EVALUATING THE RISKS OF SURFACE SPILLS ASSOCIATED WITH UNCONVENTIONAL OIL AND GAS ACTIVITY TO GROUNDWATER RESOURCES: A MODELING STUDY FOR THE SOUTH PLATTE ALLUVIAL AQUIFER

With the rise in unconventional oil and gas development over the past decade, the public is concerned about how these stimulation, extraction, and production activities may impact groundwater resources. Although there are many possible contamination pathways, the most probable leakage pathway is through a surface spill. The purpose of this study is to conduct fate and transport simulations of accidental surface spills of chemical contaminants typically found in hydraulic fracturing fluid and produced water. Accounting for degradation, sorption processes, co-contaminant interactions, and spill statistics, we seek to understand the hydrologic and site conditions under which surface spills would pose risks to groundwater quality. This study focuses on the South Platte Alluvial Aquifer, which overlaps a zone of high-density oil and gas development in the greater Denver metro area. Results suggest that the risk of groundwater pollution, based on predicted concentration at the groundwater table, is low in most areas of the South Platte system for the contaminants investigated. However, substantial risk may exist in certain areas where the groundwater table is shallow. In addition, transport of certain contaminants is influenced by interactions with other constituents in stimulation fluids. By helping to identify locations in the Front Range of Colorado that are at risk for groundwater contamination due to a surface spill, it is our hope that this work will aid in improving best management practices so that decision-makers can be better prepared to address accidental releases in Colorado.