Ground Engineering has extensive experience in the design and execution of both single purpose and combined geotechnical and geoenvironmental ground investigations. The extent of individual projects undertaken ranges from a single trial pit, to complex multi-phased investigations utilising conventional and innovative techniques on both greenfield and brownfield sites. The use of in-house drilling, engineering testing and analytical resources as part of the investigation process enables Ground Engineering to offer a comprehensive 'one stop shop' solution to clients. Investigation capabilities include:
Ground Engineering is also able to coordinate the specialist services of other subcontractors and providers within its ground investigation services (eg. geophysical logging, GPR, unexploded ordnance surveys, pressuremeter testing).
In many cases, ground investigations are designed by Ground Engineering and are based on the initial Phase I Desk Study previously undertaken, though Ground Engineering is also regularly commissioned to undertake investigation works by other consultants and specialists to their specifications, using its in-house drilling and testing resources.
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.
The photograph below shows a rig in use, the equipment required and the relatively remote nature of the pipeline
Contaminated Land Case Study
Ground Engineering was appointed to undertake a desk study and ground investigation at a former transformer manufacturing works, prior to the client’s proposed purchase of the property in order to identify potential risks and liability.
Historical research indicated that the site was first developed in 1916 as a transformer works, with subsequent expansion in the 1920s and 1930s. It was established, via reference to bomb damage plans and local knowledge, that the factory remained for the most part unscathed during World War II, with the exception of a ‘flying bomb’ which hit the gatehouse in 1944. In the 1960s a 25m high factory warehouse was constructed to house crane lifting gear used to enable the final assembly of large transformers which were subsequently lowered into a 12m long by 6m wide and 7m deep vacuum vessel used as the final part of the drying process prior to oil filling and sealing.
A site walkover survey was carried out as part of the desk study, in advance of the site work, to aid the design of the intrusive investigation.
The transformer works was sub-divided into a number of different areas used for different processes. There were about nine areas within the site which were identified as having been used for the storage of fuel/oil, including transformer oil which was used extensively within the manufacturing process. Two extensive mass concrete underground air raid shelters were also identified within the works, together with several deep underground chambers.
Intrusive ground investigation works comprised thirty-three machine excavated trial pits, twenty driven continuous sampling boreholes and five cable percussion boreholes which enabled access to all areas of the site. The exploratory holes were focused on known sources of fuel/oil storage locations and were located at 20m to 30m centres, to provide an overall coverage of the site.
Following the fieldwork, site specific laboratory chemical analysis was conducted on recovered soil and groundwater samples and an interpretative report provided including an assessment of the likely risk of ground contamination being present beneath the site. Assessment of the potential linkage between ground contamination sources, human and environmental receptors was also presented in the form of a conceptual model in accordance with UK Government guidance.
On the basis of the desk study and ground investigation works undertaken, the client was able to proceed with the site purchase with a fuller understanding of the liabilities associated with the underlying ground conditions.