Cost-effective, long-term solution for rehabilitating earthquake-compromised wastewater laterals and decreasing their vulnerability to future seismic events

Abstract

Although several years have passed since the Christchurch, New Zealand 7.1 magnitude earthquake of September 2010 and the deadly 6.3 earthquake of February 2011, it may take another five to ten years to replace and upgrade the hundreds of miles of gravity-fed, clay-pipe wastewater laterals in the city and surrounding hills. Pipe bursting technique has proven to be a fast, highly effective, long-term and low-cost pipe replacement technique using compact hydraulic pulling units. The units pull a cable-drawn bursting tool through existing pipe. As the pipein-place fractures at the bursting tool head, replacement pipe is drawn in simultaneously behind the progressing tool. Ground conditions soon return to their previous state, closing around the new pipe. Other than relatively small excavations, when necessary, to access the lateral at the beginning and end of a replacement run, the surface shows no sign of disruption. Pipe bursting technique for typical lateral-sized pipe employs equipment and tooling that is easy to learn how to use, easily transported and can be operated by one or two people. This paper explains how pipe bursting equipment and technique are being used to repair earthquake-damaged underground utilities. The report focuses on pipe bursting technique’s on-going use as an earthquake repair and mitigation strategy for wastewater laterals in Christchurch, New Zealand. Since New Zealand’s geography lies above an active fault zone, it provides a valuable pipe bursting application study for other areas of the world whose infrastructure is also susceptible to earthquake activity.