Water Quality and Supply Issues Monthly Update - March 2026
Spring greetings to everyone working across California’s construction industry. As we transition from winter to spring, regulatory activity continues to advance at both the state and local levels. These policies and permitting developments directly influence how projects are planned, approved, and built throughout California.
At CICWQ, we stay closely engaged on these issues so our members remain informed, prepared, and able to navigate changing compliance requirements with confidence.
📌 This month, we highlight three important developments shaping stormwater regulation and construction practices across the state.
🔸 Construction Stormwater Permit Renewal Begins
The State Water Resources Control Board has announced the start of the renewal process for California’s Construction General Permit (CGP). This critical permit governs stormwater compliance for construction projects statewide and must be renewed every five years under federal law.
🔸 Proposed CII Stormwater Permit Raises Industry Concerns
Regulators continue discussions around a proposed Commercial, Industrial, and Institutional stormwater permit in southwest Los Angeles County. If adopted, the permit would require existing property owners to install new runoff capture and treatment systems. It would be the first permit of its kind in California.
🔸 High-Flow Biofiltration Systems and Housing Development
High-flow biofiltration devices play an important role in helping housing projects meet stormwater compliance requirements in urban areas. Despite strong third-party testing and performance records, some projects are encountering barriers to using these systems. We explain why this matters for housing development and regulatory flexibility.
👇 Read the full updates below to better understand these developments and how they may affect construction projects and water quality compliance across California.
MARCH NEWSWORTHY ITEMS
1️⃣ State Water Resources Control Board Indicates Construction General Permit for Stormwater Renewal Process Will Start in 2026
Since the new year began, CICWQ representatives have attended several public meetings and open forums where State Water Resources Control Board management and staff indicated a permitting priority for 2026 is the timely renewal of the Construction General Permit (CGP) for stormwater. In California, compliance with the CGP is required during the construction phase for almost all land development or redevelopment projects greater than 1 acre. It can be a multi-million-dollar-per-year expense over the span of a construction project.
Based on comments from management and staff, stakeholders can expect some modifications to the existing CGP when a working draft is released, perhaps in late 2026. Staff indicated that more clarity on what is and is not a Qualified Rain Event, which triggers job site runoff sampling, monitoring, and reporting, can be expected, as can consideration of changes to the site risk determination process that establishes a job site Risk Level 1-3. A key question mark hanging over the CGP renewal is what influence, if any, the recent U.S. Supreme Court decision in City and County of San Francisco v. U.S. EPA concerning the legality of receiving water limits in general NPDES permits will have on the CGP renewal, specifically the site risk assessment process.
👉 We will be following the CGP renewal closely in the coming months!
2️⃣ Commercial, Industrial, and Institutional Stormwater Permit Adoption Process Update – Permit Redline Recommendations Submitted
The Los Angeles Regional Water Quality Control Board (Regional Board) is considering a sweeping, and certainly costly, new stormwater runoff permit specifically targeting commercial, industrial, and institutional properties larger than 5 acres within two large urban watersheds in southwest Los Angeles County.
The proposed runoff permit, abbreviated CII, is based on a final Residual Designation Authority decision from the U.S. EPA in 2024, targeting pollutants in urban runoff, primarily copper and zinc, and requiring the Regional Board to adopt the permit. The proposed CII permit is widely opposed by a range of property ownership and management interests (including CICWQ), a host of commercial and industrial businesses and trade groups operating in affected areas, and many county public works agencies, cities, and local districts.
Starting in late January and continuing through March 2026, the Regional Board is holding stakeholder meetings to discuss specific topics contained in the proposed permit, including a redline of changes suggested by the coalition, which includes CICWQ. Most contentious is the Regional Board’s expansion of pollutants covered in the CII permit, from just two, copper and zinc, to more than 30 other pollutants of concern.
Also noteworthy is the Regional Board’s insistence on imposing numeric effluent limits for the expanded list of pollutants in the proposed CII permit, as well as the requirement that each property owner conduct extensive stormwater runoff characterization and prepare a comprehensive plan, commonly known as a SWPPP. A single violation of an NEL in a permit can cost hundreds of thousands of dollars to litigate and settle with both the Regional Board and from citizen suits filed by non-governmental environmental organizations.
A few weeks ago, our stakeholder coalition submitted an extensive package of proposed redline changes to the CII permit, along with suggestions to the Regional Board. These redline CII permit changes are available below.
👉 We will continue to keep our readers updated throughout 2026 as CICWQ and our building and construction industry coalition partners work to fight back and mitigate the effects of this troublesome permit.
Coalition CII Permit Redline Documents
3️⃣ Use of High-Rate Biofiltration in Urban Stormwater Capture and Treatment
CICWQ is leading a collaborative effort of builders, developers, and device manufacturers to advocate for the specification and use of high-flow biofiltration devices (also known as proprietary biofiltration systems) for post-construction runoff capture, treatment, and discharge. Unfortunately, across California, not all local public works agencies clearly consider proprietary HFBF in meeting the permit-required maximum extent practicable standard. This is unfortunate and is a hurdle to building urgently needed housing within existing urban areas, where HFBF devices are well-suited and appropriate.
Versatile, space-efficient, and proven water-quality treatment performance make HFBF a valuable tool in the engineering toolbox for meeting the water-quality compliance requirements established by municipal separate storm sewer system (MS4) permits. HFBF systems can be sized using a volume- or flow-based approach, depending on the situation, and are subject to permit-authorized 3rd-party testing, certification programs, and protocols to demonstrate pollutant-reduction performance.
CICWQ recently authored a letter requesting clarification on the use of HFBF systems throughout Los Angeles County for MS4 permit compliance. The County is a recognized leader in California for implementing a range of different “nature-based” stormwater management best practices.
👉 Read the letter and check out our presentation from last year to Ventura County on the use of HFBF systems and the changes they made to their MS4-permit-required Technical Guidance Manual.
