What is the rain trigger for SWPPP inspections in Washington?

In Washington, an inspection is triggered by Any Discharge Event.

State Compliance Reference

Washington SWPPP Compliance

Quick Facts for Washington

Authority: Department of Ecology (WA)
Permit: Construction Stormwater General Permit (CSWGP)
Inspection Schedule: Weekly and within 24h of discharge
Rain Trigger: Any Discharge Event

View Official Permit Calculate Fine Risk

This page is a field reference, not legal advice. Confirm the current permit, local requirements, and project-specific conditions with Department of Ecology before relying on a deadline or inspection schedule.Official sources last reviewed: 2026-09-12

Regulation Overview

Permitting Authority

Department of Ecology

Official Permit

Construction Stormwater General Permit (CSWGP)

Inspection Frequency

Weekly and within 24h of discharge

Rain Event Trigger

Any Discharge Event

Check Missed Events

State vs. Federal (EPA)
Varies

Discharge Sampling and CESCL Oversight

Sampling method depends on disturbed acreage, while pH monitoring applies only under specified permit conditions. Consult the 2026 permit before assigning a universal sampling checklist.

Inspection Requirements for Washington

Construction projects that disturb one or more acres—or smaller sites that are part of a larger common plan—commonly require stormwater permit coverage in Washington. Eligibility, exemptions, local approvals, and project-specific conditions vary, so confirm coverage under the Construction Stormwater General Permit (CSWGP) before construction begins.

Operational Insight

This schedule combines recurring and event-driven duties. Record rainfall or discharge events independently from the weekly calendar and document why each event did or did not trigger an inspection.

Specific State Nuance

The current permit is effective January 1, 2026 through December 31, 2030. A CESCL inspects at least once each calendar week and within 24 hours of any discharge. Turbidity or transparency monitoring applies to discharging sites under five acres; turbidity monitoring applies at five acres or more. Weekly pH monitoring is conditional, including certain significant concrete work or engineered-soil activities.