Surface Operations, Not Wells, Account for Compound Count

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A Yale University-led investigation found no evidence that trace organic compound contamination in drinking water wells near the Marcellus Shale in northeastern Pennsylvania came from deep hydraulic fracturing, underground storage tanks, well casing failures, or surface waste containment points. Rather, the presence of organic compounds in groundwater aquifers overlying the Marcellus is likely the result of surface releases from hydraulic fracturing operations, not migration from gas wells or deep shale layers. The Yale researchers’ work was published in the journal Proceedings of the National Academy of Sciences.

During recent rapid natural gas well expansion, the researchers regularly visited the northeastern region of Pennsylvania, covering nearly 3000 square miles over three years and obtaining 64 samples from drinking water wells on residential properties. Using a suite of chemical analyses, the researchers found that a subset of the groundwater samples contained low levels of organic compounds in areas close to natural gas wells. The analyses also indicated that the compounds most likely entered the groundwater supply from gas extraction operations above the ground surface—and not subsurface migration.

A compound-specific analysis also revealed the presence of a hydraulic fracturing fluid additive in the affected water samples. Chemicals found in the water did not exceed any state or federal limits, and many were detected only because the researchers were using sophisticated and sensitive instruments. None of the contaminants were derived from the shale itself.

The researchers comment that the results are encouraging, since surface violations are known entities and the drinking water sources that have been affected by surface spills can be targeted for monitoring and treatment. They add that the study results should not be used to draw conclusions about the effects of hydraulic fracturing in other regions.

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