Final Storm Sewer Options

Board members appear to be listening to concerns about the stress, property damage, financial losses, and health issues related to frequent flooding (as detailed in our FAQs). They have narrowed down the options, and directed the village staff to start educating the public in preparation for a final board vote in April.

The Options Are…

To review our situation, during a 10-year storm, westside flooding currently looks like this:

Map Source: Village of Wilmette. See source for full-sized maps: 2017 Value Study

In comparison, the three final options for sewer improvement are described below, with maps to show how much each option would reduce flooding for a 10-year storm.

Option 1: Relief Sewer ($80M-$95M)

Map Source: Village of Wilmette. See source for full-sized maps: 2017 Value Study

In the words of the 2017 Value Study, Option 1 (conveyance) is superior because:

Conveyance improvements provide 10-year protection across west side
Increased conveyance also provides localized benefits for more severe events

Pros

  • Provides 10-year storm protection for the entire westside
  • Can be phased from “downstream” (at river) to “upstream” (near Ridge Rd)
  • Includes a new big storm trunk (pipe)
  • Fully uses our underutilized pump station and outflow permit
  • Handles back-to-back storms
     
  • Funding:
    • Could be funded solely with sewer fees, without hurting Wilmette’s AAA financial rating (annual sewer fee increase = $46 per $10M debt)
    • Eligible for funding (from MWRD and IDOT) and efficiencies (by installing pipes during roadway construction or water main replacement)
    • Flood relief per dollar is competitive (see the cost/benefit chart)
    • “Refinements in design criteria and implementation strategy could provide cost savings on the order of 5%-10%.” (2017 Value Study)

Cons

  • Total cost is the highest (possibly $10M-$15M > Option 2)
  • Upstream areas, like Kennilworth Gardens, would receive full benefits several years later than downstream areas nearer the river

UPDATE: Here’s a closeup of a possible design for a new storm trunk for Option 1. Installation along the edge of the public golf course (just north of Lake Ave.) could reduce roadside construction and traffic issues:

 

Option 2: Reduced Relief Sewer + Neighborhood Storage ($70M-$80M)

Map Source: Village of Wilmette. See source for full-sized maps: 2017 Value Study

Pros

  • Kennilworth Gardens could get relief sooner
  • Overall cost might be slightly less (possibly $10M-$15M < Option 1)

Cons

  • Leaves out the entire mid-section of westside Wilmette
  • Includes a storm trunk, but the other pipes would be too constricting to serve the entire westside for a future upgrade

 

Option 3: Neighborhood Storage ($48M-$55M)

Map Source: Village of Wilmette. See source for full-sized maps: 2017 Value Study

Pros

  • Cheapest option
  • The underground storage tanks do not have to be coordinated or built in order

Cons

  • Does not serve entire westside
  • Cannot handle back-to-back storms (tanks must be drained to recharge)
  • Cannot be easily scaled up (Option 1 could be added, but costs would rise)

On a Positive Note: Village Assets

Engineers at the December meeting appeared to agree: a huge advantage of Option 1 is that it makes good use of the valuable assets we already have, namely, the pump station and outflow permit, which are currently not fully utilized, due to the bottleneck created by our undersized storm sewer pipes.

Also, in a shift of tone, several trustees began talking about infrastructure improvement as an ongoing process, with a long-term goal of bringing the entire village up to standard.

Additional Takeaways

Other points made during the December meeting include:

  • It’s definitive: based on the 10-year storm map and flooding levels, we know that many westside roads become impassable for fire and rescue vehicles (although our service crews are committed to reaching residents in an emergency).
  • At this point, we have paid engineers to study many options, but other alternatives either wouldn’t work, or would be much more expensive than the final three conveyance and storage solutions. (See our FAQ page for details.)
  • To create a scalable solution, it’s important to use the right diameter pipe for the initial storm trunk to the pump station. If the downstream pipes are too constricting, it’s more difficult and expensive to expand service in the future.
  • There’s nothing stopping the village from immediately–right now!–starting to create a master plan for Option 1, to provide a template for phased construction, which could be fine tuned as we go along.

Links:

If you missed the meeting or did not yet email the Wilmette Village Board, there’s still time to voice your concerns. Send email to sewers@wilmette.com asking the Wilmette Village Board to approve Option 1 Relief Sewers.

Stay tuned for the next storm sewer meetings:

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