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In June 2011, EPA identified five retrospective case study locations to help the agency assess the potential impacts of hydraulic fracturing on drinking water resources. Retrospective case studies occur at sites where hydraulic fracturing has already occurred, and where contamination of drinking water resources has been reported.
The sites identified were selected following extensive input from stakeholders, including the public, local and state officials, industry, and environmental organizations. EPA began field work in some of the selected areas in the summer of 2011:
• Bakken Shale - Killdeer, Dunn County, North Dakota
• Barnett Shale - Wise County, Texas
• Marcellus Shale - Bradford and Susquehanna Counties, Pennsylvania
• Marcellus Shale - Washington County, Pennsylvania
• Raton Basin – Las Animas and Huerfano Counties, Colorado
Criteria for Case Study Location Selection
The sites were identified, prioritized and selected based on a rigorous set of criteria and represent a wide range of conditions and impacts that may result from hydraulic fracturing activities. These criteria included:
- proximity of population and drinking water supplies,
- evidence of impaired water quality (retrospective only),
- health and environmental concerns (retrospective only), and
- knowledge gaps that could be filled by the case study.
Sites were prioritized based on:
- geographic and geologic diversity,
- population at risk,
- site status (planned, active or completed),
- unique geological or hydrological features,
- characteristics of water resources, and
- land use.