A yearlong environmental study shows low levels of chemical contamination in groundwater apparently seeping out of old storage ponds on the south end of Hill Air Force Base, according to base officials.

The chemicals are mostly solvents that haven't been used on the base since 1979 and are found in shallow groundwater not used for human consumption, according to Bob James of the Hill Directorate of Environmental Management.The study was done by a private contractor between June 1987 and June 1988 and, after extensive review, released on Friday. It is part of a long-term environmental review of all Department of Defense installations, called the Installation Restoration Program.

James said the Layton groundwater investigation was generated in November 1986 when the IRP detected pollutants in agricultural field drains south of Hill's South Gate.

"After our sampling program detected contaminants in agricultural field drains in Layton, an engineering firm was contracted to perform a detailed study of the area," said James. Hunter Environmental Science and Engineering Inc., of Denver, was hired.

Hunter's study included geological characterizations, a soil gas investigation and water sampling from field drains, monitoring wells, and storm and industrial sewers.

James said low levels of chlorinated solvents were found in monitoring wells and field drains. Contaminants were generally found in the area bordered by U-193 to the north (the portion of Hill Field Road on the base's south edge), Antelope Drive to the south, Hill Field Road to the east and 12th West to the west.

"The most common was trichloroethylene at less than 10 parts per billion in the shallow monitoring wells and up to 72 parts per billion in the field drains," James said. The drinking water standard for trichloroethylene is 5 parts per billion, but James said none of the contaminated water is used for human consumption.

The chemical hasn't been used at Hill since 1979, James said, and no residue was found in waste water in the industrial or storm sewers, leading Hunter to conclude those are not the pollutant's sources.

"The actual source was not identified, but the soil gas investigation identified the most likely source as water retention ponds at the south end of the base," said James.

A storm water retention pond between the 419th Tactical Fighter Wing aircraft parking area and Foulois Drive had received excess contaminants before 1956, and a second pond, which held industrial waste water, was closed in 1956, according to James.

Since 1956, industrial waste water has been treated at the base's industrial waste water treatment plant, James said.

The remaining retention pond now takes in only storm runoff from the base's storm drains and James said it is checked for contamination before the water is discharged off base.

"The final report recommends continued water monitoring, an investigation of possible sources of the contaminants and a more detailed assessment of risks to human health and the environment," James said. "We're currently acting or planning to act on all of these recommendations."