Moss Landing’s Second Fire Started in Damaged Batteries Awaiting Removal, a Year Into an EPA-Supervised Cleanup

About 1,200 charged battery modules self-ignited at Vistra’s Moss Landing plant at roughly 6:15 a.m. on September 18. They were the modules crews had been unable to reach.

North Monterey County Fire Chief Jess Cortez said the modules “ignited on their own,” with smoke and fire on the north side of the plant, against the wall of a building that burned in January 2025. Monterey County issued a shelter-in-place order covering an area with an estimated 106 residents and lifted it at 4 p.m. the same day. By afternoon the fire chief reported no active fire and modules in a smoldering stage. No injuries were reported.

Monterey County stated that the fire involved batteries already damaged in the January 2025 blaze and that it was “not comparable” in size.

The system. Moss Landing 300 houses a 300 MW / 1,200 MWh nickel-manganese-cobalt lithium-ion installation inside a repurposed gas turbine building. That building burned in January 2025. Everything since has been demolition and removal.

The cleanup schedule. EPA has direct oversight of the module removal, supported by the US Coast Guard’s Pacific Strike Team. Battery removal began September 29, 2025. Phase 1 covers accessible, intact batteries: workers de-energize each module, transfer any remaining energy back into the local grid, and ship the module for recycling or disposal. Phase 2 covers the severely burned sections, demolition to the foundation, and treatment and disposal of burned and damaged batteries.

EPA’s response timeline recorded 8,448 batteries de-energized as of December 19, 2025. By February 13, 2026, the count was 22,984. By April 10, more than 27,800. By June 24, 33,943.

Phase 1 was expected to finish by the end of June 2026.

At the time of Friday’s fire, Vistra’s count stood at roughly 34,000 modules extracted with approximately 5,000 remaining, which the company hoped to finish later this year. EPA’s public update log was last revised June 24, so the interval since is undocumented on the agency’s page. The two figures that bracket it are 33,943 in late June and about 34,000 in mid-September.

The removal curve flattened as the accessible inventory ran out. What remains is the part that was never accessible, and 1,200 of those modules caught fire without anyone touching them, twenty months after the original incident.

What the codes cover. The performance requirements that make up NFPA 855 govern a system that exists in one piece. The 2026 edition broadens the hazard mitigation analysis requirement across most installations, adds large-scale fire testing provisions, and tightens explosion control: deflagration venting designed to NFPA 68 is no longer accepted as a standalone primary explosion control strategy, with installations directed instead toward an NFPA 69 combustible concentration reduction system holding flammable gas below 25 percent of its lower flammable limit, or toward a performance-based alternative supported by installation-level testing. Each of those provisions describes an installed, assembled, operating configuration.

The test stack runs the same direction. UL 9540A characterizes thermal runaway at the cell, module, unit, and installation levels, and the sixth edition published March 13, 2026 folded a large-scale fire test into Section 10 to align with what NFPA 855 now expects, with the scenarios in NFPA 855’s Annex G.11 centering on fire spreading from one BESS unit to an adjacent one. Every one of those levels examines a new system, correctly assembled, at a defined state of charge, with its battery management and suppression architecture intact.

Where the analysis goes from here. What follows is interpretation rather than reporting. Damaged modules holding residual charge inside a partially demolished building, for a period bounded by nothing more specific than a contractor’s stated hope to finish this year, do not correspond to any configuration the published test methods above are written to characterize.

The certification file a developer hands to a plan examiner, an underwriter, or a building owner answers a question about commissioning. It carries cell-level propagation data, unit-level test results, and now unit-to-unit spread data. That file speaks to the asset as installed, and the Moss Landing record now supplies a reference figure for the period after a failure: roughly twelve months of federally supervised removal work, a missed internal deadline, a decaying removal rate, and a self-ignition event with about 5,000 modules still on site.

The practical consequence lands on insurers first. Carriers underwriting battery installations price the loss event. The Moss Landing sequence adds a second exposure behind it, running for years, supervised by a federal agency, with no source naming a date the operator is held to or a penalty for missing one.

Fire officials and building departments will reach the same question by a different route. An authority having jurisdiction reviewing an indoor installation asks what happens when a unit fails. On the Moss Landing evidence, the answer now extends across the twenty months afterward, and the published test stack does not address that span.

The distinctions that survive. The chemistry and configuration arguments against reading Moss Landing across to building-scale storage are real. NMC racks packed wall to wall in a converted turbine hall behave nothing like certified discrete LFP units in an electrical room, and the January 2025 design predates the installation-level test expectations now written into both NFPA 855 and UL 9540A.

Those distinctions apply to ignition. They apply less cleanly to what happens after, because the removal problem at Moss Landing is a function of access and residual charge, and both of those exist in any damaged lithium installation regardless of chemistry or format.

PG&E’s adjacent Elkhorn battery, which did not burn in either fire, has been offline since January 2025 and is scheduled to return to service on July 1, 2027. That is the same date California begins enforcing the 2026 edition of NFPA 855.

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