Low levels of compound found in 42 wells

Nearly all of the 42 drinking-water samples taken in December from wells near a former U.S. military Nike missile battery in the Deep Creek area west of Spokane tested positive for low levels of perchlorate, the U.S. Environmental Protection Agency said Thursday.

Two other contaminants found in previous sampling weren’t found in the lastest round of tests.

While there is no federal drinking water standard for perchlorate, a salt found in rocket fuels, the EPA said the tests show the water does not pose an immediate health threat.

Therefore, the agency is not recommending filtering or other treatment.

At higher levels, perchlorate can disrupt thyroid function and has been linked to some cancers.

Since 2004, when the EPA first discovered trichloroethylene, or TCE, in a well that once served Nike Missile Battery 87 in the 1950s and ‘60s, the agency has taken 212 samples from 134 wells in a 35-square-mile area near Deep Creek.

In the earlier sampling, TCE, a degreaser once commonly used by the military, was found above the federal maximum contaminant level at three wells. The solvent has been linked to liver, kidney and lung cancer.

N-nitrosodimethylamine, or NDMA, a rocket fuel igniter, has been found in most of the earlier samples at very low levels.

NDMA, which also is found in chlorinated waste water, has been linked to cancer.

EPA project manager Calvin Terada called the fact that neither TCE nor NDMA was found in the latest sampling “surprising good news.”

Though the perchlorate and NDMA had been found in the same geographic area as TCE, Terada said, it has become apparent that they are likely from different sources.

“We know that the TCE is moving to the southeast, and we have wells down-gradient,” Terada said. “We need to do more work to determine how big the plume is and lay out a sampling plan.”

The U.S. Army Corps of Engineers, which is responsible for environmental cleanup at former defense sites, has said that there is insufficient evidence to link the contamination to the Nike site.

The corps is investigating past practices by the military and others that could have resulted in contamination.

The EPA expects the corps’ review to be complete by the end of the month.