Northside Storage Tunnel – Lane Cove River crossing from investigation to completion

The Northside Storage Tunnel project is a system designed to collect and store sewage that presently enters Sydney Harbour from four major overflow points on the Northern Suburbs Ocean Outfall Sewer (NSOOS). The overflow of sewage during wet weather from the NSOOS is the main source of pollution for Sydney Harbour.

The Northside Storage Tunnel is a rock tunnel system comprising a 15.8 kilometre tunnel from Lane Cove River to North Head Sewage Treatment Plant and a 3.7 kilometre northern branch to Scotts Creek, Castle Cove. The crossing beneath Lane Cove River posed particular challenges in both the investigation and construction stages. This paper presents the investigation procedure, the geology encountered, the geological model developed, and the required design and subsequent construction.