Probing technology minimises land risks
The recent use by the BBC Timeteam Series of Ground Probing Radar (GPR) for their archaeological investigations and historical sub-surface ground examinations has increased public awareness of the benefits of using GPR to locate non-metallic and metallic objects prior to any ground remediation or top soil removal for contaminated land disposal.
The depth of investigation can vary from less than one meter in mineralogical clay soils like montmorillonite to more than 5,400 meters in polar ice. There is also the additional benefit that sophisticated correlation software can take out back scatter and improve the visibility of the trace, which means the techniques are particularly useful for locating fibre optic cables, where even the slightest tear during excavations will disrupt computer and telecommunications networks.
The Health and Safety Executive (HSE) have laid down guidelines for ground remediation activities. In their document Avoiding Dangers from Underground Services they have set out a three-step process for minimising the risks. It involves a full review of all existing record drawings, a well-defined process for locating all metallic and non-metallic services and only then proceeding to dig. Insurance companies are now looking at any incidence of land remediation accidents to ensure that the HSE guidelines have been adhered to.
Two recent projects have indicated the value and efficiency of using GPR. At a recent building demolition and land clearance project in Brighton, Fitzpatrick used the services of IETG to accurately locate and protect a major communication system fibre-optic cable.
Because the object being sought was non-metallic, conventional radiolocation techniques could not find the cable and the teams knew that even the smallest interference to the cable during excavation would have resulted in severe financial and project delay penalties.
In another case, Amec used the services of IETG to locate underground services for ground remediation and clearance for National Grid infrastructure expansion programmes. National Grid is now so convinced of the value of using GPR that they are specifying its use on all similar contracts.
The benefits in cost savings may be difficult to quantify, but as utility clearance
surveys and any corporate risk reduction figures must take into account the
effectiveness of the location techniques, what it is worth to the client in
terms of 'peace of mind' is priceless.