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Characterizing Storm Water Runoff from Natural Gas Well Sites in North-Central Texas Paul F. Hudak and David J. Wachal Department of Geography University of North Texas. Introduction * Annually , 30,000+ natural gas wells drilled in U.S.
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Characterizing Storm Water Runoff from Natural Gas Well Sites in North-Central Texas Paul F. Hudak and David J. Wachal Department of Geography University of North Texas
Introduction *Annually, 30,000+ natural gas wells drilled in U.S. * Potentially adverse to surface water quality (sediment, hydrocarbons, metals) * However, few studies have been conducted
Introduction (continued) *The objective of this proposal is to characterize storm water runoff from natural gas well sites in north-central Texas
Background *Adverse effects of “typical” construction activity well known - Regulated by National Pollutant Discharge Elimination System (NPDES), requiring erosion control, storm water pollution prevention plans, site monitoring
Background (continued) *Adverse effects of gas well construction not well known -Oil and gas field operations exempt from federal NPDES permitting requirements
Methods * Collect storm water runoff from 3 natural gas well sites, 2 undisturbed reference sites in southwest Denton County - Grand Prairie, montmorilloniticclays - Average annual rainfall 99 cm, thunderstorms common * ISCO flow-interval samplers: Up to 18 discrete 1000 ml samples * 40 runoff events (total) at gas well sites, 10 at reference sites, over a two-year period
Methods (continued) • * Collect during rain events • * Metals, petroleum hydrocarbons, sediment • - Nonparametric statistics to compare differences • between gas well, reference sites • - Estimate annual sediment yields
Methods (continued) Analytical Methods and Detection Limits
Example Statistical Procedure (Preliminary Results): WilcoxonRank-Sum and Ratio of Median EMCs
Methods (continued) * Also compare observations to drinking water standards and aquatic life criteria (the level of a pollutant or other measurable parameter that allows for protection of aquatic life)
Conclusion and Expected Benefits • * Study will show which pollutants are higher at gas drilling • sites compared to other construction sites • * Helps inform monitoring strategies • *Is beneficial to academic community, drillers, • and regulatory agencies
Conclusion and Expected Benefits (continued) * If pollutant levels are similar to, or higher than, other construction sites, this may signal a need for also regulating gas well sites * Future work could focus on best management practices for reducing pollutants from gas well sites similar to construction sites (regulated under NPDES)