October 01, 2023


The California State Water Resources Control Board will begin drafting an updated aquatic weed control permit.

Following the Ninth Circuit Court of Appeals decision in the Headwaters, Inc. vs Talent Irrigation District case in 2001, California began requiring an NPDES permit for treatment of aquatic weed or algae with aquatic herbicides or algaecides if the application is made to Waters of the Unites States (WOTUS) or if treated water is discharged to WOTUS. The current aquatic weed NPDES permit became effective in December 2013 (2013 Permit). The State Water Resources Control Board (SWRCB) is in the process of drafting a new aquatic weed permit to replace the 2013 Permit.

The SWRCB held their first informal stakeholder outreach meeting at their Sacramento office on September 25 to discuss the Water Board’s permitting process, the regulatory background, project considerations, and the reissuance timeline. They also fielded questions from attendees. Blankinship and Associates staff attended the meeting in-person and virtually over Zoom and provided comments to SWRCB staff on challenges with the existing Permit and to promote a new Permit that is protective of water quality, provides dischargers with adequate flexibility to make effective vegetation management decisions, and can be easily amended to allow for new active ingredients or modifications through the life of the permit. Given that the current Permit was set to expire in 2018 and has been administratively extended for 5 years, it is critical that the new permit provides a straightforward pathway for amendments that can keep up with changes in scientific understanding, California registration of new algaecide or aquatic herbicide active ingredients, and technological advancements.

Based on information provided during the September 25 meeting, the tentative timeline for Permit Reissuance is as follows:

Tentative timeline for the new aquatic weed control permit reissuance.

We encourage any current or future permit-users to reach out to us to discuss questions, concerns, or suggestions related to aquatic pesticide use and permit requirements. Call us at (530) 757 – 0941 or send us an e-mail at 2024WeedPermit@h2osci.com.