High Density Array GPR Service ID

We encountered uncharted live pot-ended electric cables on a road junction improvement scheme. These were not recorded on the power network utility records; were not identified at design stage; were not identified by conventional GPR survey; and were not traceable by CAT and Genny survey.

We engaged with geospatial survey specialists Macleod Simmonds who undertook a High-Density Array Ground Penetrating Radar (HDA GPR) survey of the site to locate and map buried services and structures, with a primary focus on locating pot-ended cables. The density of data collected allowed for a more accurate picture to be mapped of the sub-surface environment. While detection of pot-ended cables was not guaranteed, the survey provided additional information that together with old road designs, historic maps and utility records provided improved understanding of the sub-surface and allowed introduction of ‘intelligent’ trial holes.

Main safety benefits were:

• Reduced risk of service strikes – one of Highways England’s aspirations in the ‘Home Safe and Well’ document is to halve service strikes. The HDA GPR survey increased the understanding of the sub-surface environment, reducing, but not eliminating, risk of service strikes.
• Pot-ended cables – although not 100%, the survey provided data that could help identify pot-ended electric cables or intelligently investigate anomalies that might be pot-ended cables.
• Time and cost accuracy – data collected allowed a better understanding of underground conditions including utilities and areas of hard dig. This can inform cost estimates giving improved budget accuracy with less variation during construction stage.