David Lees was asked by URS to assist in the design of refurbishment measures and the tunnel inspection and site supervision of repair work for the Snowy-Geehi tunnel.

The Snowy Mountains Hydroelectric Scheme which was completed in 1974 is one of the largest hydroelectric projects in the world and pioneered tunnelling in Australia. It consists of 134 km of tunnels, pipelines 16 major dams, 7 power stations, 20 aqueducts, pumping stations and a range of other structures. Snowy Hydro who owns and operates the Snowy Scheme commenced a new tunnel maintenance program in 2001 URS were appointed to carry out the detailed design, tunnel inspections and construction advice and. EROC Pty Ltd was awarded the contract to undertake the tunnel maintenance works in 2002.

The tunnels are horseshoe in shape and were excavated by drill and blast through granitic and metasediment rocks of Ordovician to early Devonian Age. Those tunnels and shafts, which are connected directly to power stations, were fully concrete or steel lined and are not a major connecting storages were partly concrete lined in accordance with rock conditions encountered and these tunnels are more prone to instability with time and are the focus of maintenance work.

The Snowy-Geehi tunnel is 14.5km long and has a 6.3m x6.3m profile. It was completed in 1966 and is 13% lined. An outage was undertaken in March/April 2002 to clear the rock traps, scale loose rock from the tunnel walls and clean loose rock from the invert, install rock support and carry out pressure grouting and concrete repairs, and installation of a fibre optic communication cable along the tunnel. Access was through a 3m diameter steel lined section at Jindabyne/Island Bend.
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