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Planning commission asks engineers to review dry wells, retention and catch-basin approach amid combined-sewer concerns
Summary
Commissioners asked staff to invite AEW and the city engineer to evaluate alternatives — dry wells/retention versus sending catch-basin flows into the combined sewer — and to identify options to reduce sewer-backup risk and surface flooding on residential lots.
The Planning Commission opened an extended discussion on stormwater management and sustainability measures tied to master-plan implementation. Commissioners raised concern that Clawson’s combined sanitary/storm sewer system is under strain and asked staff to solicit engineering analysis of alternatives such as dry wells, on-site retention and sewer backflow prevention.
Background: staff said current practice for new residential and nonresidential projects is to direct stormwater into the city’s combined system with on-site structures that meter runoff at a restricted flow. “Newer projects have typically underground detention where they're holding more of that water on-site underground before it goes into the system, and it is metered into the system,” Joe said. Legacy properties largely drain directly to the combined system by catch basins, staff said.
Commissioner concerns and examples: several commissioners described backyard flooding and basement backup as primary resident concerns and asked whether alternative approaches could reduce the burden on the combined sewer. One commissioner described installing a private on-site retention bladder and said that underground retention can be an effective option for homeowners.
Requested review: commissioners asked staff to invite AEW (the city’s consultant) and the engineer to explain the current strategy, evaluate the technical suitability and cost of dry wells/retention in Clawson’s clay soils, and review options such as sewer backflow valves and incentives or grants to offset homeowner costs. “I can't volunteer AEW, but I can definitely talk to them,” staff said. The commission noted that county and regional programs (for example rain-barrel incentives) could be explored as part of a broader set of incentives.
Why it matters: Clawson’s legacy combined-sewer system receives both sanitary flow and stormwater. Commissioners said modern low-impact development (LID) techniques and targeted incentives could reduce peak flow volumes, lower flood and backup risk and provide co-benefits such as groundwater recharge where soils allow it.
Next steps: staff will begin the conversation with AEW on the options and bring back engineering guidance, including whether dry wells are feasible given local soils and what programs or incentives might be available to assist homeowners or developers.
Ending: The commission characterized the problem as both an engineering and zoning question and directed staff to report engineering findings and potential ordinance options at a future meeting.
