Geophysical Survey for Locating Buried Pipes and Utilities in Enugu Urban Area, South East Nigeria

The inadequacy of as-built utility records in Enugu State capital leads to frequent accidental strikes on buried water mains, gas lines, and telecommunications ducts during civil construction work, causing disruptions, economic losses, and safety incidents. This study applies ground-penetrating radar and frequency-domain electromagnetic induction to locate and map buried pipes and utilities across a 2.5-kilometre stretch of selected urban roads in Enugu. A 400 MHz GPR antenna was used for high-resolution imaging of shallow utility installations, complemented by a Geonics EM61 instrument for detection of metallic pipes and conduits. Survey lines were acquired along both carriageways and footpaths of three major roads in the GRA and Independence Layout areas. GPR radargrams consistently resolve hyperbolic diffraction patterns at depths between 0.3 and 1.6 metres attributable to cylindrical buried utilities, while the EM61 maps metallic anomalies consistent with the positions of water and gas mains. Twenty-three previously unmapped utility crossings were identified and their positions were recorded to centimetre precision using RTK-GNSS. The resulting utility map, produced in GIS format, provides an updated subsurface infrastructure record for incorporation into the Enugu State Geographic Information System database. The study advocates for mandatory pre-construction geophysical utility surveys as part of building permit requirements to minimise strike incidents. Keywords: GPR, utility mapping, buried pipes, Enugu, urban infrastructure