Tests of a city well show levels of a cancer-causing solvent that exceed federal standards.
There is no immediate health risk, water officials said Wednesday. But the well is only a few blocks west of a private community well that was shut down in 1992 after higher levels of the same chemical were found.
“We’re not alarmed or overly excited; we’re just cautiously following it,” said Jim Markley, city water superintendent.
A June 2 test of the city’s Hanley Street well - one of five that supply the city’s water - showed 5.2 parts per billion of the chemical trichloroethylene, or TCE, commonly used as a de-greaser, Markley said. The well would violate federal regulations if levels break 5 parts per billion in four successive quarterly tests.
Trace amounts have been found in the well before - but never at this level.
TCE causes cancer in laboratory animals and is listed by the U.S. Environmental Protection Agency as a “probable human carcinogen.”
“Health risks come with lifetime exposure at a given level, but we’ll never get to that level,” Markley said.
The city will test ground water that feeds the well every two weeks. If concentrations stay the same or increase, the 4-year-old well could be shut down.
The well was drilled in late 1990 for about $500,000. It pumps about 3,400 gallons per minute and combines with the city’s other wells to provide residents with water, Markley said.
The source of contamination is unclear. Water experts investigated the area in 1990 after traces of the same compound were found in the Sunrise Terrace community well just east of the Hanley well.
By 1992, those traces had risen to more than five times what’s allowed under federal law. The well eventually was shut down.
Mark Ader, of the EPA in Seattle, said only one of 24 potential sources he has investigated may have contributed to the problem.
Soil and ground-water tests last year near Deming Industries - a company that anodizes aluminum - showed TCE levels 120 to 300 times higher than allowed in drinking water, he said.
While state officials have been working with the company to reduce any disposal of the de-greaser, Ader pointed out that significant quantities of the chemical were found in the ground water upstream from the company.
That could mean there are other sources or it could be the result of the chemical seeping upstream, he said.
Steve Tanner, with Idaho’s Division of Environmental Quality, said monitoring the problem is all that can be done.
“It may get worse; it may not,” he said. “We just don’t know.”
, DataTimes ILLUSTRATION: Map: Contaminated well site