CHEYENNE — The U.S. Army Corps of Engineers will honor a state request to temporarily halt the cleanup of groundwater contamination at an abandoned Atlas missile site west of Cheyenne.
The Wyoming Department of Environmental Quality called for the timeout pending the collection of data to determine the exact location and movement of the underground contamination plume, which some people fear threatens the city’s water supply.
Kevin Frederick is the director of the DEQ’s Water Quality Division. He said the agency met with corps officials at least a year ago to express concerns about how the corps proposed to deal with the pollution.
“They seemed to us to be intent on finalizing a remedy that involved installing a hydraulic interceptor series of pumping wells roughly in the middle of the groundwater plume,” Frederick said.
The intercept would be located about halfway between the former missile site and the city of Cheyenne’s municipal well field.
DEQ officials, Frederick said, weren’t convinced the corps had enough understanding of the geology in the interceptor trench to support the system.
“For lack of a better word, we probably reached an impasse,” he said.
Jeff Skog is the project director for the Army Corps of Engineers. He said the corps hired a contractor last month to collect data east of the known contamination area.
The data collection project will take a couple of years, he said. Then the corps will develop a GIS database and maps.
The corps also will continue its long-term monitoring work on wells in the area and perform additional delineation in the area of a proposed intercept system.
But it will not conduct a feasibility study nor take any remedial action, he said.
The corps has been monitoring wells in the affected area since the early 2000s after techlorethylene (TCE) was found in the groundwater at F.E. Warren Air Force Base’s former Atlas Missile Site No. 4. The site closed in 1964.
The corps has spent about $18 million on the project to date, including the $5 million cost of the Sherard water treatment plant.
Frederick said the DEQ believes the corps needs to do a better job of identifying where the TCE plume is, not only laterally or horizontally, but how deep it is in the Ogallala Formation.
Although the corps collected a lot of data over the years, it wasn’t in manageable form, he said.
“Our recommendation was to hire a contractor to pull the information together and interpret it and come back to us and tell us all about the plume,” Frederick said. “We felt that until we had that information we didn’t have any comfort about them proposing to us how to deal with it.”
The department also sent a letter to the corps asking for a meeting to discuss the idea of treating the source area at the missile site.
“We also are concerned that, at least in our opinion, the eastern edge of the plume hadn’t been determined or delineated,” he said.
Cheyenne residents who comprise the remediation project’s Restoration Advisory Board worry that the location of the eastern edge of the plume could endanger the city’s water supply.
They want to determine the location of the contaminated plume.
“We know it’s very close to town, within a mile or two,” board chairman George Halyak said.
The advisory board has been involved for the past two years.
From the beginning, Halyak said, the corps has been interested only in an interceptor system to filter and clean the plume of water from the missile site. Corps officials say the interceptor system has worked well elsewhere.
But the state and the advisory group wanted the corps to look at a soil vapor extraction system closer to the source of the contamination to remove subsurface contamination.
During a public meeting with the corps in 2011, a former missile mechanic, Jim Widler, said workers used cheesecloth and TCE to clean the insides of the missiles’ steel tanks.
The solvent was also used to flush the missiles’ engines. The chemical then would drain through a hole in the floor to a “flame bucket,” which crews flushed with a fire hose, Widler said.
The solvent can cause liver damage and cancer if ingested.
State and federal officials have said there is currently no public health problem from the plume.