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SBC FILE NUMBER: 156

San Justo Reservoir is part of the San Felipe Division of the Central Valley Project in California and has which has been infested with zebra mussels since 2008.

Reservoir water is delivered for agricultural and municipal uses only; no surface water outflows from San Justo are connected to other water bodies, effectively creating an isolated zebra mussel infestation. The detection of invasive mussels at San Justo prompted the closure of the area to public access in order to prevent their potential spread further. Because San Justo is essentially a terminal water body, it presents a relatively unique opportunity for eradication to eliminate the threat of invasive mussels and their spread.

The U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, CO. has shared the Final Feasibility Level Eradication Plan: Zebra Mussels in San Justo Reservoir, Hollister Conduit, and Distribution System Mid-Pacific Region in June of 2019. County staff had a conference call with the various agencies to discuss next steps.

The plan details specifics for a zebra mussel eradication effort at San Justo Reservoir initially investigated and presented in the Draft Finding of No Significant Impact (FONSI, Reclamation 2015). The selected alternative includes the use of a potassium solution (potash) to treat the reservoir and distribution system. Properties of potash such as toxicity and environmental impacts are reviewed and summarized in the draft FONSI. Essential components of the proposed eradication effort are as follows:

• Draw-down of the Reservoir to 455 feet elevation, exposing shoreline mussels to desiccation and reducing the volume of water to be treated to approximately 3,000 acre-feet (97,755,000 gallons);
• Apply nearly 716,000 gallons of commercially acquired potassium solution (~ 12% potassium by weight) to San Justo Reservoir;
• Flush and charge the distribution piping system with treated water from San Justo Reservoir;
• Hold treated water within the reservoir and distribution system for approximately 45 days before resuming operations; and
• Monitoring will be conducted to evaluate eradication treatment performance and results.

This project is identified as an inclusion in a nationwide effort as a case study for Collaborative Conservation and Adaptation Strategy Toolbox, which is a joint venture of the Southwest Climate Hub, U.S. Fish and Wildlife Service, Bureau of Reclamation, and Forest Service. County staff had a conference call with the various agencies to discuss next steps.

As the Zebra mussel in San Justo Reservoir is the only species in California, there is a significant risk of this invasive spices spreading to other nearby bodies of water through human contact. For that reason, the Bureau of Reclamation has decided to maintain the San Justo Reservoir under quarantine. The most likely avenue of transport of zebra mussels is human contact with the water in the Reservoir, making the resumption of recreation of any kind risky. Human contact with Reservoir water can lead to jeopardizing vulnerable surrounding recreation facilities with the spread of zebra mussel; like the San Luis Reservoir and State Water Project canals as well as Santa Clara Valley facilities. The Bureau of Reclamation has monitored the growth of the muscle and observed a substantial increase. The Bureau of Reclamation outlined the potential risk and expressed that it would continue closer of recreational activities.

Currently, no funding has been allocated to perform the eradication work at San Justo Reservoir. The rough estimate of eradication cost is 3 million, with 100,000 ongoing yearly monitoring cost. The eradication work would be performed under a contract managed by the Bureau of Reclamation. As they do not have aquacade staff to perform the activates outlined in the plan, contracted services. The contracting process will begin when the Bureau of Reclamation has appropriated funding for this activity.  Solicitations will inform prospective bidders of the basis on which their bids or proposals will be evaluated concerning expected performance.  The plan will be implemented when the appropriation is allocated.

If the treatment and eradication of the zebra mussels are successful, then lifting the quarantine and resumption of recreation may be possible.  However, from draw-down through treatment and monitoring (3-year period), recreation will remain closed. Opening the Reservoir to human contact cannot resume until the water is certified free of mussels (State and Federal standards, settlement plate non-settlement, polarized light microscopy, and DNA).

Once recreation is allowed again, the area will need to be brought up to a reasonable public standard.  It will also be essential to implementing protective measures to reduce the risk of re-infestation and to minimize the risk of re-infestation and possible infestation of other waters as having been taken at other waters currently believed not to be infested.  A future of recreation would have to include control measures.  A mussel management plan as stipulated in the California Fish and Game Code will be required. 

Next Steps for Bureau of Reclamation (if available appropriated funds):

1. Obtain Chemical Applicators Permit;
2. Update the Cost-Benefit Analysis;
3. Acquisition Planning;
4. Preparation of  Solicitation Package;
5. Solicitation for offers (potential contractors);
6. Review of Proposals;
7. Award Contract;
8. Implementation of Eradication Plan;
9. Evaluation of Contracted Work;
10. And monitoring the Zebra Mussels.

The County has invited San Benito Water District, Congressman Panetta’s office, California Fish and Wildlife Service, and Bureau of Reclamation to provide an update the Board of Supervisors.

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