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My heart almost skipped a beat when scanning the email from a reader pointing out the implications of an under-reported item from last week’s East Bay Municipal Utility District Board of Directors meeting: the golden mussel is starting to spread in California.
Mere mention of the bivalve froze me in full-blown flashback.
I spent dozens of hours early in my career covering government meetings in Lakeport on invasive mussels and prevention efforts.
Clear Lake has always been the economic (and political) epicenter of Lake County, so maintaining the health and vitality of the watershed was a recurring subject for the Board of Supervisors. When they weren’t talking about algae, weeds, water quality or flooding, the lake’s overseers at that time were laser-focused on the quagga quandary.
The primary goal then, as it remains now, is to stop invasive, non-native freshwater mussels (like quagga, zebra and golden) from ever even entering your body of water – in the hopes of stopping what would inevitably come next, an out-of-control infestation.
The problem is waterways are connected, and by more than just the literal streamflow. Humans are another conduit, by way of our watercraft.
A boat traveling from one lake, river or reservoir to another that isn’t properly sanitized can unknowingly transport invasive mussels to somewhere the species had never been before. The adults are smaller than a dime while juveniles are often undetectable to the naked eye, and they can attach to a boat’s hull or get sucked inside the engine system.
Thus the mantra shouted by public agencies like the California Department of Water Resources: “clean, drain and dry”.
That strategy is even more important after the golden mussel was found in the Sacramento-San Joaquin Delta near Stockton in October 2024 (the first time ever seen in North America). Within a year, the mollusk was reported as far south as the State Water Project south of Riverside and as far north as Rio Vista on the Sacramento River, according to EBMUD.
The State Water Project is the major potable water supply for Pleasanton, Dublin, Livermore and the Dougherty Valley via the Zone 7 Water Agency.
“Zone 7 is concerned about the spread of golden mussels and is actively tracking to detect and control golden mussels as they relate to the agency’s water supply infrastructure,” General Manager Valerie Pryor told me Tuesday. “The presence of mussels does not pose a public health and safety risk; however, the mussels do have the potential to impact system operations if not addressed.”
In addition to concerns for public water infrastructure and ecosystems, DWR calls out that the non-native mussels can damage watercraft engines and hydroelectric facilities and hurt recreation experiences and locations.
“Protecting our lakes and reservoirs from invasive mussels is essential to the health of our ecosystems and the long-term enjoyment of our parks,” East Bay Regional Park District officials told me this week.
EBRPD changed its boat inspection and banding policies back in May to help protect its waterways from the golden mussel, instituting new color-coded, lake-specific, tamper-proof bands and no longer accepting EBMUD’s bands. Boats without a band for that specific waterbody had to go through a full inspection and pay a fee, each time.
“Once introduced, these species are nearly impossible to remove and can cause millions of dollars in damage while disrupting native wildlife,” EBRPD officials said. “By taking a few extra minutes for inspection and adhering to banding requirements, boaters play a vital role in safeguarding the East Bay’s natural resources for future generations.”
The change seems to have largely worked, with an asterisk in Antioch.
EBRPD lakes in the Tri-Valley (Del Valle, Shadow Cliffs and Quarry Lakes) have no recorded golden mussel activity, the agency said. However, the critter was found in Contra Loma Reservoir, so boats that have been in that lake must stick there only or complete a 30-day quarantine.
Meanwhile, a half-inch-long juvenile golden mussel was recovered at Zone 7’s Patterson Pass Water Treatment Plant this year, Pryor confirmed to me.
“It was turned over to DWR for examination,” she said. “There has been no impact to water treatment facilities or operations. Golden mussels are effectively removed during the water treatment process and do not pose a risk to the treated water system.”
Pryor added, “Because we receive most of our water from the State Water Project and are connected to water infrastructure via the State Water Project, we rely heavily on the California Department of Water Resources. In response to golden mussels, DWR has implemented routine inspections of SWP facilities and expanded its efforts by applying new strategies to protect pumping plants, hydroelectric plants, and water supply deliveries.”
“In addition,” she continued, “Zone 7 keeps the untreated water users, such as the wine growers in Livermore wine region, updated on the threat of golden mussels to their intakes and DWR’s strategies.”
Most of the drinking water supply for EBMUD, which services the bulk of the San Ramon Valley, does not touch the Delta and does not involve the State Water Project, but it does get some supplemental water drawn from the Sacramento River.
So its main concern has to do with protecting its reservoirs that should otherwise be clean. The district suspended all public boat launching in its recreational facilities in 2025 in reaction to the golden mussel scare.
EBMUD staff returned to the board last week and received unanimous approval for their plan to reopen certain waterways to boaters in 2026. Camanche Reservoir in Valley Springs and San Pablo Reservoir in El Sobrante will be open part of the year to private boats under strict inspection rules.
Pardee Reservoir near Ione – dubbed “the heart of EBMUD’s drinking water supply” in the Sierra Nevada foothills – is too high-risk so private boats won’t be eligible next year again (but rentals are available there).
Specific rules will also be enacted at Bay Area reservoirs where trailered boats are typically not permitted, but smaller watercraft can be used: Lafayette, Chabot, Briones and Upper San Leandro.
The agency is now working to develop public outreach strategies and finalize boat inspection and quarantine procedures. But staff did warn that if conditions change or new golden mussel threats are identified, the planned reopenings could become nothing more than a faint memory.
Editor’s note: Jeremy Walsh is the associate publisher and editorial director for the Embarcadero Media Foundation’s East Bay Division. His “What a Week” column is a recurring feature in the Pleasanton Weekly, Livermore Vine and DanvilleSanRamon.com.
