CHARLESTON, W.Va. (AP) -- Groundwater in West Virginia is generally of good quality but iron, manganese and radon levels are potential concerns, a recent U.S. Geological Survey study found.
The majority of raw, untreated groundwater samples analyzed by USGS scientists met primary criteria for treated drinking water.
But naturally occurring iron and manganese concentrations in more than half the samples exceeded the secondary, non-enforceable guideline for treated drinking water. Radon gas concentrations in water samples from northwest West Virginia and the Eastern Panhandle frequently exceeded the U.S. Environmental Protection Agency's proposed maximum concentration level.
Organic compounds and trace elements also exceeded criteria for drinking water criteria but the frequencies were lower than iron, manganese, and radon.
Pesticides were found in higher concentrations and most frequently in limestone areas where agriculture is concentrated.
"The variability in the quality of West Virginia's groundwater resources is most strongly affected by geology. Iron in Pennsylvanian bedrock aquifers, the presence of pesticides in limestone-dominated areas, and industrial compounds in Quaternary alluvial aquifers can all be attributed to geologic characteristics, either when the rock acts as a source of the water-quality constituent or when geologic characteristics contribute to aquifer susceptibility to contamination," the study said.
Conducted from 1999 to 2008, the study analyzed raw, untreated water samples from 300 wells located in valleys and on hilltops and hillsides. Eighty percent of the wells were public-supply wells. Researchers also analyzed data from a related monitoring network of 24 wells and springs.
Contaminants targeted by the study included metals, nutrients, volatile organic compounds, fecal indicator bacteria and radon-222. Some samples also were analyzed for pesticides or semi-volatile organic compounds.
"This report shows where groundwater contamination is most likely for a variety of substances," lead researcher Doug Chambers said in a news release. "This research is intended to help inform decisions ranging from water and land management to public health. Although this study primarily sampled public-supply wells, we would remind private well owners in West Virginia that it remains important to test their water."
The USGS said the study is the most comprehensive assessment of groundwater in West Virginia, where about 42 percent of residents rely on groundwater for their water supply.