HomeMy WebLinkAbout190730 Meeting 3 Staff Report
July 30, 2019
Flood Risk Reduction Strategy Task Force
Ross Bintner, P.E., Engineering Services Manager
Martha Allen, Water Resources Intern
Flood Risk Reduction Strategy Meeting 3 – Reaction to key question list
The questions outlined below were posed during the first two meetings of the Flood Risk Reduction Task
Force. These questions are varied are organized by topic. Staff has attempted to provide more in-depth
information and organization for continued discussion on each question. This Q&A is intended to assist the
Task Force in its future conversations and eventual strategy creation. Please review the Q&A and provide
your reactions via email or at Meeting 3 during discussion.
Task Force Direction/Process
• What sectors should we consider in this inquiry? What direction should we take? What is our mission? How
should we organize our work?
o While these may be more rhetorical questions for the commission to answer, we offered a
few organizing schemes to think about. At a high level we have delineated between technical
and policy solutions. The storm utility splits its work into infrastructure, programmatic and
regulatory services. We have also talked about organizing by areas of opportunity or
constraint.
For infrastructure, opportunity areas split by area and ordered upstream to
downstream include; private property, public right of way, parks, and natural areas.
Split by system they include private systems, conveyance systems and storage areas.
For programmatic flood related services we talked about public education,
information resources, emergency services, technical support (e.g. for privately
funded and installed backflow prevention, sump drains and sump pumps, foundation
waterproofing, etc), insurance, and others.
For regulatory services we talked about WD and City regulators. The CWRMP has
policy on low floor elevations
o GL: I see the word strategy in our task force name, and believe that's part of our focus. A
strategy for mayor, city council and staff to agree to. An overall direction/set of priorities.
To address Flood Risk Reduction. Why? Because the council and staff have addressed this
issue endlessly over 15+ years. Comprehensive plans, Capstone projects, ROI analyses,
Technical solutions, Best practices. Yet they don't seem to have enough to approve projects
or funding. They seem to be asking for more.
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o GL: I wonder if they are asking us to take a fresh look everything, and see if we can see
something differently. Something that might be an overall direction for them to follow.
o ND: Perhaps we need to discuss our mission /goals - and craft a statement. What end
result are we looking at?
o Local vs. Regional Flooding. Can we address flooding on creeks? (see question below on
Watershed Districts as well.)
• What kind of product is the City Council and the City Manager asking for? How is the Task Force
responsible to the Council?
o Task Force member Comments:
LS- I think it would be helpful, sooner rather than later, to have a clearer sense of what our
end product should look like. Having some clearer direction from Scott Neal beyond the
“charge” of the Task Force that you included in our materials sure would help
KA- My sense is there is a need now to focus our scope of influence, need for clarity on
how city manager or Council will use the information.
o Staff response:
Aside from reading the charter, I think 1:1 conversations about “what does success look
like” would be helpful to have now. Just be ready to not hear a clear answer!
The task force is going to know a lot more about this issue than anyone in the community
real soon, so you’ll be in the best position to define success and the path forward. o Before our next meeting, Ross will have conversations with the City Manager, Chad Millner
and others with experience with task force groups on this topic and report back to the
group.
• How do we effectively engage other members of the community in meetings or in the overall conversation?
Can we improve how people can track the work of the Task Force and how it’s being publicized?
o Existing engagement: We have publicized initial information about the Task Force, the
original call for volunteers, and a list of the members in Scott Neal’s Friday report. If anyone
is interested in tracking the topics, the water resources library is open to all and we can
have visitors at our meetings.
o Task Force Action: Water Resources Library is public and can be shared with anyone who is
interested in learning more. Task Force Members can sign up for Friday Reports, Council,
Boards, Comp Plan, Street Closures, Projects, Water Resources Updates, etc. at
https://www.edinamn.gov/921/City-Email-Sign-Up
o Future engagement: Staff anticipates a more intentionally public approach to community
engagement after the first CC work session meeting. Before this, we can share the work of
the Task Force and the document location and meeting schedule in an upcoming water
resource update as well.
Community Impact
• How does flooding impact individuals and families? What community impacts are we willing to accept when
we look at solutions?
o Flood waters can be an inconvenience, can damage property, and/or put public health and
safety in jeopardy. From little to big, the impacts vary by storm and by location. In addition
to the physical damage, past flood history can worry an individual in future storms.
o We talked in meeting 2 about the other city services that the stormwater utility supports
like transportation (keeping flood waters off streets), sanitation (keeping flood waters away
from the sanitary sewer system, lift stations, wells, and other public infrastructure), and
public safety (keeping flood waters away from homes and structures.)
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o The committee spoke at length about home flooding and we talked about a range of what it
might mean to get water in a house, from a wet corner of basement to a total loss due to
moving water or eroded foundations.
o We used the drawing above to describe a conceptual relationship between flood risk
elevations and potential damage on a hypothetical home. As the peak elevation or flood
duration increases the typical home is put under more stress and has more potential for
damage.
• What can residents do to protect their homes? What retrofits are available? What ways can stormwater
utility educate or incentivize?
o Potential actions to reduce impacts include removing the home in a buyout, raising the
elevation of the home, or filling the basement. Potential actions to reduce susceptibility to
floods include waterproofing, new foundation walls, installed or retrofit sump pumps and
foundation drains, and raising or waterproofing window wells. Potential actions to reduce
backflow risk include backflow check valves or overhead sanitary sewer conversions.
o Utility could engage through typical City media channels to get message out. Staff regularly
engages builders, landscapers, and homeowners in our permit process, and provides
technical support on these issues in response to questions or requests for help.
• How does flooding impact home value?
o The task force touched on this issue in meeting 2. The thought was with increasing
awareness and information resources, flooding may have more of an affect in the future.
o Insurance, developers or real estate professionals might have the best insight onto how
flood risk may affect price.
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o Staff has regular conversations with builders and developer who engage in our regulatory
program. Market participants are increasingly ‘doing their homework’ to assess issues prior
to property purchase, because constraints placed at the point of permit review have a real
cost and may affect the value at sale.
• What are the top areas in the City for flood risk?
o During the development of the 2018 CWRMP, staff and consultant reviewed model data
inundations intersecting building structures at a citywide level to sort which areas to do
detailed level review or screening level review.
o
o o An additional 54 areas were not studied, totaling 381 homes/apts and 454 structures. The overall
detailed, screening, and not-studied areas had following distribution of # homes/apts per issue area.
Detailed Areas (5 areas)FID(s)
# homes/apt
buildings TOTAL # of structures
Weber Park 4, 19, 79 39 57
Concord 8 35 51
Halifax 0, 1, 81 28 42
Southdale 11 29 39
62&100 33, 53, 54, 55 26 36
Total in Detailed Areas 157 225
Screening Level areas (20 areas)FID(s)
# homes/apt
buildings TOTAL # of structures
Morningside Road, Branson Street, Grimes and 44th 21 11 20
Sally Lane 65 19 19
Northeast of Concord, Wooddale and Tower 7, 27, 28 11 17
East side of Mud Lake / Bredesen Park 44 15 17
Hawkes Lake, upstream and downstream of Vernon 39, 46, 68 16 16
North of Morningside Road, between Lynn Ave. and Crocker Ave.20 10 10
Ridgeview Drive, north of 70th, west of 100, south of 62 50, 51 10 10
South of 62, West of Gleason, Duplex/Townhomes 45 9 9
66th Street, west of 100 52 9 9
Blake Road and Belmore Lane 13 5 8
Centennial Lakes 61 0 8
South of Mirror Lake, north of Vernon, east of Blake Road 36 7 7
East of Schaefer Road, along Parkwood 38 6 6
Schaefer Road and View Lane 42 6 6
Upstream of Mirror Lake, Maloney Ave. & Tyler Ct.12 5 5
Valley View Road and Antrim, south of the High School 49 5 5
Cornelia Street, 70th and West Shore Drive 59 4 4
50th & France 6 1 3
West of 100, near the creek crossing 16 3 3
East of Braemar, south of Dewey Hill Road, east of Gleason 64 2 2
Total in Screening Level Areas 154 184
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Soil quality, hydrology
• What is the relationship between groundwater and infiltration?
o Working correctly, a stormwater infiltration system delivers surface water into the ground
by percolating the water into the soils. Local ground waters store for a time, and either
make their way to a surface water as base flow or to deeper aquifers. In the urban
environment, the local ground waters can also be pumped out via foundation drains and
sump pumps or infiltrate into leaking sanitary sewer systems.
o When installed, infiltration systems typically need >3’ separation between the infiltration
layer and existing groundwater. Depending on the permeability (flow rate) of soils, it is
possible to ‘mound’ groundwater under the infiltration devices, raising the groundwater.
There is a practical limit to how much water can be infiltrated on a neighborhood scale, but
this is not well understood or studied.
Key policy options and trade-offs
• What is the relationship between development (residential or commercial) and runoff? How does land use
and imperviousness affect flood risk?
o Meeting 2 stormwater 101 slide deck included an image from Appendix A of the CWRMP
titled “City of Edina Imperviousness Assumptions for Stormwater Modeling.” That goes
analysis into detail into trends and land use imperviousness. Sections 1, 6 and 7 provide a
good overview of the issue.
o Low density residential is modeled at 40% total impervious, 25% directly connected
impervious. Some home configurations can exceed these modeled assumption.
• What regulations affect this topic? How is impervious regulated?
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1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77
Series1
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o The two local watershed districts regulate stormwater on commercial and business areas,
and for larger project. Most single family projects are only regulated by the districts for
erosion control.
o Impervious surfaces are not directly regulated in Edina, instead hardcover is in section 36-
438 describes the limits. There are loopholes in the hardcover limit and demand for patios,
decks, pools, driveway, garages, and accessory structures cause lot imperviousness to be
>50% in some cases. The Planning Commission is currently reviewing the policy and
ordinance.
o Typically, stormwater is not the only reason to regulate impervious. Many other values
depend on the percentage of pervious area such as open space, room for trees, heat island,
views, noise, and neighborhood feel.
o The MCWD surveyed local regulation on this issue in 2010 during the update of their rules
and a summary of the community’s rules in the District at that time is attached.
• What are the components that are changing the flood equation? This could include increased density/growth,
climate change, impervious surfaces, and changing service expectations. How much does each of the drivers
matter?
o Climate change is primary. Current atlas 14 precipitation intensity/duration estimates
replaced the older TR-55 storm types and intensity/duration estimates. Both are/were
backward looking.
o Increased impervious or changing land use is secondary, and is an opportunity as well as a
risk. (eg. Commercial areas can get better upon development due to implementing modern
infrastructure systems)
o Changing service expectations and increased data and awareness are compounding trends
that affect our perception of the issue or the level of achievement required to satisfy
demand.
• What have other cities done in regard to flood regulations for residential construction?
o Unknown. We can reach out to WDs to get a sense for this.
City operations
• What is being done to maintain and operate the existing stormwater system?
o (Bike Rack, for future meeting)
• What service level would be needed to future proof for 2050 climate change?
o Current service levels include design of pipe systems to handle the 10% annual exceedance
probability for local storm conveyance, and 1% annual exceedance probability for regional
conveyance and storage areas, but no major areas of the City developed under these
standards. Even the most recent area to develops, Parkwood Knolls and Centennial Lakes
have flooding issues.
o Future climate models may provide a range of possible future 1% exceedance probability
storms. If the 1%, 24 hour storm was 6.0 inches in the past, and 7.48 inches now, it may be
10 inches or more by 2050-2100.
• What is the knowledge management strategy for building the City’s collective knowledge base with regard to
flood related information? Knowing the local related flood history (data, policy, what worked and what didn’t
work, etc,) and effectively capturing what we are doing today is essential for future leaders to adjust and
make informed decisions.
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o There is no strategy in this area but the CWRMP and its updates help in this regard.
• Gap analysis - what issues are we spending too much time on and what are we missing? Before establishing
new policies and procedures, what is already in place that we are not leveraging or doing? Following up on
maintenance that we already signed up to do but are not doing is an example.
o (Bike Rack, for future meeting)
• Are there skill gaps at the City that are preventing staff from meeting flood management objectives?
o The first question may be; do we have flood management objectives? See discussion about
service level definition and priorities.
o This may be for Chad Millner, Scott Neal or others to assess. See answer below related to
stormwater utility dollars and people.
• Technology - Are we employing the appropriate technologies to collect, manage, store, analyze, and
communicate flood related data?
o The CWRMP, interactive water resources map (and underlying XP-SWMM model), and City
website are our main ways to store, analyze and communicate flood related data. We are
currently collecting flow data in the Morningside area to calibrate the model. What can we
do in Edina to educate residents about what the City is facing with respect to flooding so that we
can get more buy in from residents for broad based solutions, support and participation.
o This FRRS effort and what we bring to the public can help.
Local, regional issues
• What can regional, state or watershed organizations do to support cities and provide flood protection?
o Future meeting idea to invite WD’s to talk about this.
o MN-DNR provides technical support on flood regulation.
o WDs have flood models to model flow
o MCWD undertook a stormwater adaptation study that provides some climate change
adaptation resources and planning examples.
• What do Watershed Districts do for creek flooding control?
o Future meeting idea to invite WD’s to talk about this.
• What actions would have the biggest impact on minimizing long term flooding in Edina without increasing
the risk of flooding downstream? Prioritize.
o (this is a non-exhaustive list, but was top of mind!)
o Maintain what we’ve got (clear inlets and outlet, check structures and pipe condition on
regular basis, do small maintenance interventions early / when needed to extend life)
o Make sure new development stays out of flood risk areas
o Reduce risk at structure level
o High value retrofits (upsize at pipe constraints, add inlet capacity, time flow when possible,
predictive pump and drain at key ponds or storage locations, control grades at and monitor
emergency overflows)
o Capital improvements, major flood works.
• How can the one-water approach help address flooding while furthering other city goals?
o The City of Edina has 3 water utilities that function to provide drinking water, removal of
sanitary waste, and flood protection and clean water. The overlap in flood risk
consequences between the sanitary and storm utilities is a good example of why co-planning
and looking for areas of shared risk and opportunity is helpful. The services provided by the
utility take the understanding and participation of customers. In meeting 2, we talked about
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the strategic goal areas of the Utility and the role of engagement, sustainability and equity in
utility operations.
Q&A from meeting 2: Archive
Prior answers from Meeting 2 updated with task force member comments.
• How is the stormwater utility organized?
o The new comprehensive plan provides the current vision and goals for the organization of
the utility.
• What are the stormwater utility’s top priorities?
o The comprehensive plan describes high level services (flood protection, drainage and
stormwater management, and clean surface waters) and their delivery, and the CWRMP
provides a review of issue and implementation actions (Table 15.1). The capital plan includes
projects in some of these issue areas (Table 15.2.) In the past the capital plan and CWRMP
have not been well coordinated and often we learn that we can’t come close to ‘solving’ the
problem with the capital allocated in the CIP. Attached to the meeting 2 report was an
example of projects in the focal geography that staff will use to describe the change around
our view of flood problems in subsequent CWRMP and internal planning efforts.
o LS: I don’t think Edina knows what its top priorities are with respect to flood risk mitigation
and resiliency. I would hope that our task force would come up with what we think are
priorities in our end report for the City Council to consider and discuss.
• What are the stormwater utilities resources (dollars and people?)
o 2018 included $1.75M capital expense (CAPEX), $1.1M operations expense (OPX), and
0.12M Overhead. People are shared and allocated based on work, with the Sanitary, Water
and road utilities. In 2018 the stormwater utility included approximately 5-6 FTE split across
15-20 positions.
o LS: I think bottom line that City resources, both dollars and human resources, allocated to
flood risk mitigation and resiliency must increase.
• How are resources deployed (and split among priorities?)
o We split the program into operations expense (OPX), capital expense (CAPX) and
administration/overhead. Both OPX and CAPX maintain infrastructure. Overhead and OPX
include staff positions that provide non-infrastructure services.
• How does the storm system work?
o The Meeting 2 staff report, part 2 went into specific issues and function in the Morningside
focal geography.
• How is the storm system paid for?
o The stormwater utility revenue is defined in City Code Chapter 28, Article III and the fee
schedule. The factors described in section 28-210 mean that acre for acre, more intense
land uses pay, commensurate with their runoff generation.
• How big are stormwater projects?
o The 2019-2023 Capital Improvement Plan (direct link) describes $21M in stormwater
improvements ranging from small to large, funded to unfunded.
• What is the history of areas prone to flooding?
o Attached to the meeting 1 report was a 1908 quad map with current day street centerlines
overlaid. While we see many of the regional flood areas align with creeks and former
wetlands, of the 5 detailed local flood areas studied in the 2018 CWRMP, 2 related to
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former wetland areas and 3 do not. Although each seems to have its own unique history,
the trends described in the first meeting seem to hold true. (perception/new data, climate
change/more rain, more runoff, increased service level expectations).
Attachments
MCWD imperviousness summary