By Jon Chown
A new study, likely the first of its kind, found that the fire at the Vistra battery energy storage system plant in Moss Landing spread enough toxic heavy metals to possibly threaten the future environmental health of Elkhorn Slough, with levels of heavy metals found at some places up to 1,000 times higher than before the fire.
The study, conducted by researchers at San José State University’s Moss Landing Marine Labs, showed that the full extent of the pollution would have gone unrecognized without baseline environmental data, rapid testing and new methods of collecting data.
“It seems that if it wasn’t for our work this could have gone largely undetected,” said Dr. Ivan Aiello, who led the study. “Our data show evidence of battery fire metals up to four kilometers away from the storage facility.”
On Jan. 16, a fire destroyed about 75% of the Moss Landing plant, the largest lithium-ion BESS facility in the world. The fire burned for two days and then reignited on Feb. 18. It spread ash and soot all around Moss Landing and north into Santa Cruz County. The study looked at where the fallout occurred and how it dispersed afterward. It noted that they were only able to get an accurate picture because the scientists had collected the same data in 2023.
“Having baseline data was essential to rapidly detect the fallout of the metals and then understand how they shifted over time, both at the surface and in the shallow subsurface,” Aiello said.
What he and the team of scientists discovered was troubling. Surface concentrations of nickel, manganese and cobalt increased dramatically — in some areas as much as 10 to 1,000 times above pre-fire levels — with the pollution clustered in distinct hotspots. The researchers estimate that roughly 55,000 pounds of heavy-metal-laden particles fell across the slough. In the weeks after the fire, surface concentrations decreased somewhat as rainfall and tidal action redistributed the particles, but the contamination did not disappear. Metals remained present in marsh soils and sediments.
“The Moss Landing battery facility is located within a complex and vulnerable landscape. It sits adjacent to Elkhorn Slough, one of California’s largest estuaries, near the town of Moss Landing, and is surrounded by intensively farmed agricultural land. The fallout from the fire’s smoke plume raises serious concerns about contamination of soils, water, and vegetation in this region,” the study, published in Scientific Reports, said.
The study focused on Hester Marsh, located about a mile or two downwind from the facility. It is a wetland restoration area within Elkhorn Slough. Three days after the fire, when the mandatory evacuation ended, researchers went to the slough and measured the metal pollution using a portable fluorescent X-ray machine. They found a widespread, shallow layer of metal pollution on the surface of the soil that began to disperse due to rain and tides. The contamination was not spread evenly, but appeared in patchy clumps of micron-sized metallic particles consistent with lithium-ion battery cathode materials.
Another important discovery was that “the most significant contamination occurred not adjacent to the site of the fire, but several kilometers downwind.” That, noted researchers, highlights the need for evacuation protocols that use plume-dispersion models, meteorological data, and continuously monitor air quality.
“Fires at lithium-ion battery storage facilities pose emerging environmental risks that remain largely undocumented under real-world conditions,” according to the study.
Because the pollution either entered water or settled into soil rather quickly, it was critical, the researchers wrote, that the measurements were taken right away. It was even more critical that they had previously taken samples from the area that could be compared. Both practices, the study noted, should be followed in regard to future development of BESS facilities and resulting accidents.
“NMC-based batteries, when subjected to fire conditions, can emit airborne particles capable of traveling significant distances before settling onto the landscape,” the study notes. “These results emphasize the need for proactive planning, site-specific risk assessment, and rapid, multi-scale environmental monitoring in the aftermath of battery fires.”
Previous soil and water test results released by the EPA had shown some increased levels of heavy metals as far north as Watsonville, but mostly lower levels than the new study found. Researchers attributed this to the FpXRF technology. “The fallout’s thin, transient and patchy distribution would have eluded standard coring methods,” according to the study.
“Our findings provide rare real-world evidence of the environmental footprint of large-scale battery fires, underscore the value of having a baseline near industrial sites that pose contamination risks, and demonstrate the utility of FpXRF as a practical tool for rapid and spatially intensive environmental monitoring,” the study said.
The Vistra plant is currently being dismantled under the oversight of the Environmental Protection Agency. All the remaining batteries are being removed. The work began in July and is expected to continue throughout most of next year. The EPA began monitoring the air for pollutants from the fire on Jan. 16 and found no risk to public health.
Meanwhile, a proposed BESS plant outside of Watsonville has many local residents afraid of a similar disaster. Santa Cruz County Supervisors will vote on Jan. 13 on a new BESS ordinance that would appear to allow the project. Even if the county tries to stop the project, there’s a chance it could get approved by state regulators, bypassing local approval and control.
“That plant would be right near my dad’s home. I definitely don’t want it there,” said Dave Kegebein, referring to his father John Kegebein, one of Watsonville’s most beloved personalities.
Aiello said he had heard about the proposed plant, but did not know enough to comment on it specifically. “I think that newer BESS are built in smaller units, which would definitely reduce the risk of major battery fires such as in the case of the phase 1 Vistra storage facility,” he said.
However, as the study notes, accidents will certainly happen again. That’s why having a baseline to compare with, as well rapid sampling are very important.
“There are lots of details and lessons to be learned from our study, including the nature of the metal deposit — a very thin dust layer that is hard to detect with conventional sampling — and the fact that much of the signal decreased in the Elkhorn Slough wetlands after the rain and we would have missed it if not for the rapid sampling we did after the fire,” he said.