The Natural Environment Research Council (NERC), through its centre/survey the British Geological Survey (BGS – known hereafter as “The Authority”), invites tenders for the provision of drilling and (possible) other site services to support project monitoring and research activities. The purpose of the project is to improve the understanding of movement of fluids and possible chemical changes in aquifers and overlying strata. It is planned that the work shall be carried out at one site to the south of Pickering, around Kirby Misperton, North Yorkshire. If the preferred site is not accessible to The Authority, any alternative site shall be in the area of a radius of approximately 5 miles of the above. At the site, two boreholes shall be required to provide: a. Improved understanding of the underlying geology and limestone/sandstone aquifers, b. Sample cuttings from the borehole to be sub-sampled and processed, c. Access to the underlying bedrock to enable aquifer properties to be determined by geophysical logging, packer testing, and hydrochemical analyses. d. The completed boreholes to be used as monitoring boreholes for scientific purposes. It is planned to drill the boreholes from Ground Level (GL) up to a Total Depth (TD) of approximately 250 and 370 metres (see Section 4 below and “Site Conditions”). The borehole at up to 250m depth will penetrate the Corallian limestone or Kellaways towards its base, with a 20m open hole section. The deeper up to 370m borehole will penetrate the Corallian or Kellaways Formation, below the Oxford Clay, with a 20m open hole section from approximately 10m below the Oxford Clay contact. On reaching TD they shall be reamed in the lower limestone/sandstone sections, cleaned, logged for geophysical parameters, (possibly packer-tested) and completed, all in a continuous sequence. Suitably specified permanent casing will be required to prevent collapse above the specified open hole section. The relevant competent limestone/sandstone section of the borehole may then be left as an open-hole monitoring borehole, completed (both downhole and at surface) according an agreed secure standard pattern .
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