The Effects of Unconventional Oil and Gas Production on Groundwater Quality
The U.S. Geological Survey (USGS) recently released a study of the effects of unconventional oil and gas production on the quality of groundwater in Arkansas, Louisiana and Texas. The study found that there is not a significant source of hydrocarbons in the drinking water supply in production areas such as the Eagle Ford (TX), Fayetteville (AR) and Haynesville (LA) shale formations, although oil and gas wells are known to produce methane and benzene.
This study is unique because it is the first to tie the presence of benzene and methane in drinking water wells to the age of the groundwater. Moreover, the USGS has pioneered techniques to determine the age of groundwater. In this regard, the USGS notes that the groundwater in the Louisiana and Texas areas entered the aquifers several thousand years ago while the Arkansas groundwater is much younger and is said to be less than 40 years old.
The study is significant because it allows scientists to determine whether the hydrocarbons were from surface or subsurface areas. In particular, USGS studied 116 domestic and public-supply wells in the three states. While methane was detected in 91 percent of the wells, 90 percent of those wells had concentrations lower than the proposed threshold of 10 milligrams per liter. Moreover, most of the methane did not originate from deep shale gas, but rather naturally occurring microbial sources. As for benzene, the hydrocarbon was detected in 8 percent of the wells, but the concentrations were far lower than the federal standard of 5 micrograms per liter.
Although the USGS' findings should bolster the efforts of energy production companies, the jury is still out since benzene and methane in drinking water pose known health risks and it will take time to completely evaluate those risks.
"Decades or longer may be needed to fully assess the effects of unconventional oil and gas production activities on the quality of groundwater used for drinking water," said Peter McMahon, USGS hydrologist and study lead.
Nonetheless, the production areas included in the study are some of the largest sources of natural gas in the country and have trillions of cubic feet of gas and unconventional production techniques like hydraulic fracturing will continue to be deployed. The question remains as to what future groundwater studies may reveal. In the meantime, understanding how to balance the demands of energy protection with protecting our natural resources requires the advice and counsel of an experienced health, safety and environmental attorney.