Review of the scientific evidence to support environmental risk assessment of shale gas development in the UK.

Interest in the development of shale gas resources using hydraulic fracturing techniques is increasing worldwide despite concerns about the environmental risks associated with this activity. In the United Kingdom (UK), early attempts to hydraulically fracture a shale gas well resulted in a seismic event that led to the suspension of all hydraulic fracturing operations. In response to this occurrence, UK regulators have requested that future shale gas operations that use hydraulic fracturing should be accompanied by a high-level environmental risk assessment (ERA). Completion of an ERA can demonstrate competency, communicate understanding, and ultimately build trust that environmental risks are being managed properly, however, this assessment requires a scientific evidence base. In this paper we discuss how the ERA became a preferred assessment technique to understand the risks related to shale gas development in the UK, and how it can be used to communicate information between stakeholders. We also provide a review of the evidence base that describes the environmental risks related to shale gas operations, which could be used to support an ERA. Finally, we conclude with an update of the current environmental risks associated with shale gas development in the UK and present recommendations for further research.