Proposed Updates to Stormwater Management Strategies

DPD transmitted legislation to City Council that proposes to amend the Land Use Code to encourage Low Impact Development (LID), a stormwater management strategy that mimics natural processes to reduce the amount of rainwater that runs off a site. LID strategies include bioretention, reducing impervious surfaces, and clustering buildings together to reduce site disturbance. In September 2015, DPD completed the SEPA review of the proposed legislation.

In undeveloped areas, most precipitation soaks into the ground, evaporates, and/or is absorbed by plants, and very little rainfall becomes surface runoff. Developed areas with pavement and rooftops have much more runoff, less infiltration, water quality challenges, and greater fluctuation in stream and lake levels. DPD has reviewed all land development rules and has proposed code amendments to remove barriers to LID. These amendments are a requirement of the City’s municipal stormwater permit from the Washington State Department of Ecology.

Our proposed code changes will make it easier to incorporate LID strategies into a broad range of development types. The changes include modifying existing language to allow implementation of LID, listing LID as a public benefit item, and broadening definitions to include LID. None of the changes requires an applicant to implement any particular strategy; the Stormwater Code is the regulatory document containing stormwater management requirements.

The City Council is expected to introduce the legislation in late November.


Nick Welch
(206) 684-8203

Maggie Glowacki
(206) 386-4036