David Lees and Associates were appointed by Hyder Consulting to carry out the initial design and review of the proposed tunnels for the M2 Gore Hill Freeway for the Environmental Impact Statement for the RTA.

This section of the M2 is the “missing link” passing beneath the Pacific Highway and Lane Cove. At the start of the route the proposed alignement passes through Ashfield Shale. There is little experience of tunneling in this material especially for large excavations. The RTA proposal included twin tunnels with three lane highways and adjacent on/off ramps.
The proposed route also passed beneath the  Creek where a potential fault swarm or set of dykes may influence the geology. Proposed tunnel profiles and rock support systems were determined for the various geotechnical and geometrical conditions along the route.