The liquid, which the Palo Alto Fire Department has deemed to be a nonhazardous mixture of borax, lye (also called sodium hydroxide) and green dye,

One of the workers told Hedblom that the liquid was a coolant. That’s also what the fire department told the Governor’s Office of Emergency Services, which wrote in its Oct. 18 spill report that the liquid was “used for the chiller system to cool the Tesla Artificial Intelligence Supercomputer.”

“The Palo Alto Fire Department recovered approximately 550 gallons of the mixture from the storm drain,” the report said. “The incident occurred while Tesla personnel were draining the system.”

That’s quite a liquid-cooled computer that they’ve got going on.