Risk of Catastrophic Blast 'Off the Table' at California Plant

The risk of a catastrophic explosion of a damaged chemical tank in Southern California has been eliminated following a close overnight inspection that confirmed a crack in the tank relieved pressure and cooled the chemical, authorities said Monday. Officials said crews conducted tank temperature checks at night to reduce risks to firefighters, avoiding daytime operations when heat from the tank made conditions around it most dangerous. The overnight mission allowed crews to verify the crack and confirm temperatures were falling, Orange County Fire Authority division chief Craig Covey said Monday morning.

• Covey said the results of overnight evaluation of the tank—that the temperature inside had dropped and that pressure had lowered—was "incredibly positive news," the AP reports. However, evacuation orders remained in place for about 50,000 people in Garden Grove, California, located south of Los Angeles.

• Covey said falling temperatures and the release of pressure from the tank were allowing officials to "turn the corner on this incident" after days of concern about a possible explosion.
• The Orange County Fire Authority said Monday that the threat of a BLEVE—Boiling Liquid Expanding Vapor Explosion—"is now off the table," ABC7 reports. Residents have been asked to remain away from the evacuation zone for now.
• After the tank overheated on Thursday and began venting vapors, firefighters have repeatedly sprayed the tank with water in an attempt to cool the chemical inside, methyl methacrylate, which is used to make plastic parts.
• The tank's interior reached 100 degrees Sunday, an increase of 10 degrees Fahrenheit since Saturday, according to Democratic state Sen. Tom Umberg. On Monday, Covey said the temperature fell to 93 degrees.

• As the interior temperature rises, methyl methacrylate converts from a liquid to a gas and increases the pressure, according to Purdue University engineering professor Andrew Whelton, who had said earlier that the crack could mean product or pressure is being released, reducing the chance of explosion. "Think of a soda can. If you leave it in a hot car it can explode," Whelton says. But if you put a hole in the can, the product is released and the can itself doesn't explode."
• Aerial photos taken by the AP showed streets in the area were empty Sunday, while several evacuation shelters were open. At a high school in neighboring La Palma, people slept in cars or on mats and sleeping bags on the asphalt. Garden Grove is next to Anaheim, home to Disneyland's two theme parks, which were not under evacuation orders. Park officials said they were monitoring the situation