Washington
Washington State Department of Ecology
Quick Summary
For most Washington projects disturbing 1 acre or more, you need a Construction Stormwater General Permit and an on-site CESCL-certified inspector. File your NOI at least 60 days before breaking ground — the longest lead time in the country. Washington's turbidity limits (5–10 NTU above background) are among the most stringent nationally.
Construction Permit
Permit Document ↗- Permit Name
- Construction Stormwater General Permit (CSGP) — effective January 1, 2026 through December 31, 2030
- Threshold
- ≥ 1 acre of land disturbance (or < 1 acre if part of a larger common plan)
- NOI Lead Time
- NOI must be submitted at least 60 days before any land-disturbing activities begin (increased from prior ~38-day target under the 2021 permit). Permit coverage must be confirmed before breaking ground.
- Application Method
- Online via Ecology's Permit and Reporting Information System (PARIS)
- Fee
- Annual fee ranging from $800 (< 1 acre) to $4,800 (≥ 100 acres)
- Permit Expires
- December 31, 2030
SWPPP Requirements
Permit Document ↗- SWPPP Required
- Yes
- PE Cert Required
- No
- Template Available
- Yes
Inspection Requirements
Permit Document ↗- Frequency
- Every 7 days and within 24 hours of a storm event producing ≥ 0.5 inches of rainfall in a 24-hour period. Turbidity monitoring required at the discharge point. Under the 2026 CSGP, sites ≤ 1 acre must also conduct weekly turbidity/transparency and pH sampling at the discharge point.
- Rain Trigger
- Within 24 hours of any storm event producing ≥ 0.5 inches of rainfall in a 24-hour period; turbidity monitoring required at all discharge points after each event
- Inspector Qualification
- Certified Erosion and Sediment Control Lead (CESCL) required for ALL site inspections under the 2026 CSGP — including sites ≤ 1 acre (previously non-certified personnel could inspect smaller sites). CESCL certification through Ecology-approved training; renewal required every 3 years.
- Accepted Certifications
- Certified Erosion and Sediment Control Lead (CESCL) REQUIRED for ALL sites including ≤ 1 acre under the 2026 CSGP; Ecology-approved training provider required; renewal every 3 years
Discharge Standards
Permit Document ↗- Turbidity Limit
- Discharges must not cause receiving water turbidity to exceed 5 NTU above background for fresh waters with naturally clear water; 10 NTU above background in other fresh waters. Numeric effluent limits apply: 25 NTU in some cases.
Post-Construction
Ecology ↗- Required
- Yes
Impaired Waterbody / TMDL Requirements
Elevated RiskWashington's Construction Stormwater General Permit (CSGP) includes specific provisions for discharges to water quality-impaired waters. Permittees who discharge to a 303(d)-listed impaired water body must implement all BMPs applicable to that impairment category. Projects near 303(d) waters listed for turbidity face specific turbidity monitoring and benchmark requirements. Projects near salmon-bearing streams face additional controls under the state's salmon recovery framework. Check Ecology's Impaired Waters Viewer before project design.
Program Contact
Contact Page ↗- Contact
- Kendra Henderson
- Phone
- (360) 870-6757
State-Specific Notes
Washington's 2026 CSGP (issued November 19, 2025, effective January 1, 2026) replaced the prior 2021 permit. Key changes: CESCL certification is now required for ALL site inspections regardless of site size; sites ≤ 1 acre must conduct weekly turbidity/transparency and pH sampling; NOI lead time increased to 60 days. Sites in watersheds with low dissolved oxygen impairments may face numeric turbidity effluent limits. Washington's CESCL certification is one of the more stringent state inspector programs in the country. The state is divided into Western and Eastern Washington stormwater regions, each with separate design manuals reflecting vastly different precipitation patterns.