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<\/p>\nWith evacuation shelters reaching capacity as more than 40,000 people were asked to leave their homes, officials laboring to prevent an explosion at a crippled chemical tank in Garden Grove reported tentative progress Sunday in ending the crisis.<\/p>\n
TJ McGovern, interim fire chief for the Orange County Fire Authority, said firefighters had discovered what appeared to be a potential crack on the tank\u2019s surface that could be alleviating some of the pressure resulting from the chemical reaction inside. <\/p>\n
If they are right, it would make a catastrophic explosion or an uncontrollable leak less likely.<\/p>\n
\u201cWith this new information, it could change our trajectory and our strategy to this event,\u201d McGovern said. \u201cThis was a step in a right direction, and there\u2019s going to be a lot more coming shortly.\u201d<\/p>\n
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Enzo Soriano, 7, left, Vitto Soriano, 11, center, and Santiago Soriano, 16, right, look at their phones while camping outside the Freedom Hall shelter on Sunday in Garden Grove.<\/p>\n
(Kayla Bartkowski\/Los Angeles Times)<\/p>\n
Lee Zeldin, U.S. Environmental Protection Agency administrator, said the new development was promising. <\/p>\n
\u201cI\u2019m being told this morning that the most likely scenario is one of a low volume release, where the local authorities are going to be able to monitor, neutralize and contain the threat,\u201d he said during a Sunday morning appearance on CNN\u2018s \u201cState of the Union.\u201d<\/p>\n
McGovern gave no indication as to when the 40,000 people who had been forced from their homes \u2014 many into shelters \u2014 due to evacuation orders would be allowed to return.<\/p>\n
\u201cWe know you\u2019re out of your homes. We want to get you back,\u201d he said. \u201cBut we cannot do that until it\u2019s deemed safe.\u201d<\/p>\n
The positive note was a welcome development in a situation that has left much of Orange County on edge since Thursday. <\/p>\n
The crisis began when the Orange County Fire Authority responded to reports of a hazardous materials incident at GKN Aerospace on Western Avenue in Garden Grove. Officials found a tank containing 7,000 gallons of a toxic chemical called methyl methacrylate, or MMA, stored in liquid form that was in danger of exploding due to a buildup of pressure from a potential runaway chemical reaction. <\/p>\n
Methyl methacrylate is used to make plastics. While the polymer itself isn\u2019t toxic, its liquid MMA predecessor is. If it gets into the air, it can harm people at high concentrations and through chronic or extended exposure.<\/p>\n
The primary solution would have been to pump a neutralizing agent into the problem tank, quenching it and making it no longer explosive, but the necessary valve clogged, leaving no way to get the neutralizing agent into the tank. <\/p>\n
Officials feared that there were only two possible outcomes: a devastating explosion or a devastating leak. <\/p>\n
A crack in a tank containing a toxic chemical may not sound like a cause for hope, but Elias Picazo, an assistant professor of chemistry at USC, said it might be the best-case scenario.<\/p>\n
\u201cIf the tank is going to fail, you want it to fail through a crack rather than fail through an explosion,\u201d he said. \u201cWith a controlled leak, you can route liquid or gas out of the tank, relieving pressure and buying more time.\u201d<\/p>\n
He explained that as material leaks out of the tank, the pressure inside increases more slowly, potentially reaching a safe equilibrium. The leak also depletes the source for a chemical reaction, which is generating heat that, in turn, accelerates the reaction in a process called \u201cthermal runaway.\u201d<\/p>\n
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An aerial view shows water being sprayed on large storage tanks at the GKN Aerospace facility on Sunday in Garden Grove.<\/p>\n
(Kayla Bartkowski\/Los Angeles Times)<\/p>\n
But the situation remains uncertain, he said. Depending on the size of the crack and the speed of the chemical reaction, it\u2019s possible that the growing pressure within the tank will exceed what can be released through the crack, leading the tank to explode.<\/p>\n
\u201cIt\u2019s a positive step, but it\u2019s not over,\u201d he said of the new development.<\/p>\n
If the failing chemical tank in Orange County does explode<\/a>, the aerospace plant where it sits and dozens of homes surrounding it could suffer severe damage, according to a map released by authorities Saturday.<\/p>\n
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