Intact batteries at Vistra's previously burned Moss Landing Power Plant ignited a new flare-up.

It's been 20 months since a catastrophic fire ignited at Vistra Corp.'s Moss Landing Power Plant. In lithium-ion battery fires, water cannot fight thermal runaway—instead, firefighters are left to create a safe perimeter and monitor the blaze from a distance, including with the use of drones from above. In January 2025, it burned until the entire facility was destroyed. 

Cleanup is a whole other matter and that process has entered phase two. Officials from the U.S. Environmental Protection Agency who are supervising the cleanup had an emergency response plan in place and when a battery ignited at about 6:15am on Friday, Sept. 18, they activated that emergency response plan. 

"Planning for a flare-up has been a priority," Kazami Brockman, on-scene coordinator with the EPA, said in a media briefing hosted by the County of Monterey on Friday, Sept. 18. "This cleanup is very complex…While there is [cleanup] work happening, obviously there is also a chance of flare-up."

Remediation has been a slow process to handle batteries that remain energized and still hold a charge. About 100,000 batteries were on the site before the 2025 fire, which destroyed about 56,000 of them. 

Of the 44,000 batteries that remained intact, crews have so far removed about 39,000 from the site, de-energized them and removed them from the property. They estimate 5,000 such energized batteries remain (5 percent of the original pre-fire total), some of which ignited on Friday morning.

"Until we are completely able to remediate the site, we will not get to the point that there is zero risk of future flare-up," plant manager Ron George said.

The Sept. 18 fire occurred in the north wall of the Moss 300 facility. About 1,500 battery modules remained in that wall that workers had previously not been able to safely access due to concerns that the wall could potentially collapse, according to North County Fire District Interim Chief Jess Cortez.

Officials issued a shelter-in-place order at about 7:30am on Friday morning for people located within one-third of a mile of the fire. That area affects mostly the plant campus itself, and an estimated 106 residents.

(The North Monterey County Unified School District also decided to issue shelter-in-place directives for its campuses, meaning no outdoor time for students on Friday morning, outside of that radius. By noon, based on information about weather conditions and air quality, they reversed that order, allowing students outside.) 

Based on the weather conditions and air monitor information collected by the Monterey Bay Air Resources District, officials said they believe the air quality  in the region is safe. 

"We have not seen anything out of the ordinary as a result of health standards," MBARD's Air Pollution Control Officer Richard Stedman said. 

The agency installed four additional monitors around the facility, plus another two nearby at Elkhorn Elementary School and Monterey Bay Ecotours, after the 2025 blaze. The sensors look at particulate matter for evidence of smoke. (To follow live air quality updates, you can look at MBARD's website.) "We are not testing for any other chemicals, such as heavy metals, although we would expect that to be in the smoke," Stedman said. 

National Weather Service officials look at two main meteorological drivers of how the smoke may travel: the marine layer that controls the vertical spread and possible mixing higher into the atmosphere, and winds, impacting the horizontal spread. 

Dylan Flynn of the National Weather Service reported that the marine layer was about 1,700 feet deep on Friday morning, its usual depth. It is expected to compress by Sunday to about 1,000 feet, which should "limit its mixing capability in the atmosphere." As for horizontal spread due to wind, the forecast calls for moderate wind up to 15mph on Friday afternoon, higher speeds than the 5mph earlier in the day. 

Fire officials will continue monitoring the fire. "The incident is very dynamic, there could be flare-ups," Cortez said. As of about noon on Friday, he said, "At this point there is no active fire, it is hot and smoldering. It could decrease, or continue going at this point.”

Vistra's Moss 300 facility has been disconnected from the grid and the Texas-based company announced its intent to retire the site as well as the Moss 100 unit next door. No decision has yet been made on the future of the Moss 350 unit. 

The cause of the January 2025 fire remains under investigation.