Edmonds, WA Environmental Rules: Erosion Control (2026)

Under Minimum Requirement No. 2 of the city's stormwater chapter, every development project is responsible for preventing erosion and the discharge of sediment and other pollutants into receiving waters; a site already covered by the Department of Ecology's general NPDES construction stormwater permit and complying with it satisfies this requirement. A written construction SWPPP with a narrative and drawings is required whenever a project adds 2,000 square feet or more of new plus replaced hard surface, demolishes a structure with at least 2,000 square feet of exterior hard surface, disturbs 7,000 square feet or more of land, or sits within an earth subsidence landslide hazard area, landslide hazard area, or steep slope critical area.

The SWPPP must address 13 required elements consistent with Volume II of the state's 2019 Stormwater Management Manual for Western Washington, and it must be implemented from initial land disturbance through final stabilization. Even projects below those thresholds must still consider all 13 SWPPP elements and put controls in place for any that apply. The city imposes an additional seasonal limitation: from October 1st through April 30th, clearing, grading, and other soil-disturbing work may only proceed if the applicant demonstrates, based on site conditions such as vegetative cover, slope, soil type, and proximity to receiving waters, that silt-laden runoff will be kept on site through limited disturbed areas and approved erosion and sediment control measures.

The city may expand or restrict this seasonal window based on local weather. Routine maintenance of existing erosion and sediment control BMPs and public utility work that does not expose soil are exempt from the seasonal limits, but earth subsidence and landslide hazard area sites are not.