County Response

On April 28, 2026, the San Joaquin County Board of Supervisors proclaimed a local emergency in response to the growing golden mussel threat, calling for strengthened State partnership, additional resources, and coordinated action. The Board directed County staff through the Office of Emergency Services to coordinate with local, regional, State, and federal partners to pursue funding, technical assistance, mitigation strategies, and infrastructure protection resources.

The Board will review the status of the emergency at least every 60 days as required by law. OES is leading an interagency working group to coordinate recovery activities across County departments and partner agencies. This page will be updated as new guidance and resources become available.

Currently, San Joaquin County OES is documenting all eligible costs, impacts, and findings to position the County for a potential future IA or PA request. OES is committed to advocating for Delta communities and will pursue every available avenue for state and federal financial assistance as the situation evolves.

View the Local Emergency Proclamation: San Joaquin County Board of Supervisors - Golden Mussel Emergency Proclamation (April 28, 2026)

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Report Your Findings

Documenting the scope and impacts of this invasion is critical to supporting requests for state and federal assistance. If you have observed golden mussels or experienced damage to infrastructure, equipment, operations, or revenue losses related to golden mussels, please report the information using one of the links below. Be sure to include any current expenses, repair costs, operational impacts, or loss of revenue associated with the report. 

Reporting damages does not guarantee financial assistance, but it helps support the County’s advocacy efforts for Individual Assistance (IA) and/or Public Assistance (PA) declarations.

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What are Golden Mussels?

The golden mussel (Limnoperna fortunei) is an invasive freshwater bivalve native to rivers and coastal areas of China and Southeast Asia. First detected in North America in October 2024 at the Port of Stockton, the species has since spread throughout the Sacramento–San Joaquin Delta and its tributaries placing San Joaquin County at the epicenter of California’s response. More than two-thirds of the Delta lies within San Joaquin County, making this both a local emergency and a critical statewide concern.

Golden mussels are capable of rapidly colonizing a wide range of surfaces, both natural and man-made, at virtually any water depth. They thrive in fresh and brackish water with temperatures between 41–95°F and can establish in conditions found throughout the Delta. Once a colony is established, it is extremely difficult to control or eradicate.

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Why It Matters

The Delta is a critical source of drinking water, agricultural production, economic activity, and recreation for San Joaquin County and communities throughout California. Protecting the Delta is protecting the water supply and economic foundation of the entire state.

The species poses serious risks across multiple sectors:

  • Water conveyance and delivery systems: mussels clog pipelines, screens, and intake structures
  • Flood control infrastructure: colonization of levees and drainage systems increases maintenance costs and flood risk
  • Agriculture: irrigation intakes and pumping equipment are vulnerable to fouling and reduced flow
  • Recreation: boat hulls, motors, and cooling lines are susceptible to mussel attachment
  • Delta ecosystems: golden mussels outcompete native species and alter aquatic food webs

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Prevention Remains Critical

Even as the County focuses on recovery in affected areas, preventing further spread into unaffected waterways is essential. All boaters and water users are required to follow the State’s “Clean, Drain, Dry” protocol:

  • Clean all equipment, boats, and gear of any visible organisms or plant material
  • Drain all water from the boat, motor, bilge, livewells, bait buckets, and any other water-holding equipment
  • Dry everything completely before entering any new waterway - a minimum of five days in warm conditions is recommended

Before transporting any watercraft from Delta or other affected waters to a new waterbody, stop at an authorized Watercraft Inspection and Decontamination (WID) station. Inspected vessels will receive a seal or sticker as proof of clearance.

Find a WID station near you: CDFW Watercraft Inspection Station Locator

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Individual Assistance (IA) and Public Assistance (PA)

San Joaquin County is actively documenting the economic and infrastructure impacts of the golden mussel invasion to support potential future requests for state and federal disaster assistance. Neither program has been activated for this event at this time.

What Is Individual Assistance (IA)?

Individual Assistance (IA) provides support directly to eligible residents, business owners, and nonprofits to help recover from a declared disaster. This can include grants for home repairs, temporary housing assistance, low-cost loans, and other recovery programs for needs not covered by insurance.

What Is Public Assistance (PA)?

Public Assistance (PA) is a FEMA program that reimburses eligible state, tribal, and local governments, as well as certain private nonprofits, for the cost of emergency protective measures, debris removal, and restoration of damaged public infrastructure.

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Recovery, Cleanup, and Health Guidance

San Joaquin County OES is leading an interagency working group with county departments - including Environmental Health, the Agricultural Commissioner’s Office, Public Works, Parks, and Public Health Services - to develop localized guidance for recovery and cleanup. Guidance will be updated on this page as it is finalized and verified. The following reflects current best-available science from CDFW and partner agencies.

Removal and Handling

Golden mussels attach firmly to submerged surfaces and should not be removed without following proper decontamination procedures. Removing mussels without precautions can transfer larvae or shell fragments to new locations. Equipment, tools, and vehicles that have been in contact with infested water should be decontaminated before use in any other waterway or water system.

Decontamination Methods

The following methods are consistent with current guidance for invasive dreissenid mussels:

  • Hot water: Water at or above 140°F (60°C) applied for at least 10 seconds kills attached mussels and larvae. This is the preferred method for equipment that can tolerate heat.
  • Drying: Mussels and larvae cannot survive extended drying. A minimum of five days of complete drying in warm conditions is recommended for equipment that cannot be heat-treated.
  • Pressure washing: High-pressure washing can physically remove attached mussels but may not kill larvae. Combine with heat or drying when possible.
  • Chemical treatment: Some chemical agents are used in controlled infrastructure settings and require appropriate permits and professional application. Do not discharge chemically treated water into any waterway without authorization.

Removed mussels and debris must be disposed of on dry land. Do not return removed material to any waterway.

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Health Considerations

There are no known public health advisories specific to human contact with golden mussels in San Joaquin County at this time. If you have concerns about water quality or contact at a specific location, contact San Joaquin County Public Health Services. This section will be updated if any health guidance is issued by county or state public health authorities.

This section will be updated with department-specific guidance from SJC Environmental Health, Ag Commissioner, Public Works, Parks, and Public Health Services as the OES working group finalizes protocols.

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Resources for Property Owners and Businesses

The following information is provided for sectors most directly affected by golden mussel impacts. As the OES working group and county departments finalize sector-specific guidance, this section will be updated. Where county-specific protocols are not yet established, links to state and federal resources are provided.

Farmers and Ranchers

Golden mussels can colonize irrigation intake structures, pipes, canals, and pumping equipment, restricting flow and increasing maintenance costs. Growers using Delta-connected water sources should inspect intake screens and infrastructure regularly.

  • Decontaminate any equipment moved between affected waterways and other farming operations
  • Report infrastructure impacts using the local damage report link above
  • Contact the SJC Agricultural Commissioner’s Office for local guidance on reporting and decontamination procedures
  • Restoration funding has not been established at this time. OES is actively advocating for state and federal financial assistance for agricultural producers. Document all observed impacts and associated costs.

SJC Agricultural Commissioner’s Office: sjgov.org/agricultural-commissioner

CDFW Golden Mussel Resources: wildlife.ca.gov/Conservation/Invasives/Species/Golden-Mussel

Landscape Professionals

Contractors working near waterways or using water sourced from the Delta should use decontaminated equipment and avoid inadvertent mussel transport via tools, hoses, or vehicles that have contacted infested water. Where restoration work is underway, native and drought-tolerant riparian plantings are encouraged to support Delta habitat recovery.

California Native Plant Society - Plant Finder: calscape.org

Homeowners Associations (HOAs)

HOAs with waterfront or water-adjacent properties, particularly in Delta communities, should inspect docks, pilings, and water features for signs of golden mussel colonization. HOAs managing shared watercraft storage should inform all members of the obligation to follow Clean, Drain, Dry protocols and use authorized Watercraft Inspection and Decontamination (WID) stations before transporting vessels to other waterways.

Construction Contractors

Contractors working in or near Delta waterways should be aware that golden mussel colonization may affect project timelines and that decontamination requirements apply to submerged equipment. Current state and federal permitting requirements for in-water work apply, including any invasive species mitigation conditions.

Learn more by visiting the State Water Resources Control Board at waterboards.ca.gov and the U.S. Army Corps of Engineers - Sacramento District at spk.usace.army.mil. 

Marinas

Marina operators play a critical role in preventing further spread. Key responsibilities include:

  • Posting Clean, Drain, Dry materials and signage at all launch ramps and fuel docks
  • Directing boaters transitioning to unaffected waters to authorized WID stations before launching elsewhere
  • Monitoring dock infrastructure, pilings, and mooring equipment for signs of colonization
  • Reporting confirmed detections to CDFW immediately at (866) 440-9530 or invasives@wildlife.ca.gov

To find a California Department of Fish and Wildlife Watercraft Inspection and Decontamination (CDFW WID) Station, visit wildlife.ca.gov/Conservation/Invasives/Species/Golden-Mussel. 

For more information from the CA Division of Boating and Waterways, visit dbw.parks.ca.gov.

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Utility Operators

Water utilities and special districts relying on Delta water sources should actively monitor intake infrastructure and consult with CDFW and the Department of Water Resources on site-specific mitigation strategies. Document all observed impacts, inspection findings, and response costs.

At the federal level, U.S. Senators Padilla and Schiff have introduced the Golden Mussel Eradication and Control Act of 2026, which would authorize $15 million per year for demonstration, monitoring, and control programs, as well as competitive grants for state and local agencies. OES will monitor this legislation and update this page as funding opportunities become available.

Learn more about how the CA Department of Water Resources is prevent the spread of the golden mussel by visiting water.ca.gov/What-We-Do/Recreation/Mussel-Mitigation. 

More information on California's response by going to the State Water Resources Control Board at waterboards.ca.gov.

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