The state of produced water generation and risk for groundwater contamination in Weld County, Colorado.

Natural gas and oil extraction, while meeting much of our current energy demand, also generates large volumes of waste water ("produced water") that creates risks for groundwater contamination when spilled. Weld County, Colorado, where the majority of extraction occurs in Colorado, was used as a case study to understand how groundwater impacts were related to spill details including volumes spilled, area impacted, and depth to groundwater. Publically available produced water production and spill data were analyzed to determine if improvements could be made to reduce the water intensity of oil and gas drilling. The depth to groundwater significantly affected the likelihood of groundwater contamination at spill sites. Since spills often occur at oil and gas well pads, extraction site selection should preclude those areas that have shallow groundwater. Evaluation of produced water generation and produced water spilled reveal that although larger-scale operations did generate less relative produced water per energy generated, the total volume of produced water spilled by an operator was linearly correlated with the scale of the operation. These results suggest that employing fewer, large-scale operators would help to reduce the overall volume of water generated but not the overall volume spilled. The results from this research have important regulation and policy implications that can help mitigate the increased threat of groundwater contamination from produced water spills.

Phytoremediation of BTEX and Naphthalene from produced-water spill sites using Poaceae.

Surface spills of water produced from hydraulic fracturing can expose soil and groundwater to organics such as BTEX and naphthalene (BTEX&N) as well as high concentrations of salt. As an alternative to soil excavation, we evaluated the effectiveness of BTEX&N soil remediation using 2 grasses present in Colorado. Perennial ryegrass and foxtail barley were grown separately in pots in the greenhouse and exposed to salt or a synthesized produced-water slurry containing relevant levels of salt and BTEX&N. Plant biomass was measured 14 days post-spill, and levels of BTEX&N were quantified using GC/MS for soil, roots, and shoots at day 7 and 14 post-spill. Foxtail barley shoot growth was limited by BTEX&N, whereas perennial ryegrass shoot growth was enhanced by salt but not BTEX&N. While BTEX&N in soil associated with foxtail barley mainly decreased over time, the soil associated with perennial ryegrass mainly saw an increase in BTEX&N with time. However, further research is needed to determine the fate of BTEX&N within grasses and soil.