Renton, WA Environmental Rules: Erosion Control (2026)

Renton Municipal Code 4-6-030 and the adopted King County Surface Water Design Manual (SWDM) require Construction Stormwater Pollution Prevention Plans (CSWPPPs) and Temporary Erosion and Sediment Control (TESC) plans on any project that clears or disturbs 7,000 square feet or more of site area, or that creates or replaces 2,000 square feet of impervious surface. Standard TESC BMPs include silt fences along downslope perimeters, straw wattles or sock logs on slopes, catch basin inlet protection, stabilized construction entrances to prevent track-out onto streets, covered stockpiles, and seeding or mulching of exposed soil by the end of the wet season. The wet season from October 1 through April 30 triggers additional requirements, with no more than 5,000 square feet of exposed soil allowed at any one time on larger sites. Land disturbance exceeding 1 acre also requires a state Construction Stormwater General Permit from Washington Department of Ecology. Violations can result in stop-work orders and fines. Illicit sediment discharge to storm drains or streams is prohibited, and sediment reaching the Cedar River is especially serious due to salmon habitat.