A new technique developed to clean up hazardous-waste sites will be used to remove solvent from an important drinking-water well.

Florence Reynolds, water quality and treatment administrator for Salt Lake City's Department of Public Utilities, said Thursday an advanced oxidation treatment method will be used to remove perchloroethylene from the well in the southeastern area of the valley.This is thought to be the first time the process has been used to treat drinking water in the United States.

Perchloroethylene, or PERC, is a colorless, non-flammable liquid used mostly by the dry cleaning industry.

The Environmental Protection Agency considers it a probable human carcinogen and prohibits use of drinking water containing more than 5 parts per billion of PERC.

Sampling by Salt Lake City two years ago detected 1.8 parts per billion of the solvent in the well, and last year the levels rose to about 2.5 parts per billion. While still below EPA's limit, the increase sent city officials in search of treatment alternatives.

"We're doing this as a precautionary thing," said Reynolds. "We're not required at this point to treat it, but if we know something is out there it is our policy to take care of it."

Abandoning the well is not an option, she added, because it is the only source of water for that portion of Salt Lake County.

The treatment system will be installed in the building where the well's pumping equipment is located. It will inject small quantities of hydrogen peroxide into the water and then expose it to ultraviolet light. The resulting chemical reaction destroys PERC. Any residual hydrogen peroxide is expected to break down in the pipes.

"It won't impact the taste or odor of the water," Reynolds said.

The equipment is expected to cost about $300,000. Operating expenses are projected at about 20 cents per 1,000 gallons of water.