Shallow EM mapping for characterization of a proposed construction site

University of Canterbury, Christchurch, New Zealand
Soils & Foundations, New Zealand

Expansion by a New Zealand company required construction on an area that (from oral and historical records) had a number of pits for disposal of manufacturing residue. The area was partly covered by mud and residue from the manufacturing process; that portion not covered by mud and residue was covered by varying thicknesses of gravel and mud. Due to the nature of the site and cover material, a shallow electromagetic (EM) survey was designed to: (1) delineate the buried stream channel; (2) determine positions and approximate sizes of the buried pits; and (3) map any other anomalous features. The working hypotheses were: (1) The old stream channel could have a conductive or resistive trend, depending on the nature of the channel fill; (2) the pits would be more conductive because of greater thickness of mud and manufacturing residue; and (3) an increased thickness of the surface mud and residue cover would increase apparent conductivity. The EM surveys were augmented by auger holes and trenching at selected locations. The EM survey of the proposed factory extension yielded excellent data quality.

This record provided courtesy of AGI/GeoRef.