Geotechnical investigations for the penstock plug of the Anthony Underground Power Station, Tasmania

From a reservoir on the Anthony River water flows through a headrace tunnel and a short power tunnel to the Anthony Power Station. The last section of the power tunnel into the underground power station chamber is lined with a concrete backfilled steel penstock. This backfilled steel penstock forms a plug to prevent high pressure water in the unlined power tunnel from penetrating into the power station. This paper describes the investigations that were carried out to determine the length of penstock required and to confirm the water tightness of the finally adopted design for the penstock plug.