HomeMy WebLinkAbout170504_Morningside flood risk_capstone student report_spring 2017
The following report is a student effort to evaluate flood risk mitigation in the Morningside neighborhood. Development
of a more formal Flood Risk Reduction Strategy to be led by the City is planned for 2019.
Each semester, the University of Minnesota - College of Science and Engineering requests proposals for senior student
capstone project ideas from local professionals who act as project mentors.
Read the November 2018 Edition: Edina story, “U of M Partners with Edina on Capstone Projects.”
Attachments:
Capstone description of commitments and benefits to mentors
Project description
Student final report
CEGE Senior Capstone Design
Mentor Commitments and Potential Benefits
Mentors provide a real world engineering project (current or past). Based on indicated areas of emphasis
and preferences, students are assigned to the projects in teams of 3-5. Ideal projects have a preliminary phase
(analyzing alternatives with a minor cost/benefit component) and some form of design phase. Past projects
have included projects in all areas of civil, environmental, and geo- engineering:
environmental: water treatment, wastewater treatment, site remediation
general civil engineering/municipal engineering: site plans (grading, utility, and hydrologic components)
geo-engineering: landslide stabilization, foundation analyses
structural: building design (overall structural analysis and detailed design of representative portion of
structure), bridge design including structural drawings
transportation: Intersection Control Evaluation (ICE), traffic impact studies, signal optimization, corridor
design
water resources/hydrology: retention ponds, sewer capacity studies, stream restoration, sediment control
Mentors provide a written description of their project, which consists of a one to two paragraph project
description and list of expected tasks. Students review those descriptions to indicate their project preferences.
The instructors assign the projects to the student teams during the first week of class, and the students
immediately contact their mentors to set up an initial meeting to complete a project development work plan. The
work plan further fleshes out the project tasks and expected timeline/deliverables. In addition, the
mentors/teams identify where and when meetings will take place and preferred methods of communication
between mentor/team meetings. Some mentors ask students to prepare detailed agenda and meeting minutes.
Mentors should expect to spend on average about one to two hours per week meeting with the students with
additional email or phone contact over a 13 week period. The students are expected to accommodate your
schedule and your preferred meeting location. Most often students meet their mentors at the mentors’ offices (it
is helpful for students to see and work in a professional office). Each student on the team is expected to work an
average of eight (8) hours per week on their selected project in addition to the time they spend in class each
week. The design project culminates in a final oral presentation and project report. The reports are 15 pages plus
appendices, which can be quite extensive (e.g., contain structural drawings and sample calculations). Students
submit three drafts of the reports (1st draft, midterm, and final) during the semester.
Commitments:
Mentors provide project description including list of tasks.
Mentors provide background information and technical assistance on the project for the students.
Mentors provide guidance to the students, but let the team make important decisions.
Mentors are encouraged to provide feedback on second (near final) draft of written reports.
Mentors are encouraged to attend final oral presentations in the Civil Engineering Building
Potential Benefits to Mentors:
Mentors receive continuing education credit towards their required PDHs.
Mentors help strengthen our profession by providing a vital education component.
Mentors work with students that your firm may want to hire in the future.
Mentors receive reimbursement for parking expenses when on campus.
Mentors are invited to attend a reception and receive a plaque or small gift honoring their service.
Mentors may obtain real help on a current project from the students in exploring various design options for
which the mentors themselves may not be able to dedicate sufficient time or budget to accomplish.
U of MN, CEGE 4102W/4103W/4104W
Project Description
CEGE 4102W/4103W/4104W, S17
Project Title: Evaluating Flood Mitigation Improvements Adjacent to Weber Pond
Mentor(s):
Ross Bintner, PE Jessica Wilson, CFM
City of Edina City of Edina
7450 Metro Boulevard 7450 Metro Boulevard
Edina, MN 55439 Edina, MN 55439
952.903.5713 952.826.0445
rbintner@EdinaMN.gov jwilson@EdinaMN.gov
Project Description:
Weber Pond is a stormwater pond that serves about 228 acres of residential area. During
the modeled 1% annual chance (100‐year) flood event, several residential structures are at
risk and incremental improvements to mitigate flood risk are necessary.
A major residential street reconstruction project in the watershed is anticipated in 2020,
presenting an opportunity for green infrastructure practices to reduce stormwater
drainage to Weber Pond. Additionally, the City recently purchased a 9.77 acre park on the
northern edge of Weber Pond that could accommodate further flood mitigation
improvements. The Capstone team would prepare feasibility studies for a variety of options
with the goal of reducing flood impacts to private property.
Project tasks include;
Feasibility study for various flood mitigation projects including 1) green
infrastructure options during the upcoming street reconstruction, 2) potential
improvements in the new adjacent park, and 3) regular pond maintenance.
Estimates of reductions in the modeled 1% annual chance (100‐year) flood
elevation for various improvements.
Estimates of costs associated with various improvements.
Required Software: None
Provided/Available through Mentor? Y/N
Group 8 Engineering Company
University of Minnesota
Department of Civil, Environmental, and Geo- Engineering
500 Pillsbury Drive SE
Minneapolis, MN 55455
May 4, 2017
Jessica Wilson, CFM
Ross Bintner, PE
City of Edina
7450 Metro Boulevard
Edina, MN 55439
RE: Weber Park Pond Flood Mitigation Feasibility Study, 08S_W_Edina
Dear Ms. Wilson and Mr. Bintner:
This letter is in response to your request for a feasibility study of flood mitigation strategies to
reduce the flood impacts of a 1% annual chance (100-year) storm event to private, residential
properties near Weber Pond in the Morningside watershed. The completed report is attached.
Multiple flood mitigation strategies were evaluated using a decision matrix that considered risk
mitigation, water quality improvement, social benefits, and overall cost. The flood mitigation
strategies that were quantitatively considered include the following: excavation of additional
pond volume, underground storage tanks, permeable pavement, predictive monitoring system,
and property acquisition.
After completing our analysis, it is recommended that the City of Edina install and operate a
predictive monitoring system in Weber Pond and excavate the recently acquired wooded area
that lies north of Weber Pond. It is also recommended that the City of Edina further evaluate the
potential benefits of installing permeable pavers in the road reconstruction area that is planned
for 2020 or 2021 in the Morningside neighborhood, which could contribute additional water
quality improvements in and downstream of Weber Pond.
It was a pleasure to work with you and your staff on this matter and please do not hesitate to
contact us if you require further analysis.
Sincerely,
Emily Caouette, Jack Cottle, Acadia Stephan, and Rena Weis
Feasibility Study for
Stormwater Flood Mitigation
Within Weber Pond
Prepared for the City of Edina, Minnesota
Prepared by Emily Caouette, Jack Cottle, Acadia Stephan, and Rena Weis
Submitted May 4, 2017
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ii | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Certification Page
By signing below, the team members submit that this report was prepared by them and is their original
work to the best of their abilities.
Rena Weis, Project Manager
Emily Caouette, Team Member
Jack Cottle, Team Member
Acadia Stephan, Team Member
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iii | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Executive Summary
The City of Edina has requested a feasibility study to evaluate various stormwater mitigation
methods designed to reduce the elevation of Weber Pond during a 1% annual chance (100-year)
storm event, which has the potential to flood and cause structural damage to six residential
properties. The Morningside neighborhood, which contains most of Weber Pond's drainage area,
is scheduled for a road reconstruction project in 2020 or 2021. During this timeframe, the City of
Edina plans to make improvements that will reduce the flood risk posed by Weber Pond’s high
floodplain.
The objective of this study was to evaluate best management practices for implementation in
the Morningside neighborhood that either reduce the total amount of water entering Weber Pond
or increase the total storage capacity of Weber Pond itself. Three options were quantitatively
evaluated. Modeling was performed using HEC-HMS to quantify their effects on the peak
flood elevation of Weber Pond. These options are:
1. Excavate additional storage in low lying areas and install predictive monitoring system.
2. Install underground storage tanks connected to the upstream storm sewer.
3. Install PaveDrain permeable pavement for the 2020 or 2021 road reconstruction.
In the course of modeling and analysis, Options 2 and 3 were found to create an insufficient
amount of additional storage or reduction of discharge to Weber Pond. The amount of required
flood reduction necessitated a large amount of additional storage, which could only be achieved
through Option 1.
The final recommendation is to increase the area and volume of Weber pond through excavation
and install a predictive monitoring system to create additional storage in anticipation of a storm
event. Additionally, the feasibility and effectiveness of permeable pavement in the 2020 or 2021
road reconstruction area should be evaluated. In whole, this recommendation creates 63.5 acre-
feet of additional storage volume and lowers the peak flood elevation by 1.9 ft. The estimated
cost of this recommendation is $1,541,000 for excavation and development, $70,000 for
the predictive monitoring system, and $3,250,000 for PaveDrain installation.
Implementation of this recommendation will reduce the risk of flooding to six residential
properties, open up the possibility of park development north of Weber Pond, and potentially
improve runoff quality if the PaveDrain is installed. It is recommended that the City of Edina
explore these options further, using a more sophisticated hydrological model of the
Morningside watershed, to confirm the results of this study and quantify any water quality
improvements.
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iv | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table of Contents
1.0 Introduction ............................................................................................................................... 1
2.0 Background and Site Information ............................................................................................. 2
2.1 Opportunities for Flood Improvements .................................................................................... 5
3.0 Methodology ............................................................................................................................. 7
3.1 Introduction to Feasible Design Options .................................................................................. 7
3.2 Model Development.................................................................................................................. 7
4.0 Feasible Design Options Analysis ............................................................................................ 9
4.1 Predictive Monitoring and Excavation ..................................................................................... 9
4.1.1 Model Results for Predictive Monitoring and Excavation .................................................. 11
4.2 Underground Storage Units .................................................................................................... 11
4.2.1 Model Results for Underground Storage Units ................................................................... 13
4.3 Permeable Pavement ............................................................................................................... 13
4.3.1 Model Results for Permeable Pavement .............................................................................. 14
4.4 Alternative Options ................................................................................................................. 14
4.5 Cost Analysis .......................................................................................................................... 14
5.0 Sustainability........................................................................................................................... 17
6.0 Final Recommendation and Summary .................................................................................... 18
7.0 References ............................................................................................................................... 22
Appendix A: Description and Photos of Temporary Inundation Area (TIA) ............................... 23
Appendix B: Final Designs ........................................................................................................... 25
Appendix C: Cost Analysis Calculations ...................................................................................... 29
Appendix D: Modeled Inflow and Outflow Hydrographs for Weber Pond ................................. 32
Appendix E: HEC-HMS Model Inputs for Feasible Design Options ........................................... 34
Appendix F: Analysis of Initial Options ....................................................................................... 38
Appendix G: HEC-HMS Model Input Data for Pre-development Model .................................... 41
Appendix H: HEC-HMS Model Output Data for Feasible Design Options (Post-Development
Model) ........................................................................................................................................... 49
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v | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
List of Tables
Table 1. Surveyed low-entry elevations of the six residential properties affected by the 1%
annual chance (100-year) flood. ..................................................................................................... 4
Table 2. 1% annual chance flood mitigation achieved through predictive monitoring and
excavation ..................................................................................................................................... 11
Table 3: Additional storage volume created through underground systems................................. 13
Table 4: 1% Annual Chance (100-year) flood mitigation achieved through underground storage
system. .......................................................................................................................................... 13
Table 5. 1% annual chance flood mitigation achieved through permeable pavement, and
permeable pavement with additional infiltration of underground storage .................................... 14
Table 6. Summary cost analysis for feasible design options ........................................................ 15
Table 7. Cost Estimate for Weber Pond expansion through excavation ....................................... 29
Table 8. Cost estimate for excavation of TIA ............................................................................... 29
Table 9. Budgetary cost estimate for underground storage located at Susan Lindgren Elementary
....................................................................................................................................................... 30
Table 10. Budgetary cost estimate for underground storage located at Weber Park Fields ......... 30
Table 11. Budgetary cost estimate for underground storage located in the 2020 or 2021 road
reconstruction area ........................................................................................................................ 30
Table 12: Budgetary cost estimate for permeable pavement 1 ...................................................... 30
Table 13: Budgetary cost estimate for bituminous pavement ....................................................... 30
Table 14. Budgetary cost estimate for property acquisitions ........................................................ 32
Table 15. Changes in initial pond elevation for predictive monitoring model ............................. 34
Table 16. The values for invert depth of stormwater mains assessed for locations of underground
storage to find feasible design volume.......................................................................................... 35
Table 17: Dimensions of streets within 2020 or 2021 Road Reconstruction area ........................ 36
Table 18: Change in percent impervious from existing conditions to proposed permeable
pavement at 2020 or 2021 Road Reconstruction area .................................................................. 37
Table 19. Flow Routing Parameters (CWRMP 2011) .................................................................. 42
Table 20. Subbasin Properties (Horton Method) (Stratton 2017) ................................................. 43
Table 21. Subbasin Properties (Green-Ampt Method) ................................................................. 45
Table 22. Inflow-Diversion Function ........................................................................................... 47
Table 23. Modeled Reservoirs ...................................................................................................... 48
Table 24. Reservoir Outlets .......................................................................................................... 48
Table 25. Water Elevation over time data for pre-development and each post development option
....................................................................................................................................................... 49
Table 26. Inflow and outflow hydrograph for pre-development and final recommendation ....... 52
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vi | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
List of Figures
Figure 1. 1% annual chance (100-year) storm FEMA floodplain of Weber Pond with threatened
properties depicted in red. ............................................................................................................... 3
Figure 2. Water elevation over time in Weber Pond, with six threatened residential properties
indicated. ......................................................................................................................................... 4
Figure 3: Figure of Edina' stormwater infrastructure, subwatersheds, and redevelopment projects
in the Morningside Neighborhood .................................................................................................. 6
Figure 4. Elevation profile of a cross section within Weber Pond. ................................................ 9
Figure 5. The TIA and area located north of Weber Pond identified as low-lying, publicly owned
areas that could be excavated ........................................................................................................ 10
Figure 6. Location of proposed placement of underground storage within the Morningside
neighborhood ................................................................................................................................ 12
Figure 7. Cost per acre-ft of added storage plotted for each feasible design option..................... 16
Figure 8. The feasible design options presented in Section 4.0 evaluated using the criteria
outlined in the Introduction (Section 1.0) of the report. ............................................................... 18
Figure 9. Pre-development and post-development stage-storage curves for 1% annual chance
floodplain, where excavation of area north of Weber Pond adds an additional 25 [ac-ft] of
storage. .......................................................................................................................................... 19
Figure 10. Final recommendation water elevation over time in Weber Pond, with six threatened
residential properties indicated. .................................................................................................... 20
Figure 11. Final recommendation design schematic, showing the proposed combination of
options ........................................................................................................................................... 21
Figure 12. The outlet structure that transports water from the TIA to Weber Pond via the
stormsewer system ........................................................................................................................ 23
Figure 13. The TIA exhibiting its current capacity to hold stormwater that will later be
transported to Weber Pond............................................................................................................ 23
Figure 14. Example of an area within the TIA that could be excavated to increase capacity ...... 24
Figure 15. CAD Excavation Proposal of Weber Pond and TIA ................................................... 26
Figure 16. Example of OptiRTC web-based dashboard ............................................................... 27
Figure 17: Proposed location of permeable pavement and underground storage in 2020 or 2021
road reconstruction area ................................................................................................................ 28
Figure 18. Pre-development inflow and outflow hydrograph for Weber Pond ............................ 33
Figure 19. Post-development inflow and outflow hydrograph of Weber Pond ............................ 33
Figure 20. Discharge over time for a slow release underground storage unit .............................. 34
Figure 21. Labeled Overview of Pre-Development Model .......................................................... 41
Figure 22. Sample of Infiltration curve comparison between Horton and Green-Ampt methods 45
Figure 23. Plan View of Diversion Location ................................................................................ 47
Figure 24. Profile View of Diversion ........................................................................................... 47
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1 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
1.0 Introduction
The City of Edina provides municipal services for its residents including stormwater and
drainage system management (City of Edina and Barr Engineering Company). The City has
requested a feasibility study for flood mitigation strategies to reduce the 1% annual chance (100-
year) storm event flood elevation of Weber Pond from 869.0-ft (Barr Engineering Company).
This elevation is above the low entry elevation of six residential properties, which puts the
homes at risk of flooding and, in turn, structural damage.
The owners of these properties have requested that actions be taken to reduce the risk of flood
damage. To protect these properties, the 1% annual chance flood elevation of Weber Pond must
be reduced by 1.9-ft.
When selecting feasible design options, consideration was given to the needs and values of the
community. Additionally, upcoming projects in the City of Edina were considered because they
may include project components that could reduce flood risk. These areas include a road
reconstruction area and a newly acquired wooded area that lies north of Weber Pond. A
successful flood mitigation design will reduce the flood elevation at Weber Pond and will be
beneficial to the City of Edina and its residents by considering the following criteria:
• Protecting and improving water quality
• Developing land with the City's values in mind
• Meeting city budgetary need
The City of Edina has outlined their commitment to stormwater management, flood control, and
water quality in their Comprehensive Water Resource Management Plan (City of Edina and Barr
Engineering Company), which was updated in 2011.
Four final feasible design options were selected, and assessed using the criteria above. Section
4.0 introduces the feasible design options analyzed in this report. HEC-HMS modeling was
performed to determine the total volume reduction for each option. In addition to evaluating each
option individually, the final options were also analyzed in conjunction with each other.
This document outlines options to mitigate flood risk by reducing the high-water level near
Weber Park in a 1% annual chance storm event and the methodology used in the selection of
these options. In addition, a final recommendation is made for the City of Edina in Section 6.0.
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2 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
2.0 Background and Site Information
Weber Pond is a stormwater detention pond that lies directly east of Weber Park between West
41st Street and West 42nd Street in Edina, Minnesota. The pond collects runoff from a 452-acre
drainage area (Barr Engineering Company). This drainage area is primarily composed of the
Morningside neighborhood – a residential area located in the northeast corner of Edina – and
small portions of St. Louis Park. The storm sewer system through the Morningside neighborhood
either drains into Weber Pond or into a temporary inundation area (TIA) that lies west of Weber
Pond. See Appendix A for a complete description of the TIA, including photos. Figure 3 shows
the complete layout of the stormwater system within the Morningside drainage area. The outlet
of Weber Pond runs north into St. Louis Park where it eventually connects with the Minneapolis
storm sewer system and discharges into Lake Calhoun.
The City of Edina designed its stormwater management systems to protect against 1% annual
chance (100-year) flood elevations (City of Edina and Barr Engineering Company). However,
Weber Pond was designed for a 2% annual chance (50-year) storm event because of site and
downstream capacity constraints. As described by a report completed by Barr Engineering
Company in 2006, the discharge capacity of Weber Pond is dictated by the capacity of the
downstream Minneapolis sewer system. The available capacity in the Minneapolis sewer system
from Weber Pond is 25 cfs (Barr Engineering Company). However, the downstream capacity
required to decrease the 1% annual chance flood elevation of Weber Pond to a substantial level is
105-cfs (Barr Engineering Company).
These restrictions in downstream capacity have implications for the City of Edina. Modeling of
existing conditions completed by Barr calculated the 1% annual chance flood level of Weber
Pond to be 869.0-feet, which was above the lowest entry elevation of four residential properties
(Barr Engineering Company). Thus, the storm event could result in structural damage to the
properties on these lots. Figure 1 illustrates the Federal Emergency Management Agency (FEMA)
1% annual chance storm floodplain and the location of the six threatened properties. In their
report, Barr investigated options for flood mitigation, but no action has been taken by the City of
Edina to implementing those options.
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3 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 1. 1% annual chance (100-year) storm FEMA floodplain of Weber Pond with threatened
properties depicted in red.
The report completed by Barr in 2006 describes four threatened properties, and the City of Edina
has recently surveyed the low-entry elevations of two additional properties located in the
floodplain. The threatened properties include three residences on France Avenue and three
residences on 42nd Street. The following table provides the lowest point of entry for each of the
six threatened properties and the needed 1% annual chance elevation change to remove each of
the properties from the 1% annual chance storm floodplain. Figure 2 depicts the water elevation
of the 1% annual chance flood event over time. The red line indicates where the flood elevation
is equal to the lowest point of entry of the six threatened properties. The low entry elevations of
each threatened property are plotted on the figure for reference.
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4 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 1. Surveyed low-entry elevations of the six residential properties affected by the 1%
annual chance (100-year) flood.
Address Lowest Point of Entry (MSL) (ft) Needed 1% annual
chance Elevation
Change1
a. 4000 42nd St W 869.00 > 0.0
b. 4003 42nd St W 868.58 > 0.0
c. 4108 France Avenue 868.50 -0.10
d. 4104 France Avenue 867.50 -1.10
e. 4100 France Avenue 866.80 -1.80
f. 4005 42nd St W 866.74 -1.86
1. Modeled peak water surface elevation is 868.6 ft under existing conditions
Figure 2. Water elevation over time in Weber Pond, with six threatened residential properties
indicated.
Using the rate of inflow and outflow from Weber Pond, the theoretical required storage for
stormwater peak attenuation is 55.8 ac-ft. See Appendix D for the inflow and outflow
hydrograph for Weber Pond used in this calculation.
a
edc
f
b
860
862
864
866
868
870
0 6 12 18 24 30 36Elevation [ft]Time [Hours]
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5 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
2.1 Opportunities for Flood Improvements
The City of Edina is currently planning for the development/redevelopment of two areas within
the Morningside drainage area. These areas were considered when selecting flood mitigation
strategies so that the implementation of the mitigation strategies could be coupled with the
ongoing projects in the City of Edina, which would save time and resources. The
development/redevelopment of these areas provides opportunities for the implementation of
various flood mitigation strategies. The city recently purchased the 9.77-acre wooded area
located north of Weber Park (Braun Intertec Corporation). This space is unoccupied and the city
is receptive to proposals for development of this land which would reduce flood levels within
Weber Pond (Braun Intertec Corporation). Additionally, a large road reconstruction project is
being planned for 2020 or 2021, which presents a unique opportunity to utilize green
infrastructure for further flood level reduction. Figure 3 shows the newly purchased parcel and
the anticipated road reconstruction areas relative to Weber Pond.
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6 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 3: Figure of Edina' stormwater infrastructure, subwatersheds, and redevelopment
projects in the Morningside Neighborhood
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7 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
3.0 Methodology
The flood mitigation strategies presented in this document were initially selected based on high-
level considerations of the site's background information. The background information
considered includes:
1. The most accurate 1% annual chance (100-year) flood information available, from
NOAA Atlas 14. See Appendix G for this information.
2. Projected plans for an anticipated road reconstruction area in 2020 or 2021.
3. Recently purchased park land north of Weber Park pond.
4. Existing storm sewer infrastructure including gravity mains and catch basin placement.
5. Topography of the Morningside drainage area, including Weber Park.
6. General political feasibility.
The initial options were classified into broad categories based on ongoing projects within the City of
Edina. A detailed description of the options that were not selected for further evaluation can be found in
the Appendix F. These initial flood mitigation strategies were then consolidated based on background
information and on the desires of the City of Edina. The feasible design options that were selected are
presented in Section 3.1.
These options were evaluated in-depth using the HEC-HMS modeling software, a cost analysis, and a
final decision matrix evaluating additional criteria. The results from the post-development models can be
found in the Model Results sections for each feasible design option. See Section 4.5 for total cost, and
cost per storage. See Section 6 .0 for evaluation of options and a decision matrix.
To quantify the change in flood elevation achieved by modeling the feasible design options, a pre-
development model was compared to post-development models. A pre-development model of the
Morningside drainage area was created in HEC-HMS and is intended to match as closely as possible the
current conditions in the watershed. A detailed description of the methods used to construct this model is
presented in Section 3.2. The post-development models incorporate the final flood mitigation strategies
outlined Section 3.1.
3.1 Introduction to Feasible Design Options
The following four feasible design options were quantitatively considered individually and in various
combinations with each other.
A. A predictive monitoring system used in combination with additional temporary and/or permanent
storage volume created through the excavation of low-lying areas located within the floodplain.
B. Subsurface storage/release system installed within Morningside drainage basin.
C. Permeable pavement installed in the anticipated road reconstruction area.
D. Evaluation of options listed above in combination with the option(s) of doing nothing and/or
acquiring the at-risk properties
3.2 Model Development
The Edina Comprehensive Water Resource Management Plan (CWRMP) contained most of the
source data for the pre-development model, including sub-basin properties, storm sewer
dimensions, and storm sewer layout (City of Edina and Barr Engineering Company). The
remaining source data, including stage-area curves and infiltration parameters, were collected in
08S_W_Edina
8 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
correspondence with Barr Engineering and the City of Edina. See Appendix G for a detailed
figure and the complete data input into the modeling software including flow routing parameters,
sub basin properties, and elevation-area relationships and outlet pipe dimensions for reservoirs.
Infiltration parameters were given in Horton, which HEC-HMS does not accept as an input
(Stratton). To model the flow lost to infiltration accurately, the rate of infiltration versus time
was plotted using the given Horton's parameters, and the total infiltrated depth was determined
by integrating the curve. A similar plot was created using the Green-Ampt equation, with
parameters chosen to yield an equal total infiltration depth. The Green-Ampt parameters were
used as inputs for the HEC-HMS model. See Figure 21, Appendix G for this figure.
There are four sub-basins in the Morningside neighborhood that do not have any connection
downstream. It has been determined that these areas do not overflow during the 1% annual
chance storm event, so they are not included in the flow to Weber Pond.
The 1% annual chance storm FEMA floodplain spans multiple sub-basins, which are not
included in the stage-storage curve for Weber Pond. To solve this, the stage-storage curve was
created directly from the 2-ft contour file to exactly match the dimensions of the 1% annual
chance floodplain area. See Appendix G for the final elevation-area relationships used.
The inlet to Weber Pond from the west bypasses the pond in low-flow conditions. To model this,
an inflow-diversion function was developed to divert the flow at this inlet. See Appendix G for a
figure and flow quantities.
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9 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
4.0 Feasible Design Options Analysis
Descriptions of the four feasible design options are provided along with a quantification of the
potential for each option to reduce the 1% annual chance flood elevation.
4.1 Predictive Monitoring and Excavation
Weber Pond is currently designed to hold a set amount of stormwater runoff volume. The
concept of this option is to create effective storage within Weber Pond and the floodplain by
using predictive monitoring and excavation.
Figure 4. Elevation profile of a cross section within Weber Pond.
Predictive monitoring systems are a form of active stormwater management that can
automatically pump water based on forecasted weather data (OptiRTC). A predictive monitoring
system installed at Weber Pond would have the potential to predict the size of an approaching
storm events and pump down the water elevation of Weber Pond to create additional storage in
the pond in anticipation of the rainfall event (OptiRTC).
This system could completely empty Weber Pond, making room for additional stormwater runoff
generated by the 1% annual chance storm event. The water pumped from Weber Pond would be
routed directly downstream to the City of Minneapolis' storm sewer system before it is fully
utilized for storm runoff. The results of a predictive monitoring system installed on the existing
Weber Pond were quantified in Table 2. The predictive monitoring system also has the potential
to improve the water quality downstream of Weber Pond (Capitol Region Watershed District).
The water that would be pumped out prior to a storm would be relatively clear compared to flood
water because it would have had time to sit, allowing for sediments to settle out (Capitol Region
Watershed District).
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10 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
To maximize the potential of the predictive monitoring system, the concept of predictive
monitoring was paired with excavation. Increasing the surface area of Weber pond allowed for
more water to be pumped out in anticipation of a storm event. The newly purchased,
approximately 10-acre parcel north of Weber Pond and the TIA were the two proposed pond
expansion areas: See Appendix B for the final design of the excavated areas. The results of a
predictive monitoring system installed at Weber Pond in conjunction with creation of additional
pond volume were quantified in Table 2. The results achieved through the use of predictive
monitoring may depend on the maximum discharge to the pond and the total upland contributing
area (Eshenaur).
The TIA excavation option requires a re-routing of the upstream storm sewer to reduce the total
amount of water flowing into Weber Pond. In its current state, the TIA receives runoff only from
small, neighboring watersheds. In the post-development model, 10% of the upstream flow is
diverted from the storm sewers into the TIA. This diverted amount is approximately the
maximum volume that the TIA can handle without overflowing.
Figure 5. The TIA and area located north of Weber Pond identified as low-lying, publicly owned
areas that could be excavated
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11 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
4.1.1 Model Results for Predictive Monitoring and Excavation
Table 2. 1% annual chance flood mitigation achieved through predictive monitoring and
excavation
Predictive Monitoring and Excavation
Excavation Area 1% Annual Chance (100-year) Flood
Elevation Change (ft)
None -0.2
North of Weber Pond -1.9
North of Weber Pond & TIA -2.3
4.2 Underground Storage Units
Underground storage tanks have the ability to detain water while keeping the land surface
available for use. Alterations would be made to the City's existing Edina stormwater system to
redirect flows to a subsurface storage tank. The discharge from a tank would be controlled to
allow for extended storage and the slow, measured release of the detained water to the City's
storm sewer system resulting in a reduction of the peak of Weber Pond's hydrograph (Lake
Superios Streams Duluth). See Figure 20 in Appendix E for a diagram illustrating the concept of
slow release.
Three flat, low-lying areas were identified where underground storage tanks could potentially be
installed. These include on the Susan Lindgren School property, at the Weber Park ball fields,
and at the anticipated road reconstruction area, as shown in Figure 6.
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12 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 6. Location of proposed placement of underground storage within the Morningside
neighborhood
The maximum underground storage volume was calculated for each of the sites, as shown in
Table 3. It was assumed that the top of the underground storage system was 18" below the
ground surface (Contech Engineered Solutions). To avoid the water table, it was assumed that
the invert of the underground storage system was at the invert elevation of the existing storm
sewer system, which is above the water table. Additionally, this allows the stormwater sewer and
underground storage system to be operated as a gravity fed system. See Table 16 in Appendix E
for the values of invert depth used in this calculation.
Proposed storage systems under the Susan Lindgren School and Weber Park Fields were
assumed to be networks of parallel solid corrugated metal pipe (CMP) (Contech Engineered
Solution). The proposed storage system beneath the anticipated road reconstruction area was
assumed to be a single manifold solid CMP. All proposed locations for underground storage will
require maintenance of the pretreatment chamber in order to prevent accumulation of sediments
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13 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
within the underground system (New York City Department of Environmental Protection). See
Appendix B for the final designs of the underground storage systems.
Table 3: Additional storage volume created through underground systems.
Location Underground Storage
Volume (ac-ft)
Susan Lindgren School 5.2
Weber Park Fields 12.0
2020 or 2021 Road
Reconstruction Area 1.7
Additionally, the system below the anticipated road reconstruction area could be installed as
perforated metal pipe or other infiltration system, such as ChamberMaxx technology (Contech
Engineered Solutions). The use of infiltration below the permeable pavement will create a
dynamic system that will increase the effective storage created.
4.2.1 Model Results for Underground Storage Units
Table 4: 1% Annual Chance (100-year) flood mitigation achieved through underground storage
system.
Underground Storage
Location 1% Annual Chance (100 year)
Flood Elevation Change (ft)
Susan Lindgren School -0.1
Weber Park Fields -0.3
2020 or 2021 Road Reconstruction
Area
-0.1
4.3 Permeable Pavement
Permeable pavement captures stormwater by filtering it through surface voids that lead to an
underlying reservoir for temporary storage and/or infiltration (Minnesota Pollution Control
Agency). The 2015 Edina Living Streets Plan discusses the need for streets to be constructed and
maintained to meet future health, economic and environmental challenges. Among these, the
City strives to promote water quality improvements (City of Edina). To accomplish this goal, the
City has already installed pervious pavement in some areas (City of Edina). Installation of
pervious pavement, rather than bituminous asphalt, was considered for use in the anticipated
2020 or 2021 road reconstruction site, and the effects on Weber Pond's 1% annual chance flood
elevation were quantified. To do so, the surface area of the road over the entire road
reconstruction area was calculated, and the percent change in impervious area was computed, as
shown in Table 18 in Appendix E.
In addition to permeable pavement's potential to manage water quantity, permeable pavement's
filtration properties can improve water runoff quality by reducing amounts of total suspended
solids (TSS) and total phosphorus (TP) loads into receiving waters (Minnesota Pollution Control
Agency). Pretreatment of water may be required in order to prevent significant clogging of the
08S_W_Edina
14 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
pavement, and pervious pavement requires regular vacuuming maintenance (Minnesota Pollution
Control Agency). Site specific water quality improvements were not quantified in this study.
4.3.1 Model Results for Permeable Pavement
Table 5. 1% annual chance flood mitigation achieved through permeable pavement, and
permeable pavement with additional infiltration of underground storage
Permeable Pavement
Description 1% Annual Chance (100 year) Flood
Elevation Change (ft)
2020 or 2021 Road Reconstruction Area 0.0
2020 or 2021 Road Reconstruction Area With
Underground Storage
-0.1
4.4 Alternative Options
The above strategies may be evaluated in combination with the options of the City of Edina
acquiring the at-risk properties or taking no action. See Table 14 in Appendix C for the cost of
property acquisition for each of the threatened six properties and the effects of taking no action.
Despite the relatively low cost of acquiring all six properties, acquisitions are not common place
in Edina and thus this option is likely not feasible overall due to other political factors. The
solution presented within this report is able to reduce the flood elevation within Weber Pond by
the required 1.9-ft and thus, succeeds in removing all six threatened properties from the 1%
annual chance floodplain. However, if an alternate solution was selected by the city, the potential
overall annual cost of damages for residents due to flooding in residential properties could be
computed using the probability of a storm event, and the elevation and duration of flooding.
4.5 Cost Analysis
The cost of each feasible design option discussed in this report is summarized in Table 6. See
Appendix C for calculations and source information used in completing the cost analysis.
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15 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 6. Summary cost analysis for feasible design options
Total Cost Additional
Storage (Acre-
ft)
Cost/Storage
($/Acre-ft)
Predictive Monitoring
Excavation Area None $70,000
6.64 $10,542
Weber Pond $1,610,605 63.5 $25,3643
Weber Pond & TIA $2,204,396 75.8 $29,1013
Underground Storage
Susan Lindgren
School
$1,485,000 12.0 $124,208
Weber Park Fields $679,800 5.2 $130,965
2020 Reconstruction $264,000 1.7 $151,453
Permeable Pavement 2020 or 2021 Road
Reconstruction Area
See below 1 0.0 N/A2
Acquire Properties $ 2,431,000 0.0 N/A
1. The cost of the permeable pavement was computed as a marginal cost analysis between
permeable pavement and bituminous materials. The marginal cost was calculated to be
$ 2,780,000.
2. The storage volume (ac-ft) created by permeable pavement is insignificant and thus,
Cost/Storage is not computed for this option.
3. Cost calculated additional excavation to ensure an acceptable standing water level in
Weber Pond
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16 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 7. Cost per acre-ft of added storage plotted for each feasible design option
The cost was estimated assuming that the bottom elevation was excavated to an elevation of 858-
ft. This elevation allows for 3.5-ft of standing water at Weber Pond. Although excavating the
bottom elevation to 860 ft would be cheaper and successfully mitigate flood risk, a more shallow
pond would foster a marshy environment which could lead to potential public health concerns.
The City could consider grant and cost-share opportunities for water quality and flood mitigation
projects from local partners including the Minnehaha Creek Watershed District (MCWD). In
addition, MCWD suggests that municipalities seeking funding reach out to Hennepin County for
natural resources grants (Minnehaha Creek Watershed District). Similar projects have been
funded by the Minnesota Board of Water and Soil Resources Clean Water Fund (Capitol Region
Watershed District).
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60 70 80Cost per Storage [$/ac-ft]ThousandsStorage [ac-ft]
Underground
StoragePM & Excavation
Predictive
Monitoring
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17 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
5.0 Sustainability
As the climate continues to warm, rain events will likely become more intense and more
prevalent, meaning the risk and severity of floods is also likely to increase. To accommodate the
changing climate, the proposed mitigation systems were designed with a focus on resilience.
This forethought will increase the lifespan of the flood mitigation systems, which will reduce the
cost and energy associated with repairing or replacing damaged infrastructure.
Sustainability was also given weight in the decision matrix and in the final recommendation. The
decision matrix was used to help select a flood mitigation strategy that solves not only the Weber
Pond flooding problem but also optimizes social, environmental, and economic benefits. Social
issues that are addressed by the recommended flood mitigation options include park development
and relief of economic burdens to the affected homeowners by preventing flood damage that is
either insured at a high cost and/or causes a disruption in the homeowners' lives.
Environmentally, options that improve the water quality of Weber Pond such as predictive
monitoring systems and permeable pavers were preferential to options that provided similar
magnitudes of flood mitigation but lacked water quality improvements. Additionally, decreasing
the amount of storm water runoff will reduce pond contamination from sediments, pollutants,
and nutrients. Finally, a cost analysis was conducted to estimate the cost associated with each
improvement option. Grants and cost-share programs through other government agencies were
also considered. For further detail on the cost analysis, see Section 4.5.
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18 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
6.0 Final Recommendation and Summary
The goal of this feasibility study, completed for the City of Edina, was to identify and
recommend a stormwater management design which would reduce the 1% annual chance flood
elevation within Weber Pond by 1.9 ft. This design was completed with consideration given to
upcoming and ongoing projects within the City of Edina including a newly purchased parcel of
park land north of Weber Pond and upcoming road reconstruction project.
Figure 8. The feasible design options presented in Section 4.0 evaluated using the criteria
outlined in the Introduction (Section 1.0) of the report.
To reduce the 1% annual chance flood elevation of Weber Pond, the total effective storage can
be increased in the floodplain, peak flows traveling to the pond captured and released more
slowly, or the total volume of stormwater runoff reaching the pond must be reduced After an
evaluation of the benefits and drawbacks of each option contained in this report, our team
recommends that the City of Edina:
• Create 25-ac-ft of additional flood storage within Weber Pond through excavation of the
wooded area north of Weber Pond.
• Install and manage a predictive monitoring system to lower the water elevation within
Weber Pond and excavated area north of Weber Pond in anticipation of a storm event.
• Utilize permeable pavement within the anticipated road reconstruction area in accordance
with the vision of the city's 2015 Living Streets Plan.
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19 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 9. Pre-development and post-development stage-storage curves for 1% annual chance
floodplain, where excavation of area north of Weber Pond adds an additional 25 [ac-ft] of
storage.
The City of Edina, through the first and second goal of their Comprehensive Water Resource
Management Plan (CWRMP), conveys their commitment to balancing stormwater management
and flood control with protecting water quality (City of Edina and Barr Engineering Company).
The combination of these options is recommended with the city's commitment to comprehensive
water resource management in mind. The recommended combination of options will provide the
city with the most cost effective flood mitigation solution for its residents while ensuring the city
is able to fulfill their commitment to water quality by using permeable pavement. Since site
specific water quality benefits were not quantified for this report, it is recommended that the City
of Edina further evaluate the potential benefits of permeable pavement. Figure 10 provides the
resulting water elevation over time in Weber Pond for the recommended solution.
856
858
860
862
864
866
868
870
872
0 20 40 60 80 100 120 140Elevation (ft)Storage (ac-ft)
Weber Pond Pre-Development
Weber Pond After Excavation
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20 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 10. Final recommendation water elevation over time in Weber Pond, with six threatened
residential properties indicated.
In summary, by implementing the recommended solution, the City of Edina will be able to
accomplish their intended goal of ensuring flood protection to their residents while
demonstrating their commitment to additional values such as water quality management, and
sustainable land use development.
a
edc
f
b
858
860
862
864
866
868
870
0 6 12 18 24 30 36Elevation [ft]Time [Hours]
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21 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 11. Final recommendation design schematic, showing the proposed combination of
options
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22 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
7.0 References
Barr Engineering Company. Weber Park Pond Report. Bloomington, 2006.
Braun Intertec Corporation. "Phase I Environmental Site Assessment." 2015.
Byers, Glenn and Mike Holmquist. Stormwater Consultant and Sales Engineer, Contech
Engineered Solutions Acadia Stephan. 27 April 2017. Email.
Capitol Region Watershed District. Curtiss Pond Improvement Project. n.d.
—. Upper Villa Stormwater Improvement Project. n.d.
City of Bloomington. Rainwater Garden Demonstration Projects. 2017.
City of Edina and Barr Engineering Company. Comprehensive Water Resource Management
Plan. Edina, 2011.
City of Edina. "Edina Living Streets Plan." 2015.
Contech Engineered Solution. Underground Stormwater Detention and Infiltration. 2017.
Contech Engineered Solutions. ChamberMaxx Stormwater Chamber System. n.d.
—. "Corrugated Metal Pipe Design Guide ." 2016.
—. Design Your Own (DYO) Project Tools. 2017.
Eshenaur, Walter. SRF Engineering Acadia Stephan and Rena Weis. n.d.
Fossum, Bob. Program Manager, CRWD Emily Caouette. 11 April 2017. Phone.
Gerk, Charles. Engineering Technician - Water Resources Jack Cottle. 19 April 2017.
Hennepin County. Property Information Search. 2017.
Hlas, Viktor. Application Engineer, OptiRTC Emily Caouette. 1 May 2017. Email.
Innovative Stormwater Management at the Neighbourhood Scale. Dir. University of British
Columbia. Master of Land and Water Systems. 2014. Youtube.
Kelley, Forrest. Regulatory Division Manager, CRWD Emily Caouette. 10 April 2017. Email.
Lake Superios Streams Duluth. Stormwater Management - Underground Storage. n.d.
Microsoft New England. Stormwater Made Sustainable - Opti Prepares Us for Tomorrow's
Storm. 2016.
Minnehaha Creek Watershed District. 2017 MCWD Grant Programs. 2017.
Minnesota Pollution Control Agency. Minnesota Stormwater Manual - Overview for Permeable
Pavement . 2017.
—. Minnesota Stormwater Manual - Overview for Stormwater and Rainwater Harvest. 2017.
National Oceanic and Atmospheric Administration. National Weather Service Atlas 14 Point
Precipitation Frequency Estimate: MN. 2017.
New York City Department of Environmental Protection. Guidelines for the Design and
Construction of Stormwater Management Systems. 2012.
OptiRTC. OptiNimbus. 2017.
PaveDrain. "PaveDrain FAQ." n.d.
Stratton, Sarah. Senior Water Resources Scientist, Barr Engineering Company Jessica Wilson. 9
March 2017. Email.
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23 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix A: Description and Photos of Temporary Inundation Area
(TIA)
As the name suggests, stormwater runoff is stored within the design capacity of the temporary
inundation area before it is piped directly to Weber Pond via the City of Edina's stormwater
system. The TIA is a low-lying, marshy area which could be further excavated to increase its
capacity, thus reducing the amount of water discharged to Weber Pond from this area.
Figure 12. The outlet structure that transports water from the TIA to Weber Pond via the
stormsewer system
Figure 13. The TIA exhibiting its current capacity to hold stormwater that will later be
transported to Weber Pond
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24 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 14. Example of an area within the TIA that could be excavated to increase capacity
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25 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix B: Final Designs
Final Design for Section 4.1 - Excavation of Weber Pond and Temporary
Inundation Area (TIA)
The final design of Weber Pond is to be excavated to 858-ft, with a side slope of 3:1 H:V, as
requested by City of Edina. The final design was completed, and its dimensions measured using
AutoCAD. Figure 15 shows the final proposed excavation plans for Weber Pond and the TIA.
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26 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 15. CAD Excavation Proposal of Weber Pond and TIA
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27 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 16 provides a web-based dashboard of the OptiRTC interface. The program provides a
graph of Pond Level over time and a precipitation forecast (Microsoft New England).
Figure 16. Example of OptiRTC web-based dashboard
Final Design for Section 4.2 - Underground Storage
These designs were completed using the online "Design Your Own Detention or Infiltration
System (DYODS)" provided by Contech Engineered Solutions (Contech Engineered Solutions).
Using GIS, the values for invert depth and limiting length and width were recorded in Table 16.
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28 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Final Design for Section 4.3 - Permeable Pavement
Figure 17: Proposed location of permeable pavement and underground storage in 2020 or 2021
road reconstruction area
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29 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix C: Cost Analysis Calculations
Cost Analysis for Section 4.1: Predictive Monitoring and Excavation
Bob Fossum (Fossum) and Forrest Kelley (Kelley) from the Capitol Region Watershed District
provided a general cost estimate for a predictive monitoring system. This estimate was based on
the cost of previous projects in the area that utilized predictive monitoring systems including the
Curtiss Field and the Upper Villa stormwater projects. Viktor Hlas at OptiRTC was contacted to
confirm this estimate; he can be contacted in the future for further information (Hlas).
Table 7. Cost Estimate for Weber Pond expansion through excavation
Item Description Unit
Estimated
Quantity
Unit Price
($) 1
Extension
($)
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 140,055
Site Work, Excavation, and Restoration
Erosion Control- Silt Fence L.F. 3100 3.5 10,850
Tree and Grub Removal L.S. 6.5 10,000 65,000
Remove and Replace Existing Fence L.S 1 1,500 1,500
Pond Excavation & Material Disposal C.Y. 87,547 15 1,313,200
Seeding- turf grass AC. 5 2,000 10,000
SUBTOTAL 1,400,550
TOTAL 1,540,605
1. Unit price provided by the City of Edina (Gerk)
Table 8. Cost estimate for excavation of TIA
Item Description Unit
Estimated
Quantity
Unit Price
($) 1
Extension
($)
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 53,981
Site Work, Excavation, and Restoration
Erosion Control- Silt Fence L.F. 1500 3.5 5,250
Tree and Grub Removal L.S. 2.6 10,000 26,000
Pond Excavation & Material Disposal C.Y. 33,557 15 503,360
Seeding- turf grass AC. 2.6 2,000 5,200
SUBTOTAL 539,810
TOTAL 593,791
1. Unit price provided by the City of Edina (Gerk)
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30 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Cost Analysis for Section 4.2: Underground Storage Units
Table 9. Budgetary cost estimate for underground storage located at Susan Lindgren Elementary
Item Description Unit
Estimated
Quantity
Unit Price
($) 1
Extension
($)
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 61,800
Underground Pipe System L.S. 1 618,000 618,000
SUBTOTAL 618,000
TOTAL 679,800
1. Unit price provided by Contech Engineered Solutions (Byers and Holmquist)
Table 10. Budgetary cost estimate for underground storage located at Weber Park Fields
Item Description Unit
Estimated
Quantity
Unit Price
($) 1
Extension
($)
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 135,000
Underground Pipe System L.S. 1 1,350,000 1,350,000
SUBTOTAL 1,350,000
TOTAL 1,485,000
1. Unit price provided by Contech Engineered Solutions (Byers and Holmquist)
Table 11. Budgetary cost estimate for underground storage located in the 2020 or 2021 road
reconstruction area
Item Description Unit
Estimated
Quantity
Unit Price
($) 1
Extension
($)
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 24,000
Underground Pipe System L.S. 1 240,000 240,000
SUBTOTAL 240,000
TOTAL 264,000
1. Unit price provided by Contech Engineered Solutions (Byers and Holmquist)
Cost Analysis for Section 4.3: Permeable Pavement
Table 12: Budgetary cost estimate for permeable pavement 1
Item Description Unit Estimated Quantity Unit Price ($) 1 Extension ($)
6" of AASHTO #57 stone S.F. 270950 0.50 140,000
Installation1 S.F. 270950 2.00 540,000
PaveDrain Material S.F. 270950 8.50 2,300,000
Delivery S.F. 270950 1.00 270,000
TOTAL 3,250,000
1. Unit price from PaveDrain (PaveDrain)
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31 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 13: Budgetary cost estimate for bituminous pavement
Item Description 1 Unit
Estimated
Quantity
Unit Price
($) 2
Extension
($)
Class V Rock Ton 9483 14.00 130,000
TYPE SP 9.5 Wearing Course Mixture
(SPWEA340B) Ton 2455 53.00 130,000
TYPE SP 12.5 Non Wearing Course Mixture
(SPNWB330B) Ton 4092 41.00 170,000
Project Mobilization/Demobilization (10%) L.S. 1 10% of Total 43,000
SUBTOTAL 430,000
TOTAL 473,000
1. Olinger road used as provided by the City of Edina (Gerk)
2. Unit Price as provided in bid tabs by the City of Edina (Gerk)
Unit price from PaveDrain
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32 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 13, the total budgetary cost of permeable pavement and bituminous pavement in the 2020
or 2021 road reconstruction area are $3,250,000 and $470,000, respectively. Both estimates
consider the cost of rock, installation, surface material, and mobilization. While other items will
contribute to the overall cost of this installation, it was assumed that these costs would be the
same, regardless of the type of pavement used. For example, the cost of installing new curb and
gutter will be the same, regardless of whether permeable pavement or bituminous asphalt is
installed. With this information, a marginal cost estimate was performed, which shows that the
additional cost of paving the 2020 or 2021 road reconstruction area with PaveDrain, rather than
bituminous pavement, is approximately $2,780,000.
Cost Analysis for Section 4.4: Alternative Options
Table 14. Budgetary cost estimate for property acquisitions
Street Address Type Value ($)1
4000 42ND ST W Residential 399,100
4100 FRANCE AVE S Residential 426,000
4104 FRANCE AVE S Residential 269,500
4108 FRANCE AVE S Residential 331,600
4005 42ND ST W Residential 365,100
4003 42ND ST W Residential 451,800
TOTAL 2,243,100
1. Values ($) from Hennepin County (Hennepin County)
Hennepin County property information database was used to determine the market price of these
houses, which totaled $2,243,100. Six additional properties lie within the 1% annual chance
flood map of Weber Pond. However, they were not considered for property acquisition because
they have a Letter of Map Amendment (LOMA). A LOMA was issued for these six properties
because, although they are mapped within a floodplain, the properties all sit on naturally high
ground that is above the base flood elevation.
Appendix D: Modeled Inflow and Outflow Hydrographs for Weber
Pond
It should be noted that the inflow and outflow values in our model are much greater than
realistically expected, and ~5 times greater than previously modeled (Barr Engineering
Company; City of Edina and Barr Engineering Company). The modeling program used, HEC-
HMS, has limited capabilities and could not account for the backup of water from the
downstream storm sewer or storage within the storm sewer system. Consequently, we chose to
keep the outlet to Minneapolis unrestricted for our model.
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33 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 18. Pre-development inflow and outflow hydrograph for Weber Pond
Figure 19. Post-development inflow and outflow hydrograph of Weber Pond
0
200
400
600
800
1000
1200
0 6 12 18 24 30 36Flow [cfs]Time [Hours]
Inflow Outflow
0
200
400
600
800
1000
1200
0 6 12 18 24 30 36Flow [cfs]Time [Hours]
Inflow Outflow
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34 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix E: HEC-HMS Model Inputs for Feasible Design Options
Model Inputs for Section 4.1: Predictive Monitoring and Excavation
Table 15. Changes in initial pond elevation for predictive monitoring model
Model Run Initial Pond Elevation [ft]
Pre-Development 861.5
PM Only 858
PM & Excavation 859
The model simulated predictive monitoring by changing the initial water surface elevation in
Weber Park Pond. This is the result of predictively discharging water in the time period leading
up to a storm event.
Underground storage tanks were modeled as one-acre rectangular reservoirs with vertical sides.
The capacities of the tanks were specified by varying the main outlet elevations. The storage in
acre-ft is equal to the height of the outlet in feet above the bottom of the tank. The main outlet is
a long weir which immediately discharges all water above the specified elevation. The secondary
outlet is a 1-ft diameter outlet pipe at the bottom of the tank. This outlet discharges the full tank
slowly once the peak inflow period is over. Figure 20 illustrates a typical storage-time
relationship for an underground storage tank.
Figure 20. Discharge over time for a 12 acre-ft Underground Storage Tank
0
2
4
6
8
10
12
14
0 10 20 30 40Storage [ac-ft]Time [hr]
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35 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Model Inputs for Section 4.2: Underground Storage
Table 16. Values for invert depth of stormwater mains assessed for locations of underground storage to find feasible design volume.
Location Description of Location Invert Depth
Upstream [ft]
Invert Depth
Upstream [ft]
Maximum
Diameter
[ft]1
Limiting
Length
[ft]
Limiting
Width
[ft]
Maximum
Volume
[ft3]
Susan Lindgren
Elementary
Deeded private property,
directly on edge of Edina
municipal boundary. Low
elevation of ~871 ft.
863.17 MSL 863.17 MSL 8.83 288 198 226,106
Weber Park Fields Deeded City property. Low
Elevation of ~870. 862.05 MSL 860.8 MSL
7.95 452 344 520,791
2020/2021 Road
Reconstruction Area
Deeds/easements necessary for
right of way. Collects small area
including MS_3/MS_7.
(Composite of two locations noted below. See below for values)
1. Grimes Avenue south of
Morningside Rd 8.5 3.8 7
See total
installed
length below.
Width limited
by the right of
way.
2. Morningside Rd near Crocker
Avenue 10 8.7 7 Total 1,973
Width limited
by the right of
way.
Total 75,9230
1. Selected using the invert depth and assumption of required 18 inches of cover material as per Contech (Contech Engineered
Solutions)
2. Limiting width will be determined by the deeds/easements which allow for installation of underground systems in right of way.
Limiting width assumed to be large enough to allow for 7-ft pipe installed.
3. Length established using a visual assessment of topographic map, selecting areas for which the grade was not too steep for the
installation of underground storage
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36 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Model Inputs for Section 4.3: Permeable Pavement
The length of streets within the 2020 or 2012 Road Reconstruction area were measured using
GIS. The paved width of each street was determined using the City of Edina’s Living Streets
Report based on the type of street (City of Edina) and aerial imagery in Google Maps. The
dimensions are shown in Table 17, which shows that the entire paved surface area of the 2020 or
2021 Road Reconstruction area is approximately 270,936-sqft.
Table 17: Dimensions of streets within 2020 or 2021 Road Reconstruction area
Street Name
(within 2020 or 2021
Road Reconstruction
Area)
Type of Street Length of
Street [ft]
Details Paved
Width
[ft]
Surface
Area [sqft]
Grimes Ave Local Street Connector 2027.8 2 sidewalk, 2 parking 30 60,834
Crocker Ave Local Street 1286.7 1 sidewalk, 1 parking 24 30,880.8
Lynn Ave Local Street 1286.7 2 sidewalk, 1 parking 24 30,880.8
Littel St Local Street Connector 274.3 2 sidewalk, 1 parking 24 6,583.2
Oakdale Ave S Local Street 1,526.5 2 sidewalk, 1 parking 24 36,636.0
West 42 St Local Street Connector 1,444.5 0 sidewalk, 2 parking 24 34,668.0
Morningside Rd Local Street Connector 1,343.8 2 sidewalk, 2 parking 30 40,314.0
Branson St Local Street 1,255.8 2 sidewalk, 1 parking 24 30,139.0
TOTAL - 10,446.1 - 270,936.0
Using the street dimensions presented in Table 17, the proposed percentage of impervious land
surface was computed for each subwatershed. It was assumed that PaveDrain is 100%
permeable. The proposed percent of impervious surface area for each subwatershed is shown in
Table 18, and these values were used in the HEC-HMS model.
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37 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 18: Change in percent impervious from existing conditions to proposed permeable
pavement at 2020 or 2021 Road Reconstruction area
Subwatershed
ID
% Impervious
Decrease 1
Existing %
Impervious 2
Proposed %
Impervious 3
MS_2 6.64 20 13.4
MS_5 10.73 20 9.3
MS_8 12.97 20 7.0
MS_18 4.08 17 12.9
MS_19 20.05 20 0.0
MS_21 9.49 20 10.5
MS_45 22.6 20 0.0
MS_47 15.68 20 4.3
MS_48 10.78 20 9.2
1. Percent impervious was calculated assuming PaveDrain product is 100% permeable.
2. Existing percent impervious was obtained from Barr’s previously developed model (Barr
Engineering Company).
3. In some cases, the % impervious decrease is less than the existing % impervious. This is due to
minor errors when measuring streets in GIS, and the errors are negligible.
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38 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix F: Analysis of Initial Options
In addition to the feasible design options outlined in Section 4.0 of this report, a number of
additional options were initially considered before it was determined that (based on the
background information outlined in Section 4.0 Methodology) these options either failed to
significantly lower the 1% annual chance flood elevation or were currently not feasible for the
City of Edina to implement. The options are classified into broad categories based on ongoing
projects within the City of Edina. Each option is given a general description, including reasoning
for rejecting each option at this time.
Park Development – Public
Direct Flow to Park Swale
In this option, the curb is altered to have gaps that redirect stormwater flow away from
stormwater catch basins and into above ground Best Management Practices (BMPs) located on
parkland (Columbia). Thus, the curb gaps are placed where stormwater runoff would typically
enter stormwater catch basins (Columbia). It is proposed that gaps be placed on the south side of
Weber Park where the flow would then enter the Park and be stored or infiltrated by a
bioretention pond or similar system. Although this option could possibly be implemented to slow
the volume of water reaching Weber Pond through stormwater pipes, the majority of available
land for the use of BMPs is currently located primarily within the 1% annual chance floodplain
and, therefore, do not allow for infiltration in the 1% annual chance event. Thus, this option was
rejected.
Underground Storage
(This option was selected for the feasibility study. See Section 4.3 for description and results)
Stormwater Reuse
A stormwater collection and reuse system could be implemented near Weber Pond and the stored
water could be used to irrigate the neighboring ball fields. This option would capture some of the
volume of stormwater before it reaches Weber Pond, reducing the peak flood elevation and the
peak discharge of the stormwater into the pond. The reuse systems could also reduce stress on
existing water and stormwater infrastructure, which, when implemented in a park area, could be
used as an education feature to inform the public about stormwater management. Public
perception is often an issue when implementing water reuse systems, so public education is
important (Minnesota Pollution Control Agency). However, as the ball fields are located mainly
within the 1% annual chance floodplain and do not require irrigation following a storm event,
this option was rejected.
Excavation
(This option was selected for the feasibility study. See Section 4.1 for description and results)
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39 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Road Reconstruction – Public
Pervious Pavement
(This option was selected for the feasibility study. See Section 4.4 for description and results)
Underground Storage
(This option was selected for the feasibility study. See Section 4.3 for description and results)
Road Reconstruction – Private
Residential Rain Gardens
Installation of rain gardens in the yards of residential properties along the street reconstruction
area has the potential to reduce stormwater runoff to Weber Pond from the south and to improve
water quality. A cost share program could be used to incentivize eligible residents to install rain
gardens in their front yards (City of Bloomington). However, there are many potential issues that
could arise from installing these projects on private land including changes in property
ownership, which places the rain gardens at risk of being under-maintained or removed. In
addition, this option is not likely to produce the amount of volume reduction desired for
decreasing flood levels in Weber Park Pond during peak rain events. For these reasons, this
option was rejected.
Pond Maintenance
Dredge Pond
Sediment buildup from runoff has the potential to reduce the total volume of the pond, reducing
the effective storage volume of the pond during the 1% annual chance storm event. Dredging
would remove the accumulated sediment from the bottom of the pond. Given the relatively large
amount of additional stormwater detention volume that would be needed to reduce the risk of
flooding, though, it is reasonable to assume that dredging Weber Pond will not significantly
reduce the risk of flooding. Dredging could, however, improve the water quality of the pond.
Forecast Based Control System
(This option was selected for the feasibility study. See Section 4.1 for description and results)
Increasing Outlet Pipe Size
The current downstream capacity of the Minneapolis sewer system from the Morningside
neighborhood is approximately 25-cfs (Barr Engineering Company). To decrease the flooding in
Weber Pond to an acceptable level, the downstream capacity would need to be increased to 105-
cfs (Barr Engineering Company). This would require structural renovations to the stormwater
infrastructure operated by the City of Minneapolis or the installation of a 48-in outlet pipe
directly to Lake Calhoun, parallel to existing outlets (Barr Engineering Company). These
improvements are not feasible at this time and, thus, this option was rejected.
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40 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Alter Outlet Structure
The current outlet structure of Weber Pond is a 42-in reinforced concrete pipe (RCP) and has an
invert elevation of 861.5-ft. These values were found using the City of Edina's CAD data. The
Manning's roughness of the pipe is 0.013 (City of Edina and Barr Engineering Company).
Choosing a smoother pipe might increase discharge capacity, but these improvements would be
marginal and likely limited by the downstream sewer capacity. Increased flow rates would be
proportional to any decrease in the roughness parameter of the outlet, up to the limit of the
downstream capacity.
The outlet invert elevation could be lowered, resulting in a lower normal water elevation in
Weber Pond. This would likely increase flow rates through the downstream storm sewer during
storm events, which would be unacceptable. Thus, this option was rejected.
Projects That Require Other Partners
Increase Infiltration for Surface Flow
Increasing infiltration within the section of land west of Weber Park Pond and the newly
acquired land north of Weber Park could ensure that sheet flow of rainfall runoff will be
infiltrated at the maximum rate. This would involve considering replacement of turf grass areas
with a land cover that allows for a higher infiltration rate. This option is not likely to produce the
amount of volume reduction desired for decreasing levels in Weber Park Pond. Thus, this option
was rejected.
Other Options
Acquire the At-Risk Properties
(This option was selected for the feasibility study. See Section 4.4 for description and results)
No Action by the City of Edina
Based on feasibility of other options, the City of Edina could decide to do nothing. Damage to
the residential properties is a likely result of this option. The total damage at each residential
property will depend on frequency, depth, and duration of flooding. Threatened properties flood
during a 1% annual chance (100-year) storm and may also be affected by other storm events. The
total depth and duration of flooding experienced by each home could be found using the
elevation over time graph of Weber Pond.
This option could be chosen if it is determined that the risk and potential loss of property from
flooding is determined to be less than the cost to implement any other option. However, although
the City of Edina has yet to implement flood mitigation options, the City has communicated their
interest in taking action through their request to complete a feasibility study for stormwater flood
mitigation within Weber Pond.
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41 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix G: HEC-HMS Model Input Data for Pre-development Model
Figure 21. Labeled Overview of Pre-Development Model
08S_W_Edina
42 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 19. Flow Routing Parameters where shape is modeled as a circle for all reaches (City of
Edina and Barr Engineering Company)
Label Length (ft) Slope (ft/ft) Manning’s n Diameter (ft)
Reach-01 901.01 0.003 0.013 1.25
Reach-02 899.48 0.0039 0.013 1.5
Reach-03 898.09 0.0032 0.013 2
Reach-04 1764.48 0.0665 0.013 1.75
Reach-05 3450.12 0.0061 0.013 2.25
Reach-06 863 0.0015 0.013 4.5
Reach-07 862.42 0.003 0.013 4.5
Reach-08 862 0.0031 0.013 4.5
Reach-09 861.5 0.0016 0.013 3.5
Reach-10 861.31 0.0015 0.013 3.5
Reach-11 901.4 0.0048 0.013 1.25
Reach-12 861 0.0016 0.013 3.5
Reach-13 860 0.0016 0.013 3.5
Reach-14 861.5 0.0001 0.014 3.5
Reach-15 864.5 0.0133 0.024 1
Reach-16 858 0.0025 0.013 2
Reach-18 2617.66 0.0065667 0.013 1
Reach-19 860 0.006567 0.013 1
Reach-20 3471.04 0.05515 0.013 2.3125
Reach-21 1776.59 0.041 0.013 2.25
Reach-22 892.66 0.0056 0.015 1.25
Reach-23 1789.77 0.0005 0.013 2.25
Reach-24 898.09 0.0001 0.013 2.25
Reach-25 2658.24 0.0123667 0.013 1.8333
Reach-26 861.02 0.0011 0.013 2.5
Reach-27 860.78 0.0011 0.013 2.5
Reach-28 866 0.0045 0.013 1.25
Reach-29 1733.38 0.013 0.013 1.25
Reach-30 864.3 0.0102 0.013 2.5
Reach-31 860.6 0.0004 0.013 3.5
Reach-32 860.28 0.0007 0.013 3.5
Reach-33 860.43 0.0028 0.013 1.25
Reach-34 1719.94 0.0029 0.013 3
Reach-35 862.62 0.001 0.013 1.75
Reach-36 1725.48 0.0007 0.013 1.75
Reach-37 1725.87 0.0056 0.013 1.5
Reach-38 1717.13 0.01195 0.013 3.75
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43 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Reach-39 876.1 0.0233 0.013 1
Reach-40 861.48 0.0056 0.024 2.08
Reach-41 860 0.0041 0.024 2
Reach-42 859.67 0.0005 0.013 2.5
Reach-43 900.4 0.0033 0.013 1.25
Reach-44 898.29 0.0001 0.013 1.25
Reach-45 865.6 0.01 0.024 1
Reach-46 865.5 0.0041 0.024 1.5
Reach-47 865.27 0.01 0.024 1
Reach-48 2585.02 0.0015 0.013 4
Reach-49 1720.77 0.00145 0.013 3.5
Reach-50 869.5 0.0375 0.013 1.25
Table 20. Subbasin Properties (Horton Method) (Stratton)
Subwatershed Area (ac) Horton fo
values
Horton fc
values
Horton α
values
MS_01 0.52 1 0.03 0.00115
MS_10 3.25 2.909 0.221 0.00115
MS_11 1.48 1.425 0.072 0.00115
MS_13 4.83 3 0.23 0.00115
MS_14 1.35 3 0.23 0.00115
MS_15 1.21 3 0.23 0.00115
MS_16 3.99 3 0.23 0.00115
MS_17 2.19 3 0.23 0.00115
MS_18 2.31 2.851 0.215 0.00115
MS_19 3.2 3 0.23 0.00115
MS_02 9.98 3 0.23 0.00115
MS_20 5.44 2.82 0.212 0.00115
MS_21 5.03 2.87 0.217 0.00115
MS_22 4.81 3 0.23 0.00115
MS_23 1.39 1.028 0.033 0.00115
MS_24 2 1 0.03 0.00115
MS_25 0.96 1 0.03 0.00115
MS_26 4.28 1.002 0.03 0.00115
MS_27 3.96 2.83 0.213 0.00115
MS_28 1.65 2.184 0.148 0.00115
MS_29 3.97 2.107 0.141 0.00115
MS_03 3.27 3 0.23 0.00115
MS_30 5.86 2.086 0.139 0.00115
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44 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
MS_31 6 1.119 0.042 0.00115
MS_32 3.62 1.526 0.083 0.00115
MS_33 5.42 2.516 0.182 0.00115
MS_34 3.42 3 0.23 0.00115
MS_35 3.83 3 0.23 0.00115
MS_36 1.82 3 0.23 0.00115
MS_37 2.15 3 0.23 0.00115
MS_38 1.45 1.764 0.106 0.00115
MS_39a 5.47 1.097 0.04 0.00115
MS_39b 8.7 1.809 0.111 0.00115
MS_04 3.69 3 0.23 0.00115
MS_40 11.98 1.672 0.097 0.00115
MS_41 0.86 1 0.03 0.00115
MS_42 4.39 2.935 0.224 0.00115
MS_43 5.2 3 0.23 0.00115
MS_44 1.11 1.095 0.04 0.00115
MS_45 2.07 2.407 0.171 0.00115
MS_46 5.52 2.486 0.179 0.00115
MS_47 4.32 3 0.23 0.00115
MS_48 10.24 3 0.23 0.00115
MS_49 5.25 2.781 0.208 0.00115
MS_05 3.26 3 0.23 0.00115
MS_50 3.34 3 0.23 0.00115
MS_51 6.9 3 0.23 0.00115
MS_52 4.5 3 0.23 0.00115
MS_53 1.04 3 0.23 0.00115
MS_54 10.13 2.869 0.209 0.00115
MS_55 6.72 1.792 0.109 0.00115
MS_56 0.77 3 0.23 0.00115
MS_57 1.77 3 0.23 0.00115
MS_58 2.83 1.344 0.064 0.00115
AREA_A 96.2 2.6 0.19 0.00115
AREA_C-1 2.1 3 0.23 0.00115
Area_C-2 7.2 2.4 0.17 0.00115
08S_W_Edina
45 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Figure 22. Sample of Infiltration curve comparison between Horton and Green-Ampt methods
Table 21. Subbasin Properties (Green-Ampt Method)
Label Area (ac) Initial Saturated Suction
(in)
Conductivity
(in/hr) % Impervious
Area A 96.2 0.2 0.4 2 0.19 20
Area C1 2.1 0.2 0.4 2.25 0.23 20
Area C2 7.2 0.2 0.4 1.9 0.17 20
MS_01 0.5 0.1 0.3 1.6 0.03 17
MS_02 10.0 0.1 0.3 2.275 0.23 20
MS_05 3.3 0.1 0.3 2.275 0.23 20
MS_08 3.8 0.1 0.3 2.275 0.23 20
MS_09 2.5 0.1 0.3 2.275 0.23 20
MS_13 4.2 0.1 0.3 2.275 0.23 20
MS_16 3.6 0.1 0.3 2.275 0.23 20
MS_17 2.2 0.1 0.3 2.275 0.23 20
MS_18 3.0 0.1 0.3 2.15 0.215 17
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5 3 3.5 4Infiltration Rate (in/hr)Time (hours)
SUBWATERSHED: AREA C-2
Green Ampt Horton's
08S_W_Edina
46 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
MS_19 3.2 0.1 0.3 2.275 0.23 20
MS_20 5.4 0.1 0.3 2.15 0.212 17
MS_21 5.0 0.1 0.3 2.2 0.217 20
MS_22 4.8 0.1 0.3 2.275 0.23 20
MS_25 1.0 0.1 0.3 1.6 0.03 17
MS_26 4.3 0.1 0.3 1.6 0.03 24
MS_27 4.0 0.1 0.3 2.15 0.213 20
MS_28 1.7 0.1 0.3 1.8 0.148 20
MS_29 4.0 0.1 0.3 1.75 0.141 20
MS_30 5.9 0.1 0.3 1.75 0.139 17
MS_32 3.6 0.1 0.3 1.5 0.083 20
MS_33 5.4 0.1 0.3 1.975 0.182 20
MS_34 3.4 0.1 0.3 2.275 0.23 20
MS_35 3.8 0.1 0.3 2.275 0.23 20
MS_36 1.8 0.1 0.3 2.275 0.23 20
MS_37 2.2 0.1 0.3 2.275 0.23 20
MS_38 1.5 0.1 0.3 1.6 0.106 14
MS_39a 14.2 0.1 0.3 1.45 0.04 0
MS_39b 14.2 0.1 0.3 1.6 0.111 0
MS_40 12.0 0.1 0.3 1.55 0.097 32
MS_41 0.9 0.1 0.3 1.6 0.03 16
MS_42 4.4 0.1 0.3 2.2 0.224 20
MS_43 5.2 0.1 0.3 2.275 0.23 20
MS_44 1.1 0.1 0.3 1.45 0.04 18
MS_45 2.1 0.1 0.3 1.925 0.171 20
MS_46 35.7 0.1 0.3 1.95 0.179 23
MS_47 4.3 0.1 0.3 2.275 0.23 20
MS_48 10.2 0.1 0.3 2.275 0.23 20
MS_49 5.2 0.1 0.3 2.15 0.208 17
MS_50 3.3 0.1 0.3 2.275 0.23 20
MS_51 7.6 0.1 0.3 2.275 0.23 20
MS_52 4.5 0.1 0.3 2.275 0.23 20
MS_53 1.0 0.1 0.3 2.275 0.23 20
MS_54 10.1 0.1 0.3 2.25 0.209 0
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47 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 22. Inflow-Diversion Function
Inflow
(cfs)
Diversion (cfs) (To
Weber Pond)
0 0
1.4605 0
6.4405 0
15.223 0
27.865 0
44.332 0
64.535 0
88.342 0
115.6 0
146.11 0
179.69 0
216.1 0
255.12 0
296.49 0
339.96 0
385.23 0
432.02 20.747
480.04 68.761
528.95 117.68
578.45 167.17
628.17 216.89
677.76 266.48
726.84 315.56
775 363.73
821.84 410.56
866.88 455.6
909.64 498.36
949.57 538.3
986.07 574.8
1018.4 607.17
1045.8 634.57
1067.2 655.93
1081 669.77
1085 673.72
Figure 24. Profile View of Diversion
Figure 23. Plan View of Diversion Location
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48 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 23. Modeled Reservoirs
Weber Elevation-Area TIA Elevation-Area
Pre-Dev Excavated Pre-Dev Excavated
Stage (ac) (ac) Stage (ac) (ac)
857.5 1.00 1.00 860 0.00 1.88
858 2.29 7.02 862 0.00 2.05
860 2.29 7.38 864 0.00 2.22
862 3.06 7.75 866 1.53 2.41
864 3.78 8.12 868 2.53 2.60
866 8.36 10.03
868 16.33 10.50
869 21.00 21.00
869.2 21.60 21.60
869.4 22.09 22.09
869.6 22.58 22.58
869.8 23.15 23.15
870 23.91 23.91
Table 24. Reservoir Outlets
Parameter Weber Pond
Outlet TIA Outlet
Length (ft) 190 100
Diameter (ft) 3.5 2.5
Inlet Elevation (ft) 858.5 866.7
Entrance Coefficient 0.5 0.5
Outlet Elevation (ft) 861.5 866
Exit Coefficient 0.5 0.5
Manning's n 0.013 0.013
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49 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Table 25. Precipitation data from NOAA Atlas 14, MSP Station (National Oceanic and
Atmospheric Administration)
Duration Partial-Duration Depth (in)
5 Minutes 1.01
15 Minutes 1.81
1 Hour 3.68
2 Hours 4.75
3 Hours
6 Hours
12 Hours
24 Hours
5.51
6.58
7.12
7.50
Appendix H: HEC-HMS Model Output Data for Feasible Design
Options (Post-Development Model)
Table 26. Water Elevation over time data for pre-development and each post development option
Pre-
develop.
model
US
Susan
Lindgren
School
US
Weber
Park
Fields
US 2020 or
2021 Road
Re-
construction
Pave
Drain
Weber
Pond
Exc.
PM
PM +
Weber
Pond
Exc.
PM +
Weber
Pond
Exc. +
TIA Exc.
Time
(hr) Elevation (ft)
0 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
0.25 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
0.5 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
0.75 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
1 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
1.25 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
1.5 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
1.75 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
2 861.5 861.5 861.5 861.5 861.5 861.5 858 859 859
2.25 861.5 861.5 861.5 861.5 861.5 861.5 858.1 859 859
2.5 861.5 861.5 861.5 861.5 861.5 861.5 858.1 859 859
2.75 861.5 861.5 861.5 861.5 861.5 861.5 858.1 859 859
3 861.5 861.6 861.5 861.5 861.5 861.5 858.1 859 859
3.25 861.6 861.6 861.5 861.5 861.5 861.5 858.1 859 859
3.5 861.6 861.6 861.5 861.5 861.5 861.5 858.1 859 859
3.75 861.6 861.6 861.5 861.6 861.5 861.5 858.1 859 859
4 861.6 861.6 861.5 861.6 861.5 861.5 858.1 859 859
4.25 861.6 861.6 861.5 861.6 861.6 861.5 858.1 859 859
4.5 861.6 861.6 861.5 861.6 861.6 861.5 858.1 859 859
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50 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
4.75 861.6 861.6 861.5 861.6 861.6 861.5 858.1 859 859
5 861.6 861.6 861.5 861.6 861.6 861.5 858.1 859 859
5.25 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
5.5 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
5.75 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
6 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
6.25 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
6.5 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859 859
6.75 861.6 861.6 861.5 861.6 861.6 861.5 858.2 859.1 859.1
7 861.6 861.7 861.5 861.6 861.6 861.6 858.2 859.1 859.1
7.25 861.7 861.7 861.6 861.6 861.6 861.6 858.3 859.1 859.1
7.5 861.7 861.7 861.6 861.6 861.6 861.6 858.3 859.1 859.1
7.75 861.7 861.7 861.6 861.6 861.6 861.6 858.3 859.1 859.1
8 861.7 861.7 861.6 861.7 861.6 861.6 858.3 859.1 859.1
8.25 861.7 861.7 861.6 861.7 861.7 861.6 858.4 859.1 859.1
8.5 861.7 861.7 861.6 861.7 861.7 861.6 858.4 859.1 859.1
8.75 861.7 861.8 861.6 861.7 861.7 861.6 858.4 859.1 859.1
9 861.8 861.8 861.6 861.7 861.7 861.6 858.5 859.1 859.1
9.25 861.8 861.9 861.6 861.8 861.7 861.6 858.5 859.1 859.1
9.5 861.9 862 861.7 861.8 861.8 861.6 858.7 859.2 859.2
9.75 862 862.1 861.8 861.9 861.9 861.7 858.8 859.2 859.2
10 862.1 862.2 861.9 862 862 861.7 859 859.2 859.2
10.25 862.2 862.3 862 862.1 862.1 861.8 859.3 859.3 859.3
10.5 862.3 862.5 862.1 862.2 862.2 861.8 859.6 859.3 859.3
10.75 862.5 862.8 862.2 862.4 862.4 861.9 860 859.4 859.4
11 862.8 863.1 862.4 862.7 862.7 862.1 860.7 859.6 859.6
11.25 863.1 863.6 862.6 863 863 862.3 861.6 859.8 859.8
11.5 863.6 864.2 862.9 863.5 863.5 862.5 862.3 860.1 860.1
11.75 864.2 865.1 863.3 864.1 864.1 862.8 863.1 860.5 860.5
12 865.2 866.7 864.2 865 865.1 863.6 864.5 861.4 861.3
12.25 866.9 867.9 866.2 866.8 866.8 865.5 866.6 863.5 863.3
12.5 868.1 868.3 867.5 868 868.1 867.1 867.9 865.4 865.1
12.75 868.4 868.4 868 868.3 868.4 867.7 868.2 866.1 865.8
13 868.5 868.5 868.2 868.4 868.5 867.9 868.4 866.4 866.1
13.25 868.6 868.5 868.3 868.5 868.5 868 868.4 866.5 866.2
13.5 868.6 868.5 868.3 868.5 868.6 868 868.4 866.6 866.3
13.75 868.6 868.4 868.3 868.5 868.5 868 868.4 866.6 866.3
14 868.6 868.4 868.3 868.5 868.5 868 868.4 866.6 866.3
14.25 868.5 868.3 868.2 868.4 868.4 867.9 868.3 866.5 866.3
14.5 868.4 868.2 868.2 868.4 868.4 867.8 868.3 866.5 866.2
14.75 868.4 868.2 868.1 868.3 868.3 867.7 868.2 866.4 866.1
15 868.3 868.1 868 868.2 868.2 867.5 868.1 866.3 866.1
15.25 868.2 868 867.9 868.1 868.1 867.4 868 866.2 866
15.5 868.1 867.9 867.8 868 868.1 867.3 867.9 866.1 865.8
15.75 868 867.7 867.7 867.9 867.9 867.1 867.8 866 865.7
16 867.9 867.6 867.6 867.8 867.8 867 867.6 865.8 865.6
16.25 867.8 867.5 867.5 867.7 867.7 866.9 867.5 865.7 865.5
16.5 867.6 867.3 867.3 867.5 867.5 866.7 867.4 865.6 865.4
16.75 867.5 867.2 867.2 867.4 867.4 866.6 867.3 865.5 865.3
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17 867.4 867.1 867.1 867.3 867.3 866.5 867.1 865.4 865.2
17.25 867.2 867 867 867.2 867.1 866.3 867 865.3 865.1
17.5 867.1 866.8 866.9 867 867 866.2 866.9 865.2 865
17.75 867 866.7 866.8 866.9 866.9 866.1 866.8 865.1 864.9
18 866.9 866.6 866.7 866.8 866.8 866 866.6 865 864.8
18.25 866.7 866.5 866.6 866.7 866.7 865.8 866.5 864.9 864.7
18.5 866.6 866.4 866.5 866.6 866.5 865.7 866.4 864.8 864.6
18.75 866.5 866.3 866.4 866.5 866.4 865.6 866.3 864.7 864.5
19 866.4 866.2 866.3 866.4 866.3 865.5 866.2 864.6 864.5
19.25 866.3 866.1 866.2 866.3 866.2 865.3 866.1 864.5 864.4
19.5 866.2 865.9 866.2 866.2 866.1 865.2 866 864.4 864.3
19.75 866.1 865.7 866.1 866.1 866 865.1 865.8 864.4 864.2
20 866 865.5 866 865.9 865.8 865 865.6 864.3 864.2
20.25 865.8 865.4 865.8 865.7 865.6 864.9 865.4 864.2 864.1
20.5 865.6 865.2 865.7 865.5 865.4 864.8 865.3 864.1 864
20.75 865.4 865 865.5 865.4 865.3 864.7 865.1 864.1 864
21 865.2 864.9 865.4 865.2 865.1 864.7 864.9 864 863.9
21.25 865.1 864.7 865.2 865 864.9 864.6 864.8 863.9 863.8
21.5 864.9 864.6 865.1 864.9 864.8 864.5 864.7 863.9 863.8
21.75 864.8 864.5 865 864.8 864.7 864.4 864.5 863.8 863.7
22 864.6 864.4 864.9 864.6 864.5 864.3 864.4 863.8 863.6
22.25 864.5 864.2 864.7 864.5 864.4 864.3 864.3 863.7 863.6
22.5 864.4 864.1 864.6 864.4 864.3 864.2 864.2 863.6 863.5
22.75 864.3 864 864.5 864.3 864.2 864.1 864.1 863.6 863.5
23 864.2 863.9 864.4 864.2 864.1 864.1 864 863.5 863.4
23.25 864.1 863.8 864.4 864.1 864 864 863.8 863.5 863.4
23.5 863.9 863.6 864.3 864 863.8 863.9 863.7 863.4 863.4
23.75 863.8 863.5 864.2 863.8 863.7 863.9 863.5 863.4 863.3
24 863.6 863.4 864.1 863.7 863.5 863.8 863.4 863.3 863.3
24.25 863.5 863.3 864 863.5 863.4 863.7 863.3 863.3 863.2
24.5 863.4 863.2 863.9 863.4 863.3 863.7 863.2 863.3 863.2
24.75 863.3 863.1 863.8 863.3 863.2 863.6 863.1 863.2 863.2
25 863.2 863 863.7 863.2 863.1 863.6 863.1 863.2 863.1
25.25 863.1 863 863.6 863.2 863.1 863.5 863 863.1 863.1
25.5 863 862.9 863.6 863.1 863 863.5 862.9 863.1 863.1
25.75 863 862.8 863.5 863 862.9 863.4 862.9 863.1 863
26 862.9 862.8 863.4 862.9 862.9 863.4 862.8 863 863
26.25 862.8 862.7 863.3 862.9 862.8 863.3 862.7 863 863
26.5 862.8 862.7 863.3 862.8 862.7 863.3 862.7 863 862.9
26.75 862.7 862.6 863.2 862.8 862.7 863.2 862.7 863 862.9
27 862.7 862.6 863.2 862.7 862.7 863.2 862.6 862.9 862.9
27.25 862.6 862.6 863.1 862.7 862.6 863.2 862.6 862.9 862.8
27.5 862.6 862.5 863.1 862.6 862.6 863.1 862.5 862.9 862.8
27.75 862.6 862.5 863 862.6 862.5 863.1 862.5 862.8 862.8
28 862.5 862.5 863 862.6 862.5 863.1 862.5 862.8 862.8
28.25 862.5 862.4 863 862.5 862.5 863 862.4 862.8 862.8
28.5 862.5 862.4 862.9 862.5 862.4 863 862.4 862.8 862.7
28.75 862.4 862.4 862.9 862.5 862.4 863 862.4 862.7 862.7
29 862.4 862.3 862.9 862.4 862.4 862.9 862.4 862.7 862.7
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29.25 862.4 862.3 862.8 862.4 862.4 862.9 862.3 862.7 862.7
29.5 862.3 862.3 862.8 862.4 862.3 862.9 862.3 862.7 862.7
29.75 862.3 862.3 862.8 862.4 862.3 862.9 862.3 862.7 862.6
30 862.3 862.3 862.8 862.3 862.3 862.8 862.3 862.6 862.6
30.25 862.3 862.2 862.7 862.3 862.3 862.8 862.2 862.6 862.6
30.5 862.3 862.2 862.7 862.3 862.2 862.8 862.2 862.6 862.6
30.75 862.2 862.2 862.7 862.3 862.2 862.8 862.2 862.6 862.6
31 862.2 862.2 862.7 862.3 862.2 862.7 862.2 862.6 862.5
31.25 862.2 862.2 862.6 862.2 862.2 862.7 862.2 862.6 862.5
31.5 862.2 862.2 862.6 862.2 862.2 862.7 862.2 862.5 862.5
31.75 862.2 862.1 862.6 862.2 862.2 862.7 862.1 862.5 862.5
32 862.2 862.1 862.6 862.2 862.1 862.7 862.1 862.5 862.5
32.25 862.1 862.1 862.6 862.2 862.1 862.6 862.1 862.5 862.5
32.5 862.1 862.1 862.5 862.2 862.1 862.6 862.1 862.5 862.5
32.75 862.1 862.1 862.5 862.1 862.1 862.6 862.1 862.5 862.4
33 862.1 862.1 862.5 862.1 862.1 862.6 862.1 862.5 862.4
33.25 862.1 862.1 862.5 862.1 862.1 862.6 862.1 862.4 862.4
33.5 862.1 862.1 862.5 862.1 862.1 862.5 862.1 862.4 862.4
33.75 862.1 862 862.4 862.1 862.1 862.5 862.1 862.4 862.4
34 862.1 862 862.4 862.1 862.1 862.5 862 862.4 862.4
34.25 862 862 862.4 862.1 862 862.5 862 862.4 862.4
34.5 862 862 862.4 862.1 862 862.5 862 862.4 862.4
34.75 862 862 862.4 862.1 862 862.5 862 862.4 862.4
35 862 862 862.3 862 862 862.5 862 862.4 862.3
35.25 862 862 862.3 862 862 862.4 862 862.4 862.3
35.5 862 862 862.3 862 862 862.4 862 862.3 862.3
35.75 862 862 862.3 862 862 862.4 862 862.3 862.3
36 862 862 862.3 862 862 862.4 862 862.3 862.3
Table 27. Inflow and outflow hydrograph for pre-development and final recommendation
Pre-development Final Recommendation
Time (hr) Inflow (cfs) Outflow (cfs) Inflow (cfs) Outflow (cfs)
0 0 0 0 0
0.25 0.2 0 0.2 0
0.5 0.3 0 0.3 0
0.75 0.4 0 0.4 0
1 0.5 0 0.5 0
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1.25 0.5 0 0.5 0
1.5 0.5 0 0.5 0
1.75 0.5 0 0.5 0
2 0.6 0 0.6 0
2.25 0.6 0 0.6 0
2.5 0.6 0 0.6 0
2.75 0.6 0 0.6 0
3 0.6 0 0.6 0
3.25 0.6 0 0.6 0
3.5 0.6 0 0.6 0
3.75 0.7 0 0.7 0
4 0.7 0 0.7 0
4.25 0.7 0 0.7 0
4.5 0.7 0 0.7 0
4.75 0.7 0 0.7 0
5 0.8 0 0.8 0
5.25 0.8 0 0.8 0
5.5 0.8 0.1 0.8 0
5.75 0.8 0.1 0.8 0
6 0.9 0.1 0.9 0
6.25 1.1 0.1 1.1 0
6.5 1.2 0.1 1.2 0
6.75 1.4 0.1 1.4 0
7 1.5 0.1 1.5 0
7.25 1.6 0.1 1.6 0
7.5 1.7 0.2 1.7 0
7.75 1.9 0.2 1.9 0
8 2.1 0.2 2.1 0
8.25 2.3 0.3 2.3 0
8.5 2.5 0.3 2.5 0
8.75 2.7 0.3 2.7 0
9 3 0.4 3 0
9.25 9.7 0.6 9.7 0
9.5 11.8 0.9 11.8 0
9.75 13.9 1.3 13.9 0
10 16.4 1.8 16.4 0
10.25 19.8 2.4 19.8 0
10.5 24.7 3.4 24.7 0
10.75 47.5 5.1 47.5 0
11 63.8 8.6 63.8 0
11.25 83.4 14 83.4 0
11.5 109.5 21.5 109.5 0
11.75 177.4 31 177.4 0
12 466.9 47.2 466.9 0
12.25 1189.4 72.3 1189.2 19.7
12.5 511.7 87.8 510.1 51.3
12.75 216.8 91.2 216.8 61.6
13 155.1 92.6 155.1 64.9
13.25 119.5 93 119.5 66.9
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13.5 95.4 93.2 95.4 68
13.75 62.6 93 62.6 68.4
14 46.6 92.7 46.6 67.9
14.25 35.7 91.9 35.7 67.3
14.5 28.4 91.2 28.4 66.3
14.75 23.3 90.3 23.3 65.2
15 19.6 89.5 19.6 63.9
15.25 8.9 88.4 8.9 62.6
15.5 6.4 87.4 6.4 60.9
15.75 4.7 86.4 4.7 59.4
16 3.6 84.9 3.6 57.6
16.25 3 83.1 3 55.8
16.5 2.7 81.6 2.7 54
16.75 2.4 79.9 2.4 52.2
17 2.3 78.2 2.3 50.5
17.25 2.1 76.7 2.1 48.7
17.5 2 75 2 47
17.75 1.9 73.3 1.9 45.4
18 1.8 71.9 1.8 43.8
18.25 1.3 70.1 1.3 42.3
18.5 1.1 68.8 1.1 40.9
18.75 1 67 1 39.5
19 0.9 65.7 0.9 38.1
19.25 0.9 64 0.9 36.7
19.5 0.8 62.6 0.8 35.2
19.75 0.8 61 0.8 33.8
20 0.8 59.3 0.8 32.7
20.25 0.7 56.3 0.7 31.7
20.5 0.7 53.4 0.7 30.3
20.75 0.7 50.6 0.7 29.2
21 0.7 47.9 0.7 28.3
21.25 0.7 45.4 0.7 27
21.5 0.6 42.9 0.6 25.7
21.75 0.6 40.6 0.6 24.8
22 0.6 38.4 0.6 23.8
22.25 0.6 36.3 0.6 22.6
22.5 0.6 34.4 0.6 22
22.75 0.6 32.4 0.6 20.9
23 0.6 30.5 0.6 20.2
23.25 0.5 28.9 0.5 19.2
23.5 0.5 26.8 0.5 18.6
23.75 0.5 24.2 0.5 17.7
24 0.5 22 0.5 17
24.25 0.3 19.7 0.3 16.5
24.5 0.2 18.1 0.2 15.7
24.75 0.1 16.5 0.1 15
25 0 15 0 14.5
25.25 0 13.6 0 14
25.5 0 12.4 0 13.6
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25.75 0 11.3 0 13
26 0 10.5 0 12.5
26.25 0 9.7 0 12
26.5 0 8.9 0 11.6
26.75 0 8.2 0 11.2
27 0 7.8 0 10.8
27.25 0 7.1 0 10.5
27.5 0 6.7 0 10.1
27.75 0 6.2 0 9.7
28 0 5.7 0 9.3
28.25 0 5.4 0 8.9
28.5 0 5.1 0 8.8
28.75 0 4.8 0 8.5
29 0 4.6 0 8.1
29.25 0 4.3 0 7.9
29.5 0 4 0 7.8
29.75 0 3.8 0 7.4
30 0 3.6 0 7.1
30.25 0 3.5 0 7.1
30.5 0 3.3 0 6.7
30.75 0 3 0 6.6
31 0 3 0 6.4
31.25 0 2.8 0 6.1
31.5 0 2.6 0 6.1
31.75 0 2.6 0 5.7
32 0 2.4 0 5.7
32.25 0 2.4 0 5.4
32.5 0 2.2 0 5.4
32.75 0 2.2 0 5.2
33 0 2 0 5.1
33.25 0 2 0 4.9
33.5 0 1.9 0 4.8
33.75 0 1.8 0 4.7
34 0 1.8 0 4.6
34.25 0 1.6 0 4.6
34.5 0 1.6 0 4.3
34.75 0 1.6 0 4.3
35 0 1.5 0 4.2
35.25 0 1.5 0 4
35.5 0 1.5 0 4
35.75 0 1.4 0 3.8
36 0 1.4 0 3.8
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56 | Feasibility Study Weber Park Stormwater Pond Flood Mitigation
Appendix I: Budget for Completion of Feasibility Study
Table 28. Budget for completion of feasibility study for flood mitigation options within Weber Pond
Project Task Projected Time
expenditure
Projected cost1 Responsible Team
Member
Actual time
Expenditure
Actual Cost
Project Development Work Plan 8 800 Acadia 10.5 1,050
Meet with City of Edina 30 3,000 All 77.5 7,750
Biweekly Project Reports 32 3,200 All 27.5 2,750
Group Meetings 32 3,200 All 92.75 9,275
Report Writing (Draft & Final) 132 13,200 Acadia 112.75 11,275
Presentation (Midterm & Final) 100 10,000 Rena 73.5 7,350
Task #1: Gain familiarity with the
project background
52 5,200 Acadia 17.5 1,750
Task #2: Conduct research and select
preliminary options
50 5,000 Jack 37.0 3,700
Task #3: Consider advantages and
disadvantages of each option/ narrow
choices down. (multiple times)
36 3,600 Emily 10.25 1,025
Task #4: Perform hydrologic and cost
estimate calculations for approximately
six options
68 6,800 Rena 41.5 4,150
Task #5: Learn modeling software 66 6,600 Jack 35.25 3,525
TOTALS: 606 60,600 536.0 53,600
1. Cost has been estimated using an hourly billing rate of $100 for each team member.