Moss Landing battery plant fire continues to smolder

(BCN) -- A fire at one of the world's largest battery storage facilities continued smoking Saturday in Moss Landing but Monterey County officials said air quality sensors found no risk to residents.

Lithium-ion batteries at the Vistra Energy facility that caught fire Thursday continued to burn out but could still reignite, officials said. There was no estimate on how long the fire would last, and the cause was still unknown.  

North County Fire Protection District Chief Joel Mendoza said about 80% of the structure and its batteries were destroyed in the fire.  

A representative for the U.S. Environmental Protection Agency said nine air quality sensors had been set up both within the perimeter of the facility and in the surrounding community. The Monterey Bay Air Resources District said there was no concentration above normal air quality conditions.  

The EPA representative, Olivia Trombadore, said instruments hadn't detected hydrocarbon fluoride gas, which is a primary concern when lithium-ion batteries catch fire.  

The cause was still unknown on Saturday afternoon, including why the plant's internal fire suppression system failed.  

It was unclear whether a phenomenon known as "thermal runaway" may have been involved, as can happen when lithium-ion batteries overheat.  

According to the peer reviewed journal Scientific Reports, "an irreversible thermal event in a lithium-ion battery can be initiated in several ways, by spontaneous internal or external short-circuit, overcharging, external heating or fire, mechanical abuse etc."  

The Moss Landing plant is operated by Texas-based Vistra Corp., which has seen its stock price soar in the last year from about $39 to about $171 at the close of trading on Friday.  

While evacuation orders were lifted, state Highway 1 remained closed in both directions at the plant, housed in a former PG&E power plant in an ecologically sensitive area known as Elkhorn Slough. Several other surrounding roads remain closed, including Dolan, Elkhorn and Hidden Valley roads.  

The Monterey County Sheriff's Office said in a Facebook post at about 3 p.m. that residents would be allowed to access the road closures operated by the county.  

PG&E also has its own battery storage facility at the site that is still online. Local elected officials including county Supervisor Glenn Church said he was urging Vistra to keep its facility offline until the cause of the fire is known and more prevention is put in place.  

Evacuations were lifted on Friday evening after about 1,200 people were told to leave the area because of concerns about air quality.  

A company official, Brad Watson, reiterated the company's apology to the community and said the company was trying to determine what caused the failure. He was noncommittal on ongoing operations, responding to a reporter's question about remaining offline by saying that the company was focused on the present situation.