Methods of site investigation for dealing with contaminated land

by | Mar 7, 2023

For geotechnical firms, the process of remediating contaminated land consists of four key phases. These are: desktop studies (Phase 1), intrusive site investigation (Phase 2), remediation (Phase 3), and validation/verification (Phase 4). Each of these phases are just as important to the remediation process as the next. Given how harmful some contaminants are, however, proper due-diligence will greatly save you in the long-run. This is why the Borehole Solutions team wanted to focus on Phase 2 – the various methods of site investigation.

Which intrusive methods of site investigation should you follow?

You’ll see from our previous post that Phase 1 outlines potential hazards and sources of contamination in a site. If a desktop study identifies potential contamination, then these intrusive investigations will fully assess the nature and severity of the contaminants:

Trial Pits

Trial pits are simple, cost-effective ways of obtaining disturbed and undisturbed samples to understand the profile of the ground. As this method requires minimal equipment and maintenance, it is often simpler to carry out than other investigative alternatives. These pits are dug by hand or a small digger, which saves considerably on fuel and transport costs. For more information on trial pits, click here!

Window Sampling

As one of the most popular methods of site investigation for smaller-scale projects, window sampling extracts samples for geotechnical analysis. With a depth limit of 5 metres, it is predominantly used in relatively shallow substrates and superficial or weathered formations. Despite this economical and environmentally considerate approach, however, window sampling still delivers high-quality sampling results.

Rotary Drilling

This form of intrusive drilling is utilised in a broad range of geological formations and projects. Cylindrical rods and sample tubes are driven into the ground to extract representative samples of sub-surface profiles for analysis. For deeper boreholes, rotary drilling with air will typically be your go-to option. More unstable, unconsolidated foundations made up of sand and gravel, however, will require a drill-coating additive to support the drilling process. Regardless of whether you use ‘mud’ or ‘air’ flush rotary, this technique is fast, flexible, and incredibly reliable.

Cable Percussion Drilling

If you’ve ever seen a drilling rig in action, then chances are that it would have been a cable percussion’s distinctive A-frame shape. After all, it’s one of the UK’s most common drilling techniques, and with good reason! These methods of site investigation offer versatile performance across both consolidated and unconsolidated superficial formations. A cutter attached to the cable is repeatedly lifted and dropped into the substance that it’s boring through. It’s as simple as that! No wonder it’s as popular as it is – especially when paired with its overall high-quality results.

Contact us

Whilst ground investigation is definitely one of our fortes, it certainly isn’t all that we offer. Alongside drilling, we provide rigs for hire, remediation services, soakaway installation, and more! So, if you’d like to find out more information about these methods of site investigation, or any other of our services, get in touch! Call us today on 01733 200501, or send an email over to to speak to the team today.