HomeMy WebLinkAboutFlood Risk Reduction Strategy_final_wappendix0
CITY OF EDINA
FLOOD RISK REDUCTION
STRATEGY
April 7, 2020
City of Edina, Engineering Department
www.EdinaMN.gov
1
Table of Contents
Executive Summary ....................................................................................................................................... 3
Problem statement ....................................................................................................................................... 6
Project initiation ....................................................................................................................................... 6
Pathways to structural flood risk .............................................................................................................. 8
Groundwater levels are increasing: summary of monitoring data ....................................................... 9
Flood risk factors ....................................................................................................................................... 9
Drivers of increasing flood risk ............................................................................................................... 10
Getting to scale: a challenging problem made even more challenging, climate change impact
analysis ................................................................................................................................................ 12
Climate Action Plan: in progress item ................................................................................................. 12
Formulating a Strategy ................................................................................................................................ 13
Comprehensively Reduce Flood Risk throughout the Community ......................................................... 13
The gap between the current Comprehensive Water Resources Management Plan and the Strategy 14
City Sectors of Work ................................................................................................................................... 15
Infrastructure .......................................................................................................................................... 15
Go Big, Go Bigger: infrastructure analysis .......................................................................................... 16
Morningside Roadway Reconstruction Engineering Study: in progress item ..................................... 17
Regulation ............................................................................................................................................... 19
Keep your water to yourself: private infrastructure analysis ............................................................. 21
From ‘ill-drained’ to impervious: impervious surface analysis ........................................................... 22
Impervious limit: in progress item ...................................................................................................... 23
Outreach and Engagement ..................................................................................................................... 23
Outreach products: in progress item .................................................................................................. 24
Emergency Services ................................................................................................................................ 24
Strategy Development ................................................................................................................................ 25
Task Force role and process .................................................................................................................... 25
Brainstorming, prioritizing, and categorizing possible actions ............................................................... 27
Conclusion ................................................................................................................................................... 27
Acknowledgement ...................................................................................................................................... 29
Appendix ..................................................................................................................................................... 30
Appendix A: Resident Task Force Report .................................................................................................. A
2
Appendix B: ‘Getting to scale: a challenging problem made even more challenging, climate change
impact analysis’, technical memo ............................................................................................................. B
Appendix C: ‘Go Big, Go Bigger: infrastructure analysis’, technical memo .............................................. C
Appendix D: ‘Keep your water to yourself: private infrastructure analysis’, technical memo ................. D
Appendix E: ‘From ‘ill-drained’ to impervious: impervious surface analysis’, technical memo ............... E
Appendix F: Actions for Flood Resilient Homes, fact sheets .................................................................... F
Appendix G: Task Force charge ................................................................................................................ G
Appendix H: Potential action matrix key, ranked response, and potential action matrix ........................H
3
Executive Summary
This flood risk reduction strategy summarizes the framework for understanding risk and how we can
connect on the promise to comprehensively reduce the risk of flooding throughout the community.
Over a ten-month period, a task force of staff and community members worked to come to a shared
understanding of what flooding is, what is valuable, and what matters, where, and to whom.
Structural flood risk occurs through a variety of pathways; over the land surface, through groundwater
seepage, and via sanitary backflow. Efforts to reduce risk depend on time. The best time to reduce flood
vulnerability is before the flood. During a flood, the focus shifts to staying safe from harm, or sustaining
or restoring services. After the flood, we focus on recovering and reviewing risk.
Over the land surface Groundwater seepage Sanitary backflow
Through the process, we come to a new understanding of the factors that define flood risk. Climate,
exposure, and vulnerability vary with time, and across the landscape, assets, and people that characterize
the community.
Short term (weather), mid-term
(seasonal), and long term
(climate) risks. Rainfall varies
over time, and climate change
increases the extremes.
The degree to which property,
homes, buildings, infrastructure
and other assets come into
contact with flood water.
The degree to which exposed
assets, both public and private,
are unable to resist flooding and
are damaged by floods.
4
Conventional flood risk management focuses primarily on reducing exposure to flooding or transferring
risk, although sometimes in unknown or unexpected ways. This often means public capital infrastructure
projects to modify the flood or regulatory standards applied when properties develop or redevelop.
Through this framework we recognize that the public realm is a large opportunity space to reduce risk,
but not the only one. Some of the simplest and most cost-effective ways to reduce risk are for people
to reduce the vulnerability of their structures and property. This framework calls for public and private
actions to reduce community flood risk. Additionally, the framework recognizes climate as a factor.
Increasing climate extremes drive exposure and demand adaptation or resilience to mitigate the change.
We explored the factors that are driving increasing flood risk. The primary and secondary drivers are
climate change and aging infrastructure. Well-drained landscapes and imperviousness also matter, but
are more historical drivers of flood risk.
Climate change is making storms more intense and increasing the chance of
extended wet periods or drought. Climate change has already, and will expose
more assets to flooding in the future. This driver is predicted to overwhelm the
other drivers in terms of scale.
Private and public assets and infrastructure are both exposed and vulnerable.
Public infrastructure can define flood exposure for different points in the
landscape, and serve as a pathway for private risk. Public infrastructure assets are
old and not capable of meeting the current demand. This is a significant driver as
infrastructure provides most stormwater service.
Development has connected the landscape to the water to make land well-
drained. While this a major historic driver, it is a minor driver increasing future
flood exposure. Most of the drainage and land development decisions have already
been made, and cannot be unmade. There is additional demand for drainage that
can reduce vulnerability, but marginally affects flood exposure downstream.
Community demand for garages, parking areas, patios, decks, pools, and bigger
homes has increased the hard cover of soils. Imperviousness drives runoff in small
storms and marginally affects flood exposure in large storms.
5
These efforts to put flooding into focus have resulted in the creation of this framework to connect on
the promise to comprehensively reduce the risk of flooding throughout the community.
Approaches for managing risk include reducing exposure, reducing vulnerability, transferring and sharing
risks, increasing resilience to changing risks, and preparing, responding and recovering from floods.
Through the following areas of work, we will work with the community to comprehensively reduce
flood risk.
INFRASTRUCTURE: We will renew our infrastructure and operate it to reduce risk.
We will plan public streets and parks to accept and transmit flood waters to reduce the risk
and disruption of related city services.
REGULATION: We acknowledge competing demands of land use and addressing
drainage, groundwater, and surface water issues. We help people solve issues without
harming another.
OUTREACH AND ENGAGEMENT: We make flood information available and give
people tools for flood resilience.
EMERGENCY SERVICES: We help people prepare for floods, remove people from
harm during floods, and recover after floods.
Staff would like to thank the Task Force for their contributions. The experience, knowledge, and
curiosity they brought to the process added value and influenced the Strategy.
Nora Davis (co-chair), Lake Cornelia Neighborhood
Kathy Amlaw (co-chair), Lake Edina Neighborhood
Greg Lincoln, Morningside Neighborhood
Michael Platteter, Morningside Neighborhood
Louise Segreto, Indian Hills Neighborhood
Roxane Lehmann, Sunny Slope Neighborhood
Richard Strong, Concord Neighborhood
Richard Manser, Todd Park Neighborhood
City of Edina budget goals
Strong Foundation: Maintain physical
assets and infrastructure. Livable City: Plan for connected and
sustainable development.
Reliable Service: Maintain service levels
that best meet the needs of the community. Better Together: Foster an inclusive
and engaged community.
6
Problem statement
Flooding can affect people, damage property, threaten health and safety, and disrupt transportation and
business. Flooding is common in Edina and climate change is expected to make flooding worse.
Flooding has historically been considered a technical problem, requiring a technical solution. Land
ownership, space, legislation, and hydrology are interwoven with values about problem ownership,
water stewardship, service tradeoffs, and transferring risk.
When there is consensus on both values and knowledge, the problem is a technical one. A scientific
problem is one in which there is consensus on values, but disagreement on knowledge. A political
problem is one in which there is consensus on knowledge, but disagreement on values. When there is
disagreement on both knowledge and values, the problem is a social one.
Timothy M. Gieseke. Shared Governance for Sustainable Working Landscapes
What was once considered purely a technical problem may be more of a mix of a technical, scientific,
political, and social one. This type of problem requires a different set of strategies, skill sets, and tools.
Project initiation
In September 2018 City Council adopted the 2018 Comprehensive Water Resources Management Plan.
The implementation section of the plan included development of a Flood Risk Reduction Strategy.
A City Manager Task Force of Edina residents was formed to provide a community voice to the process.
The City recognizes the contribution of these individuals and appreciates the value they’ve provided.
Resident Task Force members;
Nora Davis (co-chair), Lake Cornelia Neighborhood
Kathy Amlaw (co-chair), Lake Edina Neighborhood
Greg Lincoln, Morningside Neighborhood
Michael Platteter, Morningside Neighborhood
Louise Segreto, Indian Hills Neighborhood
Roxane Lehmann, Sunny Slope Neighborhood
Richard Strong, Concord Neighborhood
Richard Manser, Todd Park Neighborhood
7
The Task Force was charged with supporting and providing recommendations to inform the
development of this strategy, specifically to;
• Incorporate local challenges, opportunities, knowledge, and community values.
• Incorporate voices from throughout the City of Edina. While the Morningside neighborhood has
been identified as a focal area for case study, strategies and outcomes ought to be scalable city-
wide.
• Identify action steps for building community capacity to address flood risk and resiliency in
Edina.
In July 2019 staff began working with a resident Task Force to develop a Flood Risk Reduction Strategy.
The group met over a dozen times, investing hundreds of hours collectively.
The strategy doesn’t solve flooding. We’ve learned that it’s too big of a problem to solve outright;
however, we’ve charted a path to reduce the risk of flooding. Through this effort, we;
• Explored technical questions like, “How much does impervious cover matter?”, “What kind of
flood risk does the future hold in the wake of a changing climate?”, “How much benefit can
private storage provide?”, and “How much benefit can bigger infrastructure provide?”
• Interviewed the operators and maintainers of the system to better understand the level of
service the system currently provides and its vulnerabilities.
• Gained a better understanding of the factors and drivers that influence flood risk.
• Described the various ways in which structural flooding occurs; over the land surface, through
groundwater seepage, and sanitary sewer backflow.
• Defined the areas within which we already work and identified other actions the City could
undertake, connecting these areas of work to Council work plan goals.
• Widened our approaches for reducing flood risk.
• Heard people share their experience and knowledge about flooding. The Task Force shared
their community values around flood risk and informed the framework and strategy.
Based on Council and community feedback, the Morningside neighborhood was selected as the focal
area for the Flood Risk Reduction Strategy. Further description about how the neighborhood was used
to test ideas is provided in the Strategy Development section of this report.
Throughout this report, we briefly highlight relevant in-progress items and summaries of the technical
analyses – more detailed memorandums describing the technical analyses are provided in the Appendix.
8
Pathways to structural flood risk
Too much water from rain or melting snow can overwhelm the system. Pipes run full, intersections
flood, lakes and creeks overtop their banks, water flows over the land surface, sidewalks and paths
become impassible, yards are inundated, groundwater builds up, water seeps through basement walls
and floors, and water can back up into homes through sanitary sewers.
9
Groundwater levels are increasing: summary of monitoring data
Groundwater levels are increasing: summary of monitoring data
In the winter of 2020 Nine Mile Creek Watershed District and Minnehaha Creek Watershed District
separately convened local water resources and emergency managers to share their groundwater level
monitoring data.
After a string of exceptionally wet years and a record-breaking precipitation year in 2019, lakes and
creeks are high, the ground is saturated and, in many places, groundwater level monitoring records
show water table elevations are on the rise. Data from the Nine Mile Creek Watershed District
showed one groundwater monitoring well in Edina near Bredesen Park had an increase of about 15
feet since 2010. In areas where the depth to the regional groundwater table is shallow, structures
with basements are at an increased risk for flooding from groundwater seepage.
Groundwater is difficult to map. It’s dynamic, inconsistent, and the distribution can vary drastically
from what we see on the land surface.
Flood risk factors
Flood Risk: Flood risk is determined by climate, exposure, and vulnerability.
Flood Exposure: The degree to which property, homes, buildings, infrastructure, and other assets
come into contact with flood water.
Flood Vulnerability: The degree to which exposed assets are unable to resist flooding and are
damaged by floods.
For example, two homes side-by-side might have the same flood exposure, but one home might be less
vulnerable to the exposure. Vulnerability can be decreased with the installation of downspouts, proper
grading, a basement sump pump, waterproof or reinforced foundations, mature trees with strong root
systems, and excellent drainage through well-designed rain gardens, among other things.
Flood risk factors and definitions adapted from IPCC, 2012: Managing the Risks of Extreme Events and
Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the
Intergovernmental Panel on Climate Change.
10
Drivers of increasing flood risk
Flooding issues within the City of Edina continue to increase in frequency and severity. The following
have been identified as primary drivers leading to increased flood risk.
Climate change and changing weather patterns:
• Climate change is the lead driver of increasing flood risk in Edina. Climatologists indicate that
large, intense rainfall events are occurring more frequently, and models predict that large rainfall
events will become more intense in the future. Minnesota is already experiencing prolonged wet
periods; in fact, the years between 2015 and 2019 were the wettest in Minnesota history and we
can expect more wet years in the future. This increase is also impacting neighboring
communities, is occurring at the international, national, state, and watershed levels, and is
expected to get much worse.
• With the update to the Comprehensive Water Resources Management Plan, the most recent
precipitation frequency estimates were incorporated into the City’s flood model which showed
increased flood risk throughout the City. It should be noted that this data only brings us to
current climate conditions and does not provide protection for additional future risk caused by
climate change.
• Modeling of storms and flood risk, and visualization of that risk has improved dramatically in
recent decades, leading to better community perception of risk.
• See ‘Getting to scale: a challenging problem made even more challenging, climate change impact
analysis’ and ‘Climate Action Plan: in progress item’ sections of this report.
Aging and obsolete infrastructure:
• Infrastructure is aging, and much is in poor repair, stretching maintenance and operations staff
thin. Current resources dictate a reactive approach instead of a proactive approach.
• The current stormwater system was built for a different time and standard. Climate change has
already increased the risk and made most of the system obsolete.
• Needs far exceed available resources. Flooding issues are extensive and improvements that
address the 1%-annual-chance storm are often out of reach at current levels of funding.
11
Demand for well-drained landscapes:
• Development has connected the landscape to the water to make land well drained. Demand for
well-drained landscapes has led to private and public drain line and gutter expansion. This
expansion directly connects the landscape and the water generated there to downstream
properties and waterbodies.
• While this a major historic driver, it is a minor driver increasing future flood exposure. Most of
the drainage and land development decisions have been made, but there are some public and
private system retrofits that continue to connect landscape and water bodies, marginally
affecting flood exposure.
Imperviousness:
• Community demand for garages, parking areas, patios, decks, pools, and bigger homes has
increased the hard cover of soils.
• There is an increasing trend of imperviousness in the City of Edina. Specifically, within the focal
area of Morningside, nearly one million square feet of impervious surfaces (homes, structures,
driveways, patios, swimming pools, etc.) have been added since 1950. This equates to about 14%
of the total size of occupied parcels in the Morningside neighborhood (2019, City of Edina staff).
• This is a minor driver increasing future flood exposure. Most of the land development decisions
have been made, but small additions to impervious cover marginally affect flood exposure. Soils
can’t soak up the amounts of water floods provide.
• See ‘Keep your water to yourself: private infrastructure analysis’, ‘From ‘ill-drained’ to
impervious: impervious surface analysis’, and ‘Impervious limit: in progress item’ sections of this
report.
12
Getting to scale: a challenging problem made even more challenging, climate change impact
analysis
Getting to scale: a challenging problem made even more challenging, climate
change impact analysis
Through the Task Force process, staff heard the sentiment, “Stop studying the problem, you have the
answer, it’s time to act.” While action is needed now, this report rebuts the sentiment that we have
the answers. Our new understanding of risk in the 2018 Comprehensive Water Resources
Management Plan show the system is overloaded. We now can more easily see how ‘solving’ a
problem in one area can make a downstream problem worse. ‘Solutions’ need to review downstream
risk and be packaged together comprehensively, acknowledging or mitigating the risk transfer.
Packaging problems requires a scale of effort that has not been attempted in Edina, and the scales
contemplated still do not totally ‘solve’ the problem, instead they may not even be keeping up with
climate change.
Climate change is changing the target. Solutions of today have to accommodate more water than in
the past, and solutions have to withstand the effects of climate change in the future. We need a new
approach to planning. It is necessary to shift the approach from trying to reduce flood exposure for
some, to reducing the vulnerability to flooding for all.
A memorandum describing the analysis in more detail is available in the appendix.
Climate Action Plan: in progress item
Climate Action Plan: in progress item
Development of a Climate Action Plan would further outline and prioritize actions for climate change
mitigation and adaptation. City staff is working to scope a process for creating a Climate Action Plan
for Edina. The Energy and Environment Commission recently completed a study and report on a
timeline and parameters for such a plan, including the City’s leadership role.
Undoubtedly, carbon reduction in both the private and public sectors will be an area of opportunity.
In order to meet community-wide emission reduction goals, it will take a process that includes the
community to understand what actions are important and how to prioritize them. There is a clear
overlap between addressing flood risk and mitigating climate change. To that end, it is prudent that
the Flood Risk Reduction Strategy inform the larger Climate Action Plan work of the City’s
Sustainability Manager and Energy and Environment Commission.
13
Formulating a Strategy
Comprehensively Reduce Flood Risk throughout the Community
Flooding in Edina is not only common, it’s increasing. The City of Edina’s strategy is to
comprehensively reduce risk throughout the community. This means we address flooding
through a broad range of actions and that decisions consider the assets and people that characterize the
City. Approaches for managing risk include reducing exposure, reducing vulnerability, transferring and
sharing risks, increasing resilience to changing risks, and preparing, responding and recovering from
floods.
Adapted from IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate Change
Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change
Strategy helps answer the question, “What are we trying to accomplish?” Every community has limited
resources and deals with its own unique challenges – strategy acts as a guide to a set of actions and
filters out those that do not fit.
Tactics help answer the question, “How are we going to accomplish our goal?” Tactics are the actions
within the following City sectors of work; infrastructure, regulation, outreach and engagement, and
emergency services. Each sector of work supports a City Council budget work plan goal.
Flood Risk Reduction Approaches
Reduce Exposure
Reduce Vulnerability
Transfer and Share Risks
Increase Resilience to Changing Risks
Prepare, Respond, and Recover
14
These areas of work and the current state of practice are spelled out in greater detail in the water
resources chapter of the Comprehensive Plan and the Comprehensive Water Resources Management
Plan.
The gap between the current Comprehensive Water Resources Management Plan and
the Strategy
Past iterations and the current Comprehensive Water Resources Management Plan have focused
primarily on reducing exposure to flooding or transferring risk, although sometimes in unknown or
unexpected ways. This often means capital infrastructure projects to modify the flood or regulatory
standards applied when properties develop or redevelop. The current Comprehensive Water Resources
Management Plan outlines projects that add or upsize pipes or surface flood storage. This narrow
approach has some pitfalls.
• First, it limits the approaches, and thereby the actions that could be implemented to reduce
flood risk. The actions focus on reducing exposure only. Many opportunities exist using
15
approaches to reduce vulnerability, transfer and share risks, increase resiliency to changing risks,
and preparing, or responding, and recovering from flooding.
• Second, it ignores the risk transferred to downstream people and assets. Many of the capital
infrastructure projects don’t consider impacts outside the immediate project area. In a fully
developed landscape, many of the downstream storage areas in Edina and in our neighboring
communities are already full.
• Third, it implies that the public realm is the only opportunity space to reduce risk – some of the
simplest and most cost-effective ways to reduce risk are for people to reduce the vulnerability
of their structures and property. Some resources to this end have been developed as part of
this process (see Outreach Products in the Outreach and Education section of this report).
• Fourth, it doesn’t recognize the lead driver; climate change, and sets us on a path in which we
cannot catch up to the increasing risk. The strategy and associated actions must be able to scale
to the problem.
City Sectors of Work
The City of Edina works in the following four sectors to reduce community flood risk. Detailed in each
sector overview is; a statement of the intended outcome of the work, a list of the City departments and
partners who lead the work, a list of City departments and partners who help, are involved, or are part
of the process, a description of when and how flood risk is considered, and a summary of gaps identified
during detailed discussions with the Task Force.
Infrastructure
What is the outcome; Building stormwater infrastructure that manages areas of flood flow and
storage that, with the landscape, define areas of vulnerability. Reducing the vulnerability of infrastructure
so they are durable to extreme events or fail-safe. Reducing exposure and vulnerability of related
sanitary sewer infrastructure that can serve as a conduit for flood waters between structures. The
service provided by water resource and other infrastructure is defined in the 2018 City of Edina
Comprehensive Plan and Comprehensive Water Resources Management Plan.
Who does the work; Public Works Department, Engineering Department, property owners, private
redevelopment, and contractors.
Who is involved; Planning Department, Building Department, and future property owners.
When flooding risk is considered; At decision points, in projects, during design, failure analysis, and
during infrastructure planning.
Gaps; Actual service level falls short of expected service, aging infrastructure, reactive maintenance,
reactive emergency response, capital improvements do not have scale to ‘fix it’ or even keep up with
climate change trend.
Pace of redevelopment: Currently driven by owners of at-risk properties.
16
Enhancing public infrastructure by building new, retrofitting old, and keeping what we have in working
condition is a key action to reducing flood exposure.
Stormwater systems route water to low areas where it is temporarily stored, and then they work to
convey water downstream. The stormwater system is made up of 127 miles of gravity main ranging from
12-84” in diameter, 6800 manholes, 900 outlets, 38 miles of small diameter sump drain, 11 stormwater
lift stations, one half mile of stormwater force main, and more than 150 ponds and wetlands (2018 Draft
Comprehensive Plan Chapter 7).
The City’s stormwater system was designed to convey a certain amount of water and protect against
impacts at a certain level. This “level of protection” is based on the capacity of public infrastructure to
handle stormwater and on the probability that a storm will occur. When storms are bigger or more
intense than the infrastructure is designed to handle, or when it clogs, there are consequences such as
disruptions to services, facilities, or damage to property. The city stormwater system is exposed to
flooding and also determines the flood exposure of people and assets.
Risk is changing primarily because climate is changing and the level of protection for design is a moving
target. Designs from the past are undersized for today and there is a growing realization in technical
circles that even if designs were revised to reflect today’s climate they would quickly be obsolete due to
the changing risk brought by climate change.
Go Big, Go Bigger: infrastructure analysis
Go Big, Go Bigger: infrastructure analysis
To test the possible scale of implementation in the face of projected climate change impacts, a
preliminary evaluation and conceptual design of potential flood risk reduction options for the
Morningside neighborhood was completed.
A cursory evaluation was conducted to assess which option reduced flood exposure for the most
homes. This was completed for a range of storm events from the 20%-annual-chance storm event (5-
year storm which is 3.6 inches in 24 hours) to the 1%-annual-chance storm event (100-year storm
which is 7.5 inches in 24 hours). Infrastructure options that were evaluated included increasing storm
sewer pipe sizes, constructing flood walls, creating additional flood storage by excavating (lowering)
the ballfield area of Weber Park and then reconstructing the fields, creating additional flood storage
by excavating the wooded area north of Weber Pond and excavating and re-grading existing low
areas (e.g. low area at Lynn Avenue and Kipling Avenue north of West 42nd Street), excavating
backyards in key locations, installing predictive pumping systems for a few key areas (including Weber
Pond), and installing underground flood storage.
Seven infrastructure options were developed using combinations of some of the mitigation options
identified above with planning-level costs estimated between $3.4M and $31.6M. The option with the
largest benefit in terms of homes that would no longer be exposed to flooding up to the 1%-annual-
chance storm event (Option 7b, the ‘Go Bigger’ option) has an estimated cost of $8.5M and
completely removes approximately 24% of the homes potentially impacted under existing conditions.
17
The next best infrastructure option (Option 2b, the ‘Go Big’ option) removes approximately 16% of
the homes currently impacted and would cost approximately $4.5M.
Baseline; the current replacement value of stormwater infrastructure in the City is about $70M.
Over 16 square miles this is approximately;
• $6,800/acre
• Baseline replacement value of stormwater infrastructure
The ‘Go Big’ option contemplated a $4.5M project serving about 630 properties and 185 acres.
• $24,300/acre
• Cost 3.6 times larger than the baseline
The ‘Go Bigger’ option contemplated an $8.5M project serving about 630 properties and 185
acres.
• $45,900/acre
• Cost 6.7 times larger than the baseline
In addition to costs, the projects come with tradeoffs, contemplating major changes in parks, open
spaces, existing water bodies, and piping and utility operations changes. The projects also present
opportunity for co-planning around park and sustainability improvements as sections of aging
infrastructure are renewed.
A memorandum describing the analysis in more detail is available in the appendix.
Morningside Roadway Reconstruction Engineering Study: in progress item
Morningside Roadway Reconstruction Engineering Study: in progress item
Infrastructure options remain the foundation of reducing flood exposure, but the scale of climate
change will make transformation change a challenge. In April 2020 staff will ask Council to consider a
scope of service for preliminary engineering for the street reconstruction project in the Morningside
D/E and Morningside C neighborhoods in 2022 and 2023, respectively. Staff will also ask Council to
consider the engagement plan to go along with the project concept-level design. This would be the
first major street reconstruction project to be designed under the proposed flood risk reduction
strategy.
The operations and maintenance of public infrastructure is a key component of reducing flood risk.
Operations includes inspection and condition assessment, street cleaning, catch basin clog clearing, pipe
and outlet clog clearing, sediment control, pump and power system monitoring, and emergency
18
operations. Maintenance includes catch basin repair, pipe repair, outlet repair, sediment removal, weed
and woody debris removal, and other actions.
Stormwater models that predict flood problems assume that all pipes, catch basins, inlets, and outlets
are in good working order and free from obstructions. The reality is that material and debris often enter
the system before or during storms and can cause service disruptions. Aging infrastructure also lends to
more failures.
Staff prioritizes their stormwater operation and maintenance work based on opportunity and requests
for service within the constraints of their resources. Opportunities include repairing and renewing
stormwater infrastructure in areas where other work is already planned. For example, crews inspect
and repair stormwater catch basins in neighborhoods where street improvements are planned, thereby
extending the life of the street improvement and providing real value to the public. Requests for service
also get prioritized. As storm events occur, staff evaluate the risk and respond as resources allow.
Operations and maintenance staff were invited to talk about their work with the Task Force. Some
themes related to the challenges and opportunities emerged.
Challenges related to operation and maintenance:
• Much of the system aside from pump and power systems are managed with reactive,
run-to-failure approach and there is significant deferred maintenance in the system
leading to small items remaining unaddressed, leading to larger issues.
• The program for evaluating maintenance needs meets the minimum regulatory standard.
It is not comprehensive.
• The system is aging, much of it originating in the 1950s and 1960s.
• During events, stormwater systems and sanitary sewer systems are stressed at the same
time. When flood events coincide with snow and ice events, staff are further stretched
to provide services and must make decisions about priorities, constrained by their
resources.
• Some stormwater features in the city have been installed to intentionally capture
pollutants and debris in order to protect clean water. When not properly maintained,
they can interfere with overlapping drainage and flood protection services.
• Service levels are not clearly defined. During the peak of events, staff are receiving,
prioritizing, responding to, and communicating on requests for service. Residents often
don’t know where their issue ranks or what service level they can expect.
Opportunities for operation and maintenance:
• Proactive maintenance, the benefits of which go beyond flood protection. Proactively
cleaning and maintaining stormwater infrastructure can support clean water goals by
properly managing accumulated pollutants.
• Increased street sweeping to keep stormwater conveyances clear. This also has a clean
water benefit.
19
• Promotion of the new metro-wide adopt-a-drain program to augment city street
sweeping. Residents are asked to adopt a storm drain in their neighborhood and keep it
clear of leaves, trash, and other debris to reduce water pollution. The program also
works to provide flood protection. Often, once a system is flooded, the primary
objective for maintenance staff is to clear the obstruction. At this point, the opportunity
to clear and dispose of clogging debris before its transported to downstream
waterbodies is largely lost.
• High value infrastructure retrofits. In some cases, maintaining and optimizing existing can
be more cost effective than new infrastructure.
• Better definition of service levels to inform residents on what they can expect for given
issues.
• More general communication about the City’s flood response during and after events.
• Continued investment in the sanitary sewer system and its resiliency during floods.
An increase in resources dedicated to public works staff would be required in order to address issues
and capitalize on opportunities in operations and maintenance.
Regulation
What is the outcome; Homes and buildings have reduced exposure to floods. Those that are
exposed to floods take actions to reduce vulnerability. Private improvements such as structures,
landscaping, grading and other private systems manage their own risk, and take actions that do not
increase exposure of neighboring properties, reducing it if possible.
Who does the work; Engineering Department, Building Department, private permit applicants.
Who is involved; Public Works Department, Planning Department, future property owners.
When flooding risk is considered; At application and permit, during construction, at final inspection
and permit close.
Gaps; Added impervious marginally increases community risk, long term maintenance of private
drainage systems is uncertain, “retail” nature of permitting a variety of single family improvements is
time intensive, regulation in limited areas due to limited resources, the first point of contact that
interfaces with builders, homeowners, and describes issues in homes with existing exposure is time
intensive.
Redevelopment provides a once-in-a-generation opportunity to build-in resilience. City staff are actively
engaged with the development community through regulatory programs and provide technical support
to permitted and affected private parties. In response, new structures or additions can be required to
meet minimum elevations for low floors (such as basements) or low openings (such as the top of
windows wells). Another response to redevelopment includes requiring durable flow paths to route
water away from structures. The City could consider enhancing standards for resilience in
redevelopment plans or encourage a deeper risk conversation with the development community to
promote resilient decision-making within the permit process. Increased regulation of redevelopment in
20
Edina would reduce risk. A tradeoff would be that a change in regulation could impose additional costs
to developers and impact overall market conditions.
Future flooding is projected to get worse. The models that predict flood risk use data from the past to
estimate precipitation. The City could consider a flood risk standard that incorporates future risk due
to climate change to match the lifecycle of the private improvements that rely on them. By planning
street flood storage, lowering roads, managing overflow paths, and taking other actions based on a
future flood risk level due to climate change, capacity could be built into the system to make them
future ready for their expected design lives.
Land use is often cited as a key sector for managing flood risk, though fully developed communities such
as Edina may not be able to realize the same returns in this sector as a less developed community. Many
of the decisions about land use in Edina have already been made – that is to say that neighborhoods
emerged in places and at times that might not have otherwise happened if those land use decisions were
made today.
The regulatory program remains an effective way to reduce the consequences of flooding for the
developing property. The City could consider further enhancing the outreach to property owners,
builders and developers to promote resilient design.
Where they work: As private improvements are made, or properties redevelop, the City
provides flood risk information and holds standards that control or mitigate the exposure to
flooding through its regulatory program. Existing controls through the regulatory program are
working to raise the low elevations or low openings of structures. This raising of structures
reduces the exposure to flooding.
Where they don’t work: While the regulatory program is good to reduce exposure and
vulnerability to the property or improvement that is changing and its immediately adjacent
neighbors, it is a poor tool to reduce the flood exposure downstream.
21
Keep your water to yourself: private infrastructure analysis
Keep your water to yourself: private infrastructure analysis
The impact of comprehensive stormwater storage including underground storage within private
property, the right of way, or under streets in the Morningside neighborhood was evaluated. This
analysis was conducted as a result of Task Force discussions about the potential impacts of requiring
private homeowners to store stormwater running off from their impervious areas on-site similar to
requirements for commercial development.
The benefits achieved by storing the first 1-inch, 2-inches, and 3-inches of precipitation from storm
events of varying size, from the 20%-annual-chance storm event (5-year storm) to the 1%-annual-
chance storm event (100-year storm) are summarized in the table below. For the private storage
evaluation underground storage vaults were assumed under a portion of each of the 570 residential
parcels within the Morningside neighborhood. The analysis showed that storing the first 1-inch of
storms of this magnitude had a negligible impact on flood levels. Storing the first 2-inches and 3-inches
showed a more significant benefit with regards to reduction in peak flood levels. Depending on the
storm event, and depending on the location within in the neighborhood, the results varied anywhere
from flood level decreases of a few inches to decreasing nearly a foot and a half. However, this
apparent benefit comes at an initial cost of approximately $15,000 per inch of stormwater stored per
residential parcel. To store 2-inches of runoff in the entire neighborhood would cost approximately
$17 million. In addition, while the flood levels may be lowered, the number of homes that are
removed from potential impacts from flood inundation is small. For example, one home may
potentially be removed from flood inundation at Weber Pond depending on the storm event. Finally,
the management and maintenance of these underground stormwater storage vaults distributed
throughout an entire neighborhood is expected to be complicated and unprecedented.
This solution would provide a moderate benefit for a very high cost. Additionally, a preliminary look
at the compounding effect of climate change suggests that any improvement realized by implementing
additional storage would be taken back by climate change (i.e., increased precipitation amounts).
Inches of
Runoff Stored
on Private
Property
Approximate Cost for
All Parcels in
Morningside to Store
Runoff
Flood Level Reduction Benefit (in feet) for Weber Pond
Subwatershed (MS_40)
5-yr Storm
(3.6" of
precipitation)
10-yr Storm
(4.3" of
precipitation)
50-yr Storm
(6.4" of
precipitation)
100-yr Storm
(7.5" of
precipitation)
1 inch $ 8,550,000 0.1 <0.1 <0.1 0
2 inches $ 17,100,000 0.6 0.3 0.5 0.3
3 inches $ 25,650,000 0.7 0.9 0.6 0.5
A memorandum describing the analysis in more detail is available in the appendix.
22
From ‘ill-drained’ to impervious: impervious surface analysis
From ‘ill-drained’ to impervious: impervious surface analysis
The Task Force wanted to explore the impact of limiting impervious cover through regulating
development and redevelopment. The impact of decreased imperviousness across the Morningside
neighborhood was evaluated.
The analysis showed an impervious limit would have little impact on flood risk. Although an
impervious limit or reduction supports other values such as open space, room for trees,
neighborhood character, and limiting heat island effect, the case for flood risk reduction was weak.
Additionally, setting impervious limits would require a large financial investment.
The impervious area that is directly connected to the storm sewer system in the Morningside
neighborhood is estimated to be about 25% of the total land area, in aggregate. The analysis tested
the sensitivity to changes in impervious by modifying the stormwater model so that the
imperviousness of the entire contributing drainage area was increased, decreased, and even lowered
all the way to 0%, which reflects a pre-development condition. This sensitivity test was also
completed for a range of storm events, from the 20%-annual-chance storm event (5-year storm) to
the 1%-annual-chance storm event (100-year storm). As expected, the imperviousness sensitivity test
showed that less impervious area generates less stormwater runoff and more impervious area
generates more stormwater runoff. However, the magnitude of the runoff changes generated by
adjusting imperviousness were not as impactful as may have been expected. Additionally, the little
flood reduction benefit shown in the analysis does not consider future climate change.
A memorandum describing the analysis in more detail is available in the appendix.
23
Impervious limit: in progress item
Impervious limit: in progress item
At their February 12th, 2020 Planning Commission meeting heard an introduction to a zoning
ordinance amendment which would limit impervious cover. Current code includes only a building
coverage limit.
Outreach and Engagement
What is the outcome; People understand their vulnerability and exposure to flooding, know what
action to take to reduce each in the immediate, short and long term. People have the knowledge and
resources to take action. People are motivated to take action to protect themselves.
Who does the work; Engineering Department, Communications Department, partner agencies,
community groups.
Who is involved; The public, and public and private organizations.
When flooding risk is considered; In anticipation of spring melt, during flood events, post-hazard
recovery, at property transfer, upon FEMA flood hazard map update.
Gaps; No coordinated plan and message, limited public and private resources. Knowledge alone doesn’t
equal action. Although not at the same scale as a capital item, engaging the public still costs money.
Equity should be considered in tactics.
When people understand the risks of flooding, they can take actions to reduce the consequences of
flooding. Actions could range from simple things, like moving valuables to higher floors, to more
complex retrofit improvements like flood proofing and sanitary sewer backflow prevention.
Risk awareness could be encouraged by improved distribution of information products like the existing
flood risk map available on the City’s website. This local map is industry leading, with few small cities
producing and publicly sharing detailed local flooding information. Although the information had been
public for a long time, it had been in a format that required some technical knowledge to interpret.
With new mapping tools, increasingly detailed digital stormwater system data, and more precise data
about topography of the landscape, we’re better able to visually display the risk.
24
Outreach products: in progress item
Outreach products: in progress item
Through the process, we uncovered some ‘quick-win’ actions to be implemented immediately.
• Actions for Flood Resilient Homes Fact Sheets. These fact sheets describe common actions
that people can take to reduce their own exposure and vulnerability to flooding. A copy of
the fact sheets are provided in the appendix.
• “What is my flood risk?” interactive map. This application allows users to visualize the
flooding on the land surface for any property in the City of Edina. This information is already
available on the interactive water resources map; however, this application is more focused
on communicating flood risk specifically. The map is available on the Maps page of the City
website.
• Sandbagging how-to videos. The City provides sandbags, free of charge. This series of videos
will be used to promote the service, inform people on how to request sandbags, demonstrate
how to build a sandbag dike, and describe how to dispose of sandbags after a flood.
Emergency Services
What is the outcome; Parties respond to remove people from harm. Parties respond to prevent
damage to property if possible, or provide aid after damage occurs. Limited disturbance and damage.
Rapid return to normalcy.
Who does the work; Police Department, Fire Department, Public Works Department, Engineering
Department, County/State/Federal Emergency Responders, other infrastructure owners, and private
contractors.
Who is involved; Emergency operations command, emergency responders, the public, property
owners, visitors, other infrastructure owners.
When flooding risk is considered; In emergency operations plans, disaster planning, training and
drills, post-hazard recovery.
Gaps; Current response is triggered in major/severe events. The utility group’s first priority is to
maintain or reestablish function of infrastructure systems. Call centers can be overwhelmed and need
clear triage procedure. There is nearly no service available for property owners during a flood. The
process of after-action inquiry, questions and blame that realize long-known service gaps is adversarial
and leads to rushed planning. Requests or complaint-based reactions may not provide an equitable
distribution of services.
25
The City’s role in emergency situations include responding to life, health and safety calls and supporting
or restoring the operation of the utilities. When floods occur the ability to respond effectively quickly
degrades as phone lines and other communications channels fill with requests and reports. The ability
to sort and serve these requests goes into triage with critical system function and support measures
competing with urgent requests from the public.
Empowering people to adapt to flood risk, prepare for flood events, and mitigate the impacts of climate
change all contribute to a more resilient community. Adaptation and preparedness actions work to
mitigate the consequences of flooding.
Strategy Development
Task Force role and process
In order to incorporate community values into the process, a volunteer Task Force of eight Edina
residents was formed. Members represent homeowners with a variety of knowledge and experience.
Most have experienced flooding on their properties or have engaged with flood issues in the larger
community. Members came from all across the City of Edina. Task Force members met 12 times and
attended two City Council work sessions between July 2019 and March 2020.
The Morningside neighborhood was selected as the focus area of study due to the presence of significant
modeling and research in the area. The Morningside neighborhood faces a range of flooding challenges
that past efforts have struggled to address. As part of this effort, a 2-dimensional model was developed
and field calibrated to better refine the flood model and relate the models of St Louis Park and
Minneapolis. The Morningside neighborhood was also used as the case study neighborhood for
evaluating impervious limits, private storage, big infrastructure, and future climate change as noted in the
various analysis sections of this report.
The Task Force’s charge was to “Provide recommendations to inform a Flood Risk Reduction Strategy
to be considered for adoption by the City Council and incorporation as a major amendment to the
City’s Comprehensive Water Resources Management Plan.” The products of this process including
meeting agendas, minutes, and analyses are available for review in the Water Resources Library on the
City of Edina website.
To better understand the nature of the issue, Task Force members requested and were presented with
the following:
• Overview of the focal area of Morningside neighborhood, its historical and current flood
challenges, and previous efforts to evaluate flood risk reduction options.
• A technical exploration of City-owned stormwater infrastructure, maintenance operations,
levels of service, and the stormwater utility.
• Regulatory options that have been implemented in other comparable communities and
associated challenges and trade-offs.
26
• Modeled sensitivity analyses to explore the potential impact of comprehensive impervious limits,
private stormwater storage, and enhanced infrastructure including larger pipes and stormwater
storage.
• Communications strategies that promote preparedness and connect residents with resources
during flood events.
• Overview of the City’s floodplain management ordinance and participation in the National Flood
Insurance Program.
• The City’s policy and standards for stormwater management through the permit process,
related to development and redevelopment.
• A conversation with maintenance staff to understand routine operation and maintenance as well
as storm response.
Interacting directly with the Task Force has provided staff members with insight into public perception
of their role in flood risk reduction. During these conversations, staff began to see certain discrepancies
between the following City assumptions; perception of risk, interpretation of the term ‘flooding’, and the
role of City services.
• How does the City define flood risk? Flood risk has been seen as a combination of the statistical
probability of a flood event happening and the potential community-wide losses that occur as a
consequence of that event. In the City of Edina, the increasing value of homes located within the
floodplain is occurring in tandem with changing weather patterns that increase intensity of storm
events, both of which increase the overall risk. The City’s idea of current flood risk is also being
shaped by changing community expectations for service.
• Defining “flooding” is similarly complicated by social perception. FEMA defines flooding as “A
general and temporary condition of partial or complete inundation of 2 or more acres of
normally dry land area or of 2 or more properties…” When intense or prolonged rain events
occur, the system can become overwhelmed. A wet basement, flooded garage, or standing
water may not fit FEMA’s definition, but each impacts the community and was considered
“flooding” by Task Force members.
• City services play a critical role in the following common flooding issues; creeks outside their
banks, curb lines flowing full, storm drains clogging, pipes running full, low points in streets or
yards filling up and threatening structures, flow paths eroding, sump pumps flowing, basement
foundations leaking, and sanitary sewers backing up. Community service expectations are
mismatched with available resources for preventative maintenance and timely emergency
response to these issues.
Staff heard the following sentiments from the Task Force;
• Flooding affects quality of life by disrupting daily activities, risking safety, and damaging
structures.
• A priority should be to reduce risk to residential structures.
• Help property owners protect themselves and prevent damage to structures.
• Be ready to help the community recover after floods.
27
• Maintain the function of the existing system to maintain service.
• Be a good neighbor.
Brainstorming, prioritizing, and categorizing possible actions
A series of actions were proposed for a possible menu or toolbox of actions as a result of discussions
with the Task Force. Each action was accompanied by a detailed description, justification/motivating
factors, tradeoffs and other considerations, cost score, staff-ranked effectiveness score, community
enthusiasm ranking, and action category. The brainstorming exercise resulted in more than 40 potential
actions. Reviewing and ranking these actions was no small task.
Task Force members were asked to rank possible flood risk reduction actions based on community
enthusiasm, informed by community held positions and interests related to flooding. Positions are
surface statements of where a person or community stands. Interests are the underlying reasons, values
or motivations that explain a certain position. Based on perceived community position and interests, the
Task Force was asked to rank the action items in terms of community enthusiasm. Enthusiasm is the
community’s interest or approval of the action. Considerations for community enthusiasm include
tradeoffs, community impacts, land, sustainability, environmental outcomes, and social outcomes.
Task Force members shared their hesitation in representing the community with their rankings because
they felt that each flood experience was unique and they hadn’t had sufficient information or
opportunity to gauge community enthusiasm at this detailed level. A summary of the aggregated Task
Force rankings is included in the appendix with this caveat - in the end, the conversations around actions
provided the most value for staff in forming the framework and strategy. The process helped to identify
quick-win actions that could be implemented immediately, clarified areas of agreement and disagreement
between the Task Force and staff, and will be used as a starting point for future Comprehensive Water
Resources Management Plan program development work. We would expect rankings to be continually
refined as more people participate and more information becomes available. The exercise itself
outweighs the absolute ranking of the actions.
The full set of possible actions as well the Task Force ranking summary is included in the appendix of
this report.
Conclusion
The process has reiterated the need to address flooding with a range of strategies that span technical,
scientific, political, and social approaches. Many communities are struggling with managing increasing
flood risk.
Key takeaways:
• The current stormwater model helps to better visualize where the issues are; they are
extensive, interwoven, and difficult to solve. The existing stormwater system is overloaded and
the strategy to put water somewhere else is limited.
• Climate change impacts are significant.
28
• Groundwater levels are increasing. The years between 2015 and 2019 were the wettest in
Minnesota history.
• The Flood Risk Reduction Strategy widens our approaches, and thereby actions, to reduce flood
risk. The current Comprehensive Water Resources Management Plan is narrow and can’t keep
up with the lead driver; climate change.
• There are opportunities to empower people and institutions to adapt, prepare, and mitigate.
The Strategy opens the approach of reducing vulnerability. Often, some of the simplest and
most cost-effective ways to reduce risk are for people to reduce the vulnerability of their
structures and property.
• Impervious surfaces matter; however, the opportunity to reduce flood risk by limiting or
reducing impervious cover in the City of Edina is limited.
• Additional resources are needed to implement actions.
• Residents have high expectations for service.
• Other promising opportunities exist for operation and maintenance, public infrastructure
(though climate change will make transformational change a challenge), and redevelopment
standards anchored in resiliency.
Lastly, there is an opportunity to knit together the Flood Risk Reduction Strategy with the existing
Living Streets Plan and forthcoming Climate Adaptation Plan. Bringing these efforts into focus and
examining strategies through an equity lens are necessary to deliver high-value benefits to the
community.
29
Acknowledgement
Staff would like to thank the Task Force for their contributions. The experience, knowledge, and
curiosity they brought to the process added value and influenced the Strategy.
Nora Davis (co-chair), Lake Cornelia Neighborhood
Kathy Amlaw (co-chair), Lake Edina Neighborhood
Greg Lincoln, Morningside Neighborhood
Michael Platteter, Morningside Neighborhood
Louise Segreto, Indian Hills Neighborhood
Roxane Lehmann, Sunny Slope Neighborhood
Richard Strong, Concord Neighborhood
Richard Manser, Todd Park Neighborhood
30
Appendix
Appendix A: Resident Task Force Report
Appendix B: ‘Getting to scale: a challenging problem made even more challenging, climate change
impact analysis’, technical memo
Appendix C: ‘Go Big, Go Bigger: infrastructure analysis’, technical memo
Appendix D: ‘Keep your water to yourself: private infrastructure analysis’, technical memo
Appendix E: ‘From ‘ill-drained’ to impervious: impervious surface analysis’, technical memo
Appendix F: Actions for Flood Resilient Homes, fact sheets
Appendix G: Task Force charge
Appendix H: Potential action matrix key, ranked response, and potential action matrix
A
Appendix A: Resident Task Force Report
Resident Task Force Report
Flood Risk Reduction Task Force - 2020 City Council Report
“For decades Edina took land from the water – now the water wants the
land back”
Task Force Work
The Flood Risk Reduction Task Force began meeting in July of 2019. For the past several
months the Task Force has grappled with this increasingly complex issue. There are no simple
answers. Flooding issues will require a multi-pronged approach across multiple sectors within
the community. Many of the actions we are suggesting have environmental benefits – which will
assist Edina in achieving Climate Action Plan goals.
BACKGROUND
Edina History
Settlers first arrived in Edina in the 1800’s and by the end of 1854 all the land in Edina had been
claimed. Much of the western portion was part of the “Big Woods” – with elm, basswood,
maple and oak trees. The terrain was uneven and much of the area was poorly drained and
swampy. Over time many of the hills were bulldozed, trees felled, the wetlands filled in
– and development began. Two hundred years of development has profoundly affected
storm water management, and this is a major factor in our current flooding problems.
Scope of problem
In preparation for the 2018 Comprehensive Water Resource Management Plan, Edina staff and
consultants reviewed the city for areas of flooding concern... Five areas in the city were chosen
for further study – Weber Park, Concord, Halifax, Southdale First Addition Residential &
Crosstown 62 & Hwy 100. Another twenty areas were screened, while fifty-four areas await
further study. In total – those areas contain - 692 homes/apartment buildings, and 863
structures.
Storm water affects Edina in a variety of ways – including overflow from natural bodies of water
to runoff from developed areas causing street flooding, damage to basements from seepage and
ground water to sanitary sewer system back-ups. This is a situation affecting the health and
safety of residents and those who visit, shop, and work in our community.
Each news cycle brings yet more warnings about the damage of increasing rainfall and
ground water issues – and Edina is not immune.
Resident Task Force Report
Contributing Factors
Increased rainfall due to Climate Change – in 2019 we received 43.17 inches of rain, 12.56
inches above average.
Rains will continue to increase, and those rains will come fast, hard and more frequently. Early
snow melt compounds the flooding problem, causing additional problems for residents. Ground
water levels are rising and are difficult to measure. More residents are operating sump pumps
year-round – while other residents are discovering they now need to install a sump pump.
More development replaces vegetation and soil with impervious surfaces. Impervious surfaces
causes rainwater to runoff rather than infiltrate natural ground surface. Not only does runoff
cause surface water to accumulate in land depressions, it can cause rainwater to reach streams
faster and in greater quantities; both increasing the risk that flooding will occur sooner and more
severely than if rain were to fall on the natural ground surface.
Impervious surfaces also increase the “heat island effect” causing yet more rain.
The issue is not going away – and it’s imperative that Edina approach this situation proactively.
Reduced imperviousness results in less runoff. Any reduction in the amount of runoff translates
into increased infiltration and enhanced flood control. Limiting impervious surfaces and
increasing the City’s greenspace will help reduce runoff volume, lower summertime
temperatures, and improve both water and air quality. Increased greenspace will also make our
community more attractive and promote recreational activities that enhance the quality of life for
those who live, shop, visit and work in Edina.
Our Recommendations
Land Use
Regulate impervious surfaces to promote green space, trees and filtration. (Impervious
surfaces have increased by 80% in Morningside over the past 50 years – exposing that
neighborhood to serious flood risk.)
As property is redeveloped add below ground water storage and above ground storage.
Above ground storage (day-lighting the water) adds environmental benefits in addition to
water storage. It also serves as a “water feature” for the development.
Restrict removal of mature trees. Encourage tree planting and rain gardens
Increase green space/park areas for both temporary water storage and environmental
benefits
Voluntary buy-out of homes and converting that land to temporary storage/park /green
space. Allowing a rebuild at higher elevation does nothing to protect the neighborhood.
Resident Task Force Report
Infrastructure
Be proactive (rather than reactive) in maintenance of current system
Improve data collection to assist in planning, protection and outreach efforts
Replace aging infrastructure
At street reconstruction add larger storm sewer pipes, lower streets for temporary storage
Pumping if cost effective and doesn’t create issues for others
Education
Provide education to residents on a number of platforms to alert them to their flooding
risks and how to mitigate those risks. This effort would include information on city
services including sandbag delivery, placement and pick-up, along with information on
flood insurance.
Reach-out to plumbing contractors and other water mitigation businesses to inform
them of Edina’s permitting and regulations regarding water issues.
Continue the Technical Support Program through Edina’s Engineering Department
to help residents reduce their risk
Ongoing
Develop a comprehensive Emergency Plan to assist residents during and after a
flooding emergency. Plan should include volunteers who could assist homeowners with
sandbagging and flood clean-up. (Service clubs such as the Edina Rotary clubs, faith
communities, etc.)
Continue to work with both watershed districts and surrounding communities to address
ongoing water issues.
Respectfully submitted:
Flood Risk Reduction Task Force Members
Richard Strong, Louise Segreto, Michael Platteter, Richard Manser, Greg Lincoln,
Roxane Lehmann, Nora Davis (Co-chair), Cathy Amlaw (Co-chair)
B
Appendix B: ‘Getting to scale: a challenging problem made even more challenging,
climate change impact analysis’, technical memo
Barr Engineering Co. 4300 MarketPointe Drive, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com
Technical Memorandum
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Project: Edina Flood Risk Reduction Strategy Support (23271728.00)
Precipitation totals have been increasing in the Twin Cities for decades. The total precipitation in 2019 was
the highest amount of annual precipitation on record. Barr reviewed climatological data to evaluate
changes and long-term trends in precipitation. As shown in Figure 1, the record for the highest annual
precipitation recorded at the Minneapolis-St. Paul International Airport was in 2019 and was nearly 8%
higher than the next highest year (2016). Figure 1 shows the top 10 wettest years (most annual
precipitation) for the Twin Cities using the Minneapolis-St. Paul International Airport gage. It is worth
noting that three of the years on this plot are within the past two decades (2002, 2016, and 2019), and the
two highest years, 2016 and 2019, are very recent. The average annual precipitation total for the Twin
Cities (at the Minneapolis-St. Paul International Airport) is 30.6 inches. The driest year on record (1910)
had a precipitation total of 11.5 inches. The 2019 annual precipitation was over 40% higher than an
average year.
Figure 1 Top 10 wettest years in the Twin Cities (precipitation at Minneapolis-St. Paul International Airport)
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 2
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
Figure 2 shows annual precipitation totals for the past 50 years, including 2019. In the past 50 years, there
has been an increasing trend in average annual rainfall totals at a rate of about 0.66 inches more
precipitation per decade.
Figure 2 Annual precipitation for Hennepin County from 1970 to 2019 (Source: MNDNR State Climatology Office)
It is worth noting that the 1940s, 1950s, and 1960s were three consecutive decades with approximately
average precipitation. This was a prolonged period of relatively stable conditions when much of the
development in Edina occurred. Prior to this period, the 1930s was a dry decade; in fact, the driest on
record. From the 1960s on, there has been a clear trend in the total precipitation, both on an annual basis
(as shown in Figure 2) and by decade. Figure 3 shows the average annual precipitation depth per decade
from the end of the 19th century to the 2010s. The 2010s are the wettest decade in Minnesota’s history.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 3
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
Figure 3 Average annual precipitation by decade (Source: MNDNR State Climatology Office)
In much of Edina, the stormwater infrastructure was designed and developed decades ago (in the 1950s
and 1960s) using design storms. At the time, the design storms were estimated based decades-worth of
precipitation prior to the design. This means that stormwater infrastructure was likely designed largely
based on precipitation experienced in the first half of the 20th century, and since then, precipitation
quantities have only increased.
The City’s stormwater system was designed to convey a certain amount of water and protect against
impacts at a certain level. This “level of protection” is based on the capacity of public infrastructure to
handle stormwater and on the likelihood, or probability, that a storm will occur. When storms are bigger
or more intense than the infrastructure is designed to handle, or when it clogs, there are consequences
such as disruptions in services and facilities, or damage to property. The relationship between the
probability of these storm events occurring (defined by climate and infrastructure) and the resultant
consequences (defined by vulnerabilities of public or private infrastructure) determines the overall
community flood risk. Risk is changing primarily because climate is changing and is increasing the
probability, or chance, that large, flood-causing storms will occur.
The level of protection for design is a moving target. Designs from the past are undersized for today and
there is a growing realization in technical circles that even if designs were revised to reflect today’s
probability of storm events they may quickly be obsolete due to the changing risk brought by climate
change. The question is, should engineering designs be based on the climate models of today or on some
predicted future condition? The trade-off for future-sizing a design so that we are better prepared for
climate change would likely mean higher present costs. Figures 4, 5, and 6 show how the extent of
flooding has changed in the Weber Pond area of the Morningside neighborhood over time and what it
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 4
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
may look like in the future. The flood inundation extents shown are based on model results of storm
events using the City’s stormwater management model (XP-SWMM).
Figure 4 Flood inundation for a predicted 1% annual chance flood event in the past (~6.0 inches over a 24-hour period, based on Technical Paper 40)
Figure 5 Flood inundation for a predicted 1% annual chance flood event using more recent climate data (~7.5 inches over a 24-hour period, based on Atlas 14)
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 5
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
Figure 6 Flood inundation for a 1% annual chance flood event projected for the future (~10 inches over a 24-hour period)
In the following figure (Figure 7), we attempt to visually show the effects of infrastructure projects and the
impacts of climate change on the flood volumes stored in Weber Pond. In Figure 7, one blue rectangle
represents 10 acre-feet of stormwater storage in Weber Pond. This volume is equivalent to the storage
capacity available in Weber Pond before impacts to the adjacent park or homes would begin to occur. 10
acre-feet of water is not inconsequential. It can be thought of as one foot of water over a 10-acre area, or
10 feet of water over a 1-acre area, or more specifically, 3 feet of water over the approximately 3.3-acre
footprint of Weber Pond.
In the present climate, Weber Pond would actually need to store close to 40 acre-feet of stormwater in
the 1%-annual-chance (100-year) design storm event to avoid impacts to the park or adjacent homes; 40
acre-feet is nearly four times the amount that can currently be stored in Weber Pond without impacting
infrastructure or amenities. If directly connected imperviousness were reduced by 25% in the contributing
watershed, it reduces the flood volume that needs to be stored in Weber Pond to avoid impacts, but the
reduction is minor. There are other methods to alter the flood exposure, such as with large infrastructure
projects (pipes, pumps, storage, etc.). As shown in Figure 7, Option 2b (from Appendix C) actually transfers
risk downstream, reducing flooding in other areas of the Morningside neighborhood and increases the
volume that would need to be stored in Weber Pond (requiring additional protection for homes adjacent
to Weber Pond, for example, by constructing flood walls), while Option 7b (from Appendix C) shows the
greatest benefit in reducing flood volumes. Coincidentally, the amount of stormwater that needs to be
stored in Weber Pond with the large infrastructure project Option 7b looks a lot like the amount of water
that needed to be stored in the 1%-annual-chance (100-year) design storm event used in the past.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 6
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
Figure 7 Pictograph of effects and impacts on stormwater volumes in Weber Pond due to
climate change and infrastructure projects
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix B - Climate Change Impact Analysis Date: March 30, 2020 Page: 7
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix B - Climate Change Impact Analysis.docx
Finally, it is worth noting that in all of the conditions shown in Figure 7, Weber Pond is not able to store
the flood volume generated by these large amounts of precipitation (i.e., all conditions exceed “1 Weber
Pond Equivalent”). In other words, there will be impacts to infrastructure and amenities adjacent to Weber
Pond during a 1%-annual-chance (100-yr) storm event, even with large infrastructure projects, and/or with
decreases in imperviousness, due to system capacity constraints and climate change. The stormwater
management target continues to change as precipitation amounts continue to get larger and larger.
C
Appendix C: ‘Go Big, Go Bigger: infrastructure analysis’, technical memo
Edina Morningside Neighborhood
Flood Risk Reduction Concepts
This report will summarize analysis conducted by Annetta Wilson, Jessica Wilson and Ross Bintner to
define and describe flood risk and consequence for the Morningside Neighborhood in Edina and create a
conceptual framework that could be used to create a scope of work that would compare or judge flood
risk reduction options. The report is conceptual only and should not be relied on for actual
improvement decisions.
Context and Scope
The Morningside neighborhood has a valley and several low or landlocked areas that are prone to
flooding. The neighborhood is fully developed with primarily single family homes built between 1910
and 1960, with some infill happening later and redevelopment currently replacing some structures
(Appendix A.) Stormwater characteristics for the neighborhood are described in greater detail in
chapter 12 of the Comprehensive Water Resources Management Plan (2018 Draft, Barr Engineering).
This document is the Local Water Plan (LWP) for the city.
For this report, flood risk will be described in terms of both the probability and possible consequence of
high water on structures. Two rainfall probabilities modeled in development of the LWP are used in
this analysis, the 1% and 10% probability rainfalls. Assuming normal soil moisture conditions (AEP
neutral conditions), flood probabilities are assumed to be the same as the storm event probabilities
creating the flooding. The possible consequences of flooding are categorized and costs are estimated
assuming homeowners have taken no special effort to limit the consequence of flooding. Annualized
potential costs to homeowners are then estimated to test economic return on possible flood mitigating
infrastructure improvements to this area. Infrastructure improvement options were part of a separate
effort by Barr Engineering. These options are preliminary, non-exhaustive, and not optimized.
A variety of data and analysis was conducted to inform the analysis of flood risk. The following
subsections describe the original data sources (assembled data) and methods used to calculate criteria
relating to flood risk (derived data).
Assembled and Derived Data
Geographical data was assembled from City of Edina sources and new data was derived from the
relationships in the data to inform the flood risk analysis. The following is a summary of data and
methods. The development of methodology to derive adjacent ground elevations based on LIDAR and
home shape has applicability outside this study and is described in greater detail in Appendix B.
Assembled Data:
• Digital Elevation Map (DEM) from 2011-2012 Minnesota DNR LIDAR data with 5cm accuracy
• Subwatershed and Sewershed data (City of Edina)
• Building Footprints originally from 2002 Markhurd, Updated by City of Edina with 2012 and
2015 based on Hennepin County joint aerial photograph project
• Lot surveys from City of Edina Building Department records
• Property ID (PID), building year built, livable total and basement square footage, finished
basement %, building sales data, and building market values data from the City Assessor
• City of Edina Datalink Map, Google Streetview, Google search for Real Estate sale pictures and
descriptions of homes, Site visits
• 10% and 1% probability inundation polygon and elevation data from 2018 Comprehensive Water
Resources Management Plan.
• 2017 Flood Loss Estimations Table (Source: National Food Services, FloodTools.com, based on
national FEMA flood loss tables)
• Potential flood risk mitigation options from Barr Engineering
Derived Data:
• The following general data was derived from the assembled data to inform the analysis.
Minimum, maximum, and average adjacent grade elevations. Adjacent grades were calculated by
comparing DEM and building footprint clips using the method described in Appendix B.
The following building elevations data were derived
• Basement type was determined by looking at the elevation profile and StreetView. If it wasn’t
easy to see in StreetView or determine from the profile, the address was Google searched to
find Real Estate information and additional pictures of the house. If those were unavailable, the
site was visited to see in person, while remaining on city property. See the appendix for more
information on how the basement type was used in the elevation calculations.
• Building elevations; Elevations were overwritten if a survey was found in Building Department
survey data. Data source was recorded in a note field. Detailed information about building
elevation calculations can be found in Appendix B.
The following attributes were calculated using the derived adjacent grades:
• Low floor elevation was calculated by subtracting 8 feet from the maximum adjacent elevation
• Low opening elevation was equated to the minimum adjacent ground elevation.
• Garage floor elevation was equated to the maximum adjacent ground elevation.
• First floor elevation was calculated by adding 1 foot to the maximum adjacent ground elevation.
• The Elevation Difference was calculated by subtracting the minimum adjacent ground elevation
from the maximum adjacent ground elevation.
Property characteristics and property value were calculated to inform the analysis of consequence of
flood risk:
• Number of Sales was calculated from Excel Pivot Table using data from Assessor’s Office (see
appendix)
• Value per Square Foot was calculated (Building MV/Square Footage)
• Subwatersheds names of subwatersheds that intersect with building footprint
Analysis of Structural Flood Probability
For this analysis flood probability is categorized based on various ways water can intrude into residential
dwelling structures based on the following scheme. The thresholds defined in this scheme allow an
in/not in trigger to describe flood risk at varying probability storms and are not based on a literature
review of studies on flood effects on varying structures. A cursory review for similar work turned up
many interesting concepts, but no direct examples or industry standards that detail flood risk at this
granular a scale. The thresholds defined here are based on professional judgement and are obviously not
definitive. The categories are used to define probability of damage to each vector of flood risk.
Direct flood risk is from waters that overtop the foundation block and saturate and infiltrate through
wood framed portions of a home, overtop and flood window wells and collapse windows, or saturate
and infiltrate through low opening elevations such as windows and doors. Direct flood risk will be
categorized as follows:
• Moderate: Peak 1%/10% probability flood elevation is above minimum adjacent grade, but below
or equal to average ground elevation.
• Major: Peak 1%/10% probability is above average adjacent grade, but below or equal to
maximum adjacent grade.
• Severe: Peak 1%/10% probability is above maximum adjacent grade.
See Appendix B for GIS Methodology.
Indirect flood risk is from nearby standing flood waters saturating the ground and causing hydrostatic
pressure on foundations that typically result in water leaking from cracks and joints in foundation block
or concrete slab floors. In severe cases this hydrostatic pressure is known to collapse block
foundations. While these issues can also be attributed to raised groundwater with a variety of causes
such as temporary rises due to rainfall or flow paths, anywhere in the watershed, this category focuses
only on those areas with nearby standing flood waters. Indirect flood risk will be categorized as follows:
• Minor: Peak 1%/10% probability flood elevation in same subwatershed is </= 4’ above basement
elevation but > 2’ above basement elevation
• Moderate: Peak 1%/10% probability flood elevation in same subwatershed is >4’ above basement
elevation
Sanitary flood risk is from flood water in nearby homes subject to direct flooding flowing into the
sanitary sewer system through flooded floor drains and fixtures making its way into the public sanitary
line and overwhelming its capacity causing backup into other homes. Sanitary flood risk will be
categorized as follows:
• Moderate: Home is within the same sanitary sewershed where between 1 and 3 neighboring
homes are subject to Major or Severe Direct Flood Risk and the home is within 250’ of one of
the neighboring Direct Risk homes, and has a basement elevation lower than the flooded
basement plus 1 foot.
• Major: Home is within the same sanitary sewershed where between greater than 3 neighboring
homes are subject to Major or Severe Direct Flood Risk and the home is within 250’ of one of
the Direct Risk homes, and has a basement elevation lower than the flooded basement plus 5
feet.
The flood risk scheme above was compared to derived building low floor elevations to create effective
differential flood elevations for each affected single family dwelling. These differential elevations, along
with property characteristics were used to estimate the consequence of flooding, described in the next
section.
Overall, direct flood risk is the highest risk type followed by sanitary flood risk, with indirect flood risk
being the lowest risk. Since homes often fit into multiple risk types, they were assigned to the highest
risk of their designated risk types.
Figure 1: Morningside 10% Annual Probability Flood Risk
Figure 2: Morningside 1% Annual Probability Flood Risk
Analysis of Flood Consequence
This analysis attempts to create a decision framework to generalize costs of flood risk at the
neighborhood scale by assigning individual probability that any given home will experience damage by any
of the three risk categories described above, using best available data. The cost of flooding is then
annualized based on this probability. Using the same method, the base case condition is then compared
to neighborhood wide potential flood mitigation options.
Methodology
The following steps were used to develop flood consequence on a home by home basis for the base
case and each potential mitigation option. Only primary structures are considered.
1. Generate flood elevations. For this analysis, flood elevations were generated for 50, 20, 10, 4, 2
and 1% probability events by Barr Engineering for the existing conditions, and seven potential
flood mitigation options.
2. Apply elevations to structures. To simplify conditions where a structure was subject to risk from
more than one subwatershed (i.e. located on a subwatershed divide), each structure was assigned
to a single subwatershed, whichever was judged to be highest risk or most significant.
Figure 1:
999.5
1000.0
1000.5
1001.0
1001.5
1002.0
1002.5
1003.0
1003.5
0.0010.0100.1001.000 Peak Flood Elevation (feet)Annual Exceedance Probability
Flood Elevation -Mean
Flood Elevation - Mean
3. Determine possible damages. A square footage estimate of $40 per square foot was used. This
estimate was informed by the referenced FEMA damage tables. The square foot estimate of
damage was then factored for each risk category and a probability of damage was assigned to
factor the square foot rate consistent with the scheme described above, and depicted in the table
below. The probability of damage was based on the trigger elevations set in the section above,
and the probability factor was a guess based on experience.
Table 1:
Probabilities of Damage Occurring, given a mode and a "chance of damage"
factored with percent of maximum damage by mode
Direct
Mode
Direct
Mode2nd
Level
Indirect
Mode
Sanitary
Mode
Minor 0.0 0.0 0.1 0.0
Moderate 0.5 0.0 0.2 0.5
Major 0.9 0.0 0.2 0.8
Severe 1.0 0.5 0.2 0.8
The results are very sensitive to these factors, particularly the indirect mode since it can trigger
at lower elevations with correspondingly more probable events than the other damage types.
The factors are based on feel, and a non-exhaustive review of similar work.
4. Determine elevation damage curves. Basement floor, minimum adjacent grade, average adjacent
grade, and maximum adjacent grade were compared to subwatershed elevation data using the
trigger elevations on the subject home to develop damage curves for each structure for direct
and indirect risk.
Figure 2:
997
998
999
1000
1001
1002
1003
1004
1005
1006
$0 $10 $20 $30 $40 $50 $60 $70 $80 $90 $100Peak Flood Elevation (feet)Damage, Accounting for Probability of Damage
Thousands
Direct Damage Indirect Damage Sanitary Damage
5. Relate damages to annual exceedance probability (AEP). Damages in dollars were related to AEP
using the specified flood level elevations for the assigned subwatershed. Values for intermediate
probabilities were interpolated to create a cost versus probability damage curve for calculating
annualized damages. Two methods for combining risk types were tested, a maximum, and a
combined probability ‘or’ method. The ‘or’ method was used in the analysis.
Figure 3:
6. Calculate total annualized flood risk. The annualized damages were calculated by integrating the
potential damages by the AEP. The annualized expected damages take into account AEP for a
wide range of precipitation events, probability of damages from an event, and potential damage
cost to a home.
$0
$20,000
$40,000
$60,000
$80,000
$100,000
$120,000
0.0010.010.11 Mean Damage, Accounting forProbability of DamageAnnual Exceedance Probability
Maximum Or
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅_$=�(𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷_$)(𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑)𝐴𝐴𝐴𝐴𝐴𝐴2
𝐴𝐴𝐴𝐴𝐴𝐴1
Figure 4:
7. Calculate total neighborhood risk. The annualized damage cost for each home was then
summarized for existing conditions to determine the annualized cost impact to the neighborhood
under existing conditions.
8. Repeat steps 1 through 7 for Barr’s proposed flood risk mitigation options. Calculate the total
annualized neighborhood damage for each option, because none of the proposed options will
eliminate all risk of damage.
9. Compare to option cost. The annual benefit for each improvement was calculated by subtracting
the option annualized risk from the existing conditions annualized risk. A 60 year infrastructure
lifecycle was assumed, which is a typical conservative lifecycle estimate for stormwater
infrastructure. The option implementation cost was then annualized by the improvement
lifecycle.. The annualized Benefit Cost Ratio for each solution was calculated dividing the solution
cost avoidance by the annualized solution implementation cost. This simple, straight line
depreciation approach ignores the cost of money. A future refinement could include a present
value analysis.
Results
Potential Flood Mitigation Options
Alt 2b: Increase Storm Sewer Size (up to 60”) and add flood wall at Weber Pond.
Alt 3a: Excavate Weber Field Park, area North of Weber Pond, Open Space 5, area West of Monterey
Ave, and backyard between 44th St and Branson St. Add flood walls at Weber Pond and along Monterey
Ave. Add culvert to Weber Pond to drain north.
$0
$20,000
$40,000
$60,000
$80,000
$100,000
$120,000
0.0010.010.11 Mean Damage, Accounting forProbability of DamageAnnual Exceedance Probability
Or
Alt 4a: Excavate Open Space 5 and do predictive pumping from Open Space 5 and Weber Pond to park
north of Calvin School
Alt 5a: Add Underground Storage to Weber Park and park west of Monterey Ave
Alt 7b: Combination of 3a and 4a
Alt 8: Excavate areas North and West of Weber Pond and add flood wall.
Alt 9: Alt 8 and add Underground Storage at park west of Monterey Ave, and predictive pumping to
Weber Pond.
Table 2: Barr Engineer’s Opinion of Probable Cost for Proposed Flood Mitigation Options
Option Estimated Project Cost Minimum Estimated Cost (-30%) Maximum Estimated Cost (+50%)
Alt 2b $4,469,000.00 $3,129,000.00 $6,704,000.00
Alt 3a $5,069,000.00 $3,549,000.00 $7,604,000.00
Alt 4a $3,444,000.00 $2,411,000.00 $5,166,000.00
Alt 5a $31,681,000.00 $22,177,000.00 $47,522,000.00
Alt 7b $8,507,000.00 $5,955,000.00 $12,761,000.00
Alt 8 $5,179,000.00 $3,626,000.00 $7,769,000.00
Alt 9 $13,786,000.00 $9,651,000.00 $20,679,000.00
Table 3: Number of Homes per Option with Greatest Benefit
Option Homes with Greatest Benefit
Alt 3a 2 homes
Alt 5a 1 home
Alt 7b 69 homes
Alt 8 13 homes
Alt 9 11 homes
Table 4: Damage Risk Change from Existing Conditions
Option Risk Increase Risk Decrease
Alt 2b 15 homes 111 homes
Alt 3a 1 home 117 homes
Alt 4a 1 home 127 homes
Alt 5a 92 homes
Alt 7b 1 home 150 homes
Alt 8 74 homes
Alt 9 136 homes
The homes at increased risk are in the areas where the flood elevation increased as a result of increased
water flow to the associated subwatershed as a result of increased drain size or predictive pumping.
Berms or Flood Walls were included in the options to mitigate direct flood risk, but indirect flood risk
may still be a factor. The increased risk is minimal (less than $1000 annualized for the worst case
scenario).
Table 5: Homes at Risk of Flood Damage by Option
Option Homes at Risk Homes no longer at risk
Current 160 homes
Alt 2b 134 homes 26 homes
Alt 3a 150 homes 11 homes
Alt 4a 154 homes 6 homes
Alt 5a 155 homes 5 homes
Alt 7b 123 homes 38 homes
Alt 8 155 homes 5 homes
Alt 9 126 homes 34 homes
Table 6: Simple Annualized Costs and Benefits by Option (assuming 60 year lifecycle and simple
depreciation of capital cost and no ongoing maintenance)
Table:
Condition
Annual
Damage
Annual
Benefit
Improvement
Cost
Annual
Improvement
Cost Benefit - Cost
Benefit Cost
Ratio
Existing $404,202 --
Alt 2b $287,348 $116,854 $4,469,000.00 $74,483.33 $42,370.82 1.57
Alt 3a $271,606 $132,596 $5,069,000.00 $84,483.33 $48,112.68 1.57
Alt 4a $335,313 $68,889 $3,444,000.00 $57,400.00 $11,489.43 1.20
Alt 5a $326,616 $77,586 $31,681,000.00 $528,016.67 -$450,430.65 0.15
Alt 7b $170,765 $233,437 $8,507,000.00 $141,783.33 $91,654.14 1.65
Alt 8 $337,045 $67,157 $5,179,000.00 $86,316.67 -$19,159.21 0.78
Alt 9 $190,566 $213,636 $13,786,000.00 $229,766.67 -$16,130.51 0.93
Overall Alt 7b has the greatest benefit, based on the benefit cost ratio, greatest benefit to homes, and
number of homes improved or removed from flood risk. Options 5a, 8, and 9 are cost prohibitive, in
which the cost outweighs the benefit. Reducing the assumed lifecycle below 60 years was tested and
Option Alt 7b still is cost beneficial at a lifecycle of 40 years minimum. Increasing the improvement costs
to the maximum estimated in Table 2 still results in Alt 7b being cost beneficial and having the greatest
benefit of the proposed options, but wouldn’t be cost beneficial at a lifecycle below 60 years.
Summary of Options:
None of the mitigation options will eliminate risk, but most will reduce risk with a few exceptions of
increased risk to individual homes. Additional incentives for homeowners to decrease their risk are
recommended such as backflow preventers and sump pumps, in addition to infrastructure improvement.
Alt 2b: This option has a favorable Benefit Cost Ratio (1.57) and improvement cost ($ 4.5MM), but puts
15 homes at greater risk, mostly in the Weber Park area from the larger storm drains upstream. There
are other options that have greater impact.
Alt 3a: This option also has a favorable Benefit Cost Ratio (1.57) and reduces risk in 117 homes, but
only removes 11 homes from risk.
Alt 4a: This option has the lowest improvement cost ($3.4 MM) and decreases risk to 127 homes, but
only removes 6 homes from risk.
Alt 5a: The annualized cost outweighs the benefit for this option.
Alt 7b: This option has the highest Benefit Cost Ratio (1.65), removes the highest number of homes
from risk (38 homes), and also reduces risk in the most homes of all options (150 homes). The only
significant disadvantages are that it increases risk in one home and has the 3rd highest cost ($8.5 MM).
Alt 8: The annualized cost outweighs the benefit
Alt 9: The annualized cost outweighs the benefit
Home Sales Data Inquiry
We tested the hypothesis that homeowners that experience home flood inundation are more likely to
sell their homes. To test for a correlation, sales data was obtained from the assessor’s office for the
Morningside neighborhood. This data was on all sales from 1/1/1970 through 4/27/2018 and included
traditional sales, as well as bank sales, physical change sales (“flipping”), and estate sales. A pivot table
was used to determine the number of sales per home and the data was then added to the ArcMap
Building Data attribute table to calculate the mean number of sales for each flood condition.
Table 7: Morningside Mean Number of Sales per Home:
All homes 10% Surface Inundation
Annual Risk
1% Surface Inundation
Annual Risk
Under 1% Surface
Inundation Annual Risk
2.92 3.06 2.63 2.97
There is a higher mean number of sales per home in the 10% surface risk category, which may show a
correlation, but what this doesn’t take into account is the age of homes built post-1970, which would
have less overall tenure.
Morningside Mean Home Year Built in or post 1970
All homes 10% Surface Inundation
Annual Risk
1% Surface Inundation
Annual Risk
Under 1% Surface
Inundation Annual Risk
2004 1999 1998 2006
Appendix A:
Year Built Statistics for Morningside Single Family Homes:
The Single Family Homes were selected by attribute and the following statistics were generated:
Figure 5: Chart of ArcGIS statistics showing the majority of Morningside homes were built between
1910 and 1960.
Appendix B GIS Methodology:
Home Elevation Methodology
The adjacent grade elevations were calculated in Arc Map, using the DEM (digital elevation map) and
Building Footprint feature class. The DEM was clipped to the building footprints, converted into a
polygon feature class, and then spatially joined back to the Building Footprint feature class to add
minimum, average, and maximum elevations for each footprint. Since the DEM data needs to be in
integers to be converted to a polygon feature class (ArcGIS limitation), the elevation data was converted
from meters to feet and multiplied by 10, and converted to integers using the Map Algebra Tool before
converting to a polygon feature class. Once converted, the data was divided by 10 to get elevation data
to the nearest tenth.
Figure 6: GIS Model of Adjacent Grade Elevation calculation process
Figure 7: Example footprint with elevation data from DEM clip and derived data below.
The first floor and basement elevation data were obtained from the home lot surveys when possible. If
the survey contained a top-of- foundation or TOB (top of block) elevation, 1 foot was added to that
number to account for the sub-floor and floor. If basement elevation data wasn’t available, 9 feet was
subtracted from the First Floor Elevation.
If the lot survey was missing or didn’t contain elevation data, the first floor elevation was calculated by
adding 1 foot to the maximum footprint elevation from the DEM and the basement elevation was
determined by subtraction 8 feet from that elevation (or 9 feet total from the first floor elevation). The
critical structures at risk of surface inundation were also viewed using Street View to confirm the first
floor elevations.
First Floor Elevation: Plan versus Calculated Differences
To test the confidence level of the First Floor Elevation calculation methodology above, the homes with
known First Floor Elevations were selected (238 homes) and the calculated values subtracted from the
plan values to create a difference data. The data was then exported to Excel to be statistically analyzed
and summarized.
Figure 8: Histogram of Plan versus Calculated First Floor Elevation difference
The 95% Confidence Level is 0.2’ with the Mean being 0.17’ and a Standard Deviation of 1.72. 47.7% of
home calculated FFE’s were within ½’ of the plan FFE and 76.4% of home calculated FFE’s were within 1’
of the plan FFE. This is close enough to use for our analysis and to use for future city-wide models.
The difference outlier homes were further analyzed:
The biggest difference home (14.8’ plan above calculated FFE) was built after the LIDAR data was
collected. The landscape was significantly raised to elevate the home out of the flood plain.
The other homes with negative differences were mostly split-level walkout basement homes with FFE’s
below the maximum elevation.
The Basement Elevation calculations were also compared against the plan lFE’s in a total of 97 homes.
0
10
20
30
40
50
60
-8.5-7.5-6.5-5.5-4.5-3.5-2.5-1.5-0.50.51.52.53.54.55.56.57.58.59.510.511.512.513.514.5MoreFrequency Plan - Calculated Difference
First Floor Elevation: Plan versus Calculated
Difference
Figure 9: Histogram of Plan versus Calculated Basement Elevation difference:
The 95% Confidence Level is 0.66’ with the Mean being 0.46’ and a Standard Deviation of 3.28 . 26.8%
of home calculated FFE’s were within ½’ of the plan FFE and 43.3% of home calculated FFE’s were within
1’ of the plan FFE.
The outlier homes correspond with the outliers in the FFE analysis.
Flood Risk GIS Methodology:
In ArcMap, the 1% and 10% inundation shape polygons were overlaid on an elevation relief map (from
the DEM) and carefully inspected to remove false “artifacts” from the Barr model. Others were edited
or removed when new build landscaping elevation was done to increase the home elevation and reduce
the flood risk. Elevation contour lines from the plot surveys were used to reshape the polygons.
After editing the polygons, the structures were matched with their subwatersheds by selecting the
structures that intersected each subwatershed polygon. The subwatershed 1% and 10% inundation
elevations were added for each watershed. Since most structures overlapped 2 or more
subwatersheds, the higher inundation elevation numbers were added, unless there was surface
inundation risk by lower elevation inundation.
To determine surface flood risk, the structures overlapping the 1% and 10% inundation polygons were
selected.
0
2
4
6
8
10
12
-8.5-7.5-6.5-5.5-4.5-3.5-2.5-1.5-0.50.51.52.53.54.55.56.57.58.59.510.511.512.513.514.5Frequency Plan - Calculated Difference
Basement Elevation: Plan versus Calculated
Difference
Direct Flood Risk GIS Methodology:
The data was selected using the commands below for each 1% and 10% risk:
Moderate Flood Risk: Type = ‘Single Family’ AND SurfaceFlood10%/1% = 'Yes' AND (
FloodElevation10%/1% > Minimum Adjacent Elevation) AND ( FloodElevation10%/1% </= Average
Elevation)
Major Flood Risk: Type = ‘Single Family’ AND SurfaceFlood10%/1% = 'Yes' AND (
FloodElevation10%/1% > Average_Elevation ) AND ( FloodElevation10%/1% </=Maximum_Elevation)
Severe Flood Risk: Type = ‘Single Family’ AND SurfaceFlood10%/1% = 'Yes' AND FloodElevation10%/1%
> Maximum_Elevation
Indirect Flood Risk GIS Methodology:
The data was selected using the commands below for each 1% and 10% risk:
Minor: Type = ‘Single Family’AND FloodElevation10%/1% <=( BasementElevation + 4) AND (
FloodElevation10%/1% > BasementElevation)
Moderate: Type = ‘Single Family’AND FloodElevation10%/1% >( BasementElevation + 4)
Sanitary Flood Risk Methodology
Moderate:
• Select by Attributes: DirectFloodRisk 10%/1% = ‘Major’ OR DirectFloodRisk 10%/1% = ‘Severe’
• SanitaryRiskElevation10%/1% = BasementEvelation + 1. Sort the homes from lowest to highest
sanitary risk elevation
• Create a 250’ buffer around the selected homes, using the buffer tool
• Select by location the buildings intersecting the each buffer, starting with the buffer from the
target home with the lowest sanitary elevation and work upwards, since there will be overlap.
• Then select by attributes from that selection Type = ‘Single Family’ AND Sewershed = [the one
from the target home]
• Remove any other target homes with higher sanitary risk elevations from the selection, then
copy the SanitaryRiskElevation for the target home to the rest of the homes in the buffer
• Then Select by Attributes from current selection: SanitaryRiskElevation10%/1% >
BasementElevation. The selected homes will be your Moderate Risk homes
Major: Major is done similar to Moderate, with the following differences:
• Review Moderate flood risk buffers for clusters of over 3 homes with Major or Severe Direct
Flood risk that are on the same sanitary main. Select the buffers of these homes and export
selected to create a new feature class
• Then Select by Attributes: DirectFloodRisk 10%/1% = ‘Major’ OR DirectFloodRisk 10%/1% =
‘Severe’
• SanitaryRiskElevation10%/1% = BasementElevation +5. Sort the homes from lowest to highest
sanitary risk elevation
•Repeat the rest of the steps from the Moderate Sanitary Risk Methodology
Potential Mitigation Option Mapping
The Barr Engineering team helped created an Excel Macro-enabled spreadsheet to calculate and
summarize the annualized risk to each home, based on current conditions and each potential mitigation
option. The annualized risk data for each home and condition was then imported to ArcMap and
merged with the home data feature class.
The risk change was calculated for each option by home by subtracting the risk for the option from the
current condition risk. The homes removed from risk classifications were calculated by applying a
selection criterion for the current risk not equal to zero and the improvement option equaling zero.
These selections were exported as layers for creating the maps below.
3 sets of maps were made with this data:
-A single Greatest Impact map showing the at-risk homes categorized by the option that would
yield the greatest improvement to existing conditions. The greatest improvement option for
each home was calculated by selecting the option with the highest risk changes (positive). The
homes that had multiple options with the same improvement were left out.
-A series of maps depicting the homes at risk for current and each improvement condition. The
maps for the improvement conditions also included a category for the homes removed from risk
for the specified condition. A color gradient was used to show the risk level to each home in
$3000 increments (not noted on the maps to keep confidential).
-A series of maps showing the risk change from existing conditions for the improvement options.
Some of the improvement options had a few homes with increased risk, which were depicted in
red, while the improvement risk decrease amounts (in $3000 increments as above) were shown
on a green gradient. A category showing the homes removed from risk was also shown for each
option.
Resources
References for concept used in creating expected annual damage and damage-exceedance probability
and cost curves;
https://www.nap.edu/read/21720/chapter/5
http://www.naic.org/documents/cipr_study_1704_flood_risk.pdf
https://www.tandfonline.com/doi/pdf/10.1623/hysj.52.5.1016
https://www.fema.gov/media-library-
data/a10327c71a76f7c88d7cf403dcf60f4f/Actuarial_Methods_and_Assumptions_2013-09-04_508.pdf
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Greatest Impact Flood Mitigation Options
Greatest Impact
Alt3a (2 homes)Alt5a (1 home)Alt7b (69 homes)
Alt8 (13 homes)Alt9 (11 homes)
No Impact
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Existing Conditions (160 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 2b (134 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (26 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 3a (150 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (11 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 4a (154 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (6 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 5a (155 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (5 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 7b (123 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (38 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 8 (155 homes at risk)
1 - lowest risk
23
4
5 - highest risk
homes removed from risk (5 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
da
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Homes at Risk of Inundation
Option Alt 9 (126 homes at risk)
1 - lowest risk
2
3
4
5 - highest risk
homes removed from risk (34 homes)
No risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 2b
1 - small risk increase
no change
1 - small risk decrease23
45 - large risk decrease
removed from risk
Proposed Berm around Weber Pond may mitigate increased flood risk to surrounding homes
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 3a
1 - small risk increase
no change
1 - small risk decrease
2345 - large risk decrease
removed from risk
Proposed Flood Wall may mitigate increasedrisk to home
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 4a
1 - small risk increase
no change
1 - small risk decrease23
45 - large risk decrease
removed from risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 5a
no change
1 - small risk decrease
2345 - large risk decrease
removed from risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 7b
1 - small risk increase
no change
1 - small risk decrease
2345 - large risk decrease
removed from risk
Proposed Flood Wall may mitigate increasedrisk to home
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 8
no change
1 - small risk decrease
2345 - large risk decrease
removed from risk
Weber Field ParkOpen Space 5
Kojetin Park
Open Space 6 France4 4 th Grimes42nd
40th
LynnScottMorningsideAldenKipling
SunnysideCrockerBransonMonterey
45th EtonCur
v
eOakdaleNatchezSidellInglewoodLittelLynnOa
k
d
a
l
e
²
City of Edina Engineering DeptSemptember 2018
Morningside Flood Risk Change by Mitigation Option
Option Alt 9
no change
1 - small risk decrease
2345 - large risk decrease
removed from risk
Barr Engineering Co. 4300 MarketPointe Drive, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com
Memorandum
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Project: 23271649.00
1.0 Purpose of Project and Project Background
This technical memorandum summarizes Barr Engineering Co.’s (Barr’s) preliminary evaluation and
conceptual design of potential flood risk reduction options for the Morningside neighborhood within the
city of Edina. This work included a high-level evaluation of potential flood risk reduction options and
development of associated planning-level opinion of probable construction costs. In parallel to Barr’s
work, city of Edina staff (City) have been working on an approach for summarizing impacted structures
and estimating potential flood damages and we understand that this damage information (dollars) will be
used in conjunction with the estimated project cost data developed by Barr to help City staff further
evaluate the costs and benefits of flood risk reduction opportunities in the study area.
2.0 Description of Existing Conditions
The Morningside/Weber Park area is described in the City’s 2018 Comprehensive Water Resources
Management Plan (CWRMP, reference (1)):
The Morningside/Weber Park area is in the far northeastern corner of Edina, bordering St. Louis Park to the
north and Minneapolis to the east. The area is characterized by numerous backyard depressions and several
large low-lying areas, including Weber Park. There are two large stormwater detention basins in the area,
one located just north of West 42nd Street between Lynn Avenue and Kipling Avenue, and the other located
just north of West 42nd Street and west of France Avenue South (in Weber Park). The area is drained by a
piped outlet that conveys stormwater to Lake Bde Maka Ska (formerly named Lake Calhoun) in Minneapolis.
The storm sewer and detention basins in this area were originally designed for the 2-percent-annual-chance
(50-year) storm event using TP-40 rainfall frequency estimates. Portions of this area have experienced flood
problems historically.
Model results indicate that approximately 65 principle structures and Avail Academy – Edina Campus
(formerly Calvin Christian School) may be directly impacted by the 1-percent-annual-chance (100-year)
flood elevations within this area. In the west part of this area, the flood elevation is approximately 872.1 feet
(subwatershed MS_26). In the southwest part of this area, the flood elevation is approximately 871.7 feet
(subwatershed MS_15). In the southeast part of this area, the flood elevation is approximately 870.1 feet
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 2
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
(subwatershed MS_52). In subwatersheds MS_40 and MS_39a and MS_39b, the flood elevation is 870.0 feet.
In the smaller depressions without outlets to storm sewer such as subwatersheds MS_58, MS_20, MS_22,
MS_57, MS_17, and MS_24, the peak flood elevations are 872.9 feet, 877.3 feet, 872.4 feet, 902.5 feet, 902.5
feet, and 872.1 feet respectively. Flood elevations in subwatersheds MS_20 and MS_22 are controlled by the
10-day snowmelt event, while flood elevations in the remaining subwatersheds are controlled by the 24-
hour duration event.
Flood inundation mapping for the 1-percent-annual-chance (100-year) and the 10-percent-annual-chance
(10-year) storm events can be found on Figure 12.3 of the CWRMP and on the City’s Interactive Web Map.
3.0 Potential Flood Risk Reduction Options
Several potential flood risk reduction options were evaluated using the City’s XP-SWMM model. Five
storm recurrence intervals (i.e., 5-year, 10-year, 25-year, 50-year, and 100-year 24-hour storm events) were
simulated for each flood risk reduction option to help understand the amount of improvement each
option can achieve depending on the severity of the rainfall event. Barr conducted a cursory evaluation of
potentially impacted structures for each potential flood risk reduction option to assess which options
provided the greatest level of flood risk reduction (in terms of a reduction in the number of impacted
structures). The seven options that provided the greatest level of flood risk reduction are described below
and additional details are also shown on the figures included in Attachment A.
• Option 2b: Increase the size of the main trunk storm sewer along West 42nd Street and Crocker
Avenue (up to 60”), including some of the lateral storm sewer (e.g., along Grimes Avenue, 24” to
48”), and construct a flood wall on the east and south sides of Weber Pond, between the pond
and the adjacent residential properties, tying into West 42nd Street on the south side of Weber
Pond (Figure A-1).
• Option 3a: Provide additional flood storage by excavating (i.e., lowering) the ballfield area of
Weber Park and reconstructing the fields, excavating the wooded area north of Weber Pond,
excavating and re-grading the low area between Lynn Avenue and Kipling Avenue north of West
42nd Street, lowering the open area between Susan Lindgren Elementary School and Monterey
Avenue (Yale Gardens Park), and excavating some of the backyards between 44th Street and
Branson Street. Additionally, construct a flood wall on the east and south sides of Weber Pond,
between the pond and the adjacent residential properties (also included in Option 2b), and
construct an earthen berm along the west side of Monterey Avenue between West 41st Street and
West 42nd Street. This option would also include installation of a culvert to connect Weber Pond
to the newly excavated storage in the wooded area north of West 41st Street (Figure A-2).
• Option 4a: Provide additional flood storage by excavating and re-grading the low area between
Lynn Avenue and Kipling Avenue north of West 42nd Street, and installing predictive pumping
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 3
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
systems from the aforementioned low area and Weber Pond to the park (Minikahda Vista Park)
north of Avail Academy – Edina Campus to free up flood storage capacity prior to significant
rainfall events (Figure A-3). The predictive pumping rates were chosen to draw down these two
water bodies from their normal levels to about 6-inches of water depth over a 24 hour period
(recognizing that predicting storms more than 24 hours in advance is challenging). For modeling
purposes, the pumping rates were assumed to be the same regardless of predicted precipitation
amounts in order to maximize available flood storage.
• Option 5a: Provide additional flood storage by installing underground storage in Weber Park
and the open area between Susan Lindgren Elementary School and Monterey Avenue (Yale
Gardens Park). Water would be diverted from the storm sewer to the underground storage by
installing three diversion weirs in the existing storm sewer manholes (Figure A-4). Pumps would
be used to draw down water levels in the underground storage after precipitation events (one
pump in each underground storage unit).
• Option 7b: A combination of Options 2b, 3a, and 4a (Figure A-5), which includes:
o Increasing the size of the trunk storm sewer along West 42nd Street and Crocker Avenue
(up to 60”) and some of the lateral storm sewer (e.g., along Grimes Avenue, 24” to 48”)
o Excavating additional flood storage in the low area between Lynn Avenue and Kipling
Avenue
o Installing predictive pumping systems
o Excavating (lowering) the open area between Susan Lindgren Elementary School and
Monterey Avenue (Yale Gardens Park)
o Constructing an earthen berm west of Monterey Avenue
o Constructing a flood wall east and south of Weber Pond
• Option 8: A more simple variant of Option 3a (Figure A-6), which includes:
o Excavating (i.e., lowering) the ballfields in Weber Park and excavating (to a greater extent,
and deeper, than in Option 3a) the wooded area north of Weber Pond
o Constructing a flood wall east and south of Weber Pond
o Modifying (lowering) the inverts of the storm sewer pipe from Weber Pond to
Minneapolis so that the normal water level of Weber Pond can be lowered by less than 2
feet.
• Option 9: A combination of Option 2b, parts of 5a, and 8 (Figure A-7), which includes:
o Increasing the size of the trunk storm sewer along West 42nd Street and Crocker Avenue
(up to 60”) and some of the lateral storm sewer (e.g., along Grimes Avenue, 24” to 48”)
o Constructing a flood wall on the east and south sides of Weber Pond
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 4
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
o Excavating (i.e., lowering) the ballfields at Weber Park and excavating (to a greater extent)
the wooded area north of Weber Pond.
o Modifying (lowering) the inverts of the storm sewer from Weber Pond to Minneapolis so
that the normal water level of Weber Pond can be lowered by less than 2 feet.
o Installing underground storage in Yale Gardens Park, the required diversion weir in the
nearby manhole structure, and the low-flow pump to drain the stored water.
4.0 Results
Barr provided tables of peak flood elevations to the City for a subsequent analysis of flood consequences
and damages (reference (2)). The tables summarized flood elevations, by subwatershed, under existing
conditions and under each of the seven flood risk reduction options for each of the five modeled
recurrence intervals. Barr and City staff then developed a method to estimate flood damages based on
the peak flood elevations and approximate home elevations. The goal of the analysis was to estimate
flood risk and associated impacts at a neighborhood-scale for varying storm events. The flood damage
estimates reflect “loss potential” in dollars, based on estimated flood loss potential tables published by
the Federal Emergency Management Agency (FEMA) (reference (3)) and assumptions or judgments about
the probability of damage given a flood level relative to the assumed (LiDAR-based) home elevations.
The methodology for quantifying flood risk accounts for probability of flood events, probability of
damage, and the magnitude of damages for existing conditions and for each of the seven flood risk
reduction options. This approach for quantifying flood risk considers damage due to potential direct
flooding of homes at the surface, indirect flooding of homes via groundwater, and flooding of homes via
sanitary sewer backups. The results are detailed in the City’s documentation (reference (4)) and are
summarized below to provide a comparison of relative flood risk reduction in terms of the number of
impacted principle structures. Please note that in the City’s documentation and the summary provided
below, principle structures are referred to as “homes”. Additionally, homes that are referred to as
“removed from risk” in the summary below are homes that are no longer at risk of damage by the three
damage modes considered for storm events that have a 1%, or greater, chance of occurring each year;
however, no home is ever removed from all flood risk. Homes described as “increased risk” would expect
higher peak flood levels for some or all of the storm events modeled, and subsequently, higher expected
damages in dollars. Conversely, homes described as “decreased risk” would expect lower peak flood levels
for some or all of the storm events modeled, and subsequently lower expected damages in dollars.
• Option 2b: 26 homes were completely removed from risk, the risk was decreased for 111 homes
throughout the area, and the risk was increased for 15 homes. These 15 homes are primarily
around Weber Pond where water would accumulate due to the additional conveyance of storm
sewer upstream. 6 of those homes where the risk increased would be protected by the flood wall,
increasing the total number of homes removed from risk to 32.
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 5
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
• Option 3a: 11 homes were completely removed from risk, the risk was decreased for 117 homes
throughout the area, and the risk was increased for one home, which is near Yale Gardens Park
where additional storage and the earthen berm would allow water to be stored to a higher
elevation. However, the berm would separate this home from the stored water and it would be
protected, increasing the total number of homes removed from risk to 12.
• Option 4a: 6 homes were completely removed from risk, the risk was decreased for 127 homes
throughout the area, and the risk was increased for 1 home. This 1 house is east of Weber Pond.
Refinement of the predictive pumping scheme may help in further protecting this home.
• Option 5a: 5 homes were completely removed from risk, the risk was decreased for 92 homes
throughout the area, and the risk was not increased for any homes.
• Option 7b: 38 homes were completely removed from risk, the risk was decreased for 150 homes
throughout the area, and the risk was increased for 1 home. This 1 house is near Yale Gardens
Park where additional storage and the earthen berm would store water higher. However, the
berm would separate this home from the stored water and it would be protected, increasing the
total number of homes removed from risk to 39.
• Option 8: 5 homes were completely removed from risk, the risk was decreased for 74 homes
throughout the area, and the risk was not increased for any homes.
• Option 9: 34 homes were completely removed from risk, the risk was decreased for 136 homes
throughout the area, and the risk was not increased for any homes.
5.0 Planning-Level Opinion of Probable Construction Cost
The Engineer’s planning-level opinions of probable construction cost have been developed for each of the
flood risk reduction options discussed in Section 3.0 and are included as Attachment B. The planning-
level opinions of probable construction cost are intended to provide assistance in evaluating and
comparing flood risk reduction options and should not be assumed as absolute values for given options.
These opinions of probable cost generally correspond to standards established by the Association for the
Advancement of Cost Engineering (AACE). This cost estimate is characterized by limited project definition,
wide-scale use of parametric models to calculate estimated costs (i.e., making extensive use of order-of-
magnitude costs from similar projects or proposals), and uncertainty. At this stage of planning, the range
of uncertainty of total project cost is high. Due to the early stage of the project, it is standard practice to
place a broad accuracy range around the point cost estimate. The estimated accuracy range for the
opinions of probable cost developed as part of this analysis is -30% to +50%. All estimated construction
costs are presented in 2018 U.S. dollars and include costs for engineering and project administration.
Quantities are estimated with calculations based on site development assumptions as described for each
potential flood risk reduction option. Dimensions, areas and volumes were assumed based on LiDAR
elevation data and current understanding of proposed grading. For each potential flood risk reduction
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 6
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
option considered, planning-level opinion of costs do not include land acquisition or coordination with
residents or other subcontractors.
The opinion of probable cost provided in this report is made on the basis of Barr Engineering’s experience
and qualifications and represents our best judgment as experienced and qualified professionals familiar
with the project. It is acknowledged that additional investigations and additional site specific information
that become available in the next stage of study or design may result in changes to the assumed
configuration, cost and functioning of project features. In addition, because we have no control over the
eventual cost of labor, materials, equipment or services furnished by others, or over the contractor’s
methods of determining prices, or over competitive bidding or market conditions, Barr cannot and does
not guarantee that proposals, bids, or actual costs will not vary from the planning-level opinion of
probable costs presented.
6.0 References
1. City of Edina. 2018 Comprehensive Water Resources Management Plan. Edina, MN : s.n., July 2018.
2. Barr Engineering Co. Annualized Damage Method - Barr to Edina Round 2 - with Macro.xlsm. [Excel File]
September 14, 2018.
3. FEMA. Estimated Flood Loss Potential Tables. Flood Loss Estimations 2017. [Online] [Original data
source: National Flood Services, FloodTools.com] [Cited: September 1, 2018.]
https://www.fema.gov/media-library-data/1499290622913-
0bcd74f47bf20aa94998a5a920837710/Flood_Loss_Estimations_2017.pdf.
4. City of Edina. Edina Morningside Neighborhood Flood Risk Reduction Concepts. Edina, MN : s.n.,
September 2018.
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 7
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
Attachment A
Map Figures of the Flood Improvement Options
970 foot flood wall (top elev=871 ft)
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave C
u
r
v
e
A
v
e
Inglewood AveW 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-1
PROPOSED FLOOD RISK
REDUCTION OPTION -
OPTION 2BMorningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 12:23 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 2b.mxd User: sms
Option 2B Proposed Storm Sewer Size Increase (up to 60")
Option 2B Flood Wall
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels 0 240 480Feet
!;N
Note: Vertical datum for all listed elevations is NGVD29
Imagery: USDA NRCS NAIP, 2017
Excavate 4.3 ac-ft580 foot berm (top elev = 874 ft)
Excavate 16.3 ac-ft970 foot flood wall (top elev = 870 ft)
Excavate 8.0 ac-ft
Excavate 13.6 ac-ft
Excavate 2.3 ac-ft
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave Cu
r
v
e
A
v
e
W 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oa
k
da
le
A
ve
Figure A-2
PROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 3AMorningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 12:22 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 3a.mxd User: sms
Option 3A Berm / Flood Wall
Option 3A Excavation
Option 3A Culvert
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels 0 240 480Feet
!;N
Imagery: USDA NRCS NAIP, 2017
Note: Vertical datum for all listed elevations is NGVD29
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave C
u
r
v
e
A
v
e
Inglewood AveW 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-3
PROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 4AMorningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 12:26 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 4a.mxd User: sms
Option 4A Predictive Pumping
Option 4A Excavation
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels 0 240 480Feet
!;N
Imagery: USDA NRCS NAIP, 2017
Note: Vertical datum for all listed elevations is NGVD29
Excavate 9.4 ac-ft
Predictive Pumping at 4.2 cfs for 24 hrs Predictive Pumping at 9.3 cfs for 24 hrs
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave C
u
r
v
e
A
v
e
Inglewood AveW 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-4
PROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 5AMorningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 15:53 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 5a.mxd User: sms
Option 5A Underground Storage
Option 5A Weir
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels 0 240 480Feet
!;N
Note: Vertical datum for all listed elevations is NGVD29
Imagery: USDA NRCS NAIP, 2017
Underground Storage 5.7 ac-ft Underground Storage 47.6 ac-ft
970 foot flood wall (top elev = 871 ft)
Excavate 4.3 ac-ft580 foot berm (top elev = 874 ft)
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave Cu
r
v
e
A
v
e
Inglewood Ave W 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-5
PROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 7BMorningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 12:35 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 7b.mxd User: sms
Option 3A Berm / Flood Wall
Option 4A Predictive Pumping
Option 4A Excavation
Option 3A Excavation
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels 0 240 480Feet
!;N
Imagery: USDA NRCS NAIP, 2017
Note: Vertical datum for all listed elevations is NGVD29
Excavate 2.3 ac-ft
Excavate 9.4 ac-ft
Predictive Pumping at 9.3 cfs for 24 hrs
Predictive Pumping at 4.2 cfs for 24 hrs
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave Cu
r
v
e
A
v
e
Inglewood AveW 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-6
PPROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 8Morningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 12:49 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 8.mxd User: sms
Option 8 Proposed Storm Sewer Invert Changes
Option 8 Berm
Option 8 Excavation
Option 8 Culvert
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels
0 240 480Feet
!;N
Note: Vertical datum for all listed elevations is NGVD29
Imagery: USDA NRCS NAIP, 2017
Excavate 16.3 ac-ftLower NWL by 1.93 ft 970 foot flood wall (top elev = 870 ft)
Excavate 23.3 ac-ft
456717
45673
France Ave SW 44th St
W 42nd St Grimes Ave W 39th St Ewing Ave SMorningside Rd
W 40th St Alden Dr Scott Ter Lynn Ave Kipling Ave Wood Da
le
Ave
S
Branson St Crocker Ave Monterey Ave Sunnyside Rd Lynn Ave SVallacher Ave Joppa Ave SKipling Ave SNatchez Ave SW 41st St Inglewood Ave SDar
t
A
ve
W 40th La Eaton Pl Ottawa Ave SW 45th StOakdale Ave C
u
r
v
e
A
v
e
Inglewood AveW 42 1/2 St
Colgate
A
v
e
Glendale Ter
Little St Monterey Ave SNatchez Ave Waveland Ter Glenhurst Ave SSunnyside Ave Ewing Ave SOttawa Ave SLynn Ave W 41st St Ottawa Ave SW 40th St
W 45th St Oakdale
Ave
Figure A-7
PROPOSED FLOOD RISK
REDUCTION OPTION - OPTION 9Morningside Neighborhood City of Edina
Barr Footer: ArcGIS 10.6, 2018-07-06 15:56 File: I:\Client\Edina\Projects\Morningside FRRS 23271649\Maps\Figure X Option 9.mxd User: sms
Option 8 Proposed Storm Sewer Invert Changes
Option 5A Underground Storage
Option 5A Weir
Option 8 Berm
Option 8 Excavation
Option 8 Culvert
!>Existing Manhole/Catch Basin
Existing Storm Sewer
Subwatersheds
Parcels
0 240 480Feet
!;N
Note: Vertical datum for all listed elevations is NGVD29
Imagery: USDA NRCS NAIP, 2017
UndergroundStorage 5.7 ac-ft
Excavate 16.3 ac-ftLower NWL by 1.93 ft 970 foot flood wall (top elev = 870 ft)
Excavate 23.3 ac-ft
To: Jessica Wilson and Ross Bintner, City of Edina From: Cory Anderson, Sarah Stratton, and Janna Kieffer Subject: Morningside Neighborhood Flood Risk Reduction Strategy Conceptual Study Date: November 19, 2018 Page: 15
P:\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Technical Summary Memo\Morningside FRRS Exec Summary Memo_11192018.docx
Attachment B
Engineer’s Opinion of Probable Project Cost for Flood Improvement Options
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 1 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 2B
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $240,000.00 $240,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Flotation Silt Curtain LF 900 $11.00 $9,900.00 1,2,3,4,5,6
D Remove and Dispose of Existing Storm Sewer LF 4,580 $20.00 $91,600.00 1,2,3,4,5,6
E Remove and Dispose of Existing Manhole/Catch Basin Each 22 $750.00 $16,500.00 1,2,3,4,5,6
F 24" RC Pipe Sewer (Furnish and Install) (12 - 13' depth)LF 278 $110.00 $30,580.00 1,2,3,4,5,6,7
G 36" RC Pipe Sewer (Furnish and Install) (8 - 13' depth)LF 710 $170.00 $120,700.00 1,2,3,4,5,6,7
H 48" RC Pipe Sewer (Furnish and Install) (15' depth)LF 368 $270.00 $99,360.00 1,2,3,4,5,6,7
I 60" RC Pipe Sewer (Furnish and Install) (8 - 10' depth)LF 840 $225.00 $189,000.00 1,2,3,4,5,6,7
J 60" RC Pipe Sewer (Furnish and Install) (10 - 16' depth)LF 2,630 $340.00 $894,200.00 1,2,3,4,5,6,7
K Construct Drainage Structure SD-48 LF 14 $372.00 $5,208.00 1,2,3,4,5,6
L Construct Drainage Structure SD-60 LF 56 $608.00 $34,048.00 1,2,3,4,5,6
M Construct Drainage Structure SD-72 LF 14 $804.00 $11,256.00 1,2,3,4,5,6
N Construct Drainage Structure SD-84 LF 224 $1,450.00 $324,800.00 1,2,3,4,5,6
O Casting Assembly Each 22 $750.00 $16,500.00 1,2,3,4,5,6
P Tie-In Existing Storm Sewer Main to Manhole Each 6 $1,000.00 $6,000.00 1,2,3,4,5,6
Q Connect CB Leads to Constructed Storm Sewer Each 38 $700.00 $26,600.00 1,2,3,4,5,6
R Excavation CY 1,110 $4.00 $4,440.00 1,2,3,4,5,6
S Offsite Disposal of Excavated Material CY 890 $16.00 $14,240.00 1,2,3,4,5,6
T Site Grading SY 2,230 $2.00 $4,460.00 1,2,3,4,5,6
U Reinforced Structural Concrete Flood Wall CY 450 $1,000.00 $450,000.00 1,2,3,4,5,6
V Clearing and Grubbing AC 1 $6,000.00 $6,000.00 1,2,3,4,5,6
W Tree 2", B&B Each 20 $500.00 $10,000.00 1,2,3,4,5,6
X Turf Establishment (w/ Disc Anchored Mulch)AC 1 $3,000.00 $3,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $2,638,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$791,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $3,429,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$1,029,000.00 1,2,3,4,5,8
RESIDENTIAL/CONSTRUCTION PERMANENT EASEMENT $11,000.00 1,2,3,5,8
ESTIMATED TOTAL PROJECT COST $4,469,000.00 1,2,3,4,5,6,7,8
-30%$3,129,000.00 5,8
50%$6,704,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this
time. Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not
included at this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy
range is based on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as
scoped. The contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently
scoped or costs for risk contingency. Operation and Maintenance costs are not included.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 1
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 2 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 3A
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $270,000.00 $270,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Dewatering LS 1 $50,000.00 $50,000.00 1,2,3,4,5,6
D Flotation Silt Curtain LF 1,000 $11.00 $11,000.00 1,2,3,4,5,6
E Remove Existing Sports Infrastructure LS 1 $15,000.00 $15,000.00 1,2,3,4,5,6
F Excavation CY 72,903 $4.00 $291,613.33 1,2,3,4,5,6
G Off Site Disposal of Excavated Material CY 72,290 $16.00 $1,156,634.07 1,2,3,4,5,6
H Site Grading SY 125,540 $2.00 $251,080.00 1,2,3,4,5,6
I Place On-Site Soil for Berm Construction CY 1,504 $5.00 $7,518.52 1,2,3,4,5,6
J 36" RC Pipe Sewer (Furnish and Install) (5' - 8' depth)LF 50 $110.00 $5,500.00 1,2,3,4,5,6,7
K 36" RC Pipe Sewer Flared End Section (Furnish and Install)Each 2 $1,540.00 $3,080.00 1,2,3,4,5,6
L MnDOT Class IV RipRap with Filter Fabric TON 53 $100.00 $5,275.00 1,2,3,4,5,6
M Reinforced Structural Concrete Flood Wall CY 450 $1,000.00 $450,000.00 1,2,3,4,5,6
N Clearing and Grubbing AC 9 $6,000.00 $54,000.00 1,2,3,4,5,6
O Upland Native Vegetation AC 5 $5,000.00 $25,000.00 1,2,3,4,5,6
P Tree 2", B&B Each 150 $500.00 $75,000.00 1,2,3,4,5,6
Q Turf Establishment (w/ Disc Anchored Mulch)AC 17 $3,000.00 $52,314.05 1,2,3,4,5,6
R Sod SY 4,840 $6.00 $29,040.00 1,2,3,4,5,6
S Erosion Control Blanket SY 29,476 $2.00 $58,951.20 1,2,3,4,5,6
T Wetland Restoration AC 2.5 $10,000.00 $25,000.00 1,2,3,4,5,6
U Reconstruction of Baseball Field LS 1 $75,000.00 $75,000.00 1,2,3,4,5,6
V Reconstruction of Ice Rink LS 1 $25,000.00 $25,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $2,966,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$890,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $3,856,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$1,157,000.00 1,2,3,4,5,8
RESIDENTIAL/CONSTRUCTION PERMANENT EASEMENT $56,000.00 1,2,3,5,8
ESTIMATED TOTAL PROJECT COST $5,069,000.00 1,2,3,4,5,6,7,8
-30%$3,549,000.00 5,8
50%$7,604,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at
this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based
on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The
contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for
risk contingency. Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 2
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 3 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 4A
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $186,000.00 $186,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Excavation CY 15,165 $4.00 $60,661.33 1,2,3,4,5,6
D Off Site Disposal of Excavated Material CY 15,165 $16.00 $242,645.33 1,2,3,4,5,6
E Site Grading SY 14,520 $2.00 $29,040.00 1,2,3,4,5,6
F
Opti CMAC Predictive Pumping Control System (Furnish and
Install)Each 2 $85,000.00 $170,000.00 1,2,3,4,5,6
G
2,000 GPM Pumping Station (Includes Building Structure,
Electric Supply, Control Panel)LS 1 $500,000.00 $500,000.00 1,2,3,4,5,6
H
4,000 GPM Pumping Station (Includes Building Structure,
Electric Supply, Control Panel)LS 1 $700,000.00 $700,000.00 1,2,3,4,5,6
I Pumping Station Outlet Piping (Furnish and Install)LF 1,116 $40.00 $44,640.00 1,2,3,4,5,6,7
J Pumping Station Inlet Suction Piping (Furnish and Install)LF 24 $40.00 $960.00 1,2,3,4,5,6,7
K Tie-In Storm Sewer to Existing Manhole Each 2 $1,000.00 $2,000.00 1,2,3,4,5,6
L Clearing and Grubbing AC 3.2 $6,000.00 $19,239.67 1,2,3,4,5,6
M Upland Native Vegetation AC 0.7 $5,000.00 $3,500.00 1,2,3,4,5,6
N Tree 2", B&B Each 50 $500.00 $25,000.00 1,2,3,4,5,6
O Turf Establishment (w/ Disc Anchored Mulch)AC 0.5 $3,000.00 $1,500.00 1,2,3,4,5,6
P Erosion Control Blanket SY 1,452 $2.00 $2,904.00 1,2,3,4,5,6
Q Wetland Restoration AC 2 $10,000.00 $20,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $2,038,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$611,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $2,649,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$795,000.00 1,2,3,4,5,8
ESTIMATED TOTAL PROJECT COST $3,444,000.00 1,2,3,4,5,6,7,8
-30%$2,411,000.00 5,8
50%$5,166,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at
this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based
on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The
contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for
risk contingency. Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 3
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 4 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 5A
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization LS 1 $576,000.00 $576,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Remove Existing Sports Infrastructure LS 1 $15,000.00 $15,000.00 1,2,3,4,5,6
D Excavation CY 785,587 $4.00 $3,142,346.67 1,2,3,4,5,6
E Excavate and Haul offsite CY 112,933 $16.00 $1,806,933.33 1,2,3,4,5,6
F Site Grading SY 43,560 $2.00 $87,120.00 1,2,3,4,5,6
G Salvage and Replace Existing Topsoil CY 7,260 $9.00 $65,340.00 1,2,3,4,5,6
H StormTrap Subsurface Storage CF 2,866,250 $6.00 $17,197,500.00 1,2,3,4,5,6
I 500 GPM Pump (Subsurface Storage Drawdown)Each 1 $30,000.00 $30,000.00 1,2,3,4,5,6
J 3,500 GPM Pump (Subsurface Storage Drawndown)Each 1 $300,000.00 $300,000.00 1,2,3,4,5,6
K 36" RC Pipe Sewer (Furnish and Install) (10' - 15' depth)LF 300 $215.00 $64,500.00 1,2,3,4,5,6,7
L 42" RC Pipe Sewer (Furnish and Install) (10' - 15' depth)LF 50 $270.00 $13,500.00 1,2,3,4,5,6,7
M
Construct Drainage Structure SD-72 w/ Weir
(Diversion Structure)Each 3 $15,000.00 $45,000.00 1,2,3,4,5,6
N Tie-In Existing Storm Sewer to Manhole Each 5 $1,000.00 $5,000.00 1,2,3,4,5,6
O Clearing and Grubbing AC 1 $6,000.00 $6,000.00 1,2,3,4,5,6
P Tree 2", B&B Each 25 $500.00 $12,500.00 1,2,3,4,5,6
Q Turf Establishment (w/ Disc Anchored Mulch)AC 9.0 $3,000.00 $27,000.00 1,2,3,4,5,6
R Reconstruction of Baseball Field LS 1 $75,000.00 $75,000.00 1,2,3,4,5,6
S Reconstruction of Ice Rink LS 1 $25,000.00 $25,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $23,524,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$7,057,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $30,581,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION $1,100,000.00 1,2,3,4,5,8
ESTIMATED TOTAL PROJECT COST $31,681,000.00 1,2,3,4,5,6,7,8
-30%$22,177,000.00 5,8
50%$47,522,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at
this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based
on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The
contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for
risk contingency. Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 4
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 5 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 7B
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $455,000.00 $455,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Excavation CY 26,923 $4.00 $107,693.33 1,2,3,4,5,6
D Off Site Disposal of Excavated Material CY 25,200 $16.00 $403,194.07 1,2,3,4,5,6
E Site Grading SY 40,712 $2.00 $81,424.44 1,2,3,4,5,6
Place On-Site Soil for Berm Construction CY 1,504 $5.00 $7,518.52 1,2,3,4,5,6
F Reinforced Structural Concrete Flood Wall CY 450 $1,000.00 $450,000.00 1,2,3,4,5,6
G Flotation Silt Curtain LF 900 $11.00 $9,900.00 1,2,3,4,5,6
H Remove and Dispose of Existing Storm Sewer LF 4,580 $20.00 $91,600.00 1,2,3,4,5,6
I Remove and Dispose of Existing Manhole/Catch Basin Each 22 $750.00 $16,500.00 1,2,3,4,5,6
J 24" RC Pipe Sewer (Furnish and Install) (12 - 13' depth)LF 278 $110.00 $30,580.00 1,2,3,4,5,6,7
K 36" RC Pipe Sewer (Furnish and Install) (8 - 13' depth)LF 710 $170.00 $120,700.00 1,2,3,4,5,6,7
L 48" RC Pipe Sewer (Furnish and Install) (15' depth)LF 368 $270.00 $99,360.00 1,2,3,4,5,6,7
M 60" RC Pipe Sewer (Furnish and Install) (8 - 10' depth)LF 840 $225.00 $189,000.00 1,2,3,4,5,6,7
N 60" RC Pipe Sewer (Furnish and Install) (10 - 16' depth)LF 2,630 $340.00 $894,200.00 1,2,3,4,5,6,7
O Construct Drainage Structure SD-48 LF 14 $372.00 $5,208.00 1,2,3,4,5,6
P Construct Drainage Structure SD-60 LF 56 $608.00 $34,048.00 1,2,3,4,5,6
Q Construct Drainage Structure SD-72 LF 14 $804.00 $11,256.00 1,2,3,4,5,6
R Construct Drainage Structure SD-84 LF 224 $1,450.00 $324,800.00 1,2,3,4,5,6
S Casting Assembly Each 22 $750.00 $16,500.00 1,2,3,4,5,6
T Tie-In Storm Sewer Main to Manhole Each 9 $1,000.00 $9,000.00 1,2,3,4,5,6
U Connect CB Leads to Constructed Storm Sewer Each 38 $700.00 $26,600.00 1,2,3,4,5,6
V
Opti CMAC Predictive Pumping Control System (Furnish and
Install)Each 2 $85,000.00 $170,000.00 1,2,3,4,5,6
W
2,000 GPM Pumping Station (Includes Building Structure,
Electric Supply, Control Panel)LS 1 $500,000.00 $500,000.00 1,2,3,4,5,6
X
4,000 GPM Pumping Station (Includes Building Structure,
Electric Supply, Control Panel)LS 1 $700,000.00 $700,000.00
Y Pumping Station Outlet Piping (Furnish and Install)LF 1,116 $40.00 $44,640.00 1,2,3,4,5,6,7
Z Pumping Station Inlet Suction Piping (Furnish and Install)LF 24 $40.00 $960.00 1,2,3,4,5,6,7
AA Clearing and Grubbing AC 6 $6,000.00 $33,994.49 1,2,3,4,5,6
BB Upland Native Vegetation AC 0.7 $5,000.00 $3,500.00 1,2,3,4,5,6
CC Wetland Restoration AC 2.0 $10,000.00 $20,000.00 1,2,3,4,5,6
DD Tree 2", B&B Each 150 $500.00 $75,000.00 1,2,3,4,5,6
EE Turf Establishment (w/ Disc Anchored Mulch)AC 4.7 $3,000.00 $14,134.85 1,2,3,4,5,6
FF Sod SY 4,840 $3.00 $14,520.00 1,2,3,4,5,6
GG Erosion Control Blanket SY 5,324 $2.00 $10,648.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $5,001,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$1,500,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $6,501,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$1,950,000.00 1,2,3,4,5,8
RESIDENTIAL/CONSTRUCTION PERMANENT EASEMENT $56,000.00 1,2,3,5,8
ESTIMATED TOTAL PROJECT COST $8,507,000.00 1,2,3,4,5,6,7,8
-30%$5,955,000.00 5,8
50%$12,761,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at
this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based
on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The
contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for
risk contingency. Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 5
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 6 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 8
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $278,000.00 $278,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Dewatering LS 1 $50,000.00 $50,000.00 1,2,3,4,5,6
D Flotation Silt Curtain LF 1,000 $11.00 $11,000.00 1,2,3,4,5,6
E Remove Existing Sports Infrastructure LS 1 $15,000.00 $15,000.00 1,2,3,4,5,6
F Excavation CY 64,998 $4.00 $259,992.00 1,2,3,4,5,6
G Off Site Disposal of Excavated Material CY 64,778 $16.00 $1,036,448.00 1,2,3,4,5,6
H Site Grading SY 87,070 $2.00 $174,140.00 1,2,3,4,5,6
I Reinforced Structural Concrete Flood Wall CY 450 $1,000.00 $450,000.00 1,2,3,4,5,6
J Remove and Dispose of Existing Storm Sewer LF 1,190 $20.00 $23,800.00 1,2,3,4,5,6
K Remove and Dispose of Existing Manhole/Catch Basin Each 4 $750.00 $3,000.00 1,2,3,4,5,6
L 30" RC Pipe Sewer (Furnish and Install) (8 - 16' depth)LF 910 $160.00 $145,600.00 1,2,3,4,5,6,7
M 42" RC Pipe Sewer (Furnish and Install) (8 - 16' depth)LF 280 $250.00 $70,000.00 1,2,3,4,5,6,7
N Construct Drainage Structure SD-60 LF 16 $608.00 $9,728.00 1,2,3,4,5,6
O Construct Drainage Structure SD-72 LF 42 $804.00 $33,768.00 1,2,3,4,5,6
P Casting Assembly Each 4 $750.00 $3,000.00 1,2,3,4,5,6
Q Tie-In Storm Sewer Main to Manhole Each 3 $1,000.00 $3,000.00 1,2,3,4,5,6
R Connect CB Leads to Constructed Storm Sewer Each 2 $700.00 $1,400.00 1,2,3,4,5,6
S 6' x 8' Box Culvert (Furnish and Install)LF 100 $1,000.00 $100,000.00 1,2,3,4,5,6,7
T 6' x 8' Box Culvert End Section (Furnish and Install)Each 4 $10,000.00 $40,000.00 1,2,3,4,5,6
U MnDOT Class IV RipRap with Filter Fabric TON 248 $100.00 $24,800.00 1,2,3,4,5,6
V Clearing and Grubbing AC 5 $6,000.00 $30,000.00 1,2,3,4,5,6
W Upland Native Vegetation AC 4.5 $5,000.00 $22,500.00 1,2,3,4,5,6
X Tree 2", B&B Each 100 $500.00 $50,000.00 1,2,3,4,5,6
Y Turf Establishment (w/ Disc Anchored Mulch)AC 13.0 $3,000.00 $38,969.01 1,2,3,4,5,6
Z Erosion Control Blanket SY 24,200 $2.00 $48,400.00 1,2,3,4,5,6
AA Reconstruction of Baseball Field LS 1 $75,000.00 $75,000.00 1,2,3,4,5,6
BB Reconstruction of Ice Rink LS 1 $25,000.00 $25,000.00 1,2,3,4,5,6
CC Wetland Restoration AC 0.5 $10,000.00 $5,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $3,058,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$917,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $3,975,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$1,193,000.00 1,2,3,4,5,8
RESIDENTIAL/CONSTRUCTION PERMANENT EASEMENT $11,000.00 1,2,3,5,8
ESTIMATED TOTAL PROJECT COST $5,179,000.00 1,2,3,4,5,6,7,8
-30%$3,626,000.00 5,8
50%$7,769,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks
following construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and
unit prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at
this level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based
on professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The
contingency and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for
risk contingency. Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 6
PREPARED BY: BARR ENGINEERING COMPANY SHEET: 7 OF 7
BY:KJN2 DATE:7/6/2018
FEASIBILITY STUDY CHECKED BY: KAL DATE: 7/6/2018
ENGINEER'S OPINION OF PROBABLE PROJECT COST APPROVED BY:DATE:
PROJECT:Morningside FRRS Study ISSUED:DATE:
LOCATION:City of Edina ISSUED:DATE:
PROJECT #:23/27-1649.00 ISSUED:DATE:
OPINION OF COST - SUMMARY ISSUED:DATE:
Engineer's Opinion of Probable Project Cost
Morningside Flood Mitigation Feasibility Project
Option 9
Cat.ESTIMATED
No.ITEM DESCRIPTION UNIT QUANTITY UNIT COST ITEM COST NOTES
A Mobilization/Demobilization (10%)LS 1 $741,000.00 $741,000.00 1,2,3,4,5,6
B Temporary Erosion Control LS 1 $30,000.00 $30,000.00 1,2,3,4,5,6
C Dewatering LS 1 $50,000.00 $50,000.00 1,2,3,4,5,6
D Flotation Silt Curtain LF 1,000 $11.00 $11,000.00 1,2,3,4,5,6
E Remove Existing Sports Infrastructure LS 1 $15,000.00 $15,000.00 1,2,3,4,5,6
F Excavation CY 113,398 $4.00 $453,592.00 1,2,3,4,5,6
G Off Site Disposal of Excavated Material CY 101,885 $16.00 $1,630,154.67 1,2,3,4,5,6
H Site Grading SY 96,750 $2.00 $193,500.00 1,2,3,4,5,6
I Salvage and Replace Existing Topsoil CY 7,260 $9.00 $65,340.00 1,2,3,4,5,6
J Reinforced Structural Concrete Flood Wall CY 450 $1,000.00 $450,000.00 1,2,3,4,5,6
K 6' x 8' Box Culvert (Furnish and Install)LF 100 $1,000.00 $100,000.00 1,2,3,4,5,6,7
L 6' x 8' Box Culvert End Section (Furnish and Install)Each 4 $10,000.00 $40,000.00 1,2,3,4,5,6
M MnDOT Class IV RipRap with Filter Fabric TON 248 $100.00 $24,800.00 1,2,3,4,5,6
N Remove and Dispose of Existing Storm Sewer LF 5,770 $20.00 $115,400.00 1,2,3,4,5,6
O Remove and Dispose of Existing Manhole/Catch Basin Each 26 $750.00 $19,500.00 1,2,3,4,5,6
P 24" RC Pipe Sewer (Furnish and Install) (12 - 13' depth)LF 278 $110.00 $30,580.00 1,2,3,4,5,6,7
Q 30" RC Pipe Sewer (Furnish and Install) (8 - 16' depth)LF 910 $160.00 $145,600.00 1,2,3,4,5,6,7
R 36" RC Pipe Sewer (Furnish and Install) (8 - 13' depth)LF 710 $170.00 $120,700.00 1,2,3,4,5,6,7
S 42" RC Pipe Sewer (Furnish and Install) (8 - 16' depth)LF 280 $250.00 $70,000.00 1,2,3,4,5,6,7
T 48" RC Pipe Sewer (Furnish and Install) (15' depth)LF 368 $270.00 $99,360.00 1,2,3,4,5,6,7
U 60" RC Pipe Sewer (Furnish and Install) (8 - 10' depth)LF 840 $225.00 $189,000.00 1,2,3,4,5,6,7
V 60" RC Pipe Sewer (Furnish and Install) (10 - 16' depth)LF 2,630 $340.00 $894,200.00 1,2,3,4,5,6,7
W Construct Drainage Structure SD-48 LF 14 $372.00 $5,208.00 1,2,3,4,5,6
X Construct Drainage Structure SD-60 LF 72 $608.00 $43,776.00 1,2,3,4,5,6
Y Construct Drainage Structure SD-72 LF 70 $804.00 $56,280.00 1,2,3,4,5,6
A Construct Drainage Structure SD-84 LF 224 $1,450.00 $324,800.00 1,2,3,4,5,6
AA Casting Assembly Each 26 $750.00 $19,500.00 1,2,3,4,5,6
BB Tie-In Storm Sewer Main to Manhole Each 9 $1,000.00 $9,000.00 1,2,3,4,5,6
CC Connect CB Leads to Constructed Storm Sewer Each 40 $700.00 $28,000.00 1,2,3,4,5,6
DD 72" Diameter Weir Manhole (Diversion Structure)Each 1 $15,000.00 $15,000.00 1,2,3,4,5,6
EE StormTrap Subsurface Storage CF 304,920 $6.00 $1,829,520.00 1,2,3,4,5,6
FF 500 GPM Pump (Subsurface Storage Drawdown)Each 1 $30,000.00 $30,000.00 1,2,3,4,5,6
GG Clearing and Grubbing AC 5 $6,000.00 $30,000.00 1,2,3,4,5,6
HH Upland Native Vegetation AC 5 $5,000.00 $22,500.00 1,2,3,4,5,6
II Tree 2", B&B Each 100 $500.00 $50,000.00 1,2,3,4,5,6
JJ Turf Establishment (w/ Disc Anchored Mulch)AC 15.0 $3,000.00 $44,969.01 1,2,3,4,5,6
KK Erosion Control Blanket SY 24,200 $2.00 $48,400.00 1,2,3,4,5,6
LL Reconstruction of Baseball Field LS 1 $75,000.00 $75,000.00 1,2,3,4,5,6
MM Reconstruction of Ice Rink LS 1 $25,000.00 $25,000.00 1,2,3,4,5,6
NN Wetland Restoration AC 0.5 $10,000.00 $5,000.00 1,2,3,4,5,6
CONSTRUCTION SUBTOTAL $8,151,000.00 1,2,3,4,5,6,7,8
CONSTRUCTION CONTINGENCY (30%)$2,445,000.00 1,5,8
ESTIMATED CONSTRUCTION COST $10,596,000.00 1,2,3,4,5,6,7,8
ENGINEERING, DESIGN, PERMITTING, AND CONSTRUCTION
OBSERVATION (30%)$3,179,000.00 1,2,3,4,5,8
RESIDENTIAL/CONSTRUCTION PERMANENT EASEMENT $11,000.00 1,2,3,5,8
ESTIMATED TOTAL PROJECT COST $13,786,000.00 1,2,3,4,5,6,7,8
-30%$9,651,000.00 5,8
50%$20,679,000.00 5,8
Notes
6 Estimate costs are to design, construct, and permit each alternative. The estimated costs do not include maintenance, monitoring or additional tasks following
construction.
7 Furnish and Install pipe cost per lineal foot includes all trenching, bedding, backfilling, compaction, and disposal of excess materials
8 Estimate costs are reported to nearest thousand dollars.
ESTIMATED ACCURACY RANGE
1 Limited Design Work Completed
2 Quantities Based on Design Work Completed.
3 Unit Prices Based on Information Available at This Time.
4 Minimal Soil and Field Investigations Completed. Costs do not included remediation of contaminated soils (if found).
5 This feasibility-level (Class 4, 10-15% design completion per ASTM E 2516-06) cost estimate is based on feasibility-level designs, alignments, quantities and unit
prices. Costs will change with further design. Time value-of-money escalation costs are not included. A construction schedule is not available at this time.
Contingency is an allowance for the net sum of costs that will be in the Final Total Project Cost at the time of the completion of design, but are not included at this
level of project definition. The estimated accuracy range for the Total Project Cost as the project is defined is -30% to +50%. The accuracy range is based on
professional judgement considering the level of design completed, the complexity of the project and the uncertainties in the project as scoped. The contingency
and the accuracy range are not intended to include costs for future scope changes that are not part of the project as currently scoped or costs for risk contingency.
Operation and Maintenance costs are not included.
\\barr.com\projects\Mpls\23 MN\27\23271649 Morningside FRRS Study\WorkFiles\Cost Estimates\Engineers Opinion of Probable Cost_20180704.xlsx 7
D
Appendix D: ‘Keep your water to yourself: private infrastructure analysis’, technical
memo
Barr Engineering Co. 4300 MarketPointe Drive, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com
Technical Memorandum
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Project: Edina Flood Risk Reduction Strategy Support (23271728.00)
Executive Summary
Barr was asked to review model-predicted flood impacts in the focal geography of the Morningside
neighborhood to evaluate the sensitivity of those impacts to the magnitude of stormwater storage within
the watershed. In particular, the focus was on underground storage methods within private property, the
right-of-way, or under streets. This evaluation was conducted as a result of Task Force discussions about
the potential benefits of requiring private homeowners to store stormwater on-site similar to
requirements for commercial development.
Barr reviewed the benefits achieved by storing the first 1-inch, 2-inches, and 3-inches of precipitation
from storm events of varying size, from the 20%-annual-chance storm event (5-year storm; 3.59 inches) to
the 1%-annual-chance storm event (100-year storm; 7.49 inches). For the private storage evaluation
(underground storage vaults under a portion of each of the 570 residential parcels), storage was assumed
for every parcel within the Morningside neighborhood. Barr found that storing the first 1-inch of storms of
this magnitude had a negligible impact on flood levels. Storing the first 2-inches and 3-inches showed a
more significant benefit with regards to reduction in peak flood levels. Depending on the storm event,
and depending on the location within in the neighborhood, the results varied anywhere from flood level
decreases of a few inches to decreasing nearly a foot and a half.
However, this apparent benefit comes at an initial cost of approximately $15,000 per inch of stormwater
stored, per residential parcel. To store 2-inches of runoff in the entire neighborhood (~570 residential
parcels) would cost approximately $17 million. In addition, while the flood levels may be lowered, the
number of homes that are removed from potential impacts from flood inundation is small. For example,
one home may potentially be removed from flood inundation at Weber Pond depending on the storm
event. Finally, the management and maintenance of these underground stormwater storage vaults
distributed throughout an entire neighborhood is expected to be complicated and unprecedented. This is
all to say, this solution would provide a moderate benefit for a very high cost. Additionally, a preliminary
look at the compounding effect of climate change suggests that improvements realized by implementing
additional private storage may eventually be negated by climate change (i.e., increased precipitation
amounts, see Appendix B on Climate Change Impacts Analysis).
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 2
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Private Infrastructure Analysis Details
A common example of private stormwater management infrastructure (infrastructure on a privately
owned parcel), is a rainwater garden (Figure 1). Rainwater gardens are typically designed to store the first
one inch of runoff generated from a storm, aimed at both reducing the volume of runoff and improving
water quality downstream.
Figure 1 Photo of a rainwater garden.
Other examples of private infrastructure for stormwater
storage can include tree trenches, cisterns, permeable
pavement, and underground storage vaults. Figure 2 shows
an example of an underground stormwater storage vault.
To simplify our analysis, we assumed that all parcels in the
Morningside neighborhood are approximately 60 feet wide
(along the road), and also assumed that every parcel would
have underground storage (below grade) that is 3 feet
deep. Then we determined how wide the underground
storage vault would need to be to contain 1 inch of runoff,
2 inches of runoff, or 4 inches of runoff. We found that
underground storage vaults on every parcel in the
Morningside neighborhood would need to be 5 feet wide
to store 1 inch of runoff, 10 feet wide to store 2 inches of
runoff, and 20 feet wide to store 4 inches of runoff. Figure 3
provides a graphic that shows the extent of underground
storage needed for sample parcels in Morningside.
Figure 2 Example of an underground storage vault (37th Avenue Greenway, Minneapolis).
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 3
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 3 Private stormwater storage sizing examples for storing varying amounts of runoff.
Barr also analyzed using stormwater storage under streets and/or in the public right-of-way. Figure 4
provides a graphic that shows the approximate extent of underground storage available for a typical road
within the Morningside neighborhood. Assuming two 15-foot wide (and 3 feet deep) underground
storage vaults can be installed under all of the roads or right-of-way in the Morningside neighborhood,
3-inches of runoff could be stored in those vaults.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 4
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 4 Stormwater storage sizing (width) available for typical roads or right-of-way in the Morningside neighborhood.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 5
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 5 shows the subwatersheds in the Morningside neighborhood. Graphs are included below that
show the results and range of benefits of residential/private stormwater storage for Weber Pond
(subwatershed MS_40, Figure 6), for the area along Branson between Oakdale Avenue and Grimes Avenue
(subwatershed MS_48, Figure 7), and for the area along Crocker Avenue between West 42nd Street and
Morningside Road (subwatershed MS_2, Figure 8).
Figure 5 Map showing subwatershed divides in and around the Morningside neighborhood
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 6
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
In Figure 6, the horizontal, maroon-dashed lines represent approximate low elevations based on structure
footprints for the four lowest homes around Weber Pond. They may or may not represent actual low entry
elevations of these homes. However, they give a good representation of the home elevations and how
close they are to the flood levels.
Figure 6 Peak water surface levels resulting from varying amounts of runoff stored using private infrastructure for varying storm events in the Weber Pond subwatershed (MS_40).
At first glance, the reductions shown in Figure 6 appear smaller than would be expected. There are
multiple other factors affecting the flood volume stored in Weber Pond. First, Weber Pond ultimately
receives water from Edina and also from St. Louis Park and Minneapolis. While private infrastructure is
overall beneficial, reducing the runoff to Weber Pond from Edina may allow more water from St. Louis
Park and Minneapolis to fill the pond back up during an event. Second, at the peak flood elevations
shown in Figure 6, stormwater flows out of Weber Pond both into Weber Park and over France Avenue to
the east to Minneapolis. When ponds rise high enough to overflow banks, additional water does not tend
to have a significant impact on the water level since water can start following natural overflow paths.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 7
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 7 Peak water surface levels resulting from varying amounts of runoff stored using private infrastructure for varying storm events in subwatershed MS_48.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 8
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 8 Peak water surface levels resulting from varying amounts of runoff stored using private infrastructure for varying storm events in subwatershed MS_2.
Barr commonly estimates that the cost per cubic foot of underground stormwater storage is
approximately $10 to $20. For one inch of runoff, for one 0.25-acre parcel, storage volume equals 900
cubic feet. This equates to a little under $15,000 (+/- $5,000) per parcel per inch of runoff stored. Figure 9
shows the approximate cost per parcel of underground storage using varying widths of underground
storage units and varying amounts of runoff stored. To put the cost of private underground storage into
perspective, Figure 10 shows a portion of the Morningside neighborhood (~180 parcels) and provides a
breakdown of an approximate cost to capture two inches of runoff from every parcel.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 9
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
Figure 9 Approximate cost per parcel of underground storage using varying widths of
underground storage units and varying amounts of runoff stored.
Figure 10 Cost breakdown for using private stormwater storage for a portion of the Morningside neighborhood.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 10
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
In total, there are approximately 570 residential parcels in the Morningside neighborhood watershed
drainage area, as shown in Figure 11.
Figure 11 Parcels in the Morningside neighborhood watershed/drainage area.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix D - Private Infrastructure Analysis Date: March 30, 2020 Page: 11
\\barr.com\projects\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix D - Private Infrastructure.docx
The results of Barr’s private storage analysis are summarized in Table 1 below. Recall that storing 1-inch of
runoff from every parcel in Morningside had a marginal benefit in general on peak flood levels. Table 1
below shows that to store 2-inches of runoff in the entire neighborhood would cost approximately
$17 million. While storing 2-inches of runoff does reduce flood levels, the number of homes that are
removed from potential impacts from flood inundation is small. For example, as shown in Figure 6,
depending on the storm event, this level of effort may potentially remove only one home from flood
inundation at Weber Pond.
Table 1 Summary of costs and benefits of private stormwater storage for the whole Morningside neighborhood.
Inches of
Runoff
Stored
Cost for All Parcels to
Store the Runoff
Flood Level Reduction Benefit (in feet) for Weber Pond
Subwatershed (MS_40)
5-yr Storm
(3.59" of
precip)
10-yr Storm
(4.29" of
precip)
50-yr Storm
(6.39" of
precip)
100-yr Storm
(7.49" of
precip)
1 inch $ 8,550,000 0.1 <0.1 <0.1 0
2 inches $ 17,100,000 0.6 0.3 0.5 0.3
3 inches $ 25,650,000 0.7 0.9 0.6 0.5
E
Appendix E: ‘From ‘ill-drained’ to impervious: impervious surface analysis’, technical
memo
Barr Engineering Co. 4300 MarketPointe Drive, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com
Technical Memorandum
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Project: Edina Flood Risk Reduction Strategy Support (23271728.00)
Executive Summary
Barr was asked to review model-predicted flood impacts in the focal geography of the Morningside
neighborhood, and to review the sensitivity of those impacts to the magnitude of imperviousness (the
hard surfaces that prohibit water infiltration). For reference, the impervious area that is directly connected
to the storm sewer system in the Morningside neighborhood is estimated to be about 25% of the total
land area, in aggregate (Figure 1). The directly connected imperviousness is the portion of the watershed
that is impervious and routes flow directly to an outlet (catch basin, pond, depression, outlet, etc.). Some
prominent examples of this type of imperviousness in a low-density residential neighborhood tend to be
streets, parking lots, driveways, water bodies (i.e., Weber Pond), portions of roofs with gutters and
downspouts directed to impervious surfaces such as a driveway, etc.
Figure 1 Imperviousness raster data set from the University of Minnesota. The Morningside neighborhood is in the northeast corner.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 2
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
Barr tested the sensitivity by modifying the stormwater model so that the imperviousness of the entire
contributing drainage area was increased, decreased, and even lowered all the way to 0%, which reflects a
pre-development condition. This sensitivity test was also completed for a range of storm events, from the
20%-annual-chance storm event (5-year storm) to the 1%-annual-chance storm event (100-year storm).
As expected, the imperviousness sensitivity test showed that less impervious area generates less
stormwater runoff and more impervious area generates more stormwater runoff. However, the magnitude
of the runoff changes generated by adjusting imperviousness were not as impactful as may have been
expected.
For reference, in the Weber Pond subwatershed, the 1%-annual-chance storm event (100-year storm)
flood level would need to be reduced by just over 4 feet in order to remove the 5 lowest homes from
potential structural impacts from flood inundation. Based on Barr’s imperviousness analysis, reducing or
increasing impervious area by half (50%) tends to cause the peak water level to decrease or increase by up
to approximately half a foot. This effect is more significant for small storm events, and less so for larger
storm events. While affecting the flood level by half a foot may seem like a big gain, this change removed
one impacted home at most from the flood inundation area around Weber Pond. Again, to achieve even
this low level of impact, the entire contributing area (all of the Morningside neighborhood) would be
required to reduce imperviousness by half (i.e., road widths are cut in half, driveway widths are cut in half,
roof area cut in half and/or downspouts
Imperviousness Sensitivity Analysis Details
The sensitivity analysis focused on design storm events (NOAA Atlas 14, MSE3 temporal distribution)
rather than an observed historical event(s). Modeled design storm events included the 5-year (3.59
inches), 10-year (4.29 inches), 50-year (6.39 inches), and 100-year events (7.49 inches), all 24-hour
durations (i.e., for a 100-year storm event, 7.49 inches fall over a 24-hour period of time).
Imperviousness parameter values were adjusted relative to “base case” values from the stormwater model.
In general, the “base case” imperviousness parameter values were adjusted to +50%, +25%, -25%, -50%,
and finally a “low” case to attempt to significantly reduce runoff. The range of values for each of the
sensitivity cases is listed in Table 1. Most of the Morningside neighborhood is “low density residential”; for
simplicity, only the values for this land use type is presented in Table 1. All other land use types, with
varying imperviousness were similarly adjusted upward and downward for this sensitivity analysis.
Table 1 Imperviousness parameter values for the sensitivity analysis
Parameter Low Case -50% -25% 0% (Base) +25% +50% Directly Connected Percent Impervious1 0% 2 ~13% ~19% ~25% ~31% ~38%
1) Only the value for “low density residential” is shown here, as this covers most of the model area. All land use types were similarly modified for each of the sensitivity cases (-50%, -25%, etc.)
Subwatersheds in the Morningside neighborhood are shown in Figure 2.
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 3
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
Figure 2 Map showing subwatershed divides in and around the Morningside neighborhood
The directly connected impervious percentage tends to have an impact up to ±0.5 feet for the ±50%
change in the base value. Example graphs are included that show the results for Weber Pond (MS_40,
Figure 3), for the low area between Lynn Avenue and Kipling Avenue, north of West 42nd Street (MS_26,
Figure 4), and for a landlocked subwatershed (MS_22) between Lynn Avenue and Crocker Avenue, south
of West 42nd Street (Figure 5).
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 4
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
In these figures, the horizontal, maroon-dashed lines represent approximate low elevations based on
structure footprints for the five lowest homes around Weber Pond. They may or may not represent actual
low entry elevations of these homes. However, they give a good representation of the home elevations
and how close they are to the flood levels.
Figure 3 Sensitivity analysis results showing peak flood levels in Weber Pond (subwatershed MS_40) for a range of imperviousness and a range of storm events.
865.0
865.5
866.0
866.5
867.0
867.5
868.0
868.5
869.0
869.5
870.0
-200%-175%-150%-125%-100%-75%-50%-25%0%25%50%75%Peak Water Surface Elevation (feet)% Change in Percent Impervious
Comparing the Events for the Percent Impervious parameter, at MS_40
20% Annual Chance (5 year)
10% Annual Chance (10 year)
2% Annual Chance (50 year)
1% Annual Chance (100 year)
Low Houses
Zero Percent Impervious (undeveloped)CurrentCondition
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 5
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
Figure 4 Sensitivity analysis results showing peak flood levels in MS_26 for a range of imperviousness and a range of storm events.
868.0
869.0
870.0
871.0
872.0
873.0
874.0
-200%-175%-150%-125%-100%-75%-50%-25%0%25%50%75%Peak Water Surface Elevation (feet)% Change in Percent Impervious
Comparing the Events for the Percent Impervious parameter, at MS_26
20% Annual Chance (5 year)
10% Annual Chance (10 year)
2% Annual Chance (50 year)
1% Annual Chance (100 year)
Low Houses
Zero Percent Impervious (undeveloped)CurrentCondition
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 6
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
Figure 5 Sensitivity analysis results showing peak flood levels in MS_22 (a landlocked subwatershed) for a range of imperviousness and a range of storm events.
869.5
870.0
870.5
871.0
871.5
872.0
872.5
873.0
873.5
-200%-175%-150%-125%-100%-75%-50%-25%0%25%50%75%Peak Water Surface Elevation (feet)% Change in Percent Impervious
Comparing the Events for the Percent Impervious parameter, at MS_22
20% Annual Chance (5 year)
10% Annual Chance (10 year)
2% Annual Chance (50 year)
1% Annual Chance (100 year)
Low Houses
Zero Percent Impervious (undeveloped)CurrentCondition
To: Jessica Wilson and Ross Bintner, City of Edina From: Sarah Stratton and Cory Anderson, Barr Engineering Co. Subject: Appendix E - Appendix E - Imperviousness Sensitivity Analysis Date: March 30, 2020 Page: 7
P:\Mpls\23 MN\27\23271728 Flood Risk Reduction Strategy\WorkFiles\General Support\FRRS Appendices\FRRS Appendix E - Imperviousness Sensitivity Analysis.docx
As mentioned previously, some prominent examples of directly connected imperviousness in a low-
density residential neighborhood tend to be streets, parking lots, driveways, water bodies (i.e., Weber
Pond), portions of roofs with gutters and downspouts directed to impervious surfaces such as a driveway,
etc. To achieve a 50% decrease in this parameter, these portions of the watershed would need to decrease
in area by 50%. In essence, this means driveway and street widths would be cut in half, half of the directly
connected roof area would be rerouted to pervious surfaces, half of the parking spaces converted to
pervious surfaces and/or routed to BMPs to offset the runoff, etc. Such changes over the entire watershed
would be significant and require a coordinated effort from all parcels. This would produce a beneficial
change in the peak flood level, but would generally be limited to a benefit of about half a foot or less in
this neighborhood. For some homes adjacent to Weber Pond, for example, where the 100-year peak flood
level is multiple feet above the suspected low entry elevations, the impacts to peak flood levels shown in
Figure 3 due to changes in directly connected imperviousness do not change whether these homes are
wet or dry during a large, intense storm event.
The results of the sensitivity analysis change depending on the storm event that is being modeled (e.g., 5-
year versus 10-year). Trends and overall magnitudes do not change substantially from what is shown in
the few example figures above. Other cases of interest (different storms, different subwatersheds, etc.) can
be viewed in a companion Excel spreadsheet generated for the Morningside XP-SWMM Modeling technical
memorandum (Barr, March 2020).
Finally, it is also important to remember that the results of the sensitivity analysis depend on the input
storm itself. As described, this analysis used the NOAA Atlas 14, 24-hour design storm with a MSE3
temporal distribution. This storm is both significant in total precipitation depth and very intense in the
middle part of the storm. Storms with high intensity near the beginning or near the end of the event may
produce different results, as will storms with more moderate, consistent intensity. However, given that
flood management within the City is currently informed by Atlas 14 storms with the MSE3 temporal
distribution, this storm was used for the sensitivity analysis.
F
Appendix F: Actions for Flood Resilient Homes, fact sheets
Actions for Flood Resilient Homes:
Actions and Programs Overview
Surface water flooding
Sanitary backflow
Groundwater seepage
Where does the flood water in my home come from?
Flood waters come from different sources. No matter the source, all can cause extensive damage to your home. Depending
on the situation, different actions will work better than others to reduce damage to your property from the excess water.
Gathering more information about how the water is entering your home, such as through a home drainage assessment, will
help you choose the appropriate solution. Typical scenarios can include:
Sanitary backflow flooding can be caused by a blockage in the City’s sewer
system. This normally occurs when the sewer pipes are flooded with stormwater.
When this happens, wastewater can flow backwards—into your home.
Severe storms or prolonged periods of wet weather can cause water levels in creeks,
ponds, lakes, and rivers to rise and overflow their banks. If your home is near these water
bodies or in a low-lying area, it can be at risk of flooding. Surface water can also cause
what’s known as “flash flooding.” Because it occurs with little notice, flash flooding can catch
people off guard. This normally occurs when existing drainage systems are overwhelmed by
extremely heavy rain. Instead of soaking into the ground or draining through stormwater
sewers, the water flows over the land surface, collecting in low-lying areas. Urban areas can
be particularly vulnerable to flash flooding due to a greater amount of impervious surface.
Groundwater can also be a source of flooding. This tends to occur after long periods
of heavy rain or snowmelt, when more water infiltrates the ground and causes the
groundwater to rise above the home’s foundation level.
There’s no doubt about it. No matter where you live in the Twin Cities area, it’s been tough to stay dry. In fact, the years
between 2015 and 2019 were the wettest in Minnesota history. And, with our changing climate, we can expect more wet
years, more powerful storms—and more flooding.
The City of Edina’s strategy is to comprehensively reduce the risk of flooding throughout the community. This is accomplished
through infrastructure, regulation, emergency services, and outreach and engagement. A series of factsheets were developed
to describe actions people can take to reduce their own exposure and vulnerability to flooding. These factsheets, on topics
ranging from sump pumps to sandbags, are now available on our website to help you determine what action is right for you.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Actions can reduce exposure or vulnerabilityHome retrofitting and
flood prevention devices
The table below provides a quick overview of some
common actions you can take to create more flood
resilient buildings and landscapes. The factsheets
that follow provide in-depth information on how,
when, and where to use these actions and additional
resources for residents.
Building action Yard action
Action City permit requiredDNR permit requiredWatershed permit requiredGroundwater floodingSurface water floodingSanitary backflowRelative
Cost Before floodDuring floodAfter floodReduces exposureReduces vulnerabilitySump pump x x x Low x x
Sanitary backflow prevention x x Medium x x
Dry floodproofing x x x Med-High x x
Sandbags x Low x x
Wet floodproofing x x x High x x x
Basement and low-level area pumping x x x Low x
Rain gardens and landscape changes x1 x2 x Medium x x
Shoreline restoration x3 x x High x x
Backyard element siting x4 x x Low x x
Actions for Flood Resilient Homes:
Actions and Programs Overview
Reduces vulnerability Reduces exposure
The extent to which property,
homes, buildings, infrastructure,
and other assets come into
contact with flood water
The extent to which an
exposed asset is able to
resist flood-related damage
1Rain gardens may require a City permit if grading over 10 cubic yards.
2Rain gardens may require a permit from the watershed district. To learn more about your
watershed visit: http://www.ninemilecreek.org or http://www.minnehahacreek.org.
3DNR permit may be required; visit https://www.dnr.state.mn.us/rys/index.html for more info.
4Setbacks and structure count may apply; contact the City Planning Department for more info.
Image source: mprnews.org
Take action!
The following factsheets describe
actions that can protect your home
from damage related to flooding. Not
all actions will benefit your home; a
proper home drainage assessment can
help you understand which measures
will be best for your situation. Many
measures will require assistance
from professional contractors and
may require City permits. Please
refer to each factsheet for additional
information.
Flood insurance
The City of Edina participates in the National Flood
Insurance Program which enables anyone residing in
Edina to purchase a National Flood Insurance Program
flood insurance policy.
Your homeowner’s or renter’s insurance agent may also
be able to help you purchase flood insurance. A list of
participating providers can be found here: https://www.
floodsmart.gov/find.
Home drainage self-evaluation
Improper drainage can cause water damage during even minor rain
or snowmelt events. Whether you’re an owner or a renter, the Home
Drainage Basics factsheet can help you assess problem areas where
you live.
Adopt-A-Drain
By committing to keep drains clear of trash, leaves, grass,
snow, and ice you can help prevent flooding—not to
mention keeping Minnesota’s lakes, streams, and rivers free
of pollutants. For greater impact, consider working with a
friend or your neighbors to adopt multiple drains.
More information on the Adopt-A-Drain program can be
found by visiting: https://www.adopt-a-drain.org/.
Actions for Flood Resilient Homes:
Programs and Evaluation
Described below are a few ways to take action in the fight against flooding. Consider flood insurance and a home drainage
assessment to protect your home; consider adopting a drain to protect the environment and your community.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Actions for Flood Resilient Homes:
Flood Insurance
According to the Federal Emergency Management Agency (FEMA), flooding is the most common natural disaster in the United
States and the consequences can be costly. Even 1 inch of water can cause $25,000 damage to your home.
While homeowner’s insurance policies do not typically cover flood damage, the good news is that you can purchase separate
protection. Because the City of Edina participates in the National Flood Insurance Program (NFIP), all of its residents are eligible to
purchase flood insurance.
Who needs flood insurance?
Under federal law, if your home is within, or touches, a high-risk flood area and you have a mortgage on the property, you will be
required to purchase flood insurance. Homes considered to be at high risk are those located within the 100-year floodplain—
areas where there is a 1% annual risk of water rising above the base flood elevation.
If you live near an area of past flooding, you should consider purchasing flood insurance. Even if you don’t live in or near a high-
risk area, flood insurance can be a wise investment. In fact, more than 20 percent of flood insurance claims come from properties
outside of high-risk flood zones. And, compared to the cost of paying back a disaster loan, flood insurance is a bargain. The
Minnesota Commerce Department calculates that the average payment on a $50,000 disaster loan is $240 per month ($2,880
per year) for 30 years, while a $100,000 flood insurance premium is about $33 per month ($400 per year).
Flood insurance is not limited to homeowners; it is also available to renters and owners of non-residential buildings.
How do I find out about my risk of flooding?
To learn about your specific risk of flooding, go to the City of
Edina’s interactive flood risk map, or visit FEMA’s Flood Map
Service Area.
How do I buy insurance?
You can start by contacting the agent who provides your
auto, homeowner’s, or renter’s insurance. They may be able
to help you purchase flood insurance. If your insurance agent
does not sell flood insurance, you can contact the NFIP Help
Center at 800-427-4661.
What does flood insurance cover?
You can purchase separate coverage for your home and its
contents; both are recommended for the best protection.
Make sure your policy contains a comprehensive list of items
covered.
Almost all walled and roofed buildings above ground can be
covered. Coverage available for basements typically includes
foundation elements (including posts or other support
systems), utility connections, and necessary mechanical
equipment (e.g., furnace, hot water heater, clothes washer
and dryer, food freezer, air conditioner, electrical junction).
Items typically found in finished basements—paneling,
carpeting, furniture—are not covered.
You must normally wait 30 days after you’ve paid your
premium before your policy will be effective.
Other considerations
Losses from sewer backup are not covered by flood
insurance unless the backup occurs as a result of surface
water flooding. You may want to consider purchasing a rider
on your homeowner’s policy to protect you from sewer
backups not related to flooding.
COST: $150-$12,0001
Costs are variable based on whether the location of the
structure being insured is above or below the base flood
elevation, whether the policy holder is a homeowner or renter,
and many other factors. Due to the numerous variables, the
best way to learn what your costs would be is to contact
multiple providers and utilize the resources at the bottom of
this page.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1According to the Minnesota Department of Commerce, the average cost for a flood insurance policy is $500 per year. In low-to-moderate risk areas insurance
can cost just over $100 per year. A renter’s policy can range from $150–$900 according to the Policygenius website:
https://www.policygenius.com/renters-insurance/what-renters-need-to-know-about-flood-insurance/
Other resources: FEMA National Flood Insurance Program: www.floodsmart.gov
Minnesota Department of Commerce Flood Insurance Basics: https://mn.gov/commerce/consumers/your-home/protect/other/floods/basics.jsp
Minnesota Department of Natural Resources Flood Insurance FAQs: https://files.dnr.state.mn.us/publications/waters/floodplain_management_fact_sheet_8.pdf
Before flood action During flood action After flood action
Actions for Flood Resilient Homes:
Home Drainage Basics
The graphic below shows common home drainage issues and solutions. Basic measures such as repositioning downspouts,
grading away from your foundation, and seasonal home maintenance routines can help keep your home dry during heavy rainfall
events.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
http://www.ashireporter.org/HomeInspection/Articles/Keeping-Basements-Dry/1048
Turf to native
conversion helps
infiltrate stormwater
and prevents flooding.
The conversion can also
be a money and water
saver; native plants often
require less water than
turf lawns.
Clearing storm sewer
drains helps them perform
effectively. Drains frequently
become clogged with
stormwater debris or blocked
by snow and ice. This can
cause water to accumulate
and overflow onto roads and
lawns.
Gutter installation is the key
to directing water from your
roof away from your home’s
foundation. Too much water
falling too close to your home
can cause soil erosion, foundation
problems, and water in the
basement. To be effective, gutters
must be cleaned in spring and fall.
Installing shields can
prevent flooding through
low-level windows. To
protect window wells,
create a gravel reservoir
that allows water to
slowly dissipate into the
ground and install a cover.
Rain gardens,
soil amendments, rock
trenches, and sub-surface
systems can all assist with
stormwater infiltration
on your property. See
Rain Garden Factsheet for
details.
Proper downspout alignment helps to drain water away from
the home. Make sure the downspout extension is at least 4–6 feet
long and properly positioned to avoid water backup.
Grading away from your home
provides water with a path away
from your home’s foundation.
Inset images courtesy of: http://www.ashireporter.org/HomeInspection/Articles/Keeping-Basements-Dry/1048
Sump pump discharge
pipe locations should
follow the guidance
provided on the Sump
Pump Factsheet. Follow
similar guidance for
downspouts to ensure
water drains away from
the home.
NOTE: When stockpiling
snow during the winter, plan
ahead for the spring melt. Make
sure water can effectively drain
away from your property rather
than pooling.
Actions for Flood Resilient Homes:
Sump Pumps
What is a sump pump?
A sump pump is a small pump installed in the lowest part of your
basement. Its purpose is to collect subsurface water from the ground
near your home’s foundation and pump it out to your yard to keep
your basement dry.
Who needs a sump pump?
According to the American Society of Home Inspectors, 60% of homes
in the United States have wet basements. If yours is one of them—or
if one of the conditions below applies—you should consider installing a
sump pump.
• Your basement has flooded
• You live in a low-lying area (see the interactive flood risk map)
• You have a finished basement where you store valuables
(including appliances such as a washer/dryer)
• You live in an area that receives significant amounts of rain or
experiences rapid snowmelt
How does a sump pump work?
The sump pump usually stands in a
“sump pit,” which is a hole about 2 feet
deep and 18 inches wide. Water from the
soil around your home’s foundation flows
into the sump pit through drains. Once
that water reaches a certain level in the
pit a pressure sensor or float activator
(similar to the one in your toilet) turns
the pump on. The activated pump moves
the water out of the pit through a pipe
that should empty onto the ground at
least 20 feet away from your home. In
the City of Edina a utility connection
permit is required to drain sump water
to the storm sewer.
Reduces vulnerability
Reduces exposure
COST: $400 (median MN)1
Sump tank
Sump pump
3/4” Clear gravel
Foundation drain
tile pipe
Interior drainage system
2” Discharge pipe
Check valve
FINISHED FLOOR ELEVATION
BASEMENT FLOOR
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1According to improvenet.com (2020) for cost of replacement sump pump installation. May be substantially higher for new pumps, depending on type of pump/flooring and
location.
Groundwater
Before flood action During flood action After flood action
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Sump pump standards can be found at: https://www.edinamn.gov/DocumentCenter/View/397/Sump-Pump-Discharge-Connection-Policy-PDF.
Information on utility connection permits can be found at: https://epermits2.logis.org/home.aspx?city=ed.
Sump drain detail: https://www.edinamn.gov/DocumentCenter/View/848/310---Sump-Drain-PDF
Sump drain connection detail: https://www.edinamn.gov/DocumentCenter/View/849/311---Sump-Drain-Service-Connection-PDF
Installing sump pump requires a permit: https://www.edinamn.gov/209/Building-Permits-Resources.
Actions for Flood Resilient Homes:
Sump Pumps
Connecting your sump pump
to City of Edina storm sewers:
• The pipe exiting the house should have an air
gap and drain to an area that slopes away from
your home’s foundation. Direct the drainage
away from your home toward green areas that
infiltrate water or toward public drainage paths.
• Sump drain lines can connect your sump pump
directly to the storm sewer. This is best done
by a licensed professional and requires a permit
from the City of Edina.
AIR GAP
DIFFERENT TYPES OF AIR GAPS
The air gap is outside your home, at the
point where the sump pump’s internal
discharge line exits your basement and
connects to the external discharge line.
The air gap provides an outlet for the
footing drain flows to escape in the event
of an issue in the external discharge, the
curb collection system or the stormwater
system.
Different air gap configurations have been used in footing drain disconnections. Each type of air gap
serves its purpose as a temporary footing drain water release.
City of An n Arbor
A2gov.org/sumppumps
Atrium Air Gap
If the pump is running frequently 8 to 24 hours after a rain event, and water is splashing out of the air gap, the homeowner should contact a plumber to investigate the external discharge line.
Keep your air gap free of dirt, grass clippings and debris. Do not allow
air gap to become buried below ground or below landscaping.
WHEN TO SEEK HELP
Candy Cane Air Gap Pipe in Pipe Air Gap
AIR GAP
DIFFERENT TYPES OF AIR GAPS
The air gap is outside your home, at the
point where the sump pump’s internal
discharge line exits your basement and
connects to the external discharge line.
The air gap provides an outlet for the
footing drain flows to escape in the event
of an issue in the external discharge, the
curb collection system or the stormwater
system.
Different air gap configurations have been used in footing drain disconnections. Each type of air gap
serves its purpose as a temporary footing drain water release.
City of Ann Ar b or
A2gov.org/sumppumps
Atrium Air Gap
If the pump is running frequently 8 to 24 hours after a rain event, and water is splashing out of the air gap, the homeowner should contact a plumber to investigate the external discharge line.
Keep your air gap free of dirt, grass clippings and debris. Do not allow
air gap to become buried below ground or below landscaping.
WHEN TO SEEK HELP
Candy Cane Air Gap Pipe in Pipe Air Gap
AIR GAP
DIFFERENT TYPES OF AIR GAPS
The air gap is outside your home, at the
point where the sump pump’s internal
discharge line exits your basement and
connects to the external discharge line.
The air gap provides an outlet for the
footing drain flows to escape in the event
of an issue in the external discharge, the
curb collection system or the stormwater
system.
Different air gap configurations have been used in footing drain disconnections. Each type of air gap
serves its purpose as a temporary footing drain water release.
City o f A nn A rbo r
A2gov.org/sumppumps
Atrium Air Gap
If the pump is running frequently 8 to 24 hours after a rain event, and water is splashing out of the air gap, the homeowner should contact a plumber to investigate the external discharge line.
Keep your air gap free of dirt, grass clippings and debris. Do not allow
air gap to become buried below ground or below landscaping.
WHEN TO SEEK HELP
Candy Cane Air Gap Pipe in Pipe Air Gap
Other considerations
• Drain tile around your home is an essential part of your sump pump system. The purpose of the tile is to collect water
around the basement foundation and channel it to the sump pit.
• Gutters can significantly affect the water that gets into your basement. Make sure your gutters are well maintained and large
enough to handle heavy rains. Downspouts should be directed away from the home. Similarly, make sure that the land next to
your home is properly graded—directing water away from the foundation.
• Sump pumps should be checked regularly, particularly in early spring and when heavy rains are forecast. To test your pump,
pour a bucket of water into the pit to make sure it starts automatically and that the water pumps out quickly.
• Pump maintenance should include removing the pump from the pit and cleaning the grate on the bottom. You should also
make sure that if you are using a discharge pipe, the air gap is clear. The air gap is located outside your home, where the sump
pump’s internal discharge line exits the basement and connects to the external discharge line. Its purpose is to provide an
outlet for flows in the event there is a problem with the discharge line or the stormwater system. If the air gap is obstructed,
water can backflow, flooding the basement and causing the pump to burn out.
• A standard 15-amp, 110-volt, three-pronged grounded electrical outlet can handle a sump pump. The outlet should be an
isolated line, with no other connections between the breaker and the outlet. Because the pump is located near water you
may want to plug it into a working ground fault circuit interrupter (GFCI). However, keep in mind that lightning has been
known to trigger GFCIs and could shut off power to your pump during a heavy rainstorm. Make certain to check on the
pump during the storm so you can reset the GFCI if necessary.
• Consider replacing your sump pump every 10 years.
Make sure your sump pump is ready for whatever water comes its way …
Sump pumps often come with water-level or flood alarms to alert you if the pump fails. Some can even call your cell phone
or notify your alarm company. To minimize the risk of flooding, test your sump pump periodically to make sure it is in good
operating condition. Your user’s manual should specify when and how to test your pump. You can also consider investing
in a backup pump to operate if the primary pump fails or becomes overwhelmed with water from a large storm. Similarly,
because sump pumps operate on electricity, they are vulnerable to power outages. Pumps with backup battery power are
available, or a generator can be used.
Air gap types (left to Right): Atrium, candy cane, pipe in pipe.
Images source: City of Ann Arbor https://www.a2gov.org/departments/
engineering/Documents/AirGapInfoSheet_2018.pdf
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1According to HomeAdvisor (2020). Costs to install a backflow preventer (including device) depend on the size and type of system. Note that many insurance companies
offer discounts to homeowners who install sanitary backflow prevention devices.
What is a sanitary backflow prevention device/
backflow valve?
A sanitary backflow prevention device is a valve attached to your
plumbing system. It is designed to prevent overflow waste water
from the City’s sewer system from backing up into your home.
Who needs a sanitary backflow prevention device?
Because sanitary backflow prevention devices can prevent the
significant damage caused by sewer backup, the City of Edina
recommends them for all homes. If you have a newer home a
valve may have been installed during construction. Backflow valves
are usually located in the floor; if you have a sump pump the valve
is likely to be close by.
Note that many insurance companies offer discounts to homeowners
who install sanitary backflow prevention devices. The City
recommends that backflow prevention devices be installed by a
licensed plumber. A permit is required for this installation.
How do sanitary backflow
prevention devices work?
A backflow valve has a flap with small
floaters on both sides that allow the
flap to open and close. Under normal
conditions, the flap is open—allowing
water from your home to flow into the
main sewer system. However, if a large
storm or snowmelt overwhelms the
sewer system, causing water or sewage to
backflow toward the house, the floaters
will close the flap, effectively shutting your
home off from the street sewer system
(see detail above). Once the street sewer
system has a chance to drain and return
to normal functioning, the flap opens again
to discharge waste water. Due to the
potential for clogging, annual inspection of
the device is needed.
Reduces vulnerability
Reduces exposure
COST: $135-$1,0001
Backflow preventer
location Sewer lateral
Sewer main
BASEMENT Water level
House sanitary sewer line
Sanitary backflow
prevention device detail
(Image Credit: Mainline
Backflow Products)
Sanitary backflow prevention devices overview
Actions for Flood Resilient Homes:
Sanitary Backflow Prevention Devices
Before flood action During flood action After flood action
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Actions for Flood Resilient Homes:
Sanitary Backflow Prevention Devices
Make sure you’re ready for sewer backups …
Backflow prevention devices can function automatically or be operated manually. To protect your home, the valve must be
closed during overload periods—which will vary with the size of the storm, but typically last from 2 to 6 hours. Be aware that
during the time the valve is closed you will not be able to use your plumbing.
Other considerations
• You should have your backflow prevention device
cleaned and checked annually, preferably by the
licensed plumber who installed it.
• To avoid backflow in your home plumbing system,
keep your plumbing free of materials such as
diapers, sanitary napkins, and cigarette butts.
• Backwater from a public sewer system is
hazardous to your health. If sewer water enters
your home, you should hire a licensed and trained
professional cleaning service.
(Top) Image of sewer backup in bathroom, courtesy of https://
blueskyplumbingfl.com/wp-content/uploads/2016/10/sewer-
backup-in-bathroom.jpg
(Right) Sanitary backflow prevention device install; image
courtesy of https://www.flickr.com/photos/69302634@
N02/16327005228/in/photostream/
Sanitary backflow preventer installation
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1The cost of dry floodproofing varies depending on the building size, depth of required protection, types of material used, and number of openings. Examples of general
cost estimates can be found in FEMA publications: Homeowner’s Guide to Retrofitting: Six Ways to Protect Your House from Flooding and Engineering Principles and Practices
of Retrofitting Floodprone Residential Structures.
What is dry floodproofing?
Dry floodproofing describes a range of strategies to seal the
exterior of a building from flood waters.
Who should use dry floodproofing?
Dry floodproofing is only viable for buildings that are structurally
sound in areas with low-velocity, relatively shallow flooding (below
3 feet). It is most appropriate for slab-on-grade buildings with
concrete or solid masonry walls. Due to risk of structural failure
from excessive flood forces, dry floodproofing is not advised for
homes with basements or homes comprising weaker construction
materials (e.g., wood frame with siding).
Note that dry floodproofing residential structures will not reduce flood insurance
premiums.
What are dry floodproofing
methods?
• Temporary installation of waterproof
membranes: Heavy plastic sheeting or
a waterproof membrane along a wall’s
exterior can be effective in preventing
water from entering the home.
• Use of sealants: Waterproof sealants
can be applied to building walls,
structural joints, and openings for utility
lines. Cement and asphalt-based coatings
are effective, but can drastically change
the appearance of the home and may
be susceptible to puncturing. Clear
coatings (e.g. epoxies or polyurethanes)
can be applied to exterior walls without
changing appearance but tend to be less
effective.
(continued on next page)
Reduces exposure
Reduces vulnerability
COST: VARIES1
Actions for Flood Resilient Homes:
Dry Floodproofing
(Above) “A way to seal an existing brick-faced wall is to add an additional layer of brick
with a seal in between. Please note that weep holes (drainage) and wick drains are moved
up to prevent moisture from getting inside the walls.” Images and descriptions provided by
FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014)
(Left) Example of exterior application of asphalt
membrane (courtesy of https://staydrywaterproofing.com/)
(Right) An interior application of a fiber-reinforced polymer
wrap, image provided by FEMA P-312, Homeowner’s Guide
to Retrofitting 3rd Edition (2014)
Before flood action During flood action After flood action
Flood level
Existing walls
Brick ties
Fully grouted
Existing floor
New foundation extension tied to
existing foundation with steel dowels
Existing
foundation
New foundation
(added to support
new brick veneer)
Ground
New drain or
relocated drain,
or sump pump in
crushed stone
New masonry veneer
New masonry rowlock
Grout
Existing masonry veneer
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Other considerations
• The Federal Emergency Management Agency recommends that dry floodproofing should be designed by licensed professionals.
Failure to anticipate hydrostatic forces (force due to the pressure of a fluid at rest) may result in extensive damage.
• Placement of flood shields or waterproof membranes is not feasible during flash floods or when warning times are short.
• Ongoing maintenance is required.
• Flood shields and sealants may not be aesthetically pleasing.
• Dry floodproofing does not mitigate the potential impact of high-velocity flood flow, wave action, erosion, or debris.
Actions for Flood Resilient Homes:
Dry Floodproofing
• Addressing closures: Openings in the walls need
to be either temporarily or permanently sealed
shut. For example, low window openings at ground
level can either have a pre-sized closure fitted over
their surface or a low wall constructed around the
opening. Similarly, all or part of a low window could
be replaced with brick or glass block.
• Using flood shields: Temporary watertight
shields can be placed over windows or doors in
anticipation of flooding. Most residential shields can
be stored in the home and installed when needed
by bolting them into place or securing them in
permanently installed brackets or tracks.
• Addressing interior drainage: A good interior
drainage system to collect leaking water (e.g., a
sump pump with an emergency power source) is
an important component of a dry floodproofing
system. Sanitary backflow prevention is also
recommended.
(Above) Metal shields installed with bolts or permanently installed
tracks; image courtesy of www.psfloodbarriers.com/wp-content/uploads/
sites/4/2016/09/Flood-Plank-21.jpg
(Left) Low window raised and original opening filled with brick; image
provided by FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition
(2014)
What are dry floodproofing methods? (continued)
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1Costs vary depending on the size of the area to be protected.
Under severe flood conditions, it may be necessary to build a sandbag dike to protect your home from water damage. Sandbags
that are properly filled and placed can successfully divert water—moving it around buildings rather than allowing it to flow through
them. The information below outlines the materials and steps necessary to build a sandbag dike.
Sandbag materials
Sandbags themselves are generally made of treated
burlap or woven polypropylene and measure
approximately 24 inches by 14 inches. A sandy
soil is best for filling sandbags, but other available
materials (silt, clay, gravels, or a mixture) may be
used. Sandbags can be found online and in hardware
stores. The City does not endorse any specific
company but some local sources of sand or gravel
include:
• Bjorklund & Companies, 763-444-9301
• Hedberg Supply, Landscape & Masonry,
763-545-4400
• Marshall Concrete Products, 612-789-4303
• Plaisted Companies, 763-441-1100
Filling a sandbag
Filling and deploying sandbags is usually a three-
person job: one person to hold the bag open,
one person to shovel sand, and a third person to
position the bag. The use of gloves is advised, as well
as safety goggles.
Bags should be filled about one-half to two-
thirds full and will weigh approximately 35–40
pounds. Untied bags are recommended for most
applications.
Reduces exposure
Reduces vulnerability
COST: VARIES1
Actions for Flood Resilient Homes:
Sandbags
Placing sandbags
Remove any debris from the area before placing sandbags. To
avoid placing stress on walls, you should leave at least 8 feet
between the dike and the building you want to protect.
Place the first layer of bags lengthwise, parallel to the
direction of the water flow. The bags should be “lapped” so
that the filled portion of one bag lies on the unfilled portion
of the next. The untied end should be facing downstream.
Similar to brick laying, offset adjacent rows or layers by
one-half bag length to eliminate continuous joints. To form a
tight seal, walk on the bags as they are placed and continue
walking on them as succeeding layers are added. Because
bags may remain untied, make certain to fold under all loose
ends.
image: https://www.disaster.qld.gov.au/dmp/sandbagging/Pages/default.aspx
Before flood action During flood action After flood action
How to make a request
• During regular business hours, requests can be made by
calling in to the Public Works utility line (952-826-0375).
• On weekends, requests can be made by calling in to the
non-emergency police (952-826-1600) to get routed to the
on-call person.
• Leave name, address, and the quantity of sandbags desired.
If you’re unsure, describe the size of the area and Public
Works can help determine how many are needed.
City-provided sandbags
Public Works delivers sand bags to residents when requested
and will leave sand bag pallets at the end of the property
driveway. Requests are typically fulfilled within 24 hours.
Residents must place the sand bags themselves—Public
Works staff does not place sandbags.
When sandbags are no longer needed, residents may keep
the sandbags or place them back on the pallet and call Public
Works for pickup.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Other considerations
• Sandbags can become contaminated with bacteria and other pathogens from polluted flood waters. The sand from these bags
should never be used in children’s sandboxes.
• Full sandbags may be stored for short periods of time and reused for same-season flood fighting. However, prolonged storage
can lead to mold. According to the Minnesota Pollution Control Agency, the safest place to dispose of full sandbags is a sanitary
landfill. Sandbags may also be disposed in a demolition landfill. Be aware, however, that not all landfills will accept sandbags, so
call first.
• Even when properly installed, water can leak and rain may fall inside the barrier. Be prepared with a pump to remove water
from inside the barrier..
Actions for Flood Resilient Homes:
Sandbags
How high and how wide should my dike be?
The U.S. Army Corps of Engineers recommends that your dike should
have a base three times wider than its height, although a ratio of 2:1 is
also commonly recommended. A triangular pyramid shape should be
used for a dike that is higher than 1 foot. For heights less than a foot,
support the wall of sandbags every 5 feet with clusters of bags; this will
stabilize the structure.
How many bags will I need?
The North Dakota State Extension Service offers the following estimates
for the number of sandbags needed per 100 linear feet of dike.
Dike Height 3:1 base to height 2:1 base to height
2 foot 2,100 bags 1,700 bags
3 foot 4,500 bags 3,000 bags
4 foot 7,800 bags 5,500 bags
5 foot 12,000 bags 9,000 bags
Sealing the dike
To improve water tightness, your finished dike should be sealed with a
sheet of plastic at least 6 mils thick. First, spread a loose layer of soil or
sand about 1 inch deep and 1 foot wide along the bottom of the dike on
the water side. Then, lay the plastic sheeting so the upper edge extends
over the top of the dike and the bottom extends 1 foot beyond the
bottom of the dike (over the layer of soil and sand). Be careful not to
stretch the plastic too tight; this could lead to puncturing. Finally, put a
row of sandbags on the bottom and top edges of the plastic to form a
watertight seal and hold it in place. Be careful to avoid puncturing the
plastic by walking on it.
Sandbag alternatives
Alternatives to sandbags include “sandless” sandbags and Hydrabarriers, which can be purchased online or at some hardware
stores. The sandless bags are made of an absorbent polymer that swells on contact with water—basically self-inflating the bags
to form a water barrier. The Hydrabarrier is a tube (available in different sizes) that you fill with water to form a barrier. The
advantage of these systems is that they are lighter weight, reusable, and do not pose a disposal problem. The disadvantage is
that these systems can be expensive to purchase.
image: http://goldenlake.co/
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1Costs of wet floodproofing vary with the methods adopted. Major costs are associated with rearrangement of utility systems, installation
of flood vents, and replacement of materials that are not resistant to floods. Note that wet floodproofing will not reduce flood
insurance premium rates on residential structures.
What is wet floodproofing?
Wet floodproofing refers to a range of
strategies used to prevent or provide
resistance to flood damage—while allowing
water into the uninhabited portion of
a building (e.g., unfinished basement,
crawlspace, garage). Allowing floodwater
to enter the enclosed areas of a home
equalizes pressure, which can prevent
structural damage. Successful wetproofing
involves (1) ensuring that floodwaters inside
the home rise and fall at the same rate as
floodwaters outside the home, (2) reducing
damage through the use of flood-resistant
materials, (3) protecting service equipment
inside and outside of the home, and (4)
relocating any high-value items stored
below the designed flood elevation (DFE).
• Elevate appliances and utilities or install
barriers: Items that should be elevated or protected
with a barrier include your furnace and air-conditioning
unit, outside air-conditioner compressor, washer and
dryer, water heater, freezer, and electrical outlets and
switches. You can also relocate these to a place in your
home that is higher than the DFE (e.g., an attic), or build
a small addition that would serve as a utility room and
as storage for valuable furnishings during a flood.
• Use flood-resistant materials: The Federal
Emergency Management Agency (FEMA) publishes
flood-resistant classifications for flooring, wall, and
ceiling materials, as well as the adhesives used to install
them (Technical Bulletin 2-08). Carpeting, paneling, and
gypsum wallboard can all be replaced with materials
that would require cleaning rather than replacement.
A table on the following page lists materials that are
acceptable in wet floodproofing home projects.
(continued on next page)
Actions for Flood Resilient Homes:
Wet Floodproofing
Reduces exposure
Reduces vulnerability
COST: VARIES1
Before flood action During flood action After flood action
Wet floodproofing techniques for a house. Image from FEMA P-259 (Figure -10)
https://www.restoration1greaterminneapolis.com/how-to-deal-with-a-flooded-basement
What are wet floodproofing methods?
An advantage of wet floodproofing is that it is flexible; it can be done in stages—many of them relatively inexpensively.
A good time to employ wet floodproofing strategies is when you remodel your home. The following are some wet
floodproofing methods:
Base flood elevation
Who should use wet floodproofing?
If you are at risk of flooding and cannot elevate your home or build reliable
flood barriers, wet floodproofing of non-living spaces is an option. It is
most suitable for shallow flooding that inundates uninhabited space. It is not
practical for most slab-on-grade structures that have the living space at or
near ground level. Also, it is not a reasonable approach if the duration of a
flood is expected to be more than one day.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Other considerations
• Ongoing maintenance is required to minimize flood
risks.
• Pumping water from a basement too soon after a
flood may lead to structural damage.
• Work on electrical systems, gas systems, or air-
conditioning compressors requires a licensed
contractor, and permits may be required.
Actions for Flood Resilient Homes:
Wet Floodproofing
What are wet floodproofing methods? (continued)
Materials that are acceptable in wet floodproofing home projects:
Material Type Acceptable Unacceptable
Structural Flooring Materials • Concrete
• Naturally decay-resistant lumber
• Pressure-treated plywood
• Oriented strand board (OSB)
Finish Flooring Materials • Clay tile
• Ceramic or porcelain tile
• Terrazzo tile
• Vinyl tile or sheets
• Engineered wood or laminate flooring
• Carpeting
• Wood flooring
Structural Wall and Ceiling Materials • Brick face, concrete, or concrete block
• Cement board/fiber-cement board
• Pressure-treated plywood
• Solid, standard structural lumber (2x4)
• Non-paper-faced gypsum board
• Fiberglass insulation
• Paper-faced gypsum board
• OSB
Finish Wall and Ceiling Materials • Glass blocks
• Metal cabinets or doors
• Latex paint
• Wood cabinets and doors
• Non-latex paint
• Particleboard cabinets and doors
• Wallpaper
FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014)
• Sewage backflow prevention is important; a backflow valve
should be installed.
• Because wet floodproofing allows your home to flood,
extensive cleanup may be necessary to remove potential
chemical and biological contamination and prevent mold
growth and decay.
• Install flood vents: Flood vents (permanent openings)
allow water into the structure, equalizing interior and
exterior pressures to avoid structural damage.
(Above) “Wall openings must allow floodwaters not only to enter the home, but
also to rise and fall at the same rate as floodwaters outside the home.” Images
provided by FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014).
(Left) Base flood elevation and location of flood vents. Images provided by FEMA
Technical Bulletin 2, 2008, Openings in Foundation Walls and Walls of
Enclosures.
Base flood elevation
Actions for Flood Resilient Homes:
Pumping Guidance
If dry floodproofing methods fail during a large storm or you’ve chosen wet floodproofing, you may end up with a
significant amount of water in your basement. Though your impulse may be to remove the water as soon as possible, it’s
important to remember that moving too quickly may cause structural damage to your home. Even though flood waters
may have receded, there is still water in the ground that may be exerting force against your basement walls. If that force is
greater than the force of water inside your basement, the foundation, basement walls, or floors may rupture or crack.
Pumping procedure—when and how much to pump
If you need to pump water out of your basement or house, the Federal Emergency Management Agency (FEMA)
recommends taking the following steps to avoid serious damage to your home.
1. Begin pumping only when floodwaters are no longer covering the ground outside.
2. Pump out 1 foot of water, mark the water level, and wait overnight.
3. Check the water level the next day. If the level rose to the previous mark, it is still too early to drain the basement.
4. Wait 24 hours, pump the water down 1 foot, and mark the water level. Check the level the next day.
5. When the water level stops returning to your mark, pump out 2 to 3 feet and wait overnight. Repeat this process
daily until all of the water is out of the basement.
Safety first!
Remember that water conducts electricity. Before walking into
a flooded basement make certain the power is turned off and
wear heavy rubber boots and rubber gloves that do not leak.
Reduces vulnerability
Reduces exposure
COST: VARIES1
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1Costs rely on a number of factors—including the amount of water and whether you choose to do the pumping yourself. You can contract with a water-removal service, but you
may have to wait several days for assistance.
After flood action During flood action Before flood action
Actions for Flood Resilient Homes:
Pumping Guidance
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Pumping procedure—equipment
A submersible pump is needed to remove water from a
flooded basement. You can rent this type of equipment
from a construction rental store or a hardware store; this
will be less expensive than purchasing professional pumping
equipment. The pump is encased in a waterproof shell with a
sealed electrical cord; it connects to a regular garden hose or
a sump hose. The power source for the pump will depend
on whether you have electricity.
If you don’t have electricity you will need to connect
to a generator. Be careful! Do not use gasoline-powered
pumps or generators indoors; these can produce deadly
carbon monoxide exhaust fumes. Note: opening doors and
windows does not provide sufficient ventilation. Another
option is a pump that runs on a 12-volt marine or car
battery or a petrol/diesel driven pump.
If you do have power, you can use a heavy-duty extension
cord to run the pump on standard electricity—provided
you have a place to plug it in. If your fuse box isolates your
basement and you are absolutely sure you can disable
the power in the basement, you can use electricity on the
ground floor or higher. No matter what energy source you
use, you will need to be careful to keep the connection
between the extension cord and the pump cord away from
water. You can do this by looping the cords around a ceiling
joist or another heavy object.
Other considerations
• A second pump should be considered to provide increased capacity and act as a backup.
• Strainers should be used to protect pumps from large debris.
• Use clean, fresh fuel in your pump or generator and make sure you have enough available to act in a flood.
• Be careful around floodwater that may have been contaminated by sewage. Tetanus shots are recommended when cleaning
flooded areas.
Pumping procedure—pumping out the water
To pump water, a garden or sump hose should be attached to the fitting on the top of the pump. The end of the hose is
then pointed away from the house to drain away to the street or storm sewer If the water is low enough, you can place
the pump in the lowest part of the basement, making sure to wear rubber boots. In the event of very high water, you can
lower the pump into the basement using rope. Once the pump is in place, start the generator, plug the extension cord in,
and turn the pump on. If you’re using electricity, plug the extension cord into an upstairs wall socket.
If your water is less than an inch deep, a wet-dry vacuum can be used. These work well, but can be very labor intensive; the
tank on a wet-dry vacuum generally holds only 4 to 5 gallons of water and will need to be emptied frequently. One inch of
water in a 1,500–2,000 square foot home would be 1,000–1,200 gallons and would require approximately 250 empties!
image courtesy of https://www.forconstructionpros.com/equipment/
worksite/pumps/article/11477112/pick-the-right-submersible-pump-
for-dewatering-applications
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
1According to the Rain Garden Alliance, a do-it-yourself rain garden will cost about $3–$5 a square foot. If you use a landscaper to plan and install the garden, the cost will be
$10–$15 a square foot or more. Plants are the most costly consideration in a rain garden. Parts of the City of Edina are within the Nine Mile Creek Watershed District, which
offers cost-share grants for rain gardens. The minimum grant is $500 and requires a 25% match. To see if your home is located within the district and to learn more about the
grant program, go to https://www.ninemilecreek.org/.
Other considerations
• Rain gardens require partial to full sun. They should be built at
least 10 feet away from your home to prevent water damage to
foundations and basements.
• Rain gardens are typically 100 to 300 square feet, depending
on the slope of the surrounding landscape and the size of the
area draining to it; a garden will typically handle runoff from an
impervious area three times its size. More than one garden may be
needed to handle runoff from large surfaces (e.g., large rooftops).
• To prevent plants from drowning and mosquitoes from breeding,
a rain garden requires soil that is porous enough to soak up water
within 48 hours of a rainstorm. You can test your soil by digging a
wide 10-inch-deep hole, filling it with water, and observing whether
the water disappears within 48 hours.
• Before you dig, contact Gopher State One Call (811) or visit http://
www.gopherstateonecall.org/to locate electrical, gas, or telephone
lines.
What is a rain garden?
A rain garden is a tool used to decrease runoff and filter
pollutants from stormwater. These gardens, built in shallow
depressions, are filled with long-rooted grasses and plants
that soak up rainwater from impervious surfaces—before
the polluted flow enters lakes, rivers, and wetlands. Because
they decrease runoff, rain gardens are also useful in flood
prevention. Once established, they require little watering and
minimal maintenance.
In addition to decreasing runoff and filtering pollutants, rain
gardens also create habitat for birds and butterflies, recharge
groundwater, reduce mosquito breeding, and enhance
property value.
Actions for Flood Resilient Homes:
Rain Gardens
How do I plant a rain garden?
There are many online resources that provide
guidance on the construction and maintenance of
rain gardens, including:
Rain Garden FAQs, Rain Garden Alliance
Rain Gardens Provide a Healthy Corrective to Runoff Flooding,
WisContext
How and Why to Build a Rain Garden, U of M Extension
How Much Does a Rain Garden Cost?, Cost Helper
USDA Rain Garden Fact Sheet, USDA
Nine Mile Creek Watershed District Grants
How to Create an Effective Rain Garden, Habitat Network
Rain Gardens in Minnesota, Natural Resources Conservation Service
Who should use a rain garden?
Rain gardens are particularly beneficial for those who have a large amount of nearby impervious surface (rooftops, walkways,
driveways), have downspouts running into the lawn, or areas downhill from a downspout. They may also be helpful if you have
soil erosion. (With deep-rooted plants, rain gardens hold soil in place and prevent erosion).
image courtesy of Minnehahacreek.org
image courtesy Natural Shore:
http://www.naturalshore.com/rain-garden-project-album/
Reduces vulnerability
COST: VARIES1
Reduces exposure
Before flood action During flood action After flood action
What is shoreline restoration?
Shoreline restoration involves the use of native vegetation to
provide a buffer between your yard and the water’s edge. This
buffer (10–50 feet) replaces turf grass.
Although shoreline restoration does not reduce your exposure
to flooding, it can reduce your vulnerability. Unlike turf grass,
native trees, shrubs, forbs, and grasses have long roots that better
withstand the effects of flooding. Under lengthy, high-water
conditions, this may prevent the need to replace flooded turf.
Actions for Flood Resilient Homes:
Shoreline Restoration
How do I restore my lakeshore?
“Restore Your Shores,” offered by the Minnesota Department of Natural Resources (DNR) (https://www.dnr.state.mn.us/rys/
index.html) provides online guidance for implementing shoreland restoration projects, including steps and techniques, a plant
guide, and references and resources. Comprehensive guidance, pertinent to Minnesota landscapes, is also available in the book,
“Lakescaping for Wildlife and Water Quality,” published by the Minnesota DNR. Or, consult a local landscaper who specializes in
shoreline restoration.
Reduces exposure
COST: VARIES1
Reduces vulnerability
Before flood action During flood action After flood action
In addition to reducing flood vulnerability, shoreland
restoration has a number of ecological benefits:
• Deep-rooted native plants are more resistant to wave
and ice erosion and reduce the likelihood of slope
failure.
• Native plantings improve water quality by slowing and
filtering runoff before it enters the lake.
• A mixture of native vegetation provides diverse habitat
for fish and wildlife.
• A buffer prevents wave action from stirring up
sediment that can cause the lake to become murky.
• A buffer area provides privacy and aesthetic views while
discouraging nuisance geese.
Other considerations
• Some shoreline restoration projects will require a local
or Minnesota Department of Natural Resources permit.
Helpful websites:
https://www.dnr.state.mn.us/lakescaping/index.html
https://www.dnr.state.mn.us/publications/waters/shoreline_alteration.html
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Parts of the City of Edina are within the Nine Mile Creek Watershed District, which offers cost-share grants for rain gardens. The minimum grant is $500 and requires a 25%
match. To see if your home is located within the district and to learn more about the grant program, go to https://www.ninemilecreek.org/.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Helpful websites
https://www.epa.gov/green-infrastructure/manage-flood-risk
https://www.homeadvisor.com/r/flood-proof-landscaping/
https://www.owntheyard.com/how-to-fix-backyard-flooding/
https://aibd.org/6-backyard-flooding-solutions-landscaping-storm-proof-yard/
The damage that can be caused by flood water doesn’t stop at your front door. The way you care for your yard and how you site
and construct accessory structures can reduce both flood exposure and vulnerability.
Actions for Flood Resilient Homes:
Floodproofing Accessory Structures and Yards
Floodproofing yards
There are many options you can consider to reduce flooding in your yard.
• Make sure your yard is properly graded: Patios, driveways, walkways, flowerbeds—if possible, they should all be graded so
that the water flows away from the house.
• Install a rain garden: Rain gardens protect your yard from flooding by allowing runoff water to pool and slowly percolate
into the ground. See the City’s factsheet for more information on rain gardens.
• Install dry wells: Dry wells are underground structures that help rainwater dissipate into the ground. They can be used for
wet spots or small, flood-prone areas on your property.
• Create or take advantage of natural swales: Swales are depressions in the landscape that redirect water flow, normally
to a dry well or a garden bed with good drainage. You can slow the flow by lining the lowest point with rocks or adding
deep-rooted plants on the slope.
• Use heavier mulch: Light-weight mulch can spread under flooding conditions, clogging drains. If using mulch near your
home’s exterior, make sure the mulch is at least 6 inches from your siding to prevent moisture wicking and rotting.
• Replace impervious surfaces: Impervious (non-porous) surfaces increase runoff. Replace them with pervious materials or
landscaping.
• Drain your driveway: Driveways are a big contributor to stormwater runoff. You can mitigate the impact of that
stormwater by adding drainage on the sides of the pavement—or by replacing the pavement with a pervious surface.
• Plant a tree: Trees create a leafy canopy that intercepts rainfall and reduces runoff. According to the Chesapeake Bay
Foundation, a typical street tree can intercept from 500 to 760 gallons of water per year, depending on the species.
Before flood action During flood action After flood action
Floodproofing accessory structures
Your yard is an extension of your living space, which needs
to be protected. The first step in floodproofing is to site
the accessory structures on your property—your patio, fire
table/pit, garden shed, gazebo—on high ground. You can
also reduce your vulnerability by building these structures
with flood-resistant materials. See the City’s factsheet on
Wet Floodproofing for a list of flood-resistant materials.
You should also secure yard items to prevent them from
being damaged or swept away. Anchor them or attach
them to more stable structures.
Other considerations
Parts of the City of Edina are within the Nine Mile Creek
Watershed District, which offers cost-share grants for rain
gardens. The minimum grant is $500 and requires a 25% match.
To see if your home is located within the district and to learn
more about the grant program, go to:
https://www.ninemilecreek.org/.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Even if you don’t own a home, your property may be at risk during a flood. Below are some simple steps you can take to reduce
that risk.
Actions for Flood Resilient Homes:
Reducing Risk as a Renter or Condo Owner
Consider buying flood insurance
It’s important to know that your regular renter’s insurance
policy does not cover flooding. But, flood insurance is
available for renters and condo owners through the
National Flood Insurance Program (NFIP). The policy covers
your personal property and contents during a flood. It
does not include “loss-of-use” coverage or any additional
expenses caused by a flood.
Flood insurance premiums are based on a number of factors
including flood risk, year of building construction, building
occupancy, the number of floors, the location of your
contents, and the deductible and amount of coverage you
choose. Even if you live in a low-to-moderate risk area, it’s
worth considering flood insurance. According to the NFIP,
nearly 26 percent of all flood claims occur in these areas.
Also, you may be eligible for a “preferred risk policy,” which
carries the lowest premiums. The cost for renters’ flood
insurance generally ranges from $150 to $900 per year.
Though flood insurance is provided by the NFIP and
prices are set by the NFIP, it is sold by private insurance
companies. Contact your insurance agent to find out
whether they can provide coverage. If not, call the NFIP at
800-427-4661 to request an agent referral.
If you decide to buy insurance, don’t wait for the next
storm. There’s typically a 30-day waiting period between
when the policy is purchased and when coverage applies.
Consider the low spaces—including
underground garages
If you have personal items in the basement or garage, put
them in covered, plastic containers and store them on
shelving—off the floor. Similarly, don’t leave valuables in
your car if flood waters are predicted.
Get the facts
First, find out if the building where you live is in a high-risk flood area. You can check by going to the Federal Emergency
Management Agency (FEMA) website https://msc.fema.gov/portal/search and entering your address. It’s also helpful to
know what steps your landlord/association has taken to decrease the building’s exposure and vulnerability. Here are some
questions you might ask:
• Does the building structure have flood insurance? This may be important because it could influence your landlord’s ability
to recover following a flood—and your ability to continue living in the property.
• Has the landlord/association taken flood resilience measures (wet floodproofing, dry floodproofing)?
• Is there a sump pump in the building? Is there a sewer backflow prevention device? This is particularly important if you
store personal items in the basement of the building.
• In the event flood waters are predicted, is there available above-ground storage?
• In the event of an impending flood will the landlord/association be responsible for sandbagging? If not, will you be allowed
to sandbag? (See City factsheet on sandbagging for more information.)
Helpful websites
https://www.fema.gov/national-flood-insurance-program/How-Buy-Flood-
Insurance
https://www.policygenius.com/renters-insurance/what-renters-need-to-know-
about-flood-insurance/
Floodwater
level
G
Appendix G: Task Force charge
EDINA ADVISORY TASK FORCE I FLOOD RISK REDUCTION STRATEGY I CITY OF EDINA Page 1
CITY MANAGER TASK FORCE
PROJECT: FLOOD RISK REDUCTION STRATEGY
PURPOSE
Support the City’s development of a strategy to address flood risk and resiliency.
OBJECTIVE
Provide recommendations to inform a Flood Risk Reduction Strategy to be considered for adoption by the City
Council and incorporation as a major amendment to the City’s Comprehensive Water Resources Management
Plan.
METHODOLOGY
- Learn about technical challenges and opportunities from the Expert Panel (EP)
- Review policies and practices of other communities
- Review past City studies/initiatives
- Promote conversations with stakeholders to evaluate community values
- Apply gained knowledge on technical feasibility and community values to weigh tradeoffs
- Participate in defining the flood risk service target for the stormwater utility
TIMELINE
June 2019 through December 2019
KEY DATES
June 2019 City Manager appoints Task Force members
September 4, 2019 Task Force presents recommendations to City Council (work session)
December 17, 2019 City Council considers adoption of the final Flood Risk Reduction Strategy
COMMITMENT
- Appointed members will be asked to fulfill their work until Council adopts the final Flood Risk Reduction
Strategy in December 2019
- Appointed members should expect to meet at least monthly with additional off-line work
- Appointed members should consider project timeline prior to appointments
MEETINGS
- The Task Force will establish their schedule including meeting times and dates as needed to complete the
work
- The Task Force will be invited to attend meetings with the Expert Panel
- Conclusion of work must fall into the indicated timeline
- Meetings are open to the public
LEVEL OF AUTHORITY
EDINA ADVISORY TASK FORCE I FLOOD RISK REDUCTION STRATEGY I CITY OF EDINA Page 2
CITY MANAGER
The City Manager has the authority to:
- Establish and appoint Task Force members
- Appoint/remove members as he sees fit
- Designate the Staff Liaison and any additional staff support needed
- Authorize financial resources
- Enter into a service contract with a subject matter expert/consultant
TASK FORCE
The Task Force has the authority to:
- Conduct public engagement and collect input using the City’s public engagement protocols
- Provide input on the strategy
- Make a recommendation on the final Flood Risk Reduction Strategy which will be presented to Council for
consideration
TASK FORCE LEADERSHIP
The City Manager will designate a member of the Task Force to serve as the Chair and another member as the Vice
Chair. The role of the Chair will be to:
- Prepare the meeting agenda
- Lead meetings and facilitate discussions
- Maintain meeting decorum
- Encourage participation of all members
The Vice Chair will support the Chair as needed and perform the Chair duties if the Chair is unavailable.
STAFF LIAISON
The City Manager will designate the staff liaison to the Task Force. The role of the Liaison will be to:
- Support the Task Force Chair in preparing agendas and meeting materials
- Provide technical expertise and access to City resources
- Relay information from City Manager to Task Force and vice versa
- Submit packet materials for City Council review
The Task Force does not direct the work of the liaison.
RESOURCES AVAILABLE
The Task Force will have access to City resources available for advisory groups i.e. marketing/communications,
meeting supplies, etc. Also, see City Manager’s level of authority.
OUTCOMES
A Flood Risk Reduction Strategy that:
- Incorporates local challenges, opportunities, knowledge, and community values
EDINA ADVISORY TASK FORCE I FLOOD RISK REDUCTION STRATEGY I CITY OF EDINA Page 3
- Incorporates voices from throughout the City of Edina. The Morningside neighborhood
has been identified in the Comprehensive Water Resources Management Plan as a
focal geography for case study; however, outcomes from the strategy development ought to be able to
scale city-wide.
- Identifies action steps for building community capacity to address flood risk and resiliency in Edina.
MEMBERSHIP
APPLICATION
The City of Edina’s Volunteer Edina program will manage the recruitment, application and onboarding process.
CONSIDERATIONS & COMPOSITION
The City Manager will appoint up to seven members with a variety of perspectives and experiences on flood risk
and resiliency from throughout the City.
H
Appendix H: Potential action matrix key, ranked response, and potential action matrix
Actions Sheets Key
Sector: The sector of work under which the action would fall. Infrastructure (I), Regulatory Program
(R), Outreach and Engagement (O), and Emergency Services (E).
Task Force Rank: Based on aggregate of individual Task Force member rankings. Task Force members
were asked to rank their top 10 with the action believed to have the most community enthusiasm
ranked number 1 and the action believed to have the least community enthusiasm ranked number 10.
Actions beyond 10 were effectively not ranked.
Cost Score: Staff scored.
$ Minor; Savings or efficiency, takes minor amount of staff time, or can roll into existing duties
with existing staff time and resources, <0 to 20hrs, <0 to $2K
$$ Modest; Modest additional costs, modest amount of staff time. 20 to 100hrs, $2-10K
$$$ Moderate; Moderate additional costs, takes moderate amount of additional staff time, or
can be contracted out in future budgets. 100-500hrs, $10-50K
$$$$ High; Additional costs, takes additional staff time, can be contracted out with additional
resources. 500-2000hrs, $50-200K
$$$$$ Major; Significant costs, takes significant amount of staff time, or can be included in future
capital improvement plans. 2000+hrs, $200K+
Staff Rated Effectiveness Score: Staff scored. Based on effectiveness and confidence at reducing
community vulnerability to flooding, at reducing community exposure to flooding, and at reducing the
community share of climate change drivers.
Action Category:
Quick Win = do now or contract under flood risk reduction effort.
Planning = develop a plan as part of flood risk reduction effort, or include in Comprehensive
Water Resources Management Plan amendment, future budget, or Capital Improvement Plan
(CIP).
Development = may be worth doing with additional resources, a special circumstance, a
partnership, or as technology improvements change cost structure.
None = benefit is not worth the cost or effort.
Task ForceAverage RankCostEffectivenessCategoryI.07 Infrastructure Better Maintain Existing System 5.0 $$$$$ high Planning
I.08 Infrastructure Control Sources of Clogs 7.3 $$$$$ high Planning
E.01 Emergency Services Develop Local Flooding Emergency Response Plan 7.4 $$$ medium Planning
I.15 Infrastructure New Storage in Parks 7.6 $$$$$ high Development
I.19 Infrastructure Buy Low Homes 8.4 $$$$$ low None
I.16 Infrastructure New Storage in Roads 8.4 $$$$$ high Development
I.13 Infrastructure Search for System Constraints and Quick Wins 9.0 $$$ high Planning
I.10 Infrastructure Reduce Sanitary System Inflow 9.1 $$$$$ medium Ongoing
I.24 Infrastructure Flood Storage with Predictive Pumping 9.1 $$$$$ high Development
R.08 Regulatory Program Update Plans with Flood Risk 9.3 $$$ low Planning
R.03 Regulatory Program Regulate Impervious 9.3 $$$$ low Development
I.25 Infrastructure Capital Project Prioritization Framework 9.5 $$ medium Development
I.01 Infrastructure Citywide Risk Modeling 9.6 $$$ high Planning
R.04 Regulatory Program Require Private Flood Storage 9.8 $$$$ low None
E.02 Emergency Services Define and Communicate the Available Services 9.9 $$ medium Quick Win
I.09 Infrastructure Reduce Vulnerability of Sanitary Lift Stations 10.0 $$$$$ medium Development
I.14 Infrastructure Bigger Pipes 10.0 $$$$$ high Development
I.03 Infrastructure Peak Flood Visualization 10.1 $$$ high Planning
I.04 Infrastructure Flow Path Visualization 10.3 $$$ high Planning
O.08 Outreach and Engagement Develop Flood Intervention Fact Sheets 10.3 $$$ medium Quick Win
O.07 Outreach and Engagement Develop Frequently Asked Questions (FAQs)10.5 $$ high Quick Win
I.17 Infrastructure Design to a Future Risk Level 10.6 $$$$$ medium Planning
I.18 Infrastructure Plan Emergency Overflow Paths 10.6 $$$ high Planning
O.01 Outreach and Engagement Build Awareness of Stormwater System 10.6 $$ low Planning
I.02 Infrastructure Standardize Failure Analysis 10.6 $$$$ medium Development
O.06 Outreach and Engagement Promote Sandbag Service 10.8 $$ high Quick Win
O.10 Outreach and Engagement Host Flood Summit 10.8 $$$ medium Development
R.02 Regulatory Program Flow Path Review 10.9 $$$ high Planning
O.05 Outreach and Engagement Develop a 'What is My Flood Risk?" Map 10.9 $$$ high Quick Win
I.05 Infrastructure Predictive Snowmelt Modeling 11.0 $$$ low Development
I.06 Infrastructure Active Lake Level Monitoring, Smart Infrastructure Pilot 11.0 $$$$ high Development
I.11 Infrastructure Assess Water Supply System Risk 11.0 $$$$ medium Planning
I.12 Infrastructure Communicate Risk to Power and Utility Industry 11.0 $$ medium Development
I.20 Infrastructure Incentivize Redevelopment of Exposed Structures 11.0 $$$$$ low None
R.01 Regulatory Program More Permit Review and Regulation 11.0 $$$ medium Development
R.05 Regulatory Program Regulate Development to a Higher Flood Standard 11.0 $$ low Development
R.06 Regulatory Program Tiered Stormwater Utility Fee Based on Impervious Cover 11.0 $$$ low Development
R.07 Regulatory Program Participate in the Community Rating System 11.0 $$ low Planning
O.02 Outreach and Engagement Develop and Communicate Dynamic Flood Threat Indicator 11.0 $$$ low Development
O.03 Outreach and Engagement Groundwater Level Viewer 11.0 $$ low Planning
O.04 Outreach and Engagement Promote WaterAlert (USGS) Subscriptions 11.0 $ low Quick Win
O.09 Outreach and Engagement Provide Stormwater Technical Assistance Grant Program 11.0 $$$ medium Quick Win
O.11 Outreach and Engagement Engage With Stakeholders at Time of Capital Investment 11.0 $$ medium Development
O.12 Outreach and Engagement Engage Realtors, Developers, Insurers on Local Flood Risk 11.0 $ medium Development
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.01InfrastructureCitywide Risk ModelingCreate a standard method across the city (and potentially across other nearby cities) to analyze the risk and consequence of potential for failure of the entire storm sewer system, pipe by pipe, structure by structure. Additionally, this would include creating a standard method to determine impacts due to failure of a part of the system. Finally, reporting methods (maps, prioritized infrastructure components, etc.) would be standardized so that infrastructure risk in different parts of the city and even nearby cities can be easily compared by staff, residents, and decision-makers.A general understanding of the risk of each part of the storm sewer infrastructure system will be able to help prioritize maintenance and inspection activities. Additionally, failure analysis which is often risk based, is not currently standard and is generally quantified on a case by case basis and by the people involved. Therefore, comparing infrastructure risk in different parts of a city or between cities is quite difficult. The only way to know which parts of the infrastructure system should be prioritized in maintenance, with a finite maintenance crew, is to assess the risk of entire storm sewer system in a standard and comprehensive way. The process of evaluating risk of infrastructure may not lend itself to a process that is general. It may be a process that is so "case by case" that the standardized method may become overly complicated and onerous. TBD $$$ high PlanningI.02InfrastructureStandardize Failure AnalysisCreate a standard process for investigating reported or actual failures after significant events. Post event investigation would survey debris lines for peak flow elevations, review damage, investigate system function using hydrologic models, investigate past maintenance records and report expected and actual system performance.This is an alternative or lead-in to smart infrastructure that allows the organization to build knowledge of system function, and periodically review and plan interventions in operations and maintenance that may lead to better system function.Additional data could sit on the shelf if there is not organizational capacity to review, utilize or react to it.TBD $$$$ medium DevelopmentI.03InfrastructurePeak Flood VisualizationCreate products that visualize and explain the extent of expected flooding during storm events. The various types of products could be paper and/or digital maps, the online water resources web map, Google Earth xml files, or other innovative methods. Creating maps or other visualizations of the potential extent of flooding helps identify the locations throughout the city that are most likely to flood. Additionally, similar to the activity of education and outreach, identifying areas of potential flooding and areas that do not show flooding help the public become aware of instances when the system is not functioning as expected. As the public becomes more aware of flooding throughout the city through these products, the new knowledge can likely motivate more citizens to take part in flood risk reduction efforts when they are aware of the extent of flooding throughout the city. With new flood mapping that is far more extensive than traditional FEMA maps, flood insurance prices and home prices may be affected. Maps alone do not tell the entire story; they cannot explain other flood characteristics such as duration. The public may react to the maps by implementing a fix that doesn't appropriately address the issue, i.e., a resident might plan to place a sandbag wall when the duration of flooding is so long that they might still be exposed to basement flooding from groundwater seepage. Some interpretations of the flood maps from the public may not be accurate. Notes concerning the reliability of the tools must be included (based on a calibrated or uncalibrated model, validated with observed data, etc.). TBD $$$ high Planning
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.04InfrastructureFlow Path VisualizationCreate visual products that explain the routes that water would flow during storm events. The various types of products could be paper and/or digital maps with flow direction arrows, the online water resources web map, Google Earth xml files, animations or videos, or other innovative methods. Creating maps or other visualizations of flood water flow paths helps identify the locations throughout the city that should remain open (no obstructions, no development, no pedestrians, cars, etc.) during a flood. Additionally, similar to the activity of education and outreach, identifying areas where water should be flowing during flooding events helps the public be aware of times when the system is not functioning as expected. Areas that would be emergency overflow areas (EOFs) during a flood can also be improved prior to flooding so that when activated, they do not erode. With new flood mapping that is far more extensive than traditional FEMA maps, flood insurance prices and home prices may be affected. Maps alone do not tell the entire story; they cannot explain other flood characteristics such as duration. Some reactions to the flood maps from the public may not be entirely appropriate. Notes concerning the reliability of the tools must be included (based on a calibrated or uncalibrated model, validated with observed data, etc.). Homeowners who live adjacent to flow paths and/or emergency over flows (EOFs) may take it into their own hands, on their own property, to alter the terrain so that water does not flow adjacent to their home. This may have other adverse consequences on their own or on other people's homes. TBD $$$ high PlanningI.05InfrastructurePredictive Snowmelt ModelingForecasted/predicted snowmelt modeling to help the city better understand spring flood risk.Predictive snowmelt modeling may help city staff and the community better understand spring flood risk. Forecasted high springtime water levels associated increased flood risk may inform flood risk reduction measures by the city (e.g. preparation for emergency pumping, sandbags, etc.), especially for landlocked basins and basins with restricted outlets.While melt can be estimated, it is uncertain due to duration of melt and any intervening rainfalls. This can lead undue alarm or a 'cry-wolf' affect. This effort may be better at a watershed or metro area level. Alternatives include amplifying general messages from the NWS. Existing water levels and snowpack measurements are required to forecast spring water levels. Collecting this information may take considerable staff time; but without this information, the snowmelt modeling may only provide a limited benefit for restricted outlet and landlocked basins.TBD $$$ low DevelopmentI.06InfrastructureActive Lake Level Monitoring, Smart Infrastructure PilotConstruct water level and discharge measurement sensors at key stormwater management system points (i.e. critical lakes, ponds, streams, and pipes).Current water level measurements can be used to monitor flood exposure, and therefore inform flood management activities (i.e. emergency pumping, sandbagging) as well as optimize operation of dynamic stormwater management systems equipped with adjustable weirs and outlets. Inconsistencies between measured data and flood models has led to identification of stormwater infrastructure no longer functioning as intended (i.e. sediment filled pipes, pipes with frost heaves, sediment filled channels, clogged outlets, etc.). Increasing the number of sensors throughout the city would allow for a more widespread system performance evaluation. Sensors can be difficult to maintain and are frequently damaged by adverse weather conditions and vandalism. Discharge monitoring may lead to identification of Inflow and Infiltration (I&I) issues. Data connections could be considered to creek flow gages maintained by watershed districts.The ability to construct and utilize adjustable weirs based on forecasted data may be limited by the DNR. For these additional measurements to be useful, the existing flood models may need to be refined to provide real-time forecasting abilities.TBD $$$$ high Development
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.07InfrastructureBetter Maintain Existing SystemUse a proactive asset management strategy to proactively inspect system to 1) identify infrastructure with relatively minor issues that can be readily repaired, and 2) add operations to remove collected debris and sediment from system trash racks, storm sewer pipes, catch basins, and inlets.Repair and replace stormwater infrastructure before minor issues escalate to costly replacements (inspect concrete pipe cracks, CCTV, stormwater pump head tests, ditch/stream thalweg surveys).Additionally, trash racks, culvert inlets, and storm sewer pipes can be blocked by sediment and debris. Poorly performing infrastructure reduces the overall stormwater infrastructure system efficiency and results in additional flooding/drainage issues. Addressing minor issues may provide water quality benefits. Less complaints from residents and more confidence in the stormwater management system.TBD $$$$$ high PlanningI.08InfrastructureControl Sources of ClogsStreet and flow path debris can clogs and plug stormwater infrastructure. Proactive street sweeping and maintenance of inlets and flow paths can reduce debris sources. Trash racks, culvert inlets, and storm sewer pipes can be blocked by sediment and debris, resulting in additional flooding/drainage issues. Even if partially plugged, additional flooding can occur. To address these sources of clogs and debris, the city could evaluate the benefits of implementing/constructing more stormwater Best Management Practices (BMPs) (i.e. vegetative cover, construction stormwater management, etc.). Addressing the sources of clogs and debris may provide water quality benefits and documentation of these measures may be useful for the Municipal Separate Storm Sewer System (MS4) permit and Stormwater Pollution Prevention Program.Addressing the sources of clogs and debris may also require enforcement, which could adversely impact relationships with private property owners in the city. TBD $$$$$ high PlanningI.09InfrastructureReduce Vulnerability of Sanitary Lift Stations Assess risk, floodproof, raise or relocate sanitary lift stations out of floodplain. For those sanitary lift stations that are low in elevation and within the floodplain, it may be important to elevate the lift station, or move it entirely so that it is no longer in the floodplain.When sanitary lift stations are in the floodplain, they can become unreachable during a significant flood. Additionally, they may become inundated with stormwater. This could cause a problem by allowing stormwater into the sanitary system, overwhelming it with too much flow. Improvements could include raising the electrical and controls systems, floodproofing the hatch, planning for emergency sandbagging and pumping to access, raising a section of the structure, or relocating entirely. Often these features are placed where they are for multiple very good reasons. Moving a lift station is a significant task, especially when space in a well-developed city is hard to come by. And finding another place out of the floodplain that is still as good as the original place (with regard to the other deciding factors) is a difficult task.TBD $$$$$ medium DevelopmentI.10InfrastructureReduce Sanitary System InflowFailures in the sanitary sewer system can cause backup into structures. The long term reduction of sources of infiltration and inflow of surface and groundwaters can incrementally reduce risk.This program is ongoing and associated with the sanitary sewer utility. It is ongoing in standalone projects and the neighborhood and Municipal State Aid (MSA) street reconstruction programs.TBD $$$$$ medium OngoingI.11InfrastructureEvaluate Water Supply System RiskFor those water supply systems (for example, wells) that are low in elevation and within the floodplain, it may be important to elevate the system, or move it entirely so that it is no longer in the floodplain.When water supply systems are in the floodplain, they can become unreachable during a significant flood. Additionally, they may become inundated with stormwater. This could cause a problem by contaminating the water supply system and creating an expensive condition that requires remediation.Often these features are placed where they are for multiple very good reasons. Moving water supply systems is a significant task, especially when space in a well-developed city is hard to come by. And finding another place out of the floodplain that is still as good as the original place (with regard to the other deciding factors) is a difficult task. Often distribution pipes are buried under roads and this would require tearing up roads. TBD $$$$ medium Planning
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.12InfrastructureCommunicate Risk to Power and Utility IndustryMuch like an emergency action plan, or education and outreach, this activity would be providing the proper information to private utility companies (electric, internet, fiber optic, etc.) of the locations and facilities that are most flood prone. Ideally, the activity that publishes flood extent visualizations could feed into this one. Access to buried utilities could be very limited around flood prone facilities. During flood events, driven often by large storm events, electricity could be down in parts of the city. The private utility companies should be aware of the areas and facilities prone to flooding so that they can plan to reduce the vulnerability of exposed systems, or be better prepared to fix elements of their system during and after a storm. This could become a daunting task every time the modeling is updated and the maps are recreated. Additionally, if there are flooding issues and private utilities are down, the city could be blamed or even sued if the private utilities company feels that the provided information was not accurate enough to help them be successful. TBD $$ medium DevelopmentI.13InfrastructureSearch for System Constraints and Quick Wins The stormwater network involves a complex system of overland flow, stormwater pipes, ditches, ponds, basins, and streams to convey stormwater off of the landscape. Using existing models and infrastructure data, identify the isolated and "easy to solve" choke points that may be limiting the overall capacity of the stormwater management system. Significant reductions in flood risk may be achievable in areas with "easy to solve" stand-alone constraints. These "easy to solve" fixes are likely to be significantly less expensive than other comprehensive system changes.Some of these retrofits are likely to be located within stormwater easements on private property (i.e. backyard flooding problems). Replacement/retrofit of the storm sewer in these areas may be disruptive.(Assume this is a desktop review to find these "easy to solve" retrofits and other activities are the construction/implementation for those locations). The effort can be used to inform future project scope and selection to better target resources to flood risk reduction.TBD $$$ high PlanningI.14InfrastructureBigger Pipes Replace undersized storm sewer in specific flood areas in some areas where there are no/limited downstream impacts associated with larger discharge from bigger pipes. Replace undersized storm sewer in specific flood areas to improve discharge away from the site and reduce flooding for areas without concerns of downstream impacts.In many instances, retrofitting bigger pipes is likely to lead to downstream impacts. Furthermore, other governing agencies, such as watershed management organizations or downstream cities, may limit or refuse additional discharge associated with larger pipes because of downstream impacts. There are limited opportunities for this type of risk transfer after the affects of climate change are factored in to an already constrained system.TBD $$$$$ high DevelopmentI.15InfrastructureNew Storage in ParksRetrofit new storage into or under park spaces.There is limited available, open space for construction of stormwater storage. Utilizing the space in or under park spaces is one of the few remaining places for stormwater storage. Increased stormwater storage will reduce downstream discharge and reduce flood risk (impacts) to downstream properties.There will likely resistance from the community to flooded parks and additional resources may be required to convert the park to a multipurpose land use. The addition of new storage may not be applicable everywhere, including sites with limited infiltration capacity, polluted ground, adjacent to wellheads, or with high bedrock. To use park spaces as flood storage, the city will likely need to educate residents about the multipurpose land use and that the park space will be flooded from time to time. The Park and Recreation Department, Park and Recreation Commission, and park users would be stakeholders.Stormwater reuse for irrigation may be an option is some parks.TBD $$$$$ high Development
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.16InfrastructureNew Storage in RoadsRetrofit new stormwater storage into or under roads.There is limited available, open green space for construction of stormwater storage (i.e., a stormwater pond). As roads and parking lots are reconstructed, utilize this space in or under parking lots/roads as one of the few remaining places for stormwater storage. Increased stormwater storage can help reduce downstream discharge and reduce flood risk (impacts) to downstream properties.Flooded roads and parking lots may receive pushback from the community and additional resources may be required to educate residents about where to drive/park during wet periods. The addition of new storage may not be applicable everywhere, including sites with limited infiltration capacity, polluted ground, adjacent to wellheads, or with high bedrock. Furthermore, stormwater storage on roadways is limited by requirements for emergency vehicle access. Storage under roadways is also limited by other buried utilities.TBD $$$$$ high DevelopmentI.17InfrastructureDesign to a Future Risk LevelWhen designing a part of the stormwater infrastructure system, we can no longer rely on using design storm events that are based solely on past observed data. We should be considering what climate forecasting models are telling us, and we should be considering the expected life of the infrastructure.A part of the stormwater infrastructure system that is mean to last 5 years and then no longer function does not necessarily need to be overly concerned with what the climate may be 30 years from now. Additionally, the probability of a 1% annual chance event occurring in the next 5 years is only about 5 percent. On the contrary, a part of the system meanT to be functional for the next 50 years should most certainly be considering the changing climate and the predictions of future large storm events. The probability of a 1% annual chance event occurring in the next 50 years is 40 percent. Given that, the chance of a piece of infrastructure being tested by its design storm during its life depends on the expected life of the infrastructure. And the magnitude of the change in the characteristics of the design storm event also depends on the expected life of the infrastructure. This approach will create even more uncertainty in the design process. In all likelihood, ponds, pipes, structures, weirs, pumps, and all other infrastructure will be designed bigger, potentially uncomfortably big and uncomfortably expensive, if the future climate risk is seriously considered in design. TBD $$$$$ medium PlanningI.18InfrastructurePlan Emergency Overflow PathsPlanning emergency flow paths is the approach of understanding the natural emergency overflows, and then planning to create, maintain, and protect those that exist, that safely pass stormwater flow, and therefore protect people and structures from flooding and harm. Having a prepared understanding of the emergency flow paths, rather than surprise of where stormwater ends up flowing, is beneficial for the protection of infrastructure within the city. Additionally, similar to the activity of publishing visualizations of flow paths, this planning can help understand the function of the system and whether or not it is operating appropriately during large flood events. Some residents may not like where emergency overflows are planned, prepared, maintained and protected. This would impact park uses. There are certainly instances of unplanned overflow locations that will surprise the public, and require study and private or public action to limit exposure. There may be pushback from the public in creating or maintaining these features. Outreach and would be necessary to communicate where these areas are and how park uses may be impacted.TBD $$$ high Planning
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.19InfrastructureBuy Low HomesOffer to purchase homes that are so flood exposed that the cost to protect them from flooding (or significantly reduce their flood exposure) is so high that it is beyond the value of the home. This is much like totaling a car after an accident significant enough that it doesn't even make sense to try and fix the car.The cost of capital projects to protect some homes can be very high, particularly for some homes that are built very low and near bodies of water. The vulnerability can be due to a number of factors and decisions when the home was built. Regardless of the reason for the high vulnerability, the cost to protect homes in this condition is beyond the value of the home itself. Additionally, there may be a cost in emergency rescues for people who live in those homes during flood events. Therefore, buying the home is the most cost-effective solution. Buyouts have been shown to be a cost-saving measure for taxpayers because the damages avoided result in cost savings on both flood insurance and disaster relief.Strategies to reduce vulnerability of these homes to flood can be much more fruitful. Buying out a resident is an emotional process; it may or may not be easy for a person to move, even if it is for their protection and benefit. Often, the cost/benefit for acquisitions makes the most sense on the lowest value homes - it is important to consider offsetting acquisitions with affordable housing options. Removing the vulnerable home will also remove a property/home from the tax base of the city. The loss in tax base may make sense if a 'fix' is considerably more expensive. The city then would have to decide if it is possible to redevelop the site, raise the future structure to limit exposure, or leave it vacant. A vacant site may provide minimal temporary storage. Leaving properties vacant could also increase green space. If state or federal funding is used, it might be deed restricted as open space in perpetuity.TBD $$$$$ low NoneI.20InfrastructureIncentivize Redevelopment of Exposed StructuresThe city can create a program that is available to residents where they can redevelop or reduce the flood risk of their home and be helped financially by the city. A redevelopment project of a home is expensive financially, takes time and effort, can be stressful if the home is inhabitable for a time, and has other factors that make it difficult. Incentives offered by the city can be motivating to a homeowner to help them decide to take action and protect themselves. The incentives can also turn the necessary project from impossible to possible financially. If the voluntary acquisitions are not an option, this approach may be able to reduce flood risk while maintaining, or even improving, the tax base. This process of redevelopment is happening without incentives. Incentives complicate the financial proposition, and involve the city in a process that is atypical and may cause more uncertainty and conflict. Incentives may need to be large to convince a homeowner to take on such a big task. The overall cost of the city depends on the number of homes that they intend to provide aid to, and the number of people willing to join the incentive program. TBD $$$$$ low None
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryI.24InfrastructureFlood Storage with Predictive PumpingAdd the innovative technology that monitors current conditions, tracks forecasts, models predicted flooding, and operates pumps to respond, to pump stations on water bodies that could benefit from predictive pumping flood risk reduction strategies.Water bodies with passive outlets can only be drawn down to the outlet's invert, or sometimes below with long periods of evaporation and minimal rain. All of the water in the water body is taking up storage that cannot be filled with incoming stormwater. A water body with a pumped outlet could potentially be drawn down further than normal to create the opportunity for added stormwater storage during a flood event. This is a way to create or provide storage without actually creating additional ponds, underground storage, or other types of storage on the landscape. It's simply a way to better utilize the current volume available for storage within the city. This method (predictive pumping) requires good weather forecasts, calibrated models with proven prediction capabilities. This method will likely be a long process of working with the DNR to develop a plan that improves storage capacity for the protection of the people, but also promotes protection of the other living things in and around the water body. Retrofitting predictive pumping will require more than electronics, wiring, and programming logic. It will likely require modifications to pipes on the suction side of the pump to be able to draw the water body down further. Some lift stations are quite small (fitting in the space of a manhole perhaps) and retrofitting this type of capability may require a small box or building on the surface to house the equipment. TBD $$$$$ high DevelopmentI.25InfrastructureDevelop Capital Project Prioritization FrameworkMaximize the effectiveness of limited funds by being deliberate in examining the vulnerability to floods and the greatest sources of possible disruption. Develop a scoring system using cost benefit analysis to identify and prioritize capital projects. The method used should be objective, transparent, and easy for the public to access and understand.Capital projects don't go through a vetting process. Requests are considered without determining how a specific issue ranks in comparison to others with regard to flood exposure, effectiveness, etc.There is a feeling among the Task Force that 'the squeaky wheel gets the grease'.Some project petitioners may find their project doesn't even register when compared to others. Even among Task Force members this would likely be the case.Judging criteria would have to be determined.TBD $$ medium DevelopmentR.01Regulatory ProgramMore Permit Review and RegulationEngineering review for small additions, accessory structures (sheds), impervious expansions not related to a building (deck/patio/etc.). Permits for grading, new homes, and major remodels with footprint changes all include engineering review for flow paths, grading and drainage. Retaining wall, minor remodels, interior remodels, mechanical, and other permit types are not reviewed.Reviewing more permit types may catch additional issues relating to site-to-site, drainage.This program is staff intensive, and would require additional resources for a fairly limited benefit.TBD $$$ medium DevelopmentR.02Regulatory ProgramRegulate Flow PathsInventory overland flow paths. Consider flow paths in permit review process. Make room for and plan for flow where it occurs by grading or armoring flow paths. Divert or limit unplanned flow paths by requiring engineered grading plans during permit review, when serious issue areas are encountered. Some improvements may not be presently triggering a permit review by the Engineering Department. Staff could investigate and identify issue areas, create a comprehensive list, and require private properties to address the risk in design if at the time a permit is applied for on an issue area.Minor addition to staff review process for permits that are already reviewed by Engineering.Minor addition in permits that would trigger a review by Engineering.May limit property owners ability to implement improvements on their property or increase their costs.Policy or code revision may be necessary.TBD $$$ high Planning
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryR.03Regulatory ProgramRegulate ImperviousImpervious surfaces generate more runoff. Limiting impervious surfaces by changing ordinance can reduce runoff generation.Analysis in task force effort showed this approach is very limited in terms of effectiveness.Major additional cost to some private parties. Moderate addition to staff review process for permits that are already reviewed by Engineering.Moderate addition in permits that would trigger a review by Engineering.May limit property owners ability to implement improvements on their property or increase their costs.Policy or code revision would be necessary.Would increase green space and may promote more trees. Both cost and benefit is highly variable depending on the level of regulation, and if mitigation is allowed. The costs are born by both the public, and private parties, depending on the level of regulation.TBD $$$$ low DevelopmentR.04Regulatory ProgramRequire Private Flood StorageProjects that trigger the regulatory check would be required to store volume on their site.There is a perception that redevelopment is adding volume and contributing to flood impacts. Analysis in task force effort showed this approach is very limited in terms of effectiveness. Current regulatory program manages risk on a permit-by-permit basis for residential, commercial, and industrial sites. Sites larger than one acre in size are required to control stormwater volume under the Construction Stormwater Permit.Major addition to staff review process for permits that are already reviewed by Engineering. Additional design, coaching, and inspection necessary.Post-construction program with inspections necessary.Maintenance agreements or other legal instrument necessary.Enforcement necessary.Will limit property owners ability to implement improvements on their property and will increase their costs.Policy or code revision would be necessary. There are additional costs that would be born by private parties that is not included in the costs score.TBD $$$$ low NoneR.05Regulatory ProgramRegulate Development to a Higher Flood StandardLevel of protection is currently the 1% annual chance (100-year) storm. This would be more restrictive, applying standards for a larger storm event such as the 0.2% annual chance (500-year) storm. (i.e. higher lowest floors and potentially further setback from water).Climate change is a main driver of increased flooding. Future predictions are that flood events will be larger and more frequent. Minor addition to staff review process for permits that are already reviewed by Engineering.Minor addition in permits that would trigger a review by Engineering.May limit property owners ability to implement improvements on their property or increase their costs.Policy or code revision will be necessary.TBD $$ low Development
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryR.06Regulatory ProgramTier Stormwater Utility Fee Based on Impervious CoverHigh impervious sites pay more. Model site runoff generation and rework the land use x acreage calculations to consider specific impervious of the individual site.Make the polluter pay' concept. Applying penalties for adding impervious may deter those from implementing projects. Staff intensive. Potential for a lot of negotiating back and forth about impervious cover. Would need to consider how residential stormwater BMPs like raingardens, landscaping, permeable pavements, and rain barrels fit it. May require staff intensive site inspections/verifications and annual or biannual updates. Some owners may be willing to 'pay their way out' to still be able to complete their project.TBD $$$ low DevelopmentR.07Regulatory ProgramParticipate in the Community Rating SystemThe City of Edina participates in the National Flood Insurance Program.The National Flood Insurance Program's (NFIP) Community Rating System (CRS) is a voluntary incentive program that recognizes and encourages community floodplain management activities that exceed the minimum NFIP requirements.As a result, flood insurance premium rates are discounted to reflect the reduced flood risk resulting from the community actions.Potential cost savings for those holding policies. Number of policies and staff time required will determine if participation is cost-effective.TBD $$ low PlanningR.08Regulatory ProgramUpdate Plans with Flood RiskRoll the Flood Risk Reduction Strategy and Comprehensive Water Resources Management Plan amendment into the Comprehensive Plan with a major amendment.Promote a citywide vision for flood risk reduction. Need to collaborate with other comp plans and groups such as the Southdale work group and other small area plans.TBD $$$ low PlanningO.01Outreach and EngagementPromote Awareness of Stormwater SystemEducation and outreach to community on the function and importance of the stormwater management system.An education and outreach program will help the community understand the function and importance of the stormwater management system and its role to minimize flooding and manage water quality. Education may improve flooding issues (e.g. improved participation in Adopt-a-Drain), identify stormwater infrastructure that is no longer functioning as designed, and help residents understand multipurpose land use (e.g. flooded parks and soccer fields).Additional understanding of flood risk has the potential to impact property values may reduce some property values. Synergy with MS4 required community education/outreach may limit additional city resources required. Education of the community may also improve water quality (reducing illicit dumping, salt usage, etc.). Staff would utilize customer service standards of integrity, quality, and service to assist residents in accessing available resources.TBD $$ low Planning
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryO.02Outreach and EngagementDevelop and Communicate Dynamic Flood Threat IndicatorForecast flood threat for design storms and also scenarios such as ice jams, saturated conditions, and snow melt. Host the dynamic indicator online.Perception of flood threat determines action. Would require moderate maintenance effort.Groundwater level and extent is highly uncertain and non-continuous. May provide false sense of security. TBD $$$ low DevelopmentO.03Outreach and EngagementDevelop Groundwater Level ViewerUsers can view relative groundwater level with year over year changes.Flooding risk may increase if shallow groundwater is high and stormwater infiltration is limited.May provide false sense of comfort. Groundwater elevations and extent is extremely variable spatially and temporally. Might be difficult to relate relative groundwater level to an individual basement elevation. Money may be better spent encouraging those at greatest risk to invest in draintile and sump pump systems instead.TBD $$ low PlanningO.04Outreach and EngagementPromote WaterAlert (USGS) SubscriptionsAnyone can sign up for text alerts for available United States Geological Survey (USGS) stream gauge sites.Program already operating. Would be low cost/energy to implement. Changes can be viewed in nearly real-time. Experience may help customers to benchmark their own risk on the hydrograph (water elevation graph).May provide false sense of comfort. Urban streams tend to be flashy (i.e., flow and elevation can increase rapidly).Can add to website Frequently Asked Questions.TBD $ low Quick WinO.05Outreach and EngagementDevelop a 'What is My Flood Risk?" MapComplementary to existing water resources map with the goal of communicating flood risk clearly.Better communication of flood risk. Understanding circumstance is first step in addressing vulnerability and exposure.Concern over impact on property values as community becomes more flood aware.It may be difficult to show the depth of flooding on the map - some may be an inch whereas others may be more than a foot.Some assumptions are made about topography - more detailed surveys on a site by site basis could show structures higher or lower than the model and aerial photo suggest.Concern about accuracy and completeness. Feedback from those that use the map is critical.TBD $$$ high Quick WinO.06Outreach and EngagementPromote Sandbag ServiceCreate series of videos to communicate how to make a request for sandbags and how to build a sandbag wall. Train staff how to receive requests and provide assistance over the phone.Most are unaware of the service. Those that are aware highly value the service.Some property owners and renters may have limited ability to place their own sandbags. Unclear what service provider might do this type of work if it were hired out.Disposal of sandbags post-event.Staff would need to be trained on how to receive requests and provide assistance over the phone.TBD $$ high Quick Win
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryO.07Outreach and EngagementDevelop Frequently Asked Questions (FAQs)Available on the City website. A resource for reception staff to direct customers to.Would help to debunk myths. Help people self-serve the information. More immediate access to information versus calling a staff person, although always an option.Occasional review and minor edits would be needed. Need to inform staff that the resource is available to share with customers. Standard customer service standards of integrity, quality, and service apply.TBD $$ high Quick WinO.08Outreach and EngagementDevelop Flood Intervention Fact SheetsDevelop Fact Sheets for common interventions that property owners and renters could implement to reduce their exposure and vulnerability to flooding. Interventions may be pre, mid, or post storm. Fact sheets would provide a description, general cost information, and appropriate applications. Examples include floodproofing, elevating utilities, flood insurance, sanitary backflow prevention, sandbagging, among others. Some feedback suggests that the interactive water resources map in its current form requires technical expertise to interpret. Changes to the interactive map would make the flood risk information more accessible.A potential barrier to reducing one’s own exposure to flooding may be their perceived ability (knowledge, skills, and resources) to take action. Other barriers, such as cost may limit a property owner or renter's ability to implement.Renters may have limited ability to implement strategies.Considerations ought to be made for all residential structures, not just single dwelling units.Fact sheets may be used by sellers to show how structures are less exposed/vulnerable.TBD $$$ medium Quick WinO.09Outreach and EngagementProvide Stormwater Technical Assistance Grant ProgramPilot year completed in 2019. Competitive grants help pay for technical evaluation of an issue affecting a resident’s property. A report documents understanding of the problem and lays out a potential plan that could then be implemented by the property owner, at their cost. Some technical assistance can increase the perceived ability (expertise, knowledge, resources) for an individual to help themselves. Case studies may be useful to others in similar situations.Grant covers design, up to a cap. Grant does not cover implementation.Reformat to cover more, from 1:1 to presentation and future design consultations.This could be like a mini flood summit.$20,000/yr existing funding.Would need to ensure the program is attractive to applicants.TBD $$$ medium Quick WinO.10Outreach and EngagementHost Flood SummitDirect mail invitations to at-risk properties. Get all stakeholders together including representatives from neighborhoods, insurance, emergency service professionals, county, police and fire, landscapers, home service providers, MN DNR, engagement professionals, decision-makers, Watershed Districts, infrastructure experts, neighboring cities. All share and discuss roles and approaches for a changing climate with increasing flood risk.Incorporates various approaches involved in reducing exposure, increasing resilience to changing risks, transformation, reducing vulnerability, transferring and sharing risks, and preparing, responding, and recovering.Would require major staff effort and coordination of other parties. Would be a pilot. Unaware of a local model to follow or existing process/program to leverage.Consider equity when selecting a pilot community.TBD $$$ medium Development
ID Sector Activity Name Description Justification/Motivating factors Tradeoffs and Other Considerations Task Force RankCost ScoreStaff Rated Effectiveness ScoreAction CategoryO.11Outreach and EngagementEngage with Stakeholders at Time of Capital InvestmentIncorporate into public improvements such as street reconstruction and park improvement projects. Develop custom engagement plans as appropriate.Incorporate into public improvements such as street reconstruction and park improvement projects. Develop custom engagement plans as appropriate.Opportunities to address problem areas may lie outside of the public improvement project boundaries.Some solutions may require private property cooperation in the form of easements, agreements, and assessments.This is a long term strategy driven by private and public investment.TBD $$ medium DevelopmentO.12Outreach and EngagementEngage with Realtors, Developers, and Insurance Agents on Local Flood RiskHost a class to inform realtors, developers, and insurance agents on local flood risk. Presentation materials could be hosted online or made into a brief video.As more stakeholders understand flood risk, there will likely be a market effect.As more stakeholders understand flood risk, there may be a market effect.Desire for residents and property owners to be engaged first.Information must be accurate, current, and easy to understand.TBD $ medium DevelopmentE.01Emergency ServicesDevelop Local Flooding Emergency Response PlanSource flood threat information and predict flood threat.Define affected areas/parties and frontline communities.Develop warning system.Develop emergency response plan.Establish public information program.Develop maintenance and improvement program.Coordinate with other departments/agencies.A hazard response plan exists for major disasters only.Customers expect a higher level of service and response than the current major disaster response plan provides.The perceived flood threat likely influences property owner/renter behavior.The plan should consider frontline communities and vulnerability. Developing a plan based on historical service requests alone is not an equitable approach.This strategy doesn't effect the flood, but instead effects the preparation for and recovery after a disaster. Damages may be reduced and a return to normalcy may happen more rapidly.Would require setting a trigger condition.Opportunity to consider better protections for frontline communities.TBD $$$ medium PlanningE.02Emergency ServicesDefine and Communicate the Available ServicesInfo about what the City can and can’t do about active flooding; explanation of how the City prioritizes flood-related requests for service posted to City website. Call center training and emergency response plan inclusion. There is a gap between the status quo service level and customer expectations. Better defining available services may motivate property owners and renters to take actions to reduce their own exposure.Potential equity disparity if service delivery is driven by requests for service only. Have a plan for engaging with frontline communities, reaching out rather than only waiting for a request for service.TBD $$ medium Quick Win