Washington Statewide Rule

Washington Construction Stormwater and Erosion Control Rules

Significant RestrictionsApplies statewide across Washington (2026)

Key Facts

Governing statute: RCW 90.48.080; 90.48.260
Enforcing agency: Department of Ecology
Permit trigger: One or more acres disturbed
Required plan: Stormwater Pollution Prevention Plan
Max civil penalty: $10,000 per day

Last verified: July 31, 2026

Summary

Washington makes it unlawful under RCW 90.48.080 to discharge sediment or other polluting matter into state waters, and the Department of Ecology requires an NPDES Construction Stormwater General Permit with an erosion-control SWPPP for sites disturbing one or more acres.

It shall be unlawful for any person to throw, drain, run, or otherwise discharge into any of the waters of this state, or to cause, permit or suffer to be thrown, run, drained, allowed to seep or otherwise discharged into such waters any organic or inorganic matter that shall cause or tend to cause pollution of such waters according to the determination of the department, as provided for in this chapter.

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Full Breakdown

Under RCW 90.48.080 it is unlawful to discharge any matter that causes or tends to cause pollution of state waters, which covers construction sediment and turbid runoff. RCW 90.48.260 makes the Department of Ecology the state water pollution control agency and sole NPDES permit issuer. Ecology's Construction Stormwater General Permit requires operators clearing or grading one or more acres to obtain coverage, prepare and implement a Stormwater Pollution Prevention Plan with erosion and sediment controls, and inspect the site. The current permit runs January 1, 2026 through December 31, 2030.

Violations & Penalties

Unpermitted or polluting discharges violate Chapter 90.48 RCW. Under RCW 90.48.144 Ecology may assess a civil penalty of up to ten thousand dollars per day for every violation, alongside orders to install controls.

Frequently Asked Questions

When do I need a Construction Stormwater General Permit in Washington?

You need Ecology coverage when your project clears or grades one or more acres, or is part of a larger common plan of development reaching one acre, and discharges stormwater to state waters.

What is the penalty for uncontrolled construction runoff?

Discharging sediment-laden runoff without controls violates Chapter 90.48 RCW and can bring civil penalties up to $10,000 per day per violation under RCW 90.48.144.

Who enforces erosion control at the state level?

The Washington Department of Ecology administers the NPDES/state permit program under RCW 90.48.260 and inspects construction sites for permit and SWPPP compliance.

Sources

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