CHEYENNE, Wyoming — A new round of homeowner well testing will occur later this summer near an old nuclear missile site on the plains where the U.S. Army Corps of Engineers plans to rely on naturally present bacteria to break down a plume of groundwater pollution, Corps officials announced at a public meeting Tuesday.
To date, no residential water wells have tested positive for trichloroethylene, a chemical the U.S. Air Force used to flush out and clean the three Atlas D missiles based at the site in the early 1960s.
Samples taken from test wells suggest that remains the case. However, the last round of homeowner well testing in the area 15 miles southeast of Cheyenne occurred in 2003, said Jennifer Grimm, a Corps geologist.
"It's just time," Grimm said. "This is really just a verification that what we assume is true — that they aren't impacted — is true."
At least 10 homeowner wells could be tested. Most are down-gradient, or downstream underground, of the plume measuring roughly 1.5 miles long, half a mile wide and 200 feet deep, said Grimm.
The Corps proposes to pump vegetable oil underground to stimulate bacteria to break down the TCE — its preferred of seven courses of action it has outlined to address the problem.
"We need to give them something to eat. We need to give them vitamins," said Rob Mayer with CB&I Federal Services, a Corps contractor for the site. "It's already happening. We see the contamination, we see the breakdown points. We just want to make it happen quicker."
The project would cost at least $26 million and, over time, as much as $200 million, said Andrew Reckmeyer, district chief for the Corps' environmental restoration branch in Omaha, Nebraska.
Other options including treating the pollution with oxidizing chemicals could be even more costly.
"We looked at kind of the bang for the buck," Reckmeyer said.
No options considered would remedy the pollution in less than 200 years, and a few, such as monitoring the pollution without cleaning it up, would require more than 1,000 years for the pollution to fully dissipate. The Corps is taking public comment on its plans until Monday and will formally select its preferred action plan soon after.
The federal Centers for Disease Control links TCE — long used as a degreaser and in products ranging from plastic cement to typewriter-correction fluid — to certain kinds of cancer.
TCE concentrations beneath the Atlas D site top out at 17,000 parts per billion, more than twice as high as those in a much larger TCE plume underlying another Atlas D site west of Cheyenne. The U.S. Environmental Protection Agency's maximum contaminant level for TCE in treated municipal drinking water is 5 parts per billion.
A salvage yard now occupies the missile site, and few homes are nearby.
The site consisted of a command center and three missiles housed horizontally in concrete, coffin-style bunkers. A lid over each bunker slid sideways so the missile could be raised vertically in anticipation of launch.
After fueling exercises, the Air Force would drain the rocket fuel back into underground tanks. The missile crew then would use about 25 gallons of TCE to flush out the rocket's parts.
The used TCE wasn't recovered but dumped into the site's blast pits. The Air Force deactivated the site as it put more advanced missiles into service.
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