In case you were unable to attend the Village of Wilmette storm sewer meeting last night, I’m posting this summary.
The event was hosted by the Municipal Services Committee, village staff, and engineers, with substantial input from village residents.
Storm Sewer Agenda
Last night’s meeting was a very long, and sometimes difficult, discussion about how best to deal with westside flooding. As usual, I learned some new facts, and left with a few new questions.
At the start of the event, I chatted with fellow westside residents and discovered that homeowners have spent as much as $80,000 (or more) on flood proofing and stormwater detention systems. Also, residents have discovered that filing too many flood damage claims within a five-year time period can result in cancellation of a homeowner insurance policy–that would be a major blow for anyone.
A technical presentation was followed by a question-and-answer period with one of the consulting engineers, Darren Olson, from Christopher B. Burke Engineering Ltd. During a comment period, residents lobbied for action or for particular solutions. The board discussed options and planned next steps before adjourning.
Options on the Table
To review, the options that were up for discussion included the following:
- Option 1. Upgrade/replace sewer lines
- Option 2. Underground storage tank at Community Playfield
2.1 Above- and below-ground storage, with pump
2.2 Only above-ground storage, drained by gravity - Option 3. Neighborhood storage (at three parks)
- Options 1a, 2a, 3a, Same as 1,2,3 but with “ponding”
Many residents expressed support for Option 1, Upgrade/replace sewer lines. But there was also substantial interest in Option 2.2, Above-Ground Storage at the Community Playfield. (My opinion remains unchanged.)
Technical Points
The consulting engineer and village staff emphasized some key points:
- The Westside Bottleneck: The current bottleneck for clearing runoff from 10-year storms is the sewer lines–there are not enough pipes of large enough diameter. At the discharge end, the pumping station and North Branch of the Chicago River can handle the runoff from 10-year storms.
- Solutions: Solving flooding requires either better conveyance or better storage: Option 1 adds sewer line capacity to convey more stormwater to the river. Option 2.2 temporarily stores stormwater on Community Playfields.
- Level of Service: Both Options 1 and 2.2 will clear runoff from 10-year rain events for the entire westside. Both add pipes (lateral lines) to clear runoff from underserved areas (like Kenilworth Gardens and Wilshire Drive).
Some of the Many Concerns
Some of the potential issues with Options 1 and 2.2 include:
- Safety: Option 2.2 creates an above-ground storage area behind the middle school and junior high. Graded 10 feet down, to receive up to 8 feet of surcharged stormwater, the storage area would drain by gravity to return to use as soccer and school fields after each storm. Safety measures could include gently sloping sides (4:1 grade) or fencing.
- School Coordination: Option 2.2 requires approval and coordination from the schools, since the storage area would be unavailable for about a year during construction, and for a few hours–or as much as a day–after severe storms.
- County Coordination: Option 1 would install a new trunk on Lake Ave, which is a county road, so construction would require extensive inter-governmental coordination.
- Back-to-Back Storms: Option 2.2 would require up to 19 hours discharge time for a storm like we had in April 2013 (a 25-year storm), whereas Option 1 could handle back-to-back storms.
- Maintenance Costs: Brigitte Berger, Engineering & Public Works Director, indicated that replacing sewer lines does not eliminate the overall need for sewer maintenance, but the meeting did not provide any hard data comparing maintenance costs for each option.
Options That Do Not Resolve Westside Flooding
Some of the flood control options were either insufficient, or clearly not viable:
- Ponding: The “ponding” solutions (1a, 2a, 3a) would save an average of 10 percent by installing smaller pipes than the full-priced solutions. However, the “ponding” solutions would be as much as 50 percent less effective–not worth it.
- Neighborhood Tanks: Intuitively, it seems like neighborhood storage tanks would be a cheaper, more effective solution. But when engineers do the math, they find that the projects would be more costly overall, and would not handle 10-year storms for the entire westside.
- Green Infrastructure: Green infrastructure is especially helpful for reducing the effects of smaller storms, and should continue to be a part of stormwater management. However, green infrastructure alone cannot resolve our overwhelming westside drainage problem.
More Questions…
A number of issues remained open for debate:
- Goals: Is it enough to create a system that clears runoff from 10-year rain events, when we’re experiencing a so-called 100-year storm every 8 or 9 years?
- Phased Construction: How quickly should construction be completed? How will phasing impact residents who need flood relief? How will phasing affect project costs, which rise with inflation?
- Cost/Benefit Analysis: What is the best way to measure the benefit vs cost ratio? What is a reasonable cost? The engineering studies list multiple benefits for overhauling the storm sewer, but offer only one number to evaluate the benefits (total project cost/additional homes rescued from 100-year flooding). Is this the only, and best, measurement?
- Getting it Right: Many residents are frustrated that stormwater problems aren’t being solved faster, but others expressed concern about getting it right. What will ensure that we “get it right”? Should another engineering firm check the plans, and if so, when?
Funding Sources
The biggest challenge, by far, is figuring out how to fund a major storm sewer overhaul, and how to fund the project equitably.
Options discussed during the meeting include: issuing bonds to finance the project, paying for the project with sewer fees (related to water usage) and stormwater utility fees (based on impermeable surface area), and securing funds from other county, state, or federal sources, like the Metropolitan Water Reclamation District.
Next Steps
The village staff will be researching phasing and funding issues for Options 1 and 2.2, then the Municipal Services Committee will meet again to decide on the next steps.
Links:
I’ll be adding links as I research issues.
If you attended the meeting, what are your observations, questions, or concerns?