Cable percussion boreholes are often utilised in site investigation and assessment. They may extend many tens of metres, but typically up to around 30m depth
Controlled drilling allows good identification of strata types and properties, groundwater and contaminant zones. Depending on the objectives of the borehole investigation, they can be relatively inexpensive and have the benefit of permitting monitoring installations to be constructed.
Rotary drillholes, typically up to 50m depths, can be slightly more expensive but relatively rapid and can allow installations to be constructed.
Cone Penetration Testing (CPT) is a contemporary investigation method, typically up to 30m depth in support of other methods.
Some benefits of boreholes include:
- The SI enables information to be collected to further characterise the Conceptual Model (S-P-R).
- The presumed Conceptual Ground Model can be updated with actual site data in real time.
- The siting can be justified and compared with assumptions reasonably developed during desk-study.
- It is not limited to the collection and analysis of samples to simply ascertain contaminant concentrations – the input to engineering geology and geotechnical assessments is valuable.
- The sampling strategy can be modified whilst the investigation is in progress. It is also important to consider the Health and Safety implications of drilling boreholes, both during and after the investigation.