RISK OF CONTAMINATION OF AQUATIC RESOURCES FROM ENERGY DEVELOPMENT IN THE WILLISTON BASIN BASED ON A SPATIAL, CHEMICAL, AND GEOPHYSICAL ASSESSMENT
PRESTON, Todd M.1, TANGEN, Brian A.2, CHESLEY-PRESTON, Tara L.3, GLEASON, Robert2, HAINES, Seth S.4, POST VAN DER BURG, Max2, SMITH, Bruce4, SOJDA, Richard S.1 and THAMKE, Joanna N.5, (1)U.S. Geological Survey, Northern Rocky Mountain Science Center, 2327 University Way, Suite 2, Bozeman, MT 59715, (2)U.S. Geological Survey, Northern Prairie Wildlife Research Center, 8711 37th Street SE, Jamestown, ND 58401-7317, (3)Montana State University, Institute of the Environment, 2327 University Way, Suite 2, Bozeman, MT 59715, (4)U.S. Geological Survey, Denver Federal Center, Bld 20, ms964, Lakewood, CO 80225, (5)U.S. Geological Survey, 3162 Bozeman Ave, Helena, MT 59601, tmpreston@usgs.gov
The Williston Basin of Montana, North Dakota, and South Dakota has been a leading domestic oil producing region for over half a century, with extensive new development associated with the Bakken Formation. Overlapping the Williston Basin is the Prairie Pothole Region (PPR), an area of abundant wetlands that provide critical habitats for breeding and migrating waterfowl and other wildlife. Energy exploration, development, and production can result in the release of saline and toxic co-produced waters. Hydraulic fracturing methods have resulted in rapid development of the extensive energy resources in the Bakken Formation and potential contamination impacts from this practice are a concern to land managers. The migration of co-produced waters may pose a serious risk to prairie wetland and stream-dependent wildlife, agricultural lands, and groundwater resources.
An interdisciplinary team of U.S. Geological Survey researchers are studying the potential environmental impacts which are based on a risk assessment of oil production to aquatic and groundwater resources. The extent of contamination in the Williston Basin is unknown, resulting in the need for spatial data on energy production infrastructure and aquatic resources. In addition, water chemistry analyses and geophysical surveys were conducted at three Waterfowl Production Areas to quantify the extent of contamination and the rate of brine plume movement in the most common geologic deposits within the PPR (till, outwash, and lacustrine deposits). We characterized and mapped subsurface brine plume migration over 1.6 km (1 mile) from the likely sources. The spatial risk assessment identified 292,745 wetlands and 7,147 km of stream reach within 1.6 km of petroleum related wells. The science team organized a decision analysis workshop attended by numerous stakeholders to establish a broad framework for evaluating the potential effects of energy development from the Bakken Formation on environmental resources. The test topic was a risk assessment for the location of reserve pits relative to wetland proximity. Our contamination risk study will assist Federal and State land and resource managers make science-based decisions for allocating limited monitoring and mitigation resources to areas of highest priority.
