Napa County moves to authorize inspections of watercraft at Lake Berryessa to prevent invasive mussels

The Napa County Board of Supervisors signaled its intent Tuesday to adopt an ordinance that would authorize inspections of watercraft at Lake Berryessa aimed at preventing the spread of invasive golden mussels.

County counsel and staff told the board the draft ordinance would add chapter 6.02 to the Napa County Code and would give on‑site inspectors and law enforcement explicit authority to stop and inspect boats, trailers and other equipment at Lake Berryessa. The change codifies an inspection and tagging program already run on the reservoir and adds enforcement tools and penalties, including misdemeanor charges for knowingly trying to avoid inspection.

The move follows a presentation from Martin Peralez, a PhD aquatic ecologist with the Napa Resource Conservation District, explaining the threat posed by the golden mussel (a small, fast‑reproducing freshwater mussel native to Asia). Peralez described how the organism’s microscopic larval stage (veligers) and attached adult mussels can ride on boats, trailers, livewells and even puddles of water, survive out of water for weeks, rapidly reproduce and foul intake infrastructure. He warned that once established in a water body eradication is not feasible and that the species poses ecological and infrastructure risks, including clogged pipes and intakes and changes to water quality.

County counsel explained the current inspection program at Lake Berryessa has been administered collaboratively with the U.S. Bureau of Reclamation and the Solano County Water Agency and that the proposed ordinance primarily codifies and extends that administrative program. Under the existing practice boats that have been decontaminated are given tamper‑resistant tags; boats launched without a tag are denied entry. The proposed code text would make it a violation to launch motorized boats outside designated launch sites and would allow deputies and other authorized officers to inspect non‑trailer craft such as canoes if observers believe they might carry mussels.

The board discussed enforcement resources, signage and public education. Sheriff’s office representatives said the draft ordinance uses “may inspect” language to preserve some flexibility in deployment but that the law would give deputies clear authority to issue citations and, in extreme cases, pursue misdemeanor charges if someone deliberately tries to avoid inspection. Concessionaires and the Solano County Water Agency already operate power‑wash decontamination and tagging at many launch sites, staff said; deputies expect to rely on those partners for day‑to‑day operations and on vendors to provide decontamination services.

Supervisor questions focused on whether the state water project and nearby intakes (such as Barker Slough and the North Bay Aqueduct) could be affected and how far the mussels might spread in local rivers and creeks. Peralez said golden mussels tolerate a wider range of water conditions than zebra/quagga mussels and could establish in many freshwater systems that do not freeze or exceed salinity limits; the Napa River’s high flows could be a limiting factor in some reaches, but lower, slower freshwater reaches would be vulnerable.

The board voted unanimously on a motion expressing intent to adopt the ordinance and remand the final text through the required second public hearing process. Supervisors voting in favor were Chair Cottrell, Vice Chair Manfry, Supervisors Ramos, Alessio and Gallagher.

Officials said the county will continue monitoring, public outreach and coordination with the Bureau of Reclamation, Solano County Water Agency and state agencies while the formal ordinance process continues. The board asked staff to ensure public education (signs and outreach) and to clarify cost‑sharing responsibilities with Solano County and concessionaires for enforcement and decontamination.

The ordinance will return for a subsequent hearing as required by the county’s ordinance adoption procedures.