When Species Invade: California’s Water Infrastructure and Golden Mussels

Invasive Species and Favorable Conditions Put Infrastructure at Risk

The invasive golden mussel

(Limnopera fortunei) poses a growing risk to California watersheds and critical water infrastructure. First identified in the Port of Stockton, California, in October 2024, these mollusks have quickly spread through California's interconnected waterways and infrastructure.

"The veligers, or babies, of golden mussels are microscopic and can flow rapidly through interconnected water systems," says Dave. "They adhere to many hard surfaces, including waterways, intake structures, and diversion structures. They grow and colonize rapidly and can quickly plug or block critical water infrastructure."

Likely introduced through ballast water from ocean-going container ships, golden mussels find an ideal habitat in California waters such as the Bay-Delta watershed.

"We've got good water chemistry, no natural predators, and a nutrient-rich water column, which means they can flourish here," says Dave.

Marisa says water agencies should prepare now. "Just over a year ago, this species was just a potential threat. Its spread throughout California has been very fast. Now, all water utilities in the state need a plan to address golden mussels, whether through monitoring and prevention or through treatment of already affected systems."

California's interconnected network of waterways poses an additional threat to critical water infrastructure.

"The California Water Project, the State Water Project, the California Aqueduct, and the Los Angeles Aqueduct all connect at some point into one another," says Dave. "If you get a golden mussel infestation in one part, it can move rapidly to other core facilities."

Assessing Risk to Manage Costs

Dave and Marisa encourage water agencies to assess their risk before golden mussels become established in water infrastructure.

"The state is tracking golden mussel infestations as they have moved from the Bay Area toward Southern California. Any utility that has an intake facility or brings water from a source known to be contaminated needs to worry about their facility being infected," states Dave.

He continues, "If the infestation isn't addressed early, water utilities can face costs of more than $10 million per year to deal with equipment that has been overtaken by the mussels."

To help water utilities assess vulnerabilities in their systems, Geosyntec practitioners developed a risk assessment tool that reviews three components: environmental suitability, infrastructure susceptibility, and potential introduction pathways. The tools help water agencies understand their level of risk.

"Sometimes utilities look at their system in an isolated way," says Marisa. "This tool helps utilities and agencies understand how the system is interconnected, both upstream and down, and uses that to prioritize work."

During the assessment, a risk value is assigned to each category. Together, these categories are used to create an overall risk zone. Geosyntec practitioners then help utilities or agencies understand their risk zone.

"Water utilities companies don't usually have biologists and engineers on staff to help consider a problem like golden mussels from all angles," says Dave. "At Geosyntec, we can assemble a team that can examine water quality, assess the likelihood of infestation, identify where the system is likely to be impacted, and design potential treatments."

"Ultimately, we want to help the water agencies develop a plan that identifies highest-priority work, assesses available resources, and then considers how other priorities can be added," says Marisa.

Dave adds, "We have evidence that multi-pronged plans to address invasive species work. There are still waterways in California that are free of invasive species because water agencies implemented stringent measures to help prevent their spread."

He continues, "The Los Angeles Aqueduct has been free of quagga mussels, another invasive species, since the early 2000s due in part to a rigorous program designed to protect the aqueduct. That same level of rigor is now needed for golden mussels. Geosyntec is ready to help water agencies across California assess the risk golden mussels could pose to their infrastructure and to advise them about how they can deal with them going forward."

Marisa adds, "Golden mussels are, unfortunately, more complicated than previous invasive species like quagga mussels. They are more adapted to a wide range of water chemistry. Water agencies need thorough and adaptable plans that consider the continued need for action and management. Geosyntec has the biologists, engineers, and planners to help them identify priority areas and development long-term solutions to protect their critical infrastructure."

Learn More About our Practitioners

Marisa Escobar, PhD, a Principal Water Resources Consultant based in California with more than 20 years of experience focused on supporting public agencies, utilities, and regional organizations in water resources planning, watershed resilience, climate adaptation, and infrastructure strategy. She has developed data to support master planning and developed risk and resiliency studies for California state agencies and public utilities.

She will present "System-Scale Evaluation of Invasive Mussel Infestation Risk Across Critical Water Infrastructure: A Screening Framework for Interconnected Water Systems" at the Bay-Delta Science Conference on Wednesday, September 30, 2026, in Sacramento, California.

Dave Martin, PhD, is a Senior Consultant based in Nevada with more than 30 years of experience in natural and water resource management, agricultural management, ecological restoration, and conservation. Before joining Geosyntec, he led the development of management plans for agricultural, cultural, hydrologic, operations and maintenance, and recreational resources for the City of Los Angeles.

More Information on Managing Invasive Mussels

For more information on risk assessment and management for invasive species, contact Marisa Escobar at [email protected] or Dave Martin at [email protected].

Read about Geosyntec at the Bay-Delta Science Conference.