SWRCB Adopts Updated Stormwater Permit for Caltrans ​

The State Water Resources Control Board has adopted an updated NPDES stormwater permit for Caltrans operations, and if you thought the previous permit was a light read at 200 pages, you're going to love this 340-page masterpiece of regulatory prose that manages to make rainwater feel like a controlled substance.

The new permit incorporates PFAS monitoring requirements — because the "forever chemicals" have made their way into essentially everything, including highway runoff — and enhanced BMP performance standards for construction sites near sensitive waterways. For those unfamiliar, BMP stands for "Best Management Practice," which in the field typically translates to "did someone remember to install the fiber rolls before it rained?" The answer, historically, has been inconsistent.

Key Changes ​

The PFAS monitoring component is the headline item, requiring quarterly sampling at 45 representative outfalls statewide. This is the first time PFAS has been explicitly regulated in a Caltrans stormwater permit, which means districts across the state are currently scrambling to figure out what PFAS even is, where their outfalls actually discharge, and how much this is going to cost. The answer to the last question, as always, is "more than budgeted."

Construction site requirements now mandate real-time turbidity monitoring for projects within 500 feet of 303(d)-listed waterways, which affects roughly half of all active Caltrans projects because California has been impressively thorough about listing impaired water bodies. If a creek exists in California, there's a solid chance it's impaired for something — sediment, temperature, nutrients, mercury, or the general vibe of disappointment.

Compliance Timeline ​

Existing projects have 180 days to update their SWPPPs. New projects must comply from day one, which is perfectly reasonable as long as you don't think about it for more than five seconds and realize that permit adoption, specification updates, and RE training all take longer than 180 days.

The permit is effective July 1, 2026. Mark your calendars, update your SWPPPs, and invest in fiber rolls.