Water from shallow wells in the Helena Valley remains relatively free of pesticides and nitrates, according to a new study published by the Montana Department of Agriculture.

Staff from the department's Groundwater Program collected 13 water samples from seven monitoring wells during 2005 and 2006. A laboratory tested the samples for nitrates and a battery of 102 pesticide compounds. None of the contaminants exceeded safe drinking water standards, and all of the pesticides detected were at extremely low levels, below one part per billion.

The testing is part of an ongoing effort to monitor well water for pesticides and other contaminants and to initiate education and corrective measures, where necessary, before water quality is impaired, says Nancy K. Peterson, director of the Montana Department of Agriculture.

Advances in technology, permitting detection of pesticides and their breakdown products at concentrations as low as one part per trillion, have enhanced the ability of scientists to detect pesticides in groundwater. Detections at the levels observed do not indicate a health risk, Peterson notes. The pesticides detected by the department have been found throughout the United States in areas near homes, farms and industrial sites.

The department's Analytical Laboratory in Bozeman implemented new procedures for measuring pesticide residues in 2005. The lab also tests regional water samples for the USDA Pesticide Data Program. The new tools provide more meaningful information for tracking residues over time, and for earlier detection of contaminants, says Heidi Hickes, Analytical Laboratory Bureau chief.

In the Helena Valley, the general-use herbicide 2,4-D was detected in two water samples but at levels too low to accurately measure under current laboratory standards. Prometon, a soil sterilant used to control vegetation around buildings, industrial sites and highway signs, was found at low levels in three monitoring wells.

Deethyl atrazine was detected at extremely low levels in nine of the water samples. Groundwater Program Manager Amy Bamber notes that atrazine and its associated breakdown products are found in groundwater throughout the United States. The EPA has cancelled most uses of the herbicide.

Other herbicides detected at low levels in one or more of the samples were chlopyralid, picloram and tebuthiuron. No insecticides or fungicides were found in any of the samples.

Similar groundwater studies are planned for the Gallatin and Missoula valleys. A copy of the Helena Valley report can be obtained from the department's website at: http://agr.mt.gov/pestfert/groundwater/reports.asp. For more information about the program, contact Bamber at (406) 444-5400 or by e-mail at [email protected].