HILL AIR FORCE BASE — After decades of chemical dumping at Hill Air Force Base, groundwater cleanup here is expected to be completed in 65 years.

That will make 120 years and more than a half billion dollars spent since contamination started spreading from a number of unlined chemical dumps at Hill.

Many of the chemicals are known or suspected to cause cancer. In high concentrations, nearly all of them will kill you, but according to a 2003 report from the U.S. Agency for Toxic Substances and Disease Registry, it would take much higher concentrations than what is found around Hill. Even so, Hill and its surrounding area were declared a Superfund site in 1987 and added to the U.S. Environmental Protection Agency's National Priorities List, meaning human exposure to contaminants is not under control.

The groundwater contamination spreads between 50 feet a year in Clinton and Sunset to 300 feet a year in Roy.

"We, as a corporate entity, feel terrible that we've created this kind of problem," said Bob Elliott, Hill's environmental-restoration chief.

Contaminants include trichloroethylene, or TCE, as well as chloroform, chromium, carbon tetrachloride, benzene, toluene and xylenes.

Steve Hicken, the base's remedial project manager, said, "We will be here to clean it up until it's done. It's not a short-term fix."

Assessing risks

Elliott, Hicken and Mark Loucks, the base's restoration operations program manager, stress that contaminants from the plumes are not in area drinking water because drinking water comes from reservoirs or a deep, productive aquifer known as the Delta Aquifer, which is separated from the contamination by two clay layers with another aquifer between them.

Contamination, which flows through a shallow aquifer, gets closer to the surface as topography slopes toward the Great Salt Lake.

Sometimes, as contaminants flow through the shallow aquifer, they evaporate through the soil and into homes. Some of the contaminants come up through springs.

The ATSDR report found "no apparent health hazard" for residents exposed to the chemicals through indoor air, direct contact or eating crops that absorbed contaminants. But residents expressed concern about the report's validity during its public-comment period and questioned its thin data set. They cited other studies that showed proximity to waste sites increases health risks.

The agency said it used local and national data to check contaminant levels and relied on actual chemical exposures to make conclusions, and the other studies' conclusions were coincidental.

Residents still have their doubts.