Hill Air Force Base officials say dangerous levels of a toxic solvent have been found in water seepage north of the base's landfills Nos. 1 and 2 near the Weber-Davis county line.
However, Hill officials note that the seepage is not drinking water and say there is no danger of culinary water supplies being contaminated by trichloroethylene, an industrial solvent.Hill environmental engineer Allan Dalpias said a concentration of 190 parts per billion of trichloroethylene, which has been used at the base for decades, was found recently in water seeping out of the ground north of the Davis-Weber Canal.
The federal Environmental Protection Agency has set a standard of 5 parts per billion as the safe TCE level for drinking water.
Base spokesman Len Barry said research that uncovered the chemical seepage is part of the base's continuing Installation Restoration Program, a study to locate all toxic waste sources on the base and clean them up or control them.
Similar toxic findings near two other landfills on the base's southeast corner in 1986 led to expensive cleanup and control measures.
Dalpias said the base's findings are in conjunction with studies being done by the U.S. Geological Survey, which already has done water sampling at Hill and is preparing to do sampling off the base this year.
Kidd Waddell, a USGS investigator, said water samples taken in March of this year from a test well dug in 1986 on the Hill boundary found a TCE level of 1,422 parts per billion. He stressed that the water did not come from the deep underground supplies, but from a shallow well dug to monitor the water table near the surface of the ground.
Two years ago, that same well had a test level for TCE of 4,185 parts per billion, he said. Waddell said the decline in two years could be due to seasonal factors or the reduction in the flow of groundwater because of light rainfall.
Dalpias said the base environmental office's finding of TCE in water seeping out of the ground off-base means further study is needed to measure the extent of the seepage.
"We now know that it has gone beyond the base boundary, and therefore our next effort will be to identify the extent," he said.
The USGS will conduct further samplings in the next several months, Dalpias said.
Barry said TCE was used at Hill until 1979. Until 1975, he said, the base disposed of used solvents like TCE by burying them in landfills - a practice the government no longer allows.