Evacuation order over California chemical tank threat lifted

    Garden Grove, May 27 (AP) Officials say they are lifting evacuation orders for final 16,000 residents near a damaged chemical tank in California.
     They had said earlier that the risk of a catastrophic explosion had largely passed.
     Evacuations had been ordered in Garden Grove near Los Angeles last Thursday after the tank at an aerospace plant overheated.
     The tank contains methyl methacrylate, which is highly flammable. Health officials have assured residents that there was no contamination or fumes released. Officials say they will keep monitoring the air for several months and checking the sewer and storm drains.
     The evacuation order for 34,000 residents was lifted Monday night.
     The crisis forced 50,000 people to evacuate in and around the Orange County city of Garden Grove last week. A crack that formed by chance on the tank relieved pressure and helped avert a catastrophic explosion, allowing most evacuees to return home over the Memorial Day weekend.
     But the risk of a smaller explosion or potential spill had kept orders in place for about a third of the evacuees. Many were living out of hotel rooms, tents, emergency shelters at schools or staying with family or friends.
     Isabel Mendez said she broke out in a rash on her face and developed tingling lips and a sore throat while evacuating last week. After spending several expensive nights in a hotel, she was staying with her mother in the Los Angeles area.
     Exposure to methyl methacrylate — a highly flammable chemical used to make plastics — can cause serious respiratory problems, neurological problems and irritation to the skin, eyes and throat, according to the federal Environmental Protection Agency.
     The tank at GKN Aerospace Transparency Systems, which makes cockpit windows, canopies and windshields, contains 22,700 to 26,500 litres of the chemical.
    “We apologise for the ongoing disruption this incident is causing and our priority remains its safe resolution,” the company said.
     Separately, an implosion of a chemical tank Tuesday at a pulp and paper mill in Washington state injured at least 10 people, while an undisclosed number of others had been killed or remained missing.
     Crews at the California plant worked overnight to ensure two nearby tanks were neutralised and would not be affected by the compromised tank, Orange County Fire Capt. Brian Yau said.
     The tank overheated because a valve on the cooling system failed that kept it at at 10 degrees Celsius, said Orange County Fire Authority Division Chief Craig Covey.
     Crews sprayed water on the tank until the interior temperature stabilised to 33.3 C, down from 37.7 C over the weekend, the fire department said Tuesday.
     A sprinkler system is still dousing the tank, and the company said its technical specialists and firefighters removed insulation from the tank to help cool it.
     So far testing has found no contamination, officials said.
     Orange County Health Director Regina Chinsio-Kwong tried to reassure people returning home over the holiday weekend, saying "you should feel comfortable going home even if you're across the street from that new zone line.”
    
     Environmental risks remain
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     The South Coast Air Quality Management District will monitor the air for several months and the EPA will be checking sewer and storm drains for spills, Orange County Supervisor Janet Nguyen said.
     As the tank heated up, the chemical converted from liquid to gas, ramping up the pressure and explosion risk, said Andrew Whelton, a Purdue University engineering professor who has studied environmental contamination.
     Some of the methyl methacrylate may already have hardened into a stable plastic similar to plexiglass, reducing the danger, he said.
     “The tank was on track for a catastrophic explosion,” Whelton said. “The formation of a crack seems to have allowed pressure to vent.”
     The risk remains of a smaller blast that could send projectiles or even a chemical plume toward nearby homes, he said.
     The tank needs to get closer to 15.6 to 21.1 degrees C before conditions are considered significantly safer, he said.
     The California crisis is reminiscent of a 2014 chemical spill in Charleston, West Virginia when storage tanks failed. The disaster inspired a new state law requiring more inspections and registrations of aboveground storage tanks. (AP)
    
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(This story has not been edited by THE WEEK and is auto-generated from PTI)