**Cross posted at Energy In Depth

Nationwide examination finds high levels of trace elements in public and private water supplies, links occurrence to natural conditions.

Critics of natural gas exploration frequently assert that natural gas production — and hydraulic fracturing in particular — contaminates private drinking water supplies. Countless times they have declared, through correlative assertions and without any meaningful investigation, that hydraulic fracturing is to blame for a wide range of contaminants discovered in wells or aquifers throughout the country.

But a decade’s long study from the U.S. Geological Survey, utilizing over 5,000 samples from public and private wells, turns this idea on its head. Specifically, the USGS’s National Water-Quality Assessment Program — the nation’s preeminent unbiased water research program — finds that about one in five (20%) water wells across the country have at least one trace element of contaminants at a level that poses a risk to human health.

The study found widespread, natural occurrences of many contaminants that drilling opponents often (erroneously) link to natural gas operations.  The researchers found that naturally-occurring levels of arsenic, manganese, and uranium were the trace elements in groundwater that most frequently exceeded Environmental Protection Agency human health benchmarks.  Of the wells surveyed, high levels of arsenic were discovered in 7%, manganese in 12%, and uranium in over 4%. Side effects of over-exposure to manganese can include tremors and postural instability, symptoms many critics often wrongly attribute to nearby gas drilling.

The USGS also discovered a very high frequency of radon (Rn) gas, which is produced by the decay of naturally-occurring uranium. From the report:

Rn occurred at concentrations greater than the U.S. Environmental Protection Agency (USEPA) proposed maximum contaminant level of 300 pCi/L in more than 65 percent of water samples, and concentrations of Rn in 2.7 percent of samples were greater than the USEPA-proposed alternate maximum contaminant level of 4,000 pCi/L.

Most of these contaminants, according to USGS, “get into the water through the natural process of rock weathering.” This is an important conclusion, as the most acute areas of contamination were found in rural areas not served by public drinking water systems. These are also the areas where a significant amount of natural gas drilling occurs.

“Trace elements could be present in water from private wells that are considered to pose a risk to human health, because they aren’t subject to regulations. In many cases people might not even know they have an issue.” – Joe Ayotte, USGS Hydrologist and Lead Author

Put differently, people could be drinking and using contaminated water for years, but once a natural gas company begins production in the area, activists begin demanding water tests to check for contamination. If any is found, the link is made between drilling and water pollution. This USGS report shows, however, that such a link may be speculative at best.

The issue of water well contamination has been contentious in recent years with outlets like the New York Times jumping headlong into specious accusations about natural gas production being linked, for example, to radioactive drinking water. Of course, testing by the Commonwealth of Pennsylvania and the state’s largest drinking water utility showed these claims to be unsupported by the facts, a conclusion reinforced by this most recent USGS study, which suggests nature, not natural gas drilling, is actually the major culprit in water contamination across the country.

The USGS does note that human activities can be contributing factors to water contamination. Still, the fact that many of the wells tested contained high levels of these trace elements without any nearby gas production suggests drawing a causal connection between drilling and water contamination could be based more on preconceived notions than on any legitimate, scientific assessment.