BOISE, Idaho (AP) -- The Environmental Protection Agency on Monday ordered a chemical company to halt toxic, explosive gases leaking from a southeastern Idaho Superfund site that toxicologists concluded were an "urgent public health hazard."
Philadelphia-based FMC Corp. operated a phosphorous production plant from 1949 to 2001 on the Eastern Michaud Flats area west of Pocatello, on the Shoshone-Bannock Indian Reservation.
Nearly a decade after FMC mothballed the operation, however, its capped ponds continue to produce phosphine gas that smells of rotten fish and can damage respiratory, nervous and gastrointestinal systems, and the heart, liver, and kidneys.
The EPA in April began investigating leaks after learning that FMC and its contractors had detected concentrations at dangerous levels, said Greg Weigel, an EPA Superfund coordinator in Idaho. A meter that measured phosphine in the air at breathing height near Pond 15S was "maxed out," though no cases of sickness or injury were reported.
"Prior to April, we had no knowledge there was a problem at Pond 15S -- or any of the other ponds," Weigel said. "If phosphine gas is being generated, it's collecting under the cap. Once it collects to a high enough concentration, it tends to find the pathway of least resistance to leak out."
FMC, where former U.S. Interior secretary and Idaho Gov. Dirk Kempthorne was once a lobbyist and is now on the board of directors, didn't immediately return a phone call Monday seeking comment.
This is just the latest challenge for FMC at its defunct elemental phosphorous plant, located about a mile from the Pocatello Airport passenger terminal and a few hundred feet south of U.S. Interstate 86.
The company experienced pond fires in the decades before its facility closed. In 1998, it paid $11.9 million -- then the largest civil penalty settlement ever under a 1976 hazardous waste law -- and had to cap the ponds. In 2006, FMC had to install a treatment system at one capped pond to remedy leaking phosphine, hydrogen sulfide and hydrogen cyanide gases.
Weigel said Monday's order is an "emergency response." Additional, longterm measures must still be developed to remedy phosphine gas welling up under the ponds' caps.
Idaho Department of Health and Welfare toxicologists, working with the federal Centers for Disease Control and Prevention in Atlanta, analyzed data from the site after the EPA requested help.
The state concluded this month that phosphine gas burping from FMC's Pond 15S between February and May posed a threat to workers cleaning up the site -- and anybody else who chanced onto this land that's been on a federal list of America's most-contaminated places since 1990.
"The phosphine gas being released from Pond 15S is an urgent public health hazard to the health of people breathing the air in the proximity of Pond 15S, including workers, visitors to the pond area and any potential trespassers in the pond area," Kai Elgethun, a Health and Welfare public health toxicologist, wrote in a June 1, 2010, letter to the EPA.
In recent weeks, FMC has installed a temporary gas extraction and treatment system.
"Phosphine levels have decreased significantly," the EPA said in a statement.
But Monday's order also requires the company to address phosphine gas releases at two other ponds.
What's more, FMC will have to extract and treat hazardous gases at any other ponds on the site, should the EPA find further measures are needed to protect human health and the environment, according to the order.