Do I Need a CSGP?
Every construction project is unique, and determining whether you need coverage under the Construction Stormwater General Permit (CSGP) can be straightforward in some cases but confusing in others.
Contact Kendra Henderson at The Department of Ecology with questions regarding your specific permit requirements.
*The information provided below should be used as a general guideline to understand who typically requires coverage under the CSGP, but it is essential to consult with the Department of Ecology to confirm your specific permit requirements and ensure compliance.
Who needs a permit:
In general, Construction projects that disturb over one acre and discharge to waters of the state are required to obtain a CSGP. This one-acre threshold is for the entire life of the project, meaning that phased projects contributing to a greater plan of development are still required to obtain permit coverage even if that specific phase is under the one-acre threshold. Construction support areas such as an off-site laydown yard are also required to be calculated into the area of disturbance and will need to be managed for stormwater like the rest of your project.
In some special cases, a project may be eligible for an erosivity waiver. An erosivity waiver waives CSGP requirements for small sites under 5 acres that have a low erosivity factor and will complete all construction activities during the dry season. For more information on erosivity waiver, visit our Apply for Coverage page.
It is critical to reach out to the state and local jurisdictions to determine your specific permit requirements. While projects under an acre don’t require the state CSGP, they will often require a local erosion control permit from their municipality. See our Municipal Construction Resources page for more information. Ecology may also determine that a project that would appear to be exempt is too high of a risk to proceed without a permit and require permit coverage.
