The Prince William County Health Department has found traces of two potentially hazardous chemicals in one of three wells that serve Independent Hill Elementary School, which sits on a former military base.

The two chemicals, trichloroethene and tetrachloroethylene, are solvents commonly used to clean weapons, said Dr. Jared Florance, the county's health director. Both possibly cause cancer in laboratory animals, although there is no evidence they are human carcinogens, according to the Environmental Protection Agency.

The other two wells test chemical-free, Florance said.

The tricholorethene was discovered during a ground water test, conducted because authorities were concerned that underground rock cracks might be causing waste from a nearby county landfill to leak into ground water. Traces of tetrachloroethylene were found in a second test late last week.

According to EPA guidelines, allowable limits for tricholorethene and tetrachloroethylene are 75 parts per billion each. The former chemical is showing up in the well at 30 parts per billion, the latter at 6.4 parts per billion, Florance said.

County school authorities have decided to supply the school, which houses 110 handicapped students, with bottled water.

Officials are discussing this week the possibility of connecting the Independent Hill area to public water. If that proves infeasible, school spokeswoman Kristy Larson said, the water can be treated through a carbon filter.