Geotechnical assessment and remediation of surface subsidence areas over large sewers

By Peter Waddell & Bob Whiteley

In late 2003 the ground surrounding the Helipad at Mascot Airport was subsiding and the voids that were forming put at risk the helipad, damaged an access road and posed a hazard to airport maintenance staff. This subsidence was a result of groundwater and sand being drawn into a leaking sewer main that crosses the airport beneath the helipad. Innovative investigation techniques and methods for supporting the sewer and improving the ground above the sewer were applied to this significant problem.