Using Geoscientific Analysis and Community Engagement to Analyze Exposures to Potential Groundwater Contamination Related to Hydrocarbon Extraction in Southwestern Pennsylvania.

introductionCommunity concerns about the potential health effects of energy development have grown in recent years. This project evaluated the links between unconventional oil and gas development (UOGD) and potential water contamination in Beaver, Greene, and Washington counties of southwestern Pennsylvania (SW PA). This region, with its long history of hydrocarbon development, including coal mining and conventional oil and gas development, has many overlapping sources of potential contamination. Additionally, it is one of the most active UOGD regions globally. As the study progressed, we extended many of our statistical investigations of groundwater in SW PA to the entire state.

methodsWe used statistical analysis to isolate the influences of geogenic and anthropogenic processes on groundwater chemistry and to identify potential linkages between UOGD and water contamination using a groundwater chemistry dataset of over 7,000 samples in SW PA, each with approximately 40 reported chemical analytes. We primarily targeted contamination by salt species found in brines. We conducted six community focus groups in the tri-county region during the summers of 2022 and 2023, which helped identify areas of community concern and interpret our preliminary findings. The focus groups highlighted wastewater mismanagement as a key area of community concern, which we examined in our geoscience analysis. Where possible, we also extended our statistical analysis to the entire state (28,609 groundwater quality analyses) so we could assess the effect of different land uses and geology on water quality.

resultsAcross the SW PA region, we observe small but statistically significant increases in barium (Ba) and strontium (Sr) in groundwater within 1 km of UOGD, with higher concentrations associated with greater proximity to and density of unconventional oil and gas (UOG) wells. Statistical inferences from the groundwater data point to spills of briny wastewaters on UOG well pads as the likeliest explanation for these increases. For example, Ba and Sr have an even stronger relationship with the locations of spill-related violations at UOG well pads. We found a statistically significant increase in salt concentrations near wastewater impoundments that are no longer in operation because of reprimands by the state regulator and environmental violations. These relationships persist even after better controlling for other geogenic and anthropogenic salt sources using a fixed-effects model. The information gathered from the focus groups suggests that communities are most concerned about potential radiation exposure from UOGD wastewater management, which may increase cancer risks. The geoscientific analysis does not reveal evidence across the region of increased concentrations of species associated with radiation risks in groundwater related to UOGD. This lack of evidence is partly because few groundwater analyses measure or detect radium, the biggest source of radiation in Pennsylvania groundwater.

conclusionsOur results suggest that the statistically significant increases in salts associated with UOGD are likely due to wastewater spills or leaks from impoundments rather than hydraulic fracturing itself. Our inference that wastewater spills and leaks from impoundments are the most likely mechanism related to increases in brine concentrations aligns with community concerns about wastewater management. This research, along with other previous or ongoing studies, documents that contamination is localized in areas we refer to as "hotspots." Therefore, although geospatial analysis shows extremely small regional increases in brine salt concentrations in groundwater near UOGD, we conclude these increases are due to numerous, well-distributed spill and leak incidents across the shale play, despite their localized impact. The increases in brine salt concentrations in groundwater samples were never observed to be above contamination levels that pose risks for human health according to US Environmental Protection Agency guidelines. However, in areas with dense UOGD, our analysis indicates that some toxic species could be of local concern, given dissolved species ratios and Cl levels in the wastewaters generated through oil and gas development (known as produced water) in Pennsylvania. This result is predicated on assumptions about the average species concentrations in produced waters, the spatial density of UOG wells, and the locations of hotspots. High ionic strength wastewater released into groundwater could also induce secondary mobilization of hazardous species like radium via cation exchange. To address public concerns, additional groundwater testing, especially for radium, should be conducted in identified hotspots, near problematic impoundments, or near spills.