North-South Corridor tunnels would cost $11 billion and should be abandoned, Civil Construction Federation says
Matt Smith, Political Editor, The Advertiser
June 23, 2020 3:42pm
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Tunnels for South Australia’s largest infrastructure project should be abandoned because they will come with a price tag of more than $11 billion, the Civil Construction Federation says.
The state’s largest motoring organisation, the RAA, says the State Government should meet expectations halfway with a combination of both tunnels and above-ground roads for the final stages of the North-South corridor.
The State Government is set make an announcement on the troublesome 10.5km stretch that runs through built-up suburbs and commercial districts just north and south of Anzac Highway within weeks.
Three solutions being examined by the State Government are one super tunnel or a
hybrid option that includes traffic returning to the surface between Anzac Highway and Edward St in Melrose Park.
A tunnel-free design is also being examined, which would be similar to the Torrens to Torrens build.
An artist impression of the tunnel exiting on to South Rd.
Vocal residents in the area are calling for the government to adopt the super tunnel to help save as many houses and businesses as possible.
Civil Construction Federation boss Phil Sutherland told The Advertiser tunnels were too expensive and could not be done by locals.
“Constructing a tunnel (using a bored tunnel method) is the most complex, risky, expensive and time consuming of the available engineering options,” Mr Sutherland said.
“The road project needs to reflect the character of our city. This is Adelaide, not Sydney, New York or London.
“A tunnel would come at an estimated cost of $11 billion, twice the cost of continuing the road upgrade using the same engineering design as the already completed sections.”
Mr Sutherland wants the government to go for a hybrid design that will include continuing the corridor upgrade mostly at grade using the current engineering design methodology, and a cut-and-cover method to construct a ‘tunnel’ in designated sections.
“Cut and cover method of tunnel construction is generally used to build shallow tunnels.
“In this method, a trench is cut in the soil and covered by some support material which can be capable of bearing a load on it.”
RAA safety and infrastructure senior manager Charles Mountain said on paper the hybrid model that will include two smaller tunnels seems to be the best solution.
“It offers the best of both worlds,” Mr Mountain said.
“Having the two tunnels will reduce the level of intrusion at ground level, but it also means that there is a range of access points along the section, which we believe is critical as well to enable people to get on and off.”
Mr Mountain said the project, which Treasurer Rob Lucas told The Advertiser would go ahead despite the state’s finances, was very important.
“The sections that have been completed so far have been very successful both in terms of improving traffic flow and attracting people to the corridor,” he said.
“This has a flow-on impact of reducing traffic demand on adjacent corridors.”
Infrastructure Minister Stephan Knoll said: ”After putting tunnels on the table, we are undertaking detailed geotechnical work and want to have as much information as possible before deciding on the biggest job-creating infrastructure project in our state’s history.”
( Behind paywall.) 
( Behind paywall.)