After hearing there’s an “immediate threat” to Stockton’s water supply, the City Council has made an emergency declaration over the rapid spread of golden mussels in the Sacramento-San Joaquin Delta.
Screens on intake pipes from the Delta that prevent fish from entering Stockton’s water system were found to be 30% to 40% clogged with the tiny mussels that are wreaking havoc across California lakes and rivers, said Travis Small, deputy director of water resources in Stockton’s Municipal Utilities Department, or MUD. The city is spending $209,000 this week to clean the underwater screens and other gear.
The golden mussel invasion represents an “immediate threat to municipal water conveyance at our Delta intake station,” Small told the council. “If we lose our Delta intake station, it’s going to be really tough to meet summer (water) demand.”
The emergency declaration, which passed the council unanimously Tuesday, is aimed at making the city eligible for state and federal reimbursements. The San Joaquin County Board of Supervisors passed its own emergency declaration in April.
It’s not just Stockton that’s battling golden mussels. Small said the mollusks pose a risk to water reclamation systems, agricultural irrigation systems, hydropower plants and the entire state water project.
“We have a very, very suitable habitat for golden mussels,” he said. “They are the very definition of an invasive species.”
Golden mussels are believed to have found their way to Stockton by hitchhiking on a ship from Asia, where they are common. Usually only about an inch long, golden mussels grow atop each other after they attach to underwater objects.
The creatures were first discovered in California in October 2024 in the Port of Stockton and have since spread across the state’s inland waterways.
They can foul engine cooling systems in boats. The San Joaquin County Sheriff’s Office recently pulled a wrecked pickup truck out of a local slough. It was covered in mussels.
Farmers are alarmed how the pests have quickly clogged irrigation pipes.
And environmentalists are concerned about the prospect of mussels making their way into the state’s most pristine and treasured bodies of water, like Lake Tahoe.
The state responded by making it illegal to possess, transport or import live golden mussels, as well as requiring widespread boat inspections at lake ramps.
But in some cases, the spread of the mussels has become so extensive that officials are giving up on inspections, including in places like Lake Oroville.
Stockton officials are hoping to find a way to permanently mitigate the invasion. A couple ideas involve safe chemicals or infrared lights.
But for the moment, Small said the only realistic solution is elbow grease — having divers physically scrub underwater surfaces.
“We’ll keep working on it until we have a long-term solution,” Small vowed.