Napa supervisors signal intent to adopt Lake Berryessa boat-inspection ordinance to prevent invasive mussels

The Napa County Board of Supervisors on June 24 voted unanimously to express its intent to adopt an ordinance that would authorize on-site inspections of watercraft and water-related equipment at Lake Berryessa to prevent introduction of invasive mussels.

The vote came after county staff and outside scientists described the golden mussel, a fast-reproducing nonnative species recently detected in the Sacramento–San Joaquin Delta, as a major ecological and infrastructure threat. Martin Peralez of the Napa Resource Conservation District described the species’ ability to reproduce quickly, survive out of water for extended periods, and clog pipes and intake structures used by water utilities.

The supervisor who made the motion, Supervisor Amber Manfry, said the county must act to protect Lake Berryessa and the broader water systems that depend on it. County counsel staff explained that the ordinance would codify an inspection program already running administratively at Lake Berryessa in coordination with the U.S. Bureau of Reclamation and the Solano County Water Agency. Under the proposed rule, boats without inspection tags would be denied launch access and inspectors could examine non‑trailered craft (for example, canoes) suspected of carrying mussels.

Why it matters: testimony and staff presentations stressed that once golden mussels establish in a reservoir, eradication is not feasible, and the organisms can cause costly fouling of intake structures, create sharp shell debris on beaches, alter water quality and food webs, and increase risks of harmful algal blooms.

County staff and the sheriff said the ordinance is designed to concentrate launches at staffed access points where inspections can be performed. The draft also includes civil penalties and a misdemeanor provision for intentional attempts to avoid inspections.

The ordinance vote is an initial step. The board approved a motion expressing intent to adopt and will hold follow-up hearings required by county code before final adoption. Supporters, including county resource staff, said the measure aligns with prevention-first strategies being adopted across the state.

Ending: Supervisors voted unanimously to move forward. County staff said the inspection program will continue while the ordinance proceeds through the required public hearings and that public education and signage are already in place at key highway exits to warn visitors about the risk of invasive mussels and the launch protocols.