An auditor’s final report into Sydney’s Northside Storage Tunnel found the project’s public-private alliance formed to construct the tunnel – the first alliance of its kind in Australia – was “innovative” and “promoted an open, honest and co-operative culture in pursuit of project objectives”.
The project, that included the construction of some 20km of tunnel ranging from 3.8m to 6.6m in diameter by four TBMs, was completed in October 2001 having been designed to handle overflows in wet weather from the northern suburbs of Sydney (T&TI, Nov 2002).
Client, Sydney Water, chose the alliancing form of contract as it believed it to be the only project delivery method which could meet the tight Sydney 2000 Olympics deadline. Although not 100% complete by this time, the alliance proved its worth and the tunnel was successfully accepting overflows during the games.
The achievement of constructing more than 20km of tunnel in two years and nine months seems all the more impressive when considering the alliance lost three valuable months when it encountered extremely poor ground conditions whilst crossing one of three palaeochannels along the alignment.
As described in the report, produced by the The Audit Office of New South Wales, the alliancing helped smooth the construction process through the poor ground, saying, “unpredicted, severe construction problems were worked through co-operatively, whereas serious disputes could have arisen under a conventional contract.”
The project also managed an ‘outstanding’ environmental performance as rated by an independent environment assessor who stated that such high levels were achieved by very few construction projects of a similar magnitude.
The tunnel has so far collected over 11bn litres of diluted sewage and Sydney Harbour is said to be cleaner than for generations.
