ABSTRACT
The Warangoi hydropower project, commissioned in 1983, is located in East New Britain Province, Papua New Guinea. Water is conveyed through a 6.85 km long headrace tunnel comprised of precast concrete segments. Due to wear and tear, including significant sediment erosion, it was decided that the project’s existing infrastructure should be refurbished and modernized. The plant was stopped in June 2019 and the tunnel dewatered. A detailed condition survey of the tunnel was subsequently carried out. This paper presents a detailed analysis of the different types of tunnel lining defect recorded during the survey. These defects are compared against various factors, including chainage and which tunnelling team was undertaking excavation at the time. This paper covers the severity of the various defects, ranging from the relatively inconsequential, to those critical for stability. A brief summary of the repairs undertaken is given, as well as conclusions drawn from the survey.
