The detection of invasive golden mussels at Lake Del Valle in Del Valle Regional Park has forced the East Bay Regional Park District to implement a mandatory 30-day quarantine on watercraft launching at the reservoir. This measure applies before boats can be used at any other district-managed waterbody.
Lake Del Valle is only the second body of water in the East Bay park district to experience a golden mussel infestation, following Contra Loma Reservoir in Antioch, which is now subject to the exact same 30-day quarantine protocol. Watercraft that launch exclusively at Lake Del Valle and return with an intact local boat band are exempt from the quarantine, but all other vessels face strict inspections for golden, quagga, and zebra mussels prior to launch.
Risks to Regional Drinking Water and Infrastructure:
The threat extends well beyond recreational boating areas. According to the Zone 7 Water Agency, Lake Del Valle links directly to the South Bay Aqueduct and functions as an essential raw-water storage facility. The agency supplies drinking water to roughly 174,000 customers—primarily through retailers serving Livermore, Pleasanton, and the Dublin San Ramon Services District while also providing agricultural irrigation for thousands of acres of Tri-Valley vineyards.
Understanding the Golden Mussel Threat:
State wildlife officials note that golden mussels are native to coastal Asia and South America and were first identified in North America at the Port of Stockton in 2024. Since then, they have expanded rapidly northward, with detections reaching Washington Lake near the Port of West Sacramento.
Unlike related invasive species, golden mussels can thrive in brackish water and survive at significantly lower calcium concentrations. Their aggressive reproduction allows them to rapidly clog narrow water pipes, damage treatment facilities, and disrupt local aquatic ecosystems. These compounding challenges have driven county emergency declarations in San Joaquin, Yolo, and Sacramento counties.
Statewide and Regional Containment Efforts:
Legislative action is accelerating to address the crisis. California Assemblymember Rhodesia Ransom authored Assembly Bill 2032, known as the Golden Mussel Response Act, to streamline permits and fast-track local agency responses to invasive species spread.
Locally, the East Bay Regional Park District utilizes color-coded, lake-specific boat bands and requires inspections across multiple recreation sites, including Quarry Lakes, Shadow Cliffs, and Lake Chabot. Because these mussels can attach to hulls, anchors, ropes, and aquatic vegetation, officials urge all boaters to thoroughly clean, drain, and dry their equipment between trips.
