The General Process of Site Investigation

Any site investigation should always start with a Phase 1 Environmental and Geotechnical Desk Study Report.  This is a preliminary assessment that evaluates potential environmental and geotechnical risks associated with a site. It involves a comprehensive review of existing information, including historical land use, geological maps, and previous investigations. The report aims to identify any contamination, stability issues, or other hazards that could impact development. Key components include site history, regulatory database searches, and a preliminary risk assessment. This study helps inform decision-making, guiding further investigations if necessary, and ensuring compliance with environmental regulations and safety standards before any construction or development begins.


After we have completed a Phase 1 Desk Study and the initial Site Conceptual Model indicates that further information is required, for whatever reason, an intrusive site investigation is required.  Below is a description of instrusive methods that are commonly used on site:-


  • Trial Pits: - An easy and cost-effective way to obtain samples. Can be dug by hand or by a small digger. Also used to undertake soakway testing (BRE 365) and CBR testing.
  • Window Sampling: - Perfect for smaller-scale soil sampling projects. - Used predominantly in superficial or weathered formations. - Delivers high-quality sample results. And can also undertake dynamic probes for undermining or sinkhole identification
  • Cable Percussion Drilling: - Commonplace across the UK. - Offers versatile performance across both consolidated and unconsolidated superficial formations – cost effective
  • Rotary Drilling: - Suits projects, both big and small on rock (or where depth >30m is key). - Uses torque and rotation to bore through the rock.
  • Sonic Drilling: - Quick, and incredibly powerful. Suited in particular to site where interbedded soils and rocks are present. – advanced rotary + percussive technology.

Trial Pitting


Advantages: They allow a detailed examination of the ground in situ and provide an indication of the ‘digability’ and subsequent stability of the ground. They are cost-effective and can be excavated relatively quickly. Can provide Soakway Testing Pits and CBR plate testing using single plant.



Disadvantages: They are usually limited in depth ~<3m and Require heavy plant to access the site.

Continuous Tube or Window Sampling


Advantages: It’s cost-effective while  providing deep high-quality information to around 5/6m, or probes to 10m completing 3-4 locations in a “day”.

Highly mobile – deployed from “transit” van fits gaps of ~1m wide.

Can also be modular, to access limited access sites or inside buildings.



Disadvantages: Requires fairly even terrain, limited to 3-4 (5m) holes per day.

Cable Percussion Drilling


Advantages: It can tackle most types of soil and very weak rock situations (common in central and southwestern England) and can drill deeper than other drilling methods. It’s reliable and leaves minimal impact on the surrounding landscape.

Typically used for 10m-40m boreholes, to aid with pile foundations or ground improvement design.



Disadvantages: rigs are towed to site using a pickup truck with a total length of ~7m, works area must be fairly level and flat lying and take up approximately 6 carparking spaces.

Sonic or Rotary Drilling


Advantages: fast, reliable, and flexible. it can be used on a broad range of geological formations and go as deep as you like.



Disadvantages: the main drawback of the technique is the high relative cost. Rigs are typically delivered to site on low loaders given the size of the plant, but are tracked and quite mobile on site.







If you have any questions, would like to request a CPD talk or need help with a site investigation please call us on 01280 816409 or email us on

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