After three emergency calls to Moss Landing battery plants, county and state officials look to plan ahead.

At about 1:30am on Sept. 20, infrared cameras picked up on unusual heat in a Tesla megapack battery at PG&E’s Elkhorn Battery plant in Moss Landing. That signaled an alarm in PG&E’s Fresno operations center, prompting a call to 911.

Over the next few hours, firefighters waited as the one battery unit – one out of a sea of 256 Tesla battery units – smoldered and eventually burned out.

“The plant is designed to fail safely,” Tim Wisdom, a senior manager with PG&E told the Monterey County Board of Supervisors on Dec. 13 in a presentation revisiting the incident. “It did what it was designed to do.”

That idea of “failing safely” is built into battery storage facilities, part of the new landscape of renewable energy. Moss Landing is currently home to the world’s largest battery storage effort, and with three separate incidents at two plants – PG&E’s in September, and two at the adjacent Vistra site – the board invited executives from both utility companies to present on their emergency response plans.

While Tesla – which maintains the site in partnership with PG&E – is still investigating the burnt battery pack, Wisdom said it appears to be related to an equipment installation issue.

“Everything worked as planned, according to our plans and how we’d envisioned fighting a fire on this site,” said PG&E Vice President Jan Nimick. “Once you have thermal runaway and the battery is actually burning, there is no putting it out.”

The Sept. 20 fire put people on high alert, with a shelter-in-place advisory that didn’t lift until 7pm, about 18 hours after the fire began. Highway 1 was closed, leading to massive traffic backups.

One of the people stuck in traffic was State Sen. John Laird, D-Santa Cruz, who had to detour to get to Monterey County that day. And he began wondering what to do to plan better for this emerging technology. On Dec. 5, Laird introduced Senate Bill 38 to regulate battery storage facilities statewide.

PG&E is also at work on plume modeling to show what scenarios could potentially result in hazardous chemicals in the air.

Neighboring Vistra Corp., which experienced two smoke-related incidents – but no fires – has already done plume modeling in the event that all suppression measures fail and toxic materials are released. Only one scenario in their model showed hydrogen fluoride at ground level within a 1,360-foot radius, with steady winds at 15.8 mph – conditions that occur just 7 percent of the time. (Modeling for a third phase of Vistra’s plant, the largest at 350 megawatts, shows a radius of about 1,800 feet.)

The county will host a town hall meeting in January and work on a community response plan for notifications of battery-related incidents, including outreach to farmworkers who may be in nearby fields.

It’s likely that community outreach will be needed again. “I can’t give you a number for the likelihood [of a repeat] at this stage of the life of the technology,” Nimick said. “It’s not zero.”