Washington State Industrial Stormwater General Permit: What Industrial Facilities Need to Know in 2026

**Is Your Facility Ready to Meet Washington’s Industrial Stormwater Requirements?

**Stormwater compliance continues to be one of the most actively enforced environmental programs in Washington State. Facilities covered under the Washington State Industrial Stormwater General Permit (ISGP) must maintain compliance while continually improving stormwater management to protect water quality.

What is the Industrial Stormwater General Permit?

The Washington State Department of Ecology administers the ISGP under the federal Clean Water Act NPDES program. The current permit became effective January 1, 2025 and remains in effect through December 31, 2029. Ecology has begun early work toward the next permit reissuance, anticipated before the current permit expires.

Does Your Facility Need Permit Coverage?

Coverage commonly applies to manufacturing facilities, warehouses, transportation terminals, equipment maintenance yards, recycling facilities, concrete and asphalt plants, ports, and many other industrial operations where stormwater may contact industrial materials or activities.

Key Compliance Requirements

* Develop and maintain a current Stormwater Pollution Prevention Plan (SWPPP).

* Implement effective Best Management Practices (BMPs).

* Conduct required stormwater monitoring and respond to benchmark exceedances.

* Perform routine inspections, employee training, and maintain complete records.

* Submit required reports to Ecology on time.

Recent Regulatory Updates

The 2025 ISGP continues to emphasize source control, documentation, corrective actions, and data-driven compliance. Although portions of the permit have been appealed, the permit remains in effect and regulated facilities are expected to comply with all applicable requirements.

New PCB Assessment Requirements for Older Buildings

Washington’s 2024 Stormwater Management Manual introduced important source control requirements addressing PCBs in older buildings. Commercial and industrial buildings constructed or renovated between 1950 and 1980 may contain PCB-containing caulks, paints, sealants, coatings, and other exterior building materials. Before exterior pressure washing, surface preparation, painting, or renovation activities that could mobilize building materials, facility owners should evaluate whether PCB-containing materials may be present. If PCBs are present or suspected, wash water and debris should be properly contained and managed rather than discharged to storm drains, surface waters, or the ground. Planning for these requirements early can help avoid project delays, unexpected costs, and compliance issues.

Important Regulatory Deadlines

* Current ISGP effective period: January 1, 2025 – December 31, 2029.

• Ecology is expected to release a draft of the next permit during the current permit cycle before the 2029 expiration.
• Facilities should keep permit registrations and contact information current and monitor Ecology announcements.

Common Compliance Challenges

* Outdated SWPPPs

* Incomplete inspections or employee training

* Poor documentation

* Elevated benchmark results

* Inadequate source control

* Operational changes not reflected in permit documentation

How Proactive Compliance Protects Your Business

Strong stormwater programs reduce enforcement risk, improve operational efficiency, strengthen environmental stewardship, and help facilities prepare for agency inspections.

How Citadel EHS Can Help

Citadel EHS provides comprehensive industrial stormwater compliance services throughout Washington and the Pacific Northwest, including:

* ISGP applicability evaluations

* SWPPP preparation and updates

* Stormwater inspections and compliance audits

* Stormwater sampling and monitoring support

* Corrective action planning

* BMP evaluations

* PCB building material assessments for exterior renovation and pressure washing projects

* Employee environmental compliance training

* Agency coordination and regulatory support

* Long-term permit compliance management

For more information, please contact:

Craig Peterson, PE

Principal Environmental Engineer

Citadel EHS

Email: cpeterson@citadelEHS.com

Phone: (503) 333-0856

Protecting water quality starts with proactive compliance—and partnering with experienced environmental professionals who understand Washington’s evolving stormwater regulations.