Stormwater runoff from construction activities is regulated because it can have a significant impact on water quality by contributing sediment and other pollutants to creeks, streams, lakes, etc.
In order to discharge stormwater from a construction site, all construction projects that disturb one acre or more of land must have either:
an individual stormwater permit, or
coverage under Washington's general permit.
Disturbance includes, but is not limited to soil disturbance, clearing, grading, and excavation. Operators of sites disturbing less than one acre are also required to obtain a permit if their activity is part of a "larger common plan of development or sale" with a planned disturbance of one acre or greater.
To apply for an individual permit or for coverage under the statewide general permit you must file an application with the Department of Ecology prior to commencement of your construction activities.
Construction projects that disturb one or more acres are subject to three major requirements:
Submit a permit application (or Notice of Intent) prior to the start of construction.
Develop, submit, and implement an erosion and sediment control plan prior to initiating any on-site activities. This plan specifies the measures that will be put in place to prevent and/or control erosion and sediment run-off.
Submit a Notice of Termination when the following criteria have been met: final stabilization of the site has been achieved as defined in the permit, all temporary erosion and sediment controls have been removed, and no potential remains for construction-related sediment discharge to surface waters.
In addition to these statewide rules, you may be required to meet additional local stormwater and erosion control regulations. Check with your city or county government to determine if additional local rules apply to your construction project.
For Indian Country lands in Washington, U.S. EPA is the permitting authority for construction stormwater discharges. For more information, see EPA Construction General Permit.