Clancy, a small unincorporated town in Montana, is situated 11 miles southwest of Helena at the confluence of Clancy and Prickly Pear Creeks. Currently Clancy residences have only on-site drinking water wells and septic systems. Drinking water testing in 2012 and 2017 found nitrate levels exceeded the Environmental Protection Agency's (EPA) maximum contaminant level (MCL) of 10 mg/L in some of the residential drinking water wells. Elevated nitrate levels can cause a significant health concern for infants due to methemoglobinemia (Blue Baby Syndrome).

Due to the continued detection of elevated nitrate levels in Clancy's on--site drinking water wells further research into the drinking water quality by the Jefferson County Health Department and Montana Tech Environmental Engineering Department was conducted from February to December 2017. Six water sampling events were conducted on thirty drinking water wells spread over the community of Clancy.

The investigative study objectives were to: 1) Determine if drinking water contaminants are associated with on-site-septic systems, 2) Determine Clancy's groundwater flow, 3) Determine if nutrient rich groundwater is contaminating Clancy and Prickly Pear Creeks, and 4) Assess the effectiveness of septic effluent identifiers. Drinking water wells were sampled and analyzed for nitrate, chloride, specific conductivity, ammonia, pH, total coliform, Escherichia coli, and radon-222, uranium, and delta 15N/ delta 8O isotopes.

Results from the study found nitrate levels to exceed the Environmental Protection Agency's MCL of 10 mg/L in 18 % of drinking wells. Uranium levels were found to exceed the EPA's MCL of 30 mug/L in 37% of Clancy's drinking water wells analyzed in the study. With the information provided from the water quality study the Clancy Water and Sewer District is pursuing the development of a centralized water system for the community.

Many smaller rural communities with on-site septic systems and drinking water wells, over time could likely encounter contamination of drinking water by septic effluent. Methods used in analysis of Clancy's drinking water quality may be applied to economically identifying septic effluent contamination affecting drinking water wells in other rural communities.