Sub-surface hazard detection

Redevelopment at a site in Derbyshire had come across unexpected building foundations and ducts associated with the former land use. Phase SI were called in to use geophysics on some of the areas earmarked for future developments to check if there were any more sub-surface hazards that could impact on construction work.

The areas available for survey were quite limited due to ongoing construction work and the presence of surface obstructions. Many of these above ground features were metallic and were located in close proximity to the survey areas. This meant that two geophysical techniques commonly used for locating buried hazards, electromagnetics and magnetics, could not be effectively used. It was decided therefore to carry out the survey using ground penetrating radar (GPR) on a closely spaced profile interval.

The GPR survey successfully located a number of potential sub-surface features including possible building foundations, a duct and other service routes and also identifying the previous ground surface.