Identifying Potential Exposure Pathways And Estimating Risk From Marcellus Shale Gas Development

Concern over natural gas extraction across the U.S. and particularly from the Marcellus Shale formation, which underlies approximately two-thirds of the state of Pennsylvania, has been growing in recent years as natural gas drilling activity has increased. Identifying sources of concern and risk from shale gas development, particularly form the hydraulic fracturing process, is an important step in better understanding sources of uncertainty within the industry. Hydraulic fracturing is a well stimulation technique used in the production of natural gas from shale. While hydraulic fracturing has been in use for decades as a method for oil and gas recovery, recent advances in horizontal drilling techniques and fracturing fluid production have made previously unattainable natural gas reservoirs accessible and economically recoverable. In the years after hydraulic fracturing came into widespread use in Pennsylvania, a large amount of data on flowback characteristics became available due to public and regulatory attention to the process. Chapter 3 examines and analyzes the constituents that make up flowback waters collected from drilling sites in the states of Pennsylvania, New York, and West Virginia. Flowback sampling data were collected from four different sources and compiled into one database with a total of 35,000 entries. Descriptive statistical analysis revealed high concentrations of chlorinated solvents, disinfectants, dissolved metals, organic compounds, radionuclides and TDS. Relative prioritization scores were developed for 58 constituents by dividing observed mean concentrations by the Maximum Contamination Level (MCL) guidelines for drinking water. The following constituents were found to have mean concentrations over 10 times greater than the MCL: Barium, Benzene, Benzo(a)pyrene, Chloride, Dibromochloromethane, Radium, and Thallium. Regulatory inspection and violation reports also provide insight into the impact of natural gas extraction on the surrounding environment, human health, and public safety. Inspection reports for natural gas wells in Pennsylvania were collected from the Pennsylvania DEP Compliance Report from 2000 to 2014. Logistic regression analysis of 215,444 inspection records for 70,043 conventional and unconventional wells was conducted in order to compare the odds of violations occurring under different circumstances. The results in Chapter 4 revealed that, when inspected, conventional wells had 40% higher odds of having a violation, but unconventional wells had higher odds for environmental violations related to waste discharge as well as cementing and casing failures. From there, a list of twelve failure scenarios of concern was developed focusing on specific events that may occur during the shale gas extraction process involving an operational failure or a violation of regulations to identify and prioritize potential failure scenarios for natural gas drilling operations through an elicitation of people who work in the industry. Illegal dumping of flowback water, while rated as the least frequently occurring scenario, was considered the scenario least protected by safety controls and the one of most concern to the general public. In terms of worker safety, the highest concern came from improper or inadequate use of personal protective equipment. While safety guidelines appear to be highly protective regarding PPE usage, inadequate PPE is the most directly witnessed failure scenario. Spills of flowback water due to equipment failure are of concern both in regards to the welfare of the general public and worker safety as they occur more frequently than any other scenario examined in this study. In Chapter 6 of this study, the flowback data collected and the violation and failure scenario analyses conducted are used to develop potential exposure scenarios to wastewater from shale gas development. A risk assessment of occupational and residential exposure pathways to flowback water as carried out. Constituents of concern in flowback water were identified from the previous prioritization. The occupational cancer risk estimate for median concentrations did not exceed the target lifetime cancer risk of 10-6 except for benzo(a)pyrene, which exceeds the target risk level even at the 2.5 percentile value. The upper limit of cancer risk form exposure to heptachlor also exceeds 10-6 in this model. Hazard quotient for barium in the same model exceeds 1 (1.7) and results in a total hazard index of 2. The residential risk assessment revealed that several carcinogenic compounds found in flowback water exceed target limits and significantly increase the risk of an individual developing cancer following chronic exposure. In general, exposure from the dermal pathway posed the greatest risk to human health. Considering non-carcinogenic effects, only barium and thallium exceed target limits, where the ingestion pathway seems to be of greater concern than dermal exposure. Exposure to radionuclides in flowback water, particularly through the inhalation pathway as they volatilize from the water to the air, poses a greater threat to human health than other contaminants examined in this assessment.

This final report provides a review and synthesis of available scientific information concerning the relationship between hydraulic fracturing activities and drinking water resources in the United States. The report is organized around activities in the hydraulic fracturing water cycle and their potential to impact drinking water resources. The stages include: (1) acquiring water to be used for hydraulic fracturing (Water Acquisition), (2) mixing the water with chemical additives to prepare hydraulic fracturing fluids (Chemical Mixing), (3) injecting the hydraulic fracturing fluids into the production well to create fractures in the targeted production zone (Well Injection), (4) collecting the wastewater that returns through the well after injection (Produced Water Handling), and (5) managing the wastewater via disposal or reuse methods (Wastewater Disposal and Reuse). EPA found scientific evidence that hydraulic fracturing activities can impact drinking water resources under some circumstances. The report identifies certain conditions under which impacts from hydraulic fracturing activities can be more frequent or severe.

Proceedings of the 1988 International Conference on Drilling Wastes, Calgary, Alberta, Canada, 5-8 April 1988.

Whether the result of an oil well blowout, vessel collision or grounding, leaking pipeline, or other incident at sea, each marine oil spill will present unique circumstances and challenges. The oil type and properties, location, time of year, duration of spill, water depth, environmental conditions, affected biomes, potential human community impact, and available resources may vary significantly. Also, each spill may be governed by policy guidelines, such as those set forth in the National Response Plan, Regional Response Plans, or Area Contingency Plans. To respond effectively to the specific conditions presented during an oil spill, spill responders have used a variety of response optionsâ€"including mechanical recovery of oil using skimmers and booms, in situ burning of oil, monitored natural attenuation of oil, and dispersion of oil by chemical dispersants. Because each response method has advantages and disadvantages, it is important to understand specific scenarios where a net benefit may be achieved by using a particular tool or combination of tools. This report builds on two previous National Research Council reports on dispersant use to provide a current understanding of the state of science and to inform future marine oil spill response operations. The response to the 2010 Deepwater Horizon spill included an unprecedented use of dispersants via both surface application and subsea injection. The magnitude of the spill stimulated interest and funding for research on oil spill response, and dispersant use in particular. This study assesses the effects and efficacy of dispersants as an oil spill response tool and evaluates trade-offs associated with dispersant use.

As the shale revolution continues in North America, unconventional resource markets are emerging on every continent. In the next eight to ten years, more than 100,000 wells and one- to two-million hydraulic fracturing stages could be executed, resulting in close to one trillion dollars in industry spending. This growth has prompted professionals ex

The recent growth in unconventional natural gas production has also produced a profusion of publications on the exploration, development, production, infrastructure, economics, uses, and environmental impacts of these resources. This book summarises the current state of published descriptions of the potential environmental impacts of unconventional natural gas upstream operations within the Lower 48 United States. It also examines the technology, impacts and regulations of hydraulic fracturing, which is a key technique that has enabled the economic production of natural gas from shale deposits, or plays.

Written by an international team of authors from a range of educational, medical and research establishments, this book is an essential reference for advanced students and researchers in the areas of environmental sciences, ecology, agriculture, environmental health and medicine, in addition to industry and government personnel responsible for environmental regulations and directives. A Handbook of Environmental Toxicology focuses on two key aspects: human disorders and ecotoxicology as affected by major toxins originating from biological sources and pollutants, as well as radiation generated spontaneously or as a result of anthropogenic activity. A diverse array of these potentially harmful agents regularly appear in the atmosphere, soil, water and food, compromising both human health and biodiversity in natural and managed ecosystems.