A second chance

Abstract

At the Manapouri power station in New Zealand power is generated by diverting water from Lake Manapouri to an underground power house before discharge through a 10-km tailrace tunnel to Deep cove. Insufficient capacity in the tailrace tunnel limited power generation. A project was initiated to increase output by constructing a second tailrace tunnel. The environmental, technical and geological challenges to the project are outlined. A new tunnel boring machine was designed for the project. Construction of the tunnel is described.