For nearly a decade, natural gas drilling in Arkansas has been accused of harming the drinking water in the Fayetteville Shale play.
On Wednesday, the U.S. Geological Survey gave the industry a “not guilty” verdict.
The federal agency released a report that said no evidence of groundwater contamination caused by gas drilling in the region could be connected.
The USGS sampled water from 127 domestic water wells in Van Buren and Faulkner Counties, the heart of the drilling region.
“The study area is located in north-central Arkansas in Van Buren and Faulkner Counties; four of the sampling locations were slightly outside of these two counties but near to the county lines. The Fayetteville Shale gas-production area is approximately 2,500 square miles, and wells sampled for this study were distributed across an approximate area of 850 square miles or about one-third of the total gas-production area,” noted the report.
According to the report, natural gas drilling and production began in 2004. As of April 2012, approximately 4,000 producing gas wells had been completed in the Fayetteville Shale in Arkansas.
The surveyors were searching for unusual amounts of ions and trace metals, particularly methane and chloride concentrations which can represent the by-product of hydraulic fracking.
Fracking – the revolutionary process of pushing the gas out of the ground through horizontal drilling, water pressure and chemical combinations – has led to the drilling boom in north-central Arkansas.
The USGS said it found no indication of contamination associated with drilling in the Fayetteville Shale area.
“Major ions and trace metals additionally were lower in the data gathered for this study than in the historical analyses. Additionally, there was no statistical difference between groundwater quality for samples from 94 wells located less than 2 miles from gas-production wells and 33 wells located more than 2 miles from gas-production wells,” the report stated.
The report did note that little pre-drilling water samples existed to compare the evolution of water quality prior to the last decade. The report did analyze the chemical composition of the water compared to other regions of the country that have seen similar gas production.
“Although preproduction water-quality were lacking for the wells sampled for this study, geochemical data presented a well-defined pattern of geochemical evolution based on natural rock-water and microbially mediated processes, suggesting that the resulting water quality is derived from these natural processes with no effects from gas-production activities,” the report concluded.
The report did include several caveats, including the following: “Results from this study represent a timeframe relatively early in the gas-production life cycle, and any contaminants released during production activities may not have had sufficient time to reach the sampled wells. As such, groundwater-quality data from this study describe current conditions at the date of sampling and do not address potential legacy problems, if any should occur in the future; however, these data provide a baseline range and variation of geochemistry for groundwater in the study area, which can be used to assess future potential changes to groundwater quality in the area of gas production from the Fayetteville Shale.”
Link here to access the complete USGS report.