 acres of wetland in it.
Site D proposed conditions
• Long term storage is necessary for manure collection and distribution from the site. This would assist in the plan-
ning and timing needed for a nutrient management plan for this facility.
• Exclusion fencing to prevent the cattle from entering the wetland and buffer areas.
• Nutrient Management Plan
Site D storage and nutrient management
For this beef production facility we assumed an average of 0.25 lbs. of phosphorus reduction per acre of cropland/
paddock/feedlot area, if proper long term handling and managed disposal of livestock waste is accomplished based on
a cropland and manure nutrient management. This is based on average mean phosphorus reduction results cited from
the University of Wisconsin Discover Farm Program in cooperation with the Department of Interior USGS. These reduc-
tions can vary from 0.20 lbs. per acre to 6.0 lbs. per acre. Storage and nutrient management costs are as follows:
10-15 animal units (15 beef cattle @ 750 lbs./beef)
Construction costs for storage system (6 months)
4,000 cubic foot concrete storage facility $30,000
10 year maintenance at $0.01 c.f. $400
Design and oversight $5,000
Total = $35,400
Assume for 35 acres of crop land on this parcel, soil GPS and grid samples/applications and manure sampling
and applications for nutrient management plan costs
Crop consultant charge ($20/ac) $700/year for years 1-2 $1,400
($10/ac) $350/year for year 3-10 $2,800
Total = $4,200
Site D phosphorus reductions from manure and nutrient management
• Average soil loss in fields where manure is spread is 2.4 to 3.2 ton/year
• Delivery ratio will vary, but use 0.5 as an average
• Soil loss will not generally decrease, but phosphorus export will, based on the assumption soil p is > 21 ppm Bray
P1 or 16 ppm Olson. Assume reductions comparable to 0.25 Ib./ac on 35 acres=8.75 lbs./year. This is assumed to
be soluble. With a delivery ratio of 0.5, actual reduction will be 4.4 lbs./year.
• Nutrient management reduction will be 4.4 lbs./year for a cost of $4,200/44=$95.50 per pound of phosphorus re-
duction.
• Storage system phosphorus benefits were not analyzed as part of this report. To prevent winter spreading of ma-
nure and adequately prevent spring runoff in the cropland, a storage system is essential.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 61
Site D Exclusion Fencing (ExFn-D1)
Livestock Exclusion costs= 1100 feet of fencing
Construction costs =1,100 ft. at $2.50/ft. $2,750
Maintenance costs= 1100 ft. at $0.25/ft./yr. $2,750
Design and oversight= 5 hours at $75/hr. $375
Total cost = $5,875
• Assume a standard phosphorus coefficient load of 2 lbs. per acre per year export and a 50% delivery ratio (1 lblac/
yr.)
• 2.3 acres of pasture/wetland excluded would be 2.3 lbs. of phosphorus reduction to Lake Ardmore
• Cost per lb. of reduction is $5,875/23 = $256/Ib.
Site D wetland buffer
Specifics for the costs and phosphorus reductions from the wetland buffer for this site (see buffer #3 on page 43) are
described in the buffer section. It is proposed to be 0.73 acres in size and filter out approximately 5.1 lbs./year
phosphorus from the contributing watershed area (8.4 acres) for a cost of $239/Ib. over a 10 year period.
Table 7R: Phosphorous reduction to Lake Ardmore and associated costs of proposed
livestock projects
Project
rank
Retrofit type
(refer to
catchment profile
p
pages for
additional detail)
Projects
identified
TP
reduction
(Ib/yr)
phosphorus
delivery
ratio to Lake
Ardmore
Phosphorus
reduction to
Lake
Ardmore
(Ib/yr)
Total
project cost
10-year
maintenance)
Estimated cost/lb-
TP/year (10 year)
1
Nutrient
Management
System
Lvst D
8.8
0.5
4.4
$4,200
$96
2
Pasture &
Paddock
Management
Lvst A
2.5
1.0
2.5
$4,750
$190
3
Field Buffer
FB-Ajlvst
6.3
1.0
6.3
$12,098
$192
4
Gully Stabilization
G-1 (list
C)
22.1
0.4
6.7
$19,165
$218
5
Field Buffer
FB-3Djlvst
12.7
0.4
5.1
$12469
$239
6
Exclusion Fencing
EsFn D-1
(lust D)
4.6
0.5
2.3
$5,875
$255
7
Exclusion Fencing
ExFn A-1
(lust A)
2.0
1.0
2.0
$5,775
$289
8
Gully Stabilization
G-2 (list
A)
12.8
0.7
8.9
$36,200
$407
9
Exclusion Fencing
ExFn A-2
(lust A)
1.8
1.0
1.8
$7,875
$438
10
Grass Waterway
GW-A1
(list A)
1.8
1.0
1.8
$9,180
$510
11
Manure Storage
System
Lvst C
6.0
0.4
2.4
$14,375
$599
Ardmore Area Subwatershed Stormwater Retrofit Analysis
62
Table 7R: Phosphorous reduction to Lake Ardmore and associated costs of proposed
livestock projects (continued)
Retrofit type
Project Projects
rank (refer to identified
catchment profile
pages for
additional detail)
TP
reduction
(lb./yr.)
Phosphorus
delivery
ratio to Lake
Ardmore
Phosphorus
reduction to
Lake
Ardmore
(Ib./yr.)
Total
project cost
(includes
10-yea r
maintenance)
Estimated cost/Ib.-
TP/year(10 year)
12
13
14
15
16
Manure Storage
System
Manure Storage
System
Clean Water
Diversion
Clean Water
Diversion (roof
gutters)
Manure Storage
System
Lvst B
Lvst A
Lvst A
Lvst C
Lvst D
2.0
0.5
1.0
$7,875
$66,200
$7,325
$4,000
$35,400
$788
N/A
N/A
N/A
N/A
Figure 15R: Location of proposed livestock management BMP projects
Livestock Management Projects & Best Management Practices
Ardmore Watershed - Hennepin County, Minnesota
Hennepin
G Livestock Management Projects
QArdmore Watershed Boundary
2015 Aerial Imagery
500 000
Watershed Location Map
2.000 3.0,00
� Feet
Ardmore Area Subwatershed Stormwater Retrofit Analysis
63
Wetland restoration and new pond construction
This report looks for opportunities to reestablish or repair the hydrology, plants and soils of a former or degraded
wetland that has been drained, farmed or modified. The goal is to closely approximate the original wetland's natural
condition, resulting in multiple environmental benefits, but primarily to store additional water and assimilate nutrients.
This section also looks at new, regional pond opportunities that would maximize nutrient load reductions within this
watershed. One new pond was analyzed for these reductions within this watershed. The primary technique to analyze
the benefits of wetland and new pond projects is the PondNet model. Three wetland restoration opportunities and
one new pond opportunity were analyzed in this study.
•4..a• a� aa. •• aa�a ate. �y y+ •,
a ' A Tile Break •' —
Water Level Contra
1� C Structure Location',
• n
Functioning Tile
r ,
Non -Functioning Tat
Wetland Restoration
Figure 16R: Drained wetland restoration concept
Wetland Restoration 1 is located in the far NW corner of the Lake Ardmore Watershed. It straddles two properties.
This basin is a natural depressional area but has a functioning drain file that essentially drains all the water after a
storm event. The north portion (approximately 0.2 acres) of the basin is farmed. The south portion (approximately 1.7
acres) is grasses and shrubs. Restoration would entail disabling the existing drain file and installing an outlet control
structure at an elevation of somewhere between 978.0 + and 980.0+.
Wetland Restorations 2W and 2E are existing landlocked wetland basins that are drained with private, pipe outlets.
Wetland area 2W drains east, via 7"+ pipe into wetland area 2E. Wetland 2E drains south via 12" pipe into the Hidden
Lake Wetland Basin. Both basin restorations could be accomplished by disabling the pipes and installing outlet control
structures that would regulate the wetlands to their pre -settlement historic elevations. Wetland 2W would be raised
approximately 2 feet to 986.0 and wetland 2E would be raised 3 feet to approximately the same elevation as wetland
2W. These higher water levels will have an effect on the property located east of County Road 19. The culvert into this
property under CSAH 19 is at an approximate elevation of 985.0.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 64
Wetland restoration cost, phosphorus and volume assumptions are as follows:
Wetland Restoration 1 (WR1)
Treatment watershed = 19.75 acres
Wetland surface area = 1.8 ac.
Wetland depth = 2.5 feet @ 978.0
Wetland pool volume = 4.5 ac. ft.
Structure type = box weir
Total Phosphorus (before) = 6.4 pounds
Total Phosphorus (after) = 3.2
Phosphorus reduction = 3.2 lbs./year
Delivery Ratio = 0.10 x 3.2 = 0.32 lbs./year
Cost for 20 year lifespan
Construction and vegetation restoration cost $13,500 ($7,500/ac)
Easement Cost $ 10,250 ($30,000 ac. cropland, $2,500/ac existing wetland)
Design and administration $10,000
Maintenance $10,000 over 20 years
Total cost = $43,750
Total cost per pound of phosphorus reduction to Lake Ardmore = $6,836/Ib.
Wetland Restoration 2W (WR2W)
Treatment Watershed = 50 acres.
Wetland surface area = 18.6 acres.
Wetland pool volume = 74 acre feet
Structure type = box weir
Total Phosphorus (before) = 20.7 lbs./year
Total Phosphorus (after) = 15.7 lbs./year
Phosphorus reduction = 5.0 lbs./year
Delivery ratio = 0.40 x 5.0 = 2.0 lbs./year
Cost for 20 year lifespan
Vegetation restoration cost $20,000 ($5,000/ac on 4 acres of expanded areas )
Construction $10,000 (structure and pipe)
Easement Cost $156,500 ($30,000 ac. cropland, $2,500/ac existing wetland)
Design and administration. $20,000
Maintenance $20,000 over 20 years
Total cost = $226,500
Total cost per pound of phosphorus reduction to Lake Ardmore = $5,663/Ib.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 65
Wetland Restoration 2E (WR2E)
Treatment Watershed = 117.8 acres
Wetland surface area = 5.5 acres.
Wetland pool volume = 13.75 acre feet
Structure type = Outlet control structure
Total Phosphorus (before) = 78.0 lbs./year
Total Phosphorus (after) =47.2 lbs./year
Phosphorus Reduction = 30.8 Ibs/year.at wetland
Phosphorus Delivery Ratio = 0.4 (30.8x0.4=12.3 lbs./yr. to Lake Ardmore)
Cost for 20 year lifespan
Vegetation restoration cost
Construction costs
Easement Cost
$8,750 ($2,500/ac on 3.5 acres of expanded area)
$33,125 (925 ft. of 12" pipe @25/ft. and $10,000 for outlet structures)
$122,500 ($30,000 ac. -cropland 3.5 ac, $2,500/ac existing wetland 7.0
ac.-2 ac on west side of CSAH19 and 5 ac. on east)
Design and administration. $20,000
Maintenance $20,000 over 20 years
Total cost = $204,375
Total cost per pound of phosphorus reduction to Lake Ardmore = $831/Ib.
Wetland Restoration 3
Treatment watershed = 472 acres
Wetland surface area = 16.1 acres
Wetland pool volume = 70.6 acre feet
Structure type = Outlet control structure
Total phosphorus (before) = 391 lbs.
Total phosphorus (after) = 343 lbs.
Phosphorus delivery Ratio = 1.0
Phosphorus Reduction to Lake Ardmore = 48 lbs./yr.
Cost for 20 year lifespan
Construction costs
Structure $25,000
Roadway $120,000
Easement Cost $132,500 (17 ac. X $2,500 = 3 ac. X $30,000)
Design and administration. $58,500
Wetland restoration costs $20,000
(seed, 5 year intense maintenance)
Maintenance
Roadway (20 years) $25,000
Wetland (20 years) $5,000
Total cost = $386,000
Total cost per pound of phosphorus reduction to Lake Ardmore = $402
Ardmore Area Subwatershed Stormwater Retrofit Analysis 66
Regional Ponds
One new pond was pursued in this study. It would be located
adjacent to the existing wetland area where wetland 2E exists.
The wetland itself receives water from a 117.8 acre
watershed. The wetland would remain the same as it is today,
but instead of flowing into the existing 12" pipe that routes it
untreated into the Lake Ardmore drainage way, it would
overflow into a newly constructed pond. This new pond would
treat the phosphorus build up that has accumulated in the
wetland throughout the years. Based on NURP analysis, it
would decrease phosphorus loads similar to the wetland
restoration option shown above, at approximately the same
price. The operation and maintenance of a pond like this
would be advantageous to the city over a wetland restoration
because of ease and access to it.
Regional Pond 1 (RP-1) adjacent to existing wetland 2E.
Treatment Watershed = 117.8 acres
Pond surface area = 2.0 acres.
Pond pool volume = 8 acre feet
Structure type = Outlet control structure
Total Phosphorus (before) = 78.0 lbs./year
Total Phosphorus (after) =47.1 lbs./year
Phosphorus Reduction = 30.9 lbs./year.
Phosphorus Delivery Ratio = 0.4 (30.9x0.4=12.4 lbs./yr.
to Lake Ardmore)
Figure 17R: Photo of constructed
stormwater pond
4kitilh,
Treatment volume
•
• +•.. . •
•• •••. •*AI •••••
voiti•
gskoetzli
Permanent pool •
•
Weir
Small pipe
or opening
-4— Sediments
Figure 18R: Stormwater treatment pond
section
Cost for 20 year lifespan
Vegetation restoration cost and erosion control (lump sum)
Construction costs
Pipe and structure
Excavation
Wetland rip -rap overflow to NURP pond
Easement Cost
Design and administration
Maintenance
Total cost
$5,000
$103,125
$33,125 (925 feet of 12" pipe @25/ft. and
$10,000 for outlet control structures)
$65,000 (13,000 cu. yd. @ $5 cu. yd. assuming
on site disposal)
$5,000 (50 cu. yd. @ $100/CY= $5,000)
$65,000 ($30,000 ac. -cropland 2.0 ac, $2,500/
ac existing wetland 2.0 ac.)
$20,000
$20,000 over 20 years
$208,125
Total cost per pound of phosphorus reduction to Lake Ardmore = $846/Ib.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 67
Table 8: Phosphorous reduction to Lake Ardmore and associated costs of proposed
wetland restoration and regional pond projects
Wetland
restoratio
n and
regional
ponding
Total area of
wetland or
pond
Average
pool
elevation
an depth
Structure
Volume of Phosphorus Phosphorus
storage (ac. ft.) reduction delivery ratio
Pounds of
phosphorus
reduced going
to Lake
Ardmore per
year
Cost per
pound of
phosphorus
reduction to
Lake Ardmore
for a 20 year
lifespan
WR-2E
5.5
986.0/2.5
Structure
13.75
30.8
0.4
12.3
$831
RP-1
2.0
982.0/4.0
Structure
8.0
30.9
0.4
12.4
$846
WR-2W
18.6
986.0/4.0
Box weir
74.0
5.0
0.4
2.0
$5,663
W R-1
1.8
978.0/2.5
Box weir
4.5
3.2
0.1
0.32
$6,836
W R-3
16.1
984.0/4.3
Structure
70.0
48.0
1.0
48.0
$402
Figure 19R: Location of proposed wetland restoration and regional pond
projects
Wetland Restoration & Regional Pond Projects
Ardmore Watershed - Hennepin County, Minnesota
- Drainage Reach
Regional Ponds
Wetland Restoration Projects
QArdmore Watershed Boundary
2015 Aerial I magery
Nennepi�n'-'O11namsey
=IP
Dakota
3,000
Feet
Ardmore Area Subwatershed Stormwater Retrofit Analysis 68
Appendix
Ardmore Area Subwatershed Stormwater Retrofit Analysis 69
Figure 1: RUSLE2 field measurement locations
RUSLE2 Field Measurement Locations
Ardmore Watershed - Hennepin County, Minnesota
Hennepin
RUSLE2 Field Measurement Locations
Ardmore Watershed Boundary
EV 2015 Aerial Imagery
0 500 ' 000
Watershed Location Map
2000 3.000
I Fast
Ardmore Area Subwatershed Stormwater Retrofit Analysis 70
Modeling Methods
The following information describes each water quality model applied in this analysis and the inputs used to run the
model.
Soil and Water Assessment Tool (SWAT)
The Soil and Water Assessment Tool (SWAT) was used to model runoff from the Lake Ardmore subwatershed draining
to Lake Ardmore. SWAT is a partially physically -based and partially empirically -based watershed model (Neitsch et al.,
2005) developed at the U.S. Department of Agriculture Agricultural Research Service (SWAT is currently supported by
the Blacklands Research and Extension Center at Texas A&M University). The SWAT model runs on a daily time step
and is intended to model large agricultural watersheds. The model has been calibrated and validated to many water-
sheds in the United States and around the world
SWAT has progressed through several development releases. The release selected for this project was ArcSWAT2012
for ArcGIS version 10.1. All SWAT modeling and field assessments were conducted by Hennepin County Environment
and Energy staff during the Lake Ardmore Subwatershed Assessment. The SWAT model simulates the hydrologic cycle
accounting for the following processes: precipitation, overland runoff, infiltration, percolation through one or more soil
layers, evaporation, plant transpiration, interaction with the shallow aquifer, and loss to a deep aquifer (Arnold et al.,
1998). Water is delivered to the stream as overland runoff, lateral flow, and groundwater flow and is routed through
defined stream channels to the watershed outlet. SWAT also models off -channel, surface -water bodies such as wet-
lands and ponds and on -channel bodies such as reservoirs.
Sediment export from uplands is calculated in SWAT with the Modified Universal Soil Loss Equation (MUSLE; Williams,
1975). Factors that control sediment export predicted by the MUSLE are surface runoff, peak flow, soil erodibility, bio-
mass and residue present, cropping practices, slope length, and percentage of coarse fragments (i.e., stones) of soil.
Simulation of phosphorus and nitrogen cycles in SWAT uses inputs of inorganic fertilizer, organic fertilizer, plant resi-
due, and, for nitrogen, rainwater. Nitrogen is partitioned between five mineral and organic pools within the soil and is
transferred between and out of these pools through export, decay, mineralization, nitrification and denitrification, vo-
latilization, and plant uptake. Similarly, SWAT models five soil phosphorus pools, with transfer between and out of
these pools through export, decay, mineralization, immobilization and plant uptake. Nitrogen and phosphorus are ex-
ported via overland runoff, lateral flow, and groundwater flow to the stream channel, though they are only tracked
through overland runoff and lateral flow. In the stream reaches, in -stream nutrient processes can be simulated with
the imbedded QUAL2E submodel, or the nutrients can be delivered to the reach outlet unprocessed. Given the chan-
nelized nature of most streams and that the primary driver of nutrient dynamics throughout the Lake Ardmore subwa-
tershed is wetland processing, in -stream process subroutines were not utilized in this analysis. Plant growth is mod-
eled directly in SWAT based on simplified crop growth equations from the Erosion Productivity -Impact Calculator (EPIC)
with controlling inputs including temperature, solar radiation, nutrient availability, and water.
SWAT Spatial Inputs
Spatial inputs for the Lake Ardmore SWAT model included digital elevation, land use, and soils. All data for the Lake
Ardmore watershed were projected into the Universal Transverse Mercator Zone 15, with the North American Datum,
1983. The Lake Ardmore watershed and subbasins were delineated from the Hennepin County 2 Foot contour inter-
vals derived from the spring 2012 Minnesota DNR LIDAR digital elevation model (DEM). This delineation was updated
with water routing information from field observations. Soil Survey Geographic (SSURGO) soil data were downloaded
from the US Department of Agriculture -Natural Resources Conservation Service (USDA-NRCS) Soil Data Mart website.
These data are organized by county and are the most detailed available for the watershed. (continued)
Ardmore Area Subwatershed Stormwater Retrofit Analysis 71
The SSURGO dataset included 61 soils in the Lake Ardmore watershed. Land use input for the model was generated
from the 2014 Hennepin County parcel dataset, which includes land use as it relates to the tax code. These land uses
were updated and subdivided using 2012 high -resolution Hennepin County aerial photographs and field observations.
The resulting land use dataset was converted to a grid.
Subbasins in the Lake Ardmore subwatershed were refined using field observations and known locations of stream
channels, culverts and ponds. The final subbasin configuration included 6 subbasins ranging from 3.4 to 112 hectares.
The watershed had 484 HRUs.
Agriculture
The major land use in the Lake Ardmore watershed is fairly well divided between large lot residential/hobby farms,
woodland and wetlands. Agriculture cropland accounts for approximately 20% of the total watershed area. There are
also four farms in this study that grow corn (for grain), soybeans, alfalfa, and corn (for silage) for a mix of grain crops
and animal consumption. Hay and alfalfa are grown within the watershed for animal consumption. The number of ani-
mal units in the subwatershed was based on the results from aerial 3D high resolution photographs from 2015, 2011,
and 2008. Four parcels within the subwatershed were identified in the 2015 survey as having farm animals. Three had
horses and one had beef cattle. There were 33 horses and 15 cattle counted in the photo reviews. The specific manure
management activities of the horse and beef producer are unknown. For that reason, the HCEED did not model a ma-
nure component in this SWAT run.
Residential and Urban Land Uses
A variety of urban and residential land uses are present in the Lake Ardmore watershed. The percentage of impervious
area in each of the land uses guided how the land use type was represented in the SWAT model. Most was large lot,
rural residential with low impervious percentages.
Wetlands
Wetlands exert a large influence in the Lake Ardmore watershed, detaining water, and settling out nutrients. However,
wetland cannot be explicitly modeled in SWAT, instead, on -channel wetlands were modeled as "reservoirs" in SWAT.
Each "reservoir" was assigned to a subbasin and individually parameterized according to the normal surface area/
volume. Wetlands and ponds were parameterized with a number of days to return to the normal pool volume after
exceeding the emergency pool volume.
Calibration
Using the Curve Number method, SWAT is a daily time step model and precipitation is input as daily values. Precipita-
tion, as recorded by the cooperative observer station at Rockford, is recorded as an 8 a.m. to 8 a.m. day. Streamflow is
averaged as a midnight to midnight day.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 72
Buffer Strip Analysis
Buffer strips were analyzed using the Board of Water and Soil Resources' Pollution Reduction Calculator for Filter Strips
(www.bwsr.state.mn.us/outreach/eLINK/indes.html).
Existing conditions were modeled utilizing the USDA, NRCS Revised Universal Soil Loss Equation (RUSLE2).
Input parameters and assumptions used for the BWSR' Calculator for Filter Strips:
1. Parameters for the Filter Strip Area (Buffer);
A. Pre-existing soil loss in Filter Strip Area = 1.33 tons/acre
B. Post -construction soil loss in Filter Strip Area = 0.044 tons/acre
C. Soil type = Silt (85 Ibs/cu.ft.)
D. Buffer Width = 35 feet
E. Filter Strip Area is variable (Length of Filter Strip x 35' buffer width.
2. Parameters for Upland Runoff treatment
A. Filter strip watershed areas are variable for each site. Surface area drainage across the filter strip was
measures from two -foot (2') topographic data (LiDAR) overlaid on aerial photographs of the areas being
analyzed. Areas are measured in acres.
B. Upland Soil Loss Before treatment is based on the average soil loss within the contributing area leading to
the filter strip. Average soil loss was estimated using the USDA NRCS RUSLE2 program on all farm fields with
in the watershed. Where filter strips are located, the average soil loss from the upland surface area from
the contributing field area draining to the filter strip was used
C. Filter strip function as designed (yes or no input in the BWSR Calculator for Filter Strips) was considered yes
on all filter strips.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 73
Grassed Waterway and Gully Stabilization Analysis
The estimates for reductions in soil loss, sediment, and attached phosphorus delivery for gully stabilization and grassed
waterways are based on estimation of soil volume voided per year. The estimate assumes that once the practice is in
place, the stabilized condition controls gully erosion. Soil loss reduction from the practice is equal to soil erosion before
the project was put in place. A sediment delivery ratio (SDR) is assigned based on characteristics of flow from the gully
or waterway and is applied to estimate sediment reduction. Sediment -attached phosphorus reduction is estimated
from the sediment reduction, default phosphorus content of 1.0 lb. of phosphorus per 1 ton of soil, and a correction for
soil texture. The inputs and assumptions used for this calculator were as follows: (http://www.bwsr.state.mn.us/
practices/pollution reduction.html)
A. Soil type. (in this watershed we used silt on all sites)
B. Soil volume voided per year (cubic feet). For gullies GS1 and GS3 this report assumes a 4" deep gully in a 3
feet wide parabolic shape. For gully GS 2, we assumed 4" deep by 5 foot wide.
C. Number of years to form the gully. This report assumes a yearly occurrence.
D. Gully condition. This report assumes the gully fans out before entering the receiving water. For the
calculator the input is'non-channelized'.
E. Distance to receiving surface water (feet to main ditch or wetland) measured along the route the water
takes to get to the receiving water.
F. Presence of a filter strip before waterway instillation (in all cases there were no filter strips)
Wetland Restoration/Enhancement and Pond Excavation/Maintenance
These sites were analyzed utilizing the National Urban Runoff Program, Design Calculations for Wet Detention Ponds
developed by Wm. Walker (http://www.wwwalker.net/pdf/spwudes.pdf). This program estimates nutrient loads from
existing ponds and wetlands based on the land use (% impervious area and phosphorus concentration), watershed area
and average mean pond depth. Surface area was measured from 2012 aerial photographs. Impervious areas for agri-
culture watershed were adjusted to 25% impervious area to account for an average phosphorus load of 1.0 pounds per
acre based on average nutrient loads produced from agriculture production fields from research and the Elm Creek
WMC and Pioneer -Sarah Creek WMC water quality standards. (http://elmcreekwatershed.org/files/342.pdf) (http://
pioneersarahcreek.org/files/455.pdf) (http://www.pca.state.mn.us/index.phaview-document.html?gid=3977) (http://
www.ars.usda.gov/research/publications/publications.htm?SEQ NO 115=280936) Pre- construction average mean
depth was measured by photographic and in -field evidence of emergent vegetation or lack thereof (cattails-2 feet,
sedges-6 inches, reed canary grass- less than 6 inches, open water-3.0 feet or greater). Watershed areas varied for
each pond/wetland area but were based on LiDAR topographic delineations. Post construction average mean depth
for the NURP program input was 1.5 meters for the new pond and and For Wetland restorations/enhancements spe-
cific depths and average volumes were based on LIDAR information.. Wetlands 1 and 2E restoration was assumed with
a mean average depth of 2.5 feet after construction. Pond 2W was assumed at 4.0 feet after construction.
Livestock
We utilized a variety of programs for our analysis of soil loss and nutrient loads for the livestock section of this report.
Nutrient and storage management analysis for utilized the recent Sauk River nutrient management program and Uni-
versity of Wisconsin Discovery Farms results which showed an average reduction in phosphorus loads to the Sauk River
and other study farms of 0.25 Ibs/ac. per acre of cropland nutrient management enrolled in their program.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 74
For all pasture land nutrient assumptions for exclusion fencing, an average phosphorus load of 2.0 pounds per acre of
phosphorus export was used as the base average nutrient load produced on pasture land. This amount of load was
based on research into studies identifying nutrient loads from various sources (http://www.pca.state.mn.us/index.php/
view-document.html?gid=3977) For the waterway load reductions, we assumed a higher rate of 6.0 Ibs/ac because of
the concentrated flows that occur in this waterway.
http://www.ars.usda.gov/research/publications/publications.htm?SEQ NO 115=280936 and the loads the Pioneer -
Sarah Creek and Elm Creek Watersheds water quality standard for pasture areas. (http://elmcreekwatershed.org/
files/342.pdf) (http://pioneersarahcreek.org/files/455.pdf) (http://www.pca.state.mn.us/index.php/view-
document.html?gid=3977) (http://www.ars.usda.gov/research/publications/publications.htm?SEQ NO 115=280936)
Cropland RUSLE2
The Revised Universal Soil Loss Equation was used on all cropland within the Lake Ardmore Watershed. This in turn
was incorporated into various other models to determine before and after nutrient loads. The existing conditions
were measured using LiDAR topographic information to determine the average length and steepness of slope. The Soil
Survey for Hennepin County was used to determine the soil type in the field being analyzed.
Crop abbreviations used were c for corn, sb for soybean, sg for small grain and h for hay.
Climate location parameters for the program were from the NRCS Climate database website http://
fargo.nserl.purdue.edu/rusle2 dataweb/NRCS Climate Database.htm. Minnesota, Hennepin County averages were
used. Base crop management parameters used Climate Management Zone 4 from the NRCS Climate Database (http://
fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Program.htm). General crop management used conventional tillage
and an average 150 bushels per acre for corn. Mulch tillage and 45 bushels per acre was used for soybeans.
The following map corresponds to the preceding table that lists the field identifiers and input parameters used for each
measurement in each field.
RUSLE2 Field Measurement Locations
Ardmore Watershed - Hennepin County, Minnesota
Hennepin
ika
ik0
Field 1
RUSLE2 Field Measurement Locations
OArdmore Watershed Boundary
2015 Aerial Imagery
26 2a d" '2t
3a 3b
3h
m Field 3
Field 2 —
+. Field 4 , f
Fieltl5 �_��
Watershed Location Map
Anoka
Career
ey
Feet
Ardmore Area Subwatershed Stormwater Retrofit Analysis 75
Farm
field ID
Line ID
Length
(ft.)
Fall (ft.)
Average
slope (%)
RUSLE2
soil loss
Total field
soil loss
Soils
Average
field soil
loss
Gully
erosion
Field
acreage
Crop
rotation
1
1a
102
11
10.8
9.6
-L41D2
3.6 acres
corn continuous
3.6 ac in
wateshe
d
1b
107
6
5.6
5.5
L36A
-1c
87
10
11.5
9.2
_L41D2
-1d
87
16
18.4
20.0
44.3
L41E
11.1
2
2a
108
13
12.0
8.8
_L41D2
70 acres
c-sb
70 acres
2b
82
6
7.3
3.6
_L26B
c-sb
-2c
108
15
13.9
9.4
_L132A
c-sb
-2d
88
16
18.2
14.0
_L41C2
c-sb
-2e
108
15
13.9
11.0
_L41C2
c-sb
-2f
109
8
7.3
4.1
-L132A
c-sb
-2g
115
16
13.9
11.0
_L41D2
c-sb
-2h
95
18
18.9
15.0
_L41D2
c-sb
-2i
162
7
4.3
2.6
-L36A
c-sb
-2j
153
15
9.8
7.6
_L41D2
c-sb
-2k
152
14
9.2
6.5
_L41C2
c-sb
-21
141
13
9.2
6.3
_L41C2
c-sb
-2m
176
9
5.1
3.8
_35A
c-sb
-2n
151
9
5.9
4.1
_35A
c-sb
-20
185
16
8.6
9.0
_L41C2
c-sb
-2p
155
13
8.4
5.8
_L41C2
c-sb
-2q
125
10
8.0
5.4
_L41C2
c-sb
-2r
156
12
7.7
5.6
_L41C2
c-sb
-2s
180
12
6.7
5.0
_L41C2
c-sb
Ardmore Area Subwatershed Stormwater Retrofit Analysis
76
Farm
field ID
Line ID
Length
(ft.)
Fall (ft.)
Average
slope (%)
RUSLE2
soil loss
Total field
soil loss
Soils
Average
field soil
loss
Gully
erosion
Field
acreage
Crop
rotation
-2t
128
9
7.0
5.2
-L41C2
c-sb
2u
139
12
9.4
6.7
L41C2
c-sb
-2v
151
10
6.6
4.6
155.1
L41C2
7.1
c-sb
-2buffer
115
14
12.1
7.8
_L36A
7.8
3
3a
111
14
12.6
5.2
-L41D2
17 acres
c-csilage-w-
alf-alf-alf
17 acres
3b
80
6
7.5
4.7
-L41C2
c-csilage-w-
alf-alf-alf
-3c
98
6
6,1
1.0
-L49A
alf-alf alfw-
-3d
145
22
15.2
7.6
-L41D2
alf-alf alfw-
-3e
135
13
9.6
3.3
-L36A
alf-alf alfw-
-3f
110
11
10.0
2.8
-L40B
alf-alf alfw-
-3g
170
25
14.7
7.2
-L41C2
c-csilage-w-
alf-alf-alf
-3h
89
8
9.0
3.0
34.8
L41C2
3.9
c-csilage-w-
alf-alf-alf
4
4a
61
6
9.8
4.4
_L36A
4.2 acres
c-c-sb
4.2
acres
acres
4b
135
14
10.4
6.0
-L36A
c-c-sb
-4c
131
18
13.7
8.8
19.2
L41D2
6.4
c-c-sb
average
soil loss in
all buffer
strips
--35
2
use 3%
5
5a
186
17
9.1
2.3
2.3
L41C2
pasture
cont graze,
mod
overuse
pasture
cont graze,
mod
overuse
Ardmore Area Subwatershed Stormwater Retrofit Analysis
77
Unless otherwise mentioned in the individual practice, this section includes the tables used to calculate the cost esti
BMP
ID
Initial Construction
Cost ($/unit)
Contracted
Maintenance
Cost ($/unit)
Q & M
Term
(yr)
Design Cost
for Average
Site ($70lhr)
Installation
Oversight Cost
g
for Average
Site ($701hr)
Size of
Proposed
BMP {USER
ENTERED)
Total Installation
Cost
10 Year Cost
(Includes design &
13rrmaintenance)
{Includes
installation cost&
10 years of
maintenance)
Contour Burr Strips (AC)
CBS
$
500.00
$ 10.00
10
$ 560.00
$ 280.00
10
S
5,940.00
S
6,840.00
Contour Farming (AC)
CF
$
25.00
$
10
$ 560.00
$ 280.00
10
S
1,090.00
S
1,090.0C
Cover Crop (AC)
CC
$
25.00
$
10
$ 560.00
$ 280.00
40
S
1,840.00
�S
18,400.00
Diversions (LF)
D
$
7.00
$ 0.25
10
$ 56o.0o
$ 280.00
500
S
4.465.00
S
5,590.00
Filter Strip (AC)
FS
$
500.00
$ 10.00
10
$ 1,120.00
$ 560.00
10
S
6,780.00
S
7.680.00
Grade Stabilization Structure - drainage area of 0 to 10 acres (NO)
GSS
$
9,250.00
$ 100.00
10
$ 925.00
$ 462.50
1
S
10,737.50
S
11.637.50
Grade Stabilization Structure - drainage area of 10 to 20 acres (NO)
GSS
$
15,000.00
$ 150.00
10
$ 1,500.00
$ 750.00
1
S
17,400.00
S
18,750.00
Grade Stabilization Structure - drainage area of 20 to 40 acres (NO)
GSS
$
28.125.00
$ 200.00
10
$ 2,812.50
$ 1,406.25
1
S
32.543.75
S
34.343.75
Grade Stabilization Structure - drainage area of 40 to 80 acres (NO)
GSS
$
37,500.M
$ 250.00
10
$ 3,750.00
$ 1,875.00
1
$
43,375.00
S
45.625.00
Grade Stabilization Structure - drainage area of 80 to 250 acres (NO)
GSS
$
56,250.00
$ 300.00
10
$ 5,625.00
$ 2,81250
1
$
6-4,987.50
S
67,687.50
Grade Stabilization Structure - drainage area of25C to 500 acres (NO)
GSS
$
112.500.00
$ 350.00
10
$ 11,250.00
$ 5,625.00
1
$
129,725.00
S
132,875.00
Grade Stabilization Structure -drainage area of greater than 500 acres (NO)
GSS
$
150.000.00
$ 400.00
10
$ 15.000.00
$ 7,500.00
1
$
172,900.00
S
176,500.00
Grassed Waterway (LF)
GW
$
4.00
$ 0.25
10
$ 1,120.00
$ 560.00
1,000
$
5.930.00
S
8,180.00
Nutrient Management (AC)
NM
$
11.00
$
10
$ 560.00
$ 280.00
10
$
960.00
S
950.00
Nutrient Management (NO)
NM
$
3,375.00
$
10
$ 560.CO
$ 280.00
1
$
4,215.00
S
4,215.0C
Prescribed Grazing (AC)
PG
$
93.00
$
10
$ 560.00
$ 280.00
10
$
1,770.00
S
1,77C.00
Residue Management (AC)
RM
$
58.00
$
10
$ 5E0.00
$ 280.00
1
$
898.00
S
898.00
Restoration and Management of Declining Habitats (AC)
RMDH
$
1,500.00
$ 500.00
15
$ 1.120.00
$ 560.00
10
$
21,680.M
S
66,680.00
Streambank and Shoreline Protection (SF)
SSP
$
7.00
$ 0.25
10
$ 2,240.00
$ 1,120.00
1,000
$
10,610.00
S
12.860.00
Striperopping (AC)
Strip
$
98.00
$
10
$ 560.00
$ 280.00
10
p.$
1,820.00
S
1.820.00
Terrace (LF)
Ter
$
8.00
$ 0.25
10
$ 1,120.00
$ 560.00
1,000
S
9.930.00
S
12.1 M.00
Water and Sediment Control Basin - drainage area of 0 to 1C acres (NO)
SB
$
12,500.00
$ 100.00
10
$ 1,250.00
3 625.00
1
S
14,475.00
S
15.375.00
Water and Sediment Control Basin- drainage area of 1C to 20 acres (NO)
SB
$
11,250.00
$ 150.00
10
$ 1,125.00
$ 562.50
1
S
13,087.50
S
1-1437.50
Water and Sediment Control Basin - drainage area of2Cto40acres (NO)
SB
$
16,875.00
$ 200.00
10
$ 1,687.50
$ 843.75
1
S
19,606.25
S
21,406.25
Wetland Creation (AC)
WetC
$
7,000.00
$ 45.M
10
$ 2,800.00
$ 1,400.00
10
S
74,650.00
78,700.00
Wetland Enhancement (AC)
WetE
$
3,000.00
$ 45.00
10
$ 2,800.00
$ 1,400.00
10
S
34,650.00
S
38,700.00
Wetland Restoration (AC)
WeIR
$
3,000.00
$ 45.00
10
$ 2,800.00
$ 1,400.00
10
S
34,650.00
S
38,700.00
Windbreak - per foot of single row, planted (LF)
Wind
$
2.00
$
10
$ 560.00
$ 280.00
1,000
S
2,840.00
S
2,840.00
Septic fx (NO)
Sep
$
15,000.00
$
n!a
$
$ -
1
PS
15,000.00
S
15,000.00
Feedlot Fx - Pit - f rst 500,000 CF of storage (CF)
FF
$
1.55
$ 0.01
10
$ 11,200.00
$ 5,600.00
500,000
S
795,050.00
S
824.300.00
Feedlot Fx - Pit - additional above 500.000 CF of storage (CF)
FF
$
1.13
$ 0.01
10
$ 11,200.00
$ 5,600.00
500,000
S
585,050.00
S
614.300.00
Feedlot Fx -Treatment Swale (SF)
FF
$
4,00
$ 0.25
10
$ 2,800.00
$ 1,400.00
1,000
S
8,450.00
S
10,700.00
Feedlot Fx -Relocation (NO)
FF
$
50,000.00
$ -
n1a
$ 11,200.00
$ 5,600.00
1
$
66,800.00
S
66,800.00
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References
• Best Management Practices Construction Costs, Maintenance Costs and Land Requirements, BARR Engineering, Prepared for
MN Pollution Control Agency June 2011
• Board of Water and Soil Resources Pollution Reduction Estimator, Microsoft Excel Version, 2010
• Centers for Watershed Protection, Urban Subwatershed Restoration Manual, August 2007
• Center for Watershed Protection & Chesapeake Stormwater Network. Runoff Reduction Methods, Appendices A to G April,
2008.
• Environmental Protection Agency, 1983. Results of the Nationwide Urban Runoff Program, Volume 1: Final Report. http://
www3.epa.gov/npdes/pubs/sw_nurp_vol_1_finalreport.pdf.
• Fact sheet, Ohio State University Extension, Food, Agricultural and Biological Engineering, 590 Woody Hayes Dr., Columbus,
Ohio 43210
• HydroCAD, 2011. HydroCAD Stormwater Modeling. http://www.hydrocad.net/.
• Impacts of Cattle Grazing Management on Sediment and Phosphorus Loads in Surface Waters. Iowa State University 2004
Animal Industry Report. Haan, M.M., J.R. Russell, W. Powers, J.L. Boehm, S. Mickelson, and R. Schultz Iowa State University,
Ames, IA J.L. Kovar, USDA National Soil Tilth Laboratory, Ames, IA
• Johnson, James et. al., 2007. Lake Independence Phosphorus TMDL. https://www.pca.state.mn.us/sites/default/files/wq-iw8-
03e. pdf.
• Lake Independence Phosphorus TMDL, January 2007. Three Rivers Park District,
• Lake Independence Nutrient TMDL Implementation Plan, March 12, 2007, Three Rivers Park District, Minnesota Pollution
Control Agency
• Maestre, A. and Pitt, R., 2005. The National Stormwater Quality Database, Version 1.1: A Compilation and Analysis of NPDES
Stormwater Monitoring Information. Dept. of Civil and Environmental Engineering, University of Alabama.
• Minnesota Board of Water & Soil Resources, 2010. Pollution Reduction Estimator Worksheet. Conservation Implementation:
Tools for calculating pollution reduction estimates. http://www.bwsr.state.mn.us/practices/pollution_reduction.html.
• Minnesota Pollution Control Agency, 2015. Calculating credits for iron enhanced sand filter. Minnesota Stormwater Manual.
http://stormwater.pca.state.mn.us/index.php/Calculating_credits_for_iron_enhanced_sand_filter.
• Minnesota Pollution Control Agency, 2015. MIDS Calculator. Minnesota Stormwater Manual. http://
stormwater.pca.state.mn.us/index.php/MIDS_calculator
• Minnesota Pollution Control Agency, 2016. Calculating credits for biorention. Minnesota Stormwater Manual. http://
stormwater.pca.state.mn.us/index.php/Calculating_credits_for_bioretention.
• Minnesota Pollution Control Agency, Minnesota Stormwater Manual
• Minnesota Department of Agriculture. The Agricultural BMP Handbook for Minnesota, September 2012.
• Minnesota Pollution Control Agency, Best Management Practices Construction Costs, Maintenance Costs, and Land
Requirements, June 2011.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 80
References (continued)
• Minnesota Feedlot Annualized Runoff Model (MinnFARM) Version 2.1, October 2008 University of Minnesota Extension -
Manure Management and Air Quality Education and Research.
• Model Simulation of Soil Loss, Nutrient Loss, and Change in Soil Organic Carbon Associated with Crop Production, June 2006,
N RCS
• Phosphorus Run off Reduction and Annual Ongoing Cost Estimates for common Vermont Agronomic Practices. Dr. Kent E
Henderson, FNLC Chair
• PONDNET, Flow and Phosphorus Routing in Pond Networks, William W. Walker, March 1989.
• Potential phosphorus and sediment loads from sources within a dairy farmed catchment. G. M. Lucci, ,R.W.Mcdowell &
L.M.Condron. AgResearch, Invermay Agricultural Centre, Private Bag 50034 Mosgiel, New Zealand, and Agriculture and Life
Sciences, Lincoln University, P.O. Box 84 Lincoln 7647, New Zealand.
• Quantifying Phosphorus Loss In Runoff From Grazing Cattle. Peter Vadas: USDA-ARS Dairy Forage Research Center, Madison,
WI Dennis Busch: UW-Platteville Pioneer Farm, Platteville, WI Mark Powell: USDA-ARS Dairy Forage Research Center, Madison,
WI Geoff Brink: USDA-ARS Dairy Forage Research Center, Madison, WI
• Storm Water Assessment Tool (SWAT) USDA Agricultural Research Service (USDA-ARS) and Texas A&M Agri Life Research.
2014.
• USDA Agriculture Research Service Revised Universal Soil Loss Equation (RUSLE2) April 2010.
• Vegetated filter strip image, University of Florida, Department of Agricultural and Biological Engineering.
• Walker, William W. Jr., 1990. P8 Urban Catchment Model. http://wwwalker.net/p8/.
Ardmore Area Subwatershed Stormwater Retrofit Analysis 81
Hennepin County
Public Works
Environment and Energy
1-mi=lilHakanson
111Anderson
Ardmore Area Subwatershed Stormwater Retrofit Analysis