TOXIC LEAK IN O.C. PROMPTS THOUSANDS TO FLEE

Chemical tank at aerospace firm is expected to fail or explode, officials say.

- SALVADOR HERNANDEZ, CLARA HARTER, TONY BRISCOE AND RONG-GONG LIN II

ALLEN J. SCHABEN Los Angeles Times VICTOR ROMERO of Stanton with daughter Victoria at an evacuation site.

A leaking chemical tank at an aerospace firm is going to fail or explode in an “unprecedented” event that saw officials order thousands of Orange County residents to evacuate parts of six cities until it happens, authorities announced Friday afternoon.

“At that point, we know the tank is going into thermal runaway,” Orange County Fire Authority Division Chief Craig Covey said during a news conference Friday. “And we're going to pull everybody out of the area, make sure it’s safe and let the tank do what it’s going to do.”

The fire authority's hazardous materials response team began dousing the tanks at a Garden Grove facility Thursday, prompting an initial evacuation order that was lifted later that day. But on Friday morning, officials said a faulty valve and the inability to remove and neutralize the toxic chemical inside the tank had escalated the incident and left them certain that the large tank would, at some point, either fail, leaking thousands of gallons, or explode.

“People need to get out of their houses and get into a safe space,” Covey said.

Evacuations around the failing tank in Garden Grove expanded to include tens of thousands of residents in six Orange County cities: Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster.

The tank, holding about 6,000 to 7,000 gallons of highly toxic methyl methacrylate, or MMA, was described as being “in crisis” Friday.

“There are literally two options left remaining,” Covey said. “The tank fails and spills a total of about [6,000] to 7,000 gallons of very bad chemicals into the parking lot in that area. Or, two, the tank goes into a thermal runaway and blows up, affecting the tanks around them that have fuel or chemicals in them as well.”