The Barnett Shale: From problem formulation to risk management

There is a nationwide trend to develop shale formations due to advances in horizontal drilling and hydraulic fracturing technology. The Barnett Shale in north Texas is one of the largest onshore natural gas fields in the US, and has experienced exponential growth since the 1990’s. This immense amount of well development and gas production has occurred near heavily populated, urban areas, leading to increased public concern regarding the impacts of these activities on human health and welfare. The Texas Commission on Environmental Quality (TCEQ) is charged with regulating sources of air emissions from natural gas operations (NGOs) and is in a unique position to evaluate any associated risks. The goal of this manuscript is to describe the problem formulation process used by the TCEQ to characterize risks associated with air emissions from NGOs, and the subsequent risk management strategies implemented. Details on how potential sources of risk to human health were identified and quantified are provided. Initial assessments identified volatile organic compounds (VOCs) as chemicals of concern. Over 4.7 million data points for VOCs were used in this assessment on both a short-term and long-term basis. Only three short-term samples measured VOCs above short-term health-based air monitoring comparison values (AMCVs). Several short-term samples measured VOCs above odor-based AMCVs. Long-term VOC levels were below long-term health-based AMCVs. We describe efforts to engage stakeholders early in the risk assessment process and outreach programs used. Finally, details on new rules and regulations that are being used to more efficiently manage risks are provided. Given the resources and experience TCEQ possesses to evaluate environmental impacts that may be caused by shale gas development and production, it is our hope that this manuscript may serve as a resource to others to identify and manage risks associated with oil and gas activities in their area.