Ground Engineering’s Client, a major national contractor, was awarded a contract by National Grid to construct a 30km long gas pipeline across the low-lying Fen between King’s Lynn, Norfolk and Wisbech, Cambridgeshire.
Ground Engineering was instructed to undertake a ground investigation with an approximate contract value of £100,000 comprising sixty-five cable percussive boreholes along the route of the pipeline to depths of between 8.0m and 30.0m below ground level. The aim of the investigation was to determine the nature and geotechnical properties of the underlying soils in relation to the proposed route, particularly at the critical road, rail and river crossings. Following health and safety briefings and various site meetings, work was completed within seven to eight weeks using two drilling rigs and crews with an experienced supervising Engineering Geologist logging the recovered samples and organising the logistics of moving from position to position.
The locations of the boreholes, and the routes to them, were organised by land liaison officers and depended on farmers’ schedules of harvesting, ploughing and seeding. This often meant travelling long distances along rough farm tracks to move only half a mile from the previous borehole position. Following inclement weather conditions during the fieldwork and the ploughing and seeding of fields following harvest, tracking to many of the positions with normal plant became impossible. This necessitated the use of 4WD tractors and mobilisation of additional drilling resources at short notice to maintain the agreed investigation programme.
Following the fieldwork, an extensive programme of geotechnical and chemical laboratory testing was carried out at our in-house laboratories, to provide data for detailed design of the pipeline. Factual reports on the works were subsequently prepared.
