Journal Article

While the proposed Transfield-Kumugai Sydney Harbour Tunnel continues to attract much public attention and debate, Sydney's first submarine tunnel lies disused and almost forgotten beneath the harbour floor. This tunnel, which is owned by the State Rail Authority, crosses from Mann's Point at Greenwich to Long Nose Point at Birchgrove, and was excavated entirely in Hawkesbury Sandstone beneath the harbour floor between 1913 and 1924. It was originally constructed to carry 11 kV and 6.6 kV cables, which supplied power from White Bay and Ultimo Power Stations to the tramways and railways on the north shore. These cables replaced submarine cables which had suffered damage on several occasions from ships anchors. In the early 1960's when power for the railways became available from the Electricity Commission substations north of the harbour, the under harbour cables were no longer required by the SRA. They were then leased to the Sydney County Council for bulk supply purposes until 1969. This paper examines the construction history and geotechnical aspects of the tunnel, and assesses the implications for future tunnelling under the harbour.