Impact on surface waters 

A recent modeling study focuses on the Marcellus Shale in Pennsylvania and estimates the effect of shale gas wells and the release of treated shale gas waste by permitted treatment facilities on observed downstream concentrations of chloride (Cl-) and total suspended solids (TSS). 

Results suggest that the treatment of shale gas waste by treatment plants in a watershed raises downstream Cl- concentrations. This indicates that surface water disposal of treated waste from shale gas wells could represent a potentially important water quality burden. The presence of shale gas wells in a watershed raises downstream TSS concentrations.

According to the study, however, the particular mechanisms through which shale gas infrastructure may increase TSS in local water bodies are unclear. The authors suggest that their results could inform future voluntary measures taken by shale gas operators, and the policy approaches taken by regulators to protect surface water quality.

Contaminant travel times

In April, 2012 Tom Myers published an article in the journal ‘Groundwater’ suggesting that "… transport times [from hydraulically fractured shale to near surface aquifers] could be decreased from geologic time scales to as few as tens of years. Preferential flow through natural fractures or fracking-induced fractures could further decrease the travel times to as little as just a few years." The study was funded by two organizations opposed to gas fracking and gained some public attention. 

The paper was recently criticized in the same journal in September, 2012 by J.E. Saiers and E. Barth, who stated that “…Myers numerical model is based on a flawed conceptualization of the hydrology, and suffers from several other – mostly avoidable – deficiencies. [This would render] the model forecasts of frack-fluid transit times from the Marcellus to overlying drinking-water aquifers suspect.” Read the first page of the critique here.

In response, Myers defends his overall approach and many of his assumptions, but concedes, “…because there is little data to verify the model, it must be considered interpretative. [The] critiques do not prove the hypothesis wrong, but point to a need for more complex three-dimensional (3D) modeling and for data collection...”.

Improved simulations and additional field measurements to parameterize and calibrate models were also suggested by J.E. Saiers and E. Barth.

Safe distance between hydraulic fracturing and freshwater aquifers

In November, 2012 a research team led by scientists at Durham University, U.K., suggested that "… a minimum distance of 600 meters should be maintained between the fracture zone and an aquifer." (Davies et al. 2012: Hydraulic Fractures: How far can they go?). A comment on this article by Lacazette and Geiser (2013), adds new considerations to the debate, stemming from the results of a new tomographic fracture imaging method.

From the reply by Davies et al. (2013): "Lacazette and Geiser (2013) in their comment propose that fluid pressure pulses triggered by hydraulic fracturing, move vertical distances of about 1 km through pre-existing natural fracture systems, hundreds of meters further than the maximum propagation distance for stimulated hydraulic fractures (Fischer and Warpinski, 2011; Davies et al., 2012). [The new method is] potentially a very significant addition to existing seismic approaches used to monitor fracking operations."

Davies et al. (2013) emphasize that the key question regarding freshwater protection is whether induced fractures or natural fractures connected by induced fractures, stay open after the fracturing operation ceases, and pressure in the fluid drops. Confining stresses would cause fractures to close up, but this does not rule out permeable routes in the pre-existing natural fracture system.

Is hydraulic fracturing behind the contamination of Wyoming groundwater?

This question is still not resolved. The U.S. Environmental Protection Agency (EPA) is leading the groundwater investigation and its draft report (Dec., 2011) concludes that hydraulic fracturing operations are likely to have impacted on groundwater quality. In October, 2012, ‘Nature’ magazine published an overview on the ongoing discussion. Visit also the U.S. Environmental Protection Agency (EPA) website page on the Pavillion groundwater investigation for additional information.