Moss Landing Battery Fire Update
Dear Friends & Neighbors,
After the latest fire at the Moss Landing battery facility, I feel it is important to review how we got here and the potential future.
There is some confusion about how many Battery Energy Storage Systems (BESS) facilities exist in Moss Landing. There are two. Vistra and PG&E each have separate sites, although Vistra had several phases of development. Both announced an intention to develop BESS facilities in 2018, Vistra’s Moss 300 and PG&E’s Elkhorn.
At that time, neither proposal was controversial. There was significant public attention given to the projects with business, labor and environmental groups expressing support. The Planning Commission approved both, and neither was appealed to the Board of Supervisors.
Vistra would propose more phases in 2019 and 2020 to the Planning Commission. Again, both applications were approved. However, the Planning Commission approval was later appealed to the Board of Supervisors. That appeal was withdrawn before ever coming to the Board of Supervisors for a vote. From that decision, Moss 100 and 350 were built.
Although Monterey County permitted the land use and physical development of battery-storage facilities, such as grading, inverters, converters, substations and buildings, it did not independently approve or certify the battery cells, modules or system design. That was done elsewhere. Operations and maintenance safety is largely the responsibility of the California Public Utilities Commission (CPUC). Approval of the battery technology itself is done at nationally recognized testing laboratories which is standard for industrial equipment.
Vistra’s Moss 300 and Moss 100 were approved as stacked batteries inside buildings. This was not an uncommon practice and continues at many BESS facilities around the world today, although the industry is now moving away from doing that largely because of the Moss Landing fire. Moss 350 and PG&E’s Elkhorn are outdoor containerized systems. The batteries are not stacked as the indoor ones were. Vistra uses LG batteries while PG&E uses Tesla batteries. All are lithium-ion.
Some people have asked why these plants are allowed in Moss Landing, with agricultural fields, population centers, fishing, businesses and environmentally sensitive areas of the Elkhorn Slough and Monterey Bay nearby. The answer goes back to just after World War II when PG&E built what would eventually become the second largest fossil-fuel power plant in the world. At one time, Mighty Moss, as it was known, produced electricity equivalent to all the power plants in Los Angeles. The answer to why Moss Landing is where the power plants are is because the electrical transmission infrastructure is already in place to receive and provide energy.
In 2021 and 2022, Moss 300 and Moss 100 overheated and smoke occurred but there was no thermal runaway. A thermal runaway occurs when a lithium-ion battery overheats, causing a chemical reaction that releases more heat and more reactions. That is what happened in 2022 with Elkhorn and last year at Vistra. In 2022, a fire developed, closing Highway 1 and forcing a shelter-in-place. While water or other materials can cool a thermal runaway and appear to extinguish the flames, what this often does is prolong the fire. In 2024, a thermal runaway occurred at Otay Mesa in San Diego County. Fire officials there tried to repeatedly knock down the fire, but it reignited every time, extending the fire for fourteen days. During the Moss Landing fires, North County Fire Protection District chose to let the fire burn itself out, limiting the fire to three days.
The 2025 fire was at the Moss 300 building, and 56,000 of the 100,000 battery modules in the building burned. Last July, the U.S. EPA announced that it would oversee the cleanup of the fire debris and remaining 44,000 modules. The EPA did announce that there was a possibility that the batteries could reignite during the cleanup. That is what happened on September 18. There were only about 3,000 battery modules left to remove when it happened and 1,200 of those were burned. The cleanup is now very close to finishing. Until it is complete, there is the risk of another fire.
Where does this leave us now? Both PG&E and Vistra disengaged from the electric grid after the 2025 fire. Falling ash required PG&E to shut its operation down and Vistra did so out of precaution. When PG&E tried to return to normal grid service last year, it found a clamp failure and coolant leak in one of the Tesla megapacks. The Tesla systems are undergoing upgrades to correct those failures. There is no date for when Vistra or PG&E will reengage with the electric grid. Both remain under review and coordination with state regulators. Unfortunately, Monterey County has little influence in making those decisions. After the 2025, the CPUC announced an investigation into the cause of the fire. Nearly 21 months later, we are still waiting for an answer.
However, the only batteries that will return to use are those at PG&E’s Elkhorn and Vistra’s Moss 350. Both are outdoor containerized batteries. Throughout last year, I had several discussions with Vistra representatives that their other BESS building with stacked batteries, Moss 100, was unsafe and asked that it be decommissioned. Earlier this year, Vistra decided to decommission Moss 100, although they said it was for financial reasons.
Both companies do intend to expand. Prior to the 2025 fire, both submitted applications to do so, but those applications are currently on hold and neither company has made efforts to move forward. I expect Monterey County to have a much stronger ordinance in place when those applications move forward.
Monterey County is currently working on an ordinance for BESS facilities. There will be public hearings and a committee representing broad interests has been formed to develop it. Monterey County can develop a strong BESS ordinance as Santa Cruz County has, although Santa Cruz has not yet adopted its ordinance. Monterey County could also reject any future BESS expansion or new facilities under that ordinance. There’s just one problem, and it’s a big one: AB 205. AB 205 was put into law in 2022 by the State. It allows a company to bypass a local jurisdiction and go straight to the California Energy Commission (CEC) for a permit decision in 270 days. That is exactly what is happening in Santa Cruz County where a BESS facility was proposed outside Watsonville. New Leaf Energy decided the Santa Cruz County ordinance was too strict and is now seeking approval from the CEC.
Although the CEC must take into consideration local standards, the decision is still made in Sacramento, not locally. Taking into consideration does not mean implementing those standards either. The CEC has already approved three statewide projects. It did deny one project in Shasta County that had some local concerns, but a major reason was because the proposed wind turbines on mountainsides were considered to be a hindrance for aerial firefighting. Regardless of where the decision is made, the next step is to make sure that Monterey County has an ordinance for BESS facilities so that it can have the strongest influence possible, whether the final decision is made here or in Sacramento.
As always, don't hesitate to reach out to my office for assistance. You can reach us at 831-755-5022 or district2@countyofmonterey.gov.
Sincerely,
Glenn Church
District 2 Supervisor
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