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Today’s engineers face a range of challenges when it comes to sustainable, robust and affordable design. Projects are often developed where ground conditions are unknown or undocumented and the more extreme weather conditions due to climate change are putting assets and structures to the test. A relatively small amount of investment in ground investigation at the outset of a project can provide large savings in the long term.

In addition, protection of the environment has become increasingly important with the development of brownfield sites, changes in legislation and increased public awareness around environmental issues. Ground investigation provides a means of establishing levels and extent of contamination in the ground and enables risk assessment to be undertaken with regards to risk to human health and the environment. It is now more important than ever that accurate information is gathered to establish the cost implications and estimates for remediating sites.

Our Geo team provides integrated site investigation services, including all aspects of drilling, in-situ testing, reporting, and laboratory testing under our sister companies UKAS-accredited laboratories. Our offices in Wakefield and Bristol offer significant local resource to the North & South West of England and Wales; however, with satellite offices and support from RSK-affiliated companies scattered throughout mainland UK, we can resource and support projects nationwide. We are problem-solvers, happy to engage collaboratively with clients and support projects at the early contractor involvement stage with a best-for-project approach.

Our Geo team has grown with the business since it was founded in 2006. We are an experienced team of engineering geologists and geo-environmental engineers with a strong background in ground investigation. We operate across all sectors all over the UK which has given us a great depth of knowledge of client needs, UK ground conditions and how to deliver complex GI’s, often in challenging environments.

Central Alliance rotary ground investigation at Parsons Tunnel in Teignmouth, Devon.


We own and operate our own fleet of drilling rigs, which are continuously updated with a significant capex budget, to meet modern standards. Our experienced team of drilling crews work across all sectors get the best out of every investigation, balancing production with high quality sampling. Investment in plant and equipment allows to stay ahead of the competition, combined with our inherent desire to innovate. 

Our extensive fleet of drilling rigs include multi-purpose rotary rigs, cable percussion, dynamic sampling, and Cone Penetration Testing (CPT) rigs. In addition, we have several bespoke drilling rigs designed and built for operating on slopes and restricted access sites.


Boreholes formed by rotary drilling equipment are normally used when rock or hard ground is anticipated. Rotary techniques are used to drill through rock / solid geology.  There are two types of rotary borehole frequently used on ground investigation projects, rotary open holes and rotary cored holes.


Also referred to as “cable tool” or “shell & auger” these tripod rigs can reach significant depths but are limited to drilling through soils or weak weathered rock.  Cable percussion boreholes are used where ground conditions may be variable and when information is required at depths greater than around 6.00mbgl from the ground investigation.


Dynamic sampling rigs are a very useful tool for quick shallow unconsolidated ground investigations. Our rigs are rubber tracked, low ground pressure self-propelled units so they can access any site where shallow soft soil sampling is required.


Slope failures on linear infrastructure earthworks and on natural slopes are increasingly common due to climate change causing more extreme weather events. Site investigations are important to characterise the ground conditions in these areas of instability, allowing clients to monitor assets and enabling geotechnical engineers to design appropriate remedial measures.

Central Alliance slope solutions slope climbing rigs.
Central alliance vehicle with a helicopter used to mobilise a drilling rig in remote Scotland


The process of mobilising drilling rigs to remote regions requires a strategic approach exceeding conventional methods. Central Alliance use innovative solutions, enabling us to overcome these unique challenges associated with remote locations. To overcome the challenging terrain for Whitelaw Brae, Scotland, a helicopter lift was used. 


Machine excavated trial pits can often provide the most practical and economical method of site investigation and assessment. Trial pits allow observations on the mass characteristics of soils and is often used to obtain larger soil samples for laboratory testing, to facilitate in-situ testing and engineering logs of shallow strata which can be important when dealing with variable ground conditions.


In-situ testing is an essential part of geotechnical engineering. Measurement of parameters in-situ can have significant advantages over laboratory testing. Our engineers, technicians and drillers are skilled at using the standard in-situ testing methods, including the Standard Penetration Test (SPT), the cone penetration test (CPT), dynamic probing, Mackintosh and TRL Probes, California Bearing Ratio (CBR), Plate Bearing Test, in-situ density tests, field shear vane, permeability testing, soakaway testing, infiltration testing and Continuous Surface Wave testing.

Backed by its extensive history in the industry, our sister company CJ Associates has built a dedicated team of expert in-situ testing technicians. Our team provides an integrated service in wider site investigations to support projects by acquiring high-quality, on-site data. These services are in addition to more standard tests undertaken in exploratory holes, such as standard penetration testing, shear vanes and dynamic probing. We also acquire and test samples of fresh concrete, in addition to concrete slumps or making concrete cubes for compressive strength tests. We can provide further concrete and tarmac related services, including diamond coring with either road towable trailer mounted rigs or hand-held rig, tarmac – air voids content (non-nuclear gauge), macrotexture, texture depth and rolling-straight edge.

For any requirement to take a reading of in-situ resistance to a depth of 850mm (or deeper), we can provide the transport research laboratory, dynamic cone penetrometer, which is a non-UKAS accredited test. We can also provide continuous surface wave testing for ground stiffness profiling along with cone penetration testing.


To realise the full value of ground investigations, Measure Whilst Drilling (MWD) Systems, OR Drilling Parameter Recording (DPR) allows the capture of a vast amount of data to provide insights that may otherwise be missed using conventional drilling and logging techniques. Depth, penetration rate, rotation speed, rotation torque, head pressure, holdback pressure, pressure and flow rate of the injection fluid, inclination and reflected vibration can all be recorded.

Measure whilst drilling equipment on a Central Alliance slope climbing rig.


Our in-group laboratories can undertake a wide range of laboratory testing services with a strong emphasis on quality. We provide the full range of soil and materials testing via our laboratories across the UK. The laboratories can carry out the full suite of tests classification tests including as specified by British and ISO standards (BS, BS EN, ISO), where all tests are performed in strict accordance with set methodologies and guidelines. The laboratories also carry out International Society for Rock Mechanics rock tests and are able to test in accordance with less commonly requested ASTM International test methods. We can also work with clients to create bespoke site- or project-specific testing solutions.

  • Laboratory data deliverables includes digital data in both AGS and PDF formats.

Our sister company CJ Associates offer a range of concrete testing options. We can test the compressive strength and density of concrete cubes. We can also test the unconfined compressive strength of concrete cores (non-UKAS accredited). For help aggregates, we also provide aggregate grading. We can also provide a full range of all geotechnical and environmental testing laboratories in RSK.


Our geotechnical engineers have extensive experience in the logging of soil and rock to BS 5930-2015, BS EN ISO 14688-1 2002 and BS EN ISO 14688-2 2002 along with relevant CIRIA guidance.


Factual reports are written by our highly qualified and experienced team of Geotechnical and Geo-environmental engineers and cover every aspect of the site investigation, including:

  • Purpose and scope of the investigation
  • Accounts of all field and laboratory work
  • Exploratory hole records (trial pits, window sample holes and boreholes), including grid co-ordinates and levels
  • Any in-situ test results
  • Any laboratory test results
  • Any instrumentation and monitoring results
  • Site plans include locations of any exploratory holes
  • The provision of data in various format

Technical advice can be provided from our Geo-technical team who are highly qualified experts in a wide range of fields including engineering geology and foundation design so well qualified to offer solutions to geotechnical problems connected with:

  • Adequate load bearing for shallow and deep foundations
  • Settlement estimations
  • Slope instability/stability
  • Causes of failure
  • Ground improvement solutions
  • Interpretative Reporting