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source in dispute resolution; furthermore, groundwater managers need additional data on residence times and flow volumes in vari- ous aquifers. Therefore much hydrogeological research is needed to understand and safeguard the groundwater resources on which modern life and commerce in Northeastern BC will depend. This will necessitate an expanded network of monitoring wells that spatially characterize the hydraulic heads and groundwater quality, including dissolved gases and age-dating isotopes, at various depths throughout the region. By undertaking this work prior to shale gas development, it will be possible to minimize regulatory disputes that continue to affect such development in the US. Acknowledgement and Note The authors appreciate the review comments of Bernhard Mayer, Ian Clark, Ken Raven and Kevin Ronneseth on this manuscript. A version of this article with references is available from Richard Jackson PEng at rjackson@geofirma.ca. v Dr Richard Jackson PEng is a Principal with Geofirma Engineering of Ottawa and Waterloo, Ontario. He was formerly with the National Water Research Institute in Burlington, Ontario and INTERA in Austin, Texas. Alan Kohut PEng is the President of Hy-Geo Consulting in Victoria, BC. He worked for 28 years as a groundwater engineer for the BC Ministry of Water, Lands and Air Protection and was Manager of the Groundwater Section.

Furthermore, the development of groundwater monitoring networks is well understood when the sources of potential contami- nation are at ground surface, but this is not the case for poten- tial contamination from deep sources and from deep wells with multiple casings. Experience with nuclear waste disposal indicates that such monitoring will have to rely on multiple-depth monitor- ing using multi level wells resistant to brine and hydrogen sulphide corrosion and capable of groundwater sampling and hydraulic-head measurement at various depths Summary The first line of defence for protecting shallow groundwater from contamination in an area of shale gas development is the integrity of the gas well itself. A gas well with properly completed cement grouts between all casings and the adjacent formations will provide adequate protection of shallow groundwater. In addition, surface impoundments must be properly engineered to prevent seepage of brine or fracking chemicals from them. These are tasks well under- stood in modern drilling and geoenvironmental practice. If legacy wells—abandoned wells lacking proper plugging—are identified and properly sealed, and if flow systems are characterized, then buried valley and shallow bedrock aquifers should not be threatened by shale gas development in Northeastern BC. Baseline measurements of the carbon and hydrogen isotopes of methane are critical in the unambiguous identification of its

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