Lakewood, WA Environmental Rules: Stormwater Management (2026)

LMC 12.11.010 sets four goals for the chapter: reducing flooding, erosion and sedimentation; preventing habitat loss; enhancing groundwater recharge; and preventing surface and subsurface water pollution through permit review and construction inspection. Section 12.11.020 requires every proposal to use a stormwater system the City Engineer certifies as consistent with adopted design, operating and procedural standards, and the project engineer must submit a completeness certification letter under LMC 12.01.090. The City has formally adopted the current edition of the Department of Ecology's Stormwater Management Manual for Western Washington (SWMMWW) as the technical basis for meeting its NPDES municipal stormwater permit and protecting surface water quality; LMC 12.01.070 supplies local definitions, but the SWMMWW itself controls detailed design questions.

Review requirements scale with project size. Under Table 12.11-1 at LMC 12.11.030, projects adding less than 2,000 square feet of new impervious surface generally need no separate drainage review unless the site sits in a critical area or buffer. Between 2,000 and 5,000 square feet, an applicant must submit a site plan showing grading, drainage flow paths and BMPs and satisfy SWMMWW Minimum Requirements 1 through 5. Above 5,000 square feet, the project needs a full engineered drainage plan, report and site development permit meeting all nine Minimum Requirements, covering source control, natural drainage preservation, on-site management, runoff treatment, flow control and long-term operation and maintenance. For formal subdivisions, special use permits or rezones, LMC 12.11.020(B) requires the phased installation schedule for stormwater improvements to be written into the approving documents.