Construction Stormwater General Permit

Construction sites must obtain permit coverage, from the state, when construction activities disturb one or more acres of land (through activities such as clearing, grading, excavating, and/or demolition) or construction activities are part of a larger common plan of development or sale that will ultimately disturb one or more acres and the site discharges stormwater into state surface waters. Construction sites must also develop and utilize a stormwater pollution prevention plan (SWPPP) and include in the SWPPP best management practices or the practices and physical structures used on-site to prevent pollution of stormwater runoff. Best management practices must be installed prior to the start of construction and continue throughout the life of the construction project.

The SWPPP must be designed to address the following elements: preserve vegetation and mark clearing limits, establish construction access, control flow rates, install sediment controls, stabilize soils, protect slopes, protect drain inlets, stabilize channels and outlets, control pollutants, control de-watering, maintain best management practices, and manage the project.

The operator of the construction site must also comply with weekly sampling guidelines and visual site inspections. The sampling results must be reported monthly to the Department of Ecology through discharge monitoring reports even if no discharges occurred during the month. See the Construction Stormwater General Permit for additional information about sampling requirements and best management practices.