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Water Resources Commission reviews stormwater ordinance updates, debates 'performance fee' and 1981 rainfall standard
Summary
The commission reviewed proposed stormwater ordinance changes, including use of the 1981 rainfall file in design modeling, crediting green infrastructure and a renamed 'performance fee' to replace 'fee in lieu.' Staff will refine wording, check legal constraints and bring fee-schedule options to council.
The Water Resources Commission spent its meeting reviewing updates to the city’s stormwater ordinance, focusing on how infiltration and recharge are measured, how rainfall files are used in design models and how the city will treat projects that cannot meet on-site infiltration standards.
Unidentified Speaker 3, the meeting chair, opened the ordinance discussion and framed the committee’s approach: technical points should be resolved by staff and the chair, while substantive policy choices come back to the commission. Commissioners identified three central issues: reliance on the 1981 rainfall file for modeling, how to credit evapotranspiration and native vegetation in design, and whether to retain a payment option for projects that cannot meet specific infiltration targets.
Why it matters: the ordinance sets how developers size basins and permit projects. Unidentified Speaker 1 noted a change in local precipitation patterns — "That's a 18% increase" between the 1981 average and recent decades — and commissioners said that a single large event in the 1981 file can control basin sizing in WinSlam/WinSlam models. Staff warned that while the Department of Natural Resources (DNR) has been urged to update state guidance, changing the municipality’s approach may pose legal or regulatory constraints.
Commissioners and staff debated modeling choices. Technical staff explained that a 2.6-inch event in the 1981 file often governs basin design and that if a modeled basin overflows under that event, WinSlam results can be unreliable. Members asked staff to return with options, including whether an administratively adjusted approach (for example, documented justification for different design inputs) is legally defensible.
On green infrastructure, members discussed moving some prescriptive language about evapotranspiration and vegetation from the ordinance’s 'standards' section into a 'considerations' section so it encourages — but does not require — specific plantings. Commissioners said prairie or deep-rooted planting can increase both infiltration and evapotranspiration but worried about enforceability and long-term maintenance.
The commission also moved to remove the term 'fees in lieu' from the draft and instead describe a "performance fee" for the narrow set of cases where on-site infiltration or recharge targets cannot be met. Unidentified Speaker 4 said the fee per square foot of impervious area is currently "on file with the city engineer" (noted in staff materials as 20¢ now, with prior discussion of increasing to 50¢). Staff clarified that changing the fee rate would be done through a council resolution updating the fee schedule rather than by ordinance amendment, and that the fee schedule can be publicly posted and adjusted for inflation.
What’s next: staff agreed to (1) research whether the 1981 rainfall file or alternative approaches are appropriate for local design practice; (2) prepare clearer ordinance wording that distinguishes mandatory standards from considerations around vegetation and evapotranspiration; and (3) prepare a public, council-actionable fee-schedule proposal (including documentation for any change from 20¢ to a higher rate). The commission will revisit the ordinance after staff brings these clarifications.
The meeting closed with assignments for staff to return with modeling guidance, fee documentation and suggested ordinance edits for a future agenda.
