This information comes from the Washington State Department of Ecology and covers the state Construction Stormwater General Permit. For additional information call 360-407-6467 or visit the Department of Ecology’s website.
Stormwater runoff from construction sites can carry muddy water, debris and chemicals into local waterways. Sediments, chemicals and debris can harm aquatic life and reduce water quality.
The Washington State Department of Ecology requires construction sites to get coverage under the Construction Stormwater General Permit (CSWGP). Following the requirements in this permit helps control and reduce water pollution. If water on your construction site is contaminated, refer to Guidance for Contaminated Water on Construction Sites.
Operators of regulated construction sites are required to:
- Develop stormwater pollution prevention plans.
- Implement sediment, erosion and pollution prevention control measures.
- Obtain coverage under this permit.
The current modified permit went into effect May 5, 2017, and expires December 31, 2020.
Who Needs Coverage?
Many construction sites will need to apply for coverage under the CSWGP. Construction site operators are required to be covered if both of these apply:
- Your construction project disturbs land* through clearing, grading, excavating or stockpiling of fill material.
- Sites that disturb one acre or more.
- Sites that are smaller than one acre that are part of a larger common plan of development that will ultimately disturb one acre or more and discharge stormwater to surface waters.
- Sites of any size discharging stormwater to state waters (Waters of the State) that are determined to be a significant contributor of pollutants.
- Sites of any size that are reasonably expected to cause a violation of any water quality standard.
- There is any possibility that during construction, stormwater could run off your site or enter a conveyance system that leads to surface waters. In almost every case it does. If the location of your site poses no possibility that rainfall or snow melt could leave the site or enter a waterway, you do not need a permit.
*count the cumulative acreage of the whole project, whether it's single or multi-phase. Include off-site disturbance acreage from support activities related to the construction site. This applies if your project is a portion (less than one acre) of a larger project planned over time.