U. PITTSBURGH (US) — No proof of groundwater contamination in Pennsylvania from hydrofracking doesn’t guarantee the water’s clean. More monitoring is needed to know for sure, experts say.
What to do with Marcellus Shale wastewater is one of the biggest concerns in Pennsylvania, and few published studies have evaluated wastewater effects on regional groundwater, according to a newly published review in the journal Science.
The review stresses the need for scientific data on water pollution caused by hydraulic fracturing and cites a lack of monitoring stations and confidentiality requirements for documentation as potential causes.
“Since the advent of hydraulic fracturing, more than one million treatments have been conducted with perhaps only one documented case of direct groundwater pollution resulting from the injection of chemicals,” says Radisav Vidic, lead author of the review and Chair in the Swanson School of Engineering’s Department of Civil and Environmental Engineering at the University of Pittsburgh. “There is no evidence of groundwater contamination—even if it does exist.”
Vidic cites state regulations as a possible cause.
“This gaping hole is likely there because Pennsylvania is one of only two states in the entire United States that doesn’t require monitoring for water quality in individual well supplies,” he says.
Intensive gas extraction from the Marcellus Shale began in the eastern United States in 2005, which has quickly become one of the top five unconventional gas reservoirs in the country. Previous studies have estimated this area could yield 489 trillion cubic feet of natural gas—an amount requiring high volumes of water use for what is often referred to as “slickwater fracturing.” In this method, no viscosity modifiers (thickening agents) are added to the water before being injected into wells.
“It is likely that the water needs will change from these initial projections as the industry continues to improve and implement water reuse,” says Vidic. “However, it is still necessary to develop specific policies regarding when and where water can be taken from streams to be used for fracturing.”
Vidic notes that it is well known that a large portion—nearly 90 percent—of slickwater is not recovered during the flowback period, indicating the importance of documenting potential transport pathways and the ultimate disposition of the water. In addition, “stray gas” or gas leakage is a concern for the region.
“While stray gas can be minor and easily remedied, there has been one case attributed to Marcellus shale drillings in which gas accumulation caused a private well water explosion in Pennsylvania,” says Susan Brantley, coauthor of the review and Distinguished Professor of Geosciences at the Pennsylvania State University.
“However, there is no evidence for widespread increase in methane concentration in Pennsylvania groundwater where levels are similar to those recorded in New York, which has a moratorium on large-volume hydraulic fracturing.”
“As these well fields mature and the opportunities for wastewater reuse diminishes, the need to find alternative management strategies for this wastewater will likely intensify. Now is the time to work on these issues in order to avoid an adverse environmental legacy similar to that from abandoned coal mine discharges in Pennsylvania,” Vidic says.
Source: University of Pittsburgh