Piping Failure of the Poihipi Reservoir
Author: Don R. Tate
Presented/Published: NZ Geotechnical Society, Tauranga, 2003
Keywords: Piping Failure, Active Fault, Volcanic Terrain, Pohipi, reservior.
Abstract:
The Poihipi Reservoir formed a water storage for fire fighting purposes at the Poihipi Geothermal Scheme located near Taupo. Soon after initial filling of the HDPE lined reservoir, the reservoir breached by a piping mechanism. The nature of the failure was remarkable in several respects. The outflow from the breach occurred at two separate locations, located 500m and 300m respectively from the reservoir in opposite directions. The failure seepage path followed a linear active fault which was present beneath the footprint of the reservoir.
This paper describes the mechanism of the piping process, the investigations which were carried out for an alternative reservoir site and the design solutions adopted. A discussion of recent research by Australian researchers on piping failures in the context of this failure is also presented. This event highlighted many risk factors associated with seepage from water retaining structures in general, and specific risks associated with water retaining structures in volcanic terrain.
