Characterizing anecdotal claims of groundwater contamination in shale energy basins

The increased societal monitoring of unconventional oil and gas development (UD) has brought forth tremendous scrutiny over the environmental stewardship and subsequent public health impacts of surface and sub-surface activities. Concerns over groundwater quality in shale energy basins have prompted concerned citizens into monitoring UD activities for a series of qualitative parameters, and even coordinating sampling efforts for chemical analysis. Here we present a list of analytical parameters, hierarchically structured to guide concerned citizens through an efficient and cost-effective monitoring program. Utilizing this multi-step testing regime, we assessed groundwater quality from 36 private water wells involved in 19 anecdotal claims of alleged UD-related contamination across the Barnett, Eagle Ford, Haynesville, and Marcellus Shale formations in the United States. Our analytical findings aligned with the landowners' accounts of their situation in only 5 of the 36 collected samples, with several cases revealing environmental abnormalities that were unbeknownst to the landowners but likely unrelated to UD activities. These data are some of the first to assess the relationship between landowner perception and analytical determination in a cohort of highly variable anecdotal cases of alleged groundwater contamination, revealing a notable disconnect that is likely attributable to a myriad of societal and environmental factors. The analytical modalities presented here also serve as a step-wise method in a weight of evidence approach to assess the presence or absence of anthropogenic contamination under the most variable hydrogeological conditions.