Environmental Engineering Reference
In-Depth Information
are prohibited within SPZ1. The Environment Agency has indicated that it
will also object to any shale gas infrastructure being located in SPZ1. 41
In order for an operator to carry out an activity that may potentially impact
groundwater (surface water or habitats) they must demonstrate to the en-
vironment agencies that they have assessed the risks to groundwater as part
of the environmental permitting process. Whilst the environment agencies
already have directly applicable procedures (as they permit many other in-
dustrial activities) there are unique aspects of shale gas exploitation that
will need to be considered. This is particularly the case because the risks
to groundwater are not only from activities on (or close to) the land surface -
'top down' - but also from below - 'bottom up'. This requires a new approach
to groundwater vulnerability assessment and risk assessment. The British
Geological Survey in partnership with the Environment Agency is currently
mapping the 3D spatial relationship between shale gas source rocks and
the principal aquifers of the UK as a preliminary step in this process
(www.bgs.ac.uk/research/groundwater/shaleGas/aquifersAndShales).
7 Evidence of Shale-gas-related Groundwater Contamination
There have been only a few published peer-reviewed scientific studies that
have assessed the impact of shale gas extraction on groundwater, but the
number is increasing as concern has grown about the environmental impact
of the industry. As the United States has seen the most rapid development of
shale gas it is inevitable that the focus of most studies is here. One of the
challenges that has emerged is the fact very little, if any, baseline monitoring
took place before development, which has led to considerable uncertainty in
attributing contamination directly to shale gas as the specific cause(s). In the
UK, as development has not yet taken place, there is an opportunity to es-
tablish a pre-industry baseline and the British Geological Survey (BGS) has
initiated such a study. 6 It is expected that the industry will also be required
to undertake more localised baseline monitoring (as well as on-going
monitoring) around any exploration/production sites as a condition of their
environmental permit.
From the studies in the United States that have been published, the most
common problems appear to be related to well integrity, where poor installation
of wells and/or their degradation over time has been identified as a potential
mechanism for contamination of shallow aquifers. As described earlier, studies
of available datasets on well integrity show the extent of the problem. 46
In 2007, a well that had been drilled almost 1200 m into a tight sand
formation in Bainbridge, Ohio, was not properly completed and methane
migrated upwards to contaminate a shallow aquifer and private water sup-
ply. A build-up of methane in the basement led to an explosion which alerted
state ocials to the problem. 42
In aquifers overlying the Marcellus and Utica shale formations of north-
eastern Pennsylvania and upstate New York, Osborn et al. 43 have docu-
mented evidence for methane contamination of drinking water and
 
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