3D Groundwater Vulnerability

This report is the product of a joint British Geological Survey (BGS) – Environment Agency (EA) study to assess the vulnerability of groundwater in relation to deep sub-surface hydrocarbon activity (3D Groundwater Vulnerability) in England. Since the late 1980s, groundwater protection in England has benefited from a series of national groundwater vulnerability maps. These are now routinely used to inform decisions around allowing and/or managing activities on, or just below, the land surface that are potentially polluting. The recent increased interest in onshore exploration and exploitation of the deeper subsurface and concerns about the risk to groundwater has highlighted the fact that the existing groundwater vulnerability assessment methodology focuses solely on risks from hazards that are above the groundwater that requires protection. Plans to exploit the deep sub-surface, in particular for shale gas using hydraulic fracturing, have attracted considerable public interest and concerns over the potential for these activities to cause pollution of groundwater. It is therefore essential that in considering any proposals for use of the deep sub-surface, tools and methods for assessing groundwater vulnerability and risk are fit for purpose. Hence, the aim of this project was to develop a new vulnerability method that could address the potential risks to groundwater from activities below, or at similar depths to, groundwater systems (aquifers) that are currently used or have the potential to be used in the future. These systems are those requiring protection under current EU and UK legislation. To this end we present a methodology along with five different hydrocarbon activity case study examples from across England. The report describes how information can be compiled, interpreted and presented in order to assess the vulnerability of groundwater and an indication of the risks associated with a hydrocarbon development activity at a site. The outputs are designed for use primarily by those needing to understand better the hydrogeological context of subsurface developments, the vulnerability of groundwater and the potential risks. It is also hoped that the hydrogeological data and methodology will aid decision making and provide impartial information to inform public debate. The report is not designed to set out in a formal way how information and modelling should be used to reach regulatory decisions. A wider set of site-specific information will be required for this and this is outside the scope of the research presented here.