Study shows well water contamination highest near natural gas drilling

studyELEVATED levels of heavy metals have been discovered near natural gas extraction sites in the Barnett Shale area of North Texas, according to a report from the University of Texas, Arlington.
The study, An evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett Shale Formation by Brian Fontenot and Kevin Shug et al, tested 100 private water wells of varying depths during a four month period in 2011 to evaluate the levels of potential contaminants.
Arsenic, selenium, strontium and total dissolved solids were found to exceed the Environmental Protection Agency’s Drinking Water Maximum Contaminant Limit (MCL) in some samples from private water wells located within 3km of active natural gas wells.
The paper noted that many of the heavy metals occurred naturally at low levels in groundwater, but suggested that disturbances from natural gas extraction activities could cause them to occur at elevated levels.
“Arsenic concentrations in active extraction areas ranged from 2.2 [to] 161.2 [microgram per litre], with an average of 12.6 ?g/L,” the report stated.
“The maximum concentration of arsenic detected in a sample from an active extraction area was almost 18 times higher than both the maximum concentration among the non-active/ reference area samples and historical levels from this region.
“Notably, 29 of 90 water wells in active extraction areas exceeded EPA’s arsenic MCL for drinking water of 10 ?g/L.”
The study concluded that the highest concentrations of arsenic, selenium, strontium, barium and TDS were found in areas of active extraction in close proximity to natural gas wells.
“Samples that exceeded the MCL for TDS, arsenic, and selenium were located an average of 1.1km from the nearest natural gas well. Similarly, the highest values for both strontium and barium were over twice as high in areas less than
2km from the nearest natural gas well compared to more distant gas wells,” the report stated.
Methanol and ethanol were also detected in 29 per cent of samples.
In a statement, lead author Brian Fontenot explained that although the study couldn’t “conclusively identify the exact causes of elevated levels of contaminants in areas near natural gas drilling”, it did “provide a powerful argument for continued research”.
“We expect this to be the first of multiple projects that will ultimately help the scientific community, the natural gas industry, and most importantly, the public, understand the effects of natural gas drilling on water quality,” he said.
The Barnett Shale is a geological formation in the Bend Arch-Fort Worth Basin, underlying 17 counties and the city of Fort Worth. It is a tight gas reservoir that is not amenable to conventional mining. Recent improvements in hydraulic fracturing technology and horizontal drilling have rendered the shale viable for the production of commercial quantities.
An abstract of the study concluded that “the spatial patterns in … data suggest that elevated constituent levels could be due to a variety of factors including mobilisation of natural constituents, hydrogeochemical changes from lowering of the water table, or industrial accidents such as faulty gas well casings”; however the authors said that “not all gas well sites were associated with higher levels of the metals in well water”.
The researchers accepted no outside funding to ensure the integrity of the research. The team is now turning its attention to the Permian basin in West Texas, where it will establish a baseline set of data prior to gas well drilling activities there.