Drain or natural water course blamed for collapse in South Rd Darlington motorway

A rainwater drain or natural water course not identified during planning has been blamed for both collapses of the South Rd Darlington motorway works.

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A rainwater drain or natural water course not identified during planning has been blamed for both collapses of the South Rd Darlington motorway works.

Workers dealing with a Monday landslide at the site were confronted with the same problem 50m away on Wednesday morning when they returned to work and found another 30m section of concrete wall washed away.

Revelations of errors in water course mapping through the area came as Opposition transport spokesman Tom Koutsantonis called for an urgent meeting of State Parliament’s Public Works Committee to intervene in the crisis because “this is the only way we find out what is going on down there”.

A second piece of concrete has now fallen at Darlington. Picture: AAP/ Keryn Stevens

Transport Minister Stephan Knoll was forced to explain the second incident on Wednesday – and said the entire 220m of embankment between Sturt Rd and Flinders Drive was now under threat – after the Transport Department assured the public on Tuesday that the problem was isolated and under control. He said six experts – three to be flown in from interstate today – were on the case and the Government would insist the contractor pay if it could be shown the work carried out was unsatisfactory.

The damaged area is downhill from the long west-facing slope which accommodates most of the Flinders University campus and its sporting oval.

More rain = another concrete slide at the Darlington underpass project. #7NEWS pic.twitter.com/Ptmmm3EDHy

— Tim Yeatman (@TimYeatman) May 7, 2019

The Advertiser understands hydrology studies carried out during the dry summer months did not identify water draining courses running through the area, causing the mini-landslides when the first significant autumn rain run-off came through the area on the weekend. But Mr Knoll, pictured, could not say if natural water flow was the source of the water, or if it was human-made drainage which had been mistakenly blocked by the motorway’s dirt and concrete embankment.

“What we are talking about is a water source that is coming in behind the concrete and soil that has not been identified before,’’ he said.

“There are a whole lot of places it could be coming from.

“Given how dry it has been (over summer) and the lack of rainfall, is why the drainage wasn’t identified (in planning).”

The first wall collapse on the Darlington motorway. Picture: Dean Martin.

Mr Koutsantonis wrote to the presiding member of the Public Works Committee, which normally scrutinises budget issues before works are carried out, stating: “I am, as I imagine all members of the committee would be, very concerned at this development’’.

Traffic restrictions are expected to blow out past the six-week period announced after the first landslide, with lane limitations in place for southbound traffic on Main South Rd. Mr Knoll said the cost was not yet known, but the contractor was required to produce works that were up to standard in the $620 million project. “Taxpayers will be protected to the greatest extent possible,” he said.