Brisbane averts underground works inundation
Brisbane averts underground works inundation Jan 2011
Shani Wallis, TunnelTalk
A torrent of floodwater sweeping down the Brisbane River catchments wiped out all before it and threatened catastrophic inundation of the state capital. As well as residents and businesses preparing for the worst, the city's $4.8 billion Airport Link construction project doubled precautions to avert flooding of the tunnelling works.
Fig 1. Underground Airport Link route

Fig 1. Underground Airport Link

A total 15km of tunnelling needed for the project is advancing from four main construction sites, each of them lying near one of Brisbane's many waterways or in low-lying areas north of Brisbane River (Fig 1).
Roadhearder excavation has completed 2.75km of twin tunnelling from the Federation Street jobsite in Bowen Hills in the south and to the Kedron Brook site in Kedron and from the intermediate access at Truro Street in Windsor. Roadheaders have also completed 1.5km of the project's associated 4km long Northern Busway tunnels between Windsor to Kedron.
From the Kalinga Park job site at the northern end of the project in Toombul near the airport, two 12.48m diameter Herrenknecht TBMs are more than 500m into their twin 2.5km drives towards Lutwyche where they will junction with the roadheader excavations.
When contracted by TunnelTalk on Wednesday 12 Jan, the project's Public Relations Manager Deirdre McCue said that all the worksites were being monitored closely. "There are no immediate concerns with worksites in Kedron and Toombul which are adjacent to Kedron Brook/Schulz Canal since this stormwater channel is not affected by the flood levels in the Brisbane River, but the potential for the Bowen Hills worksite, adjacent to Breakfast Creek, to be affected by the rising tide levels in conjunction with the flood waters flowing downstream to the sea, was a concern.

Work is progressing from the Bowen Hills site (left), a site at Kedron (centre) with an intermediate work site at Truro Street in Windsor, and the TBM site at Toombul (right)

To mitigate against these possible extreme water levels an additional levee was constructed within the perimeter flood bund of the site to protect the underground works from inundation."
Flood devastation across Brisbane suburbs

Flood devastation across Brisbane suburbs

As further precautions, tunnelling activities ceased in this area, primary equipment and materials were removed from the tunnels to higher ground and the Bowen Hills site office was also evacuated. Construction of the $4.8 billion project for the BrisConnections PPP concession is in the hands of the Thiess John Holland design-build contract JV.
"Mercifully the rain has stopped elminating one of a three-pronged perfect storm scenario," said McCue. "Today is a clear blue-sky day and while there are vast amounts of flood water being release from the Wivenhoe Dam, which was built to protect the city after the devastating 1974 floods, and this is the season for high tides up the river from the sea, this is not being added to by heavy rainfalls and so, while large parts of the city are flooded, the water didn't reach the 5.5m high predicted and is receding fairly quickly from the 4.8m or so maximum. Many workers on the project have been affected personally by the devastation but thankfully the works are okay. The situation will be monitored closely however until this incredible event and the real danger has passed."
CLEM7 under river highway in Brisbane

CLEM7 under river highway in Brisbane

Brisbane's other major element of underground highway infrastructure, the CLEM7 highway tunnel, passes 60m directly below the river and was also a concern for the week's 'perfect storm' scenario. The 4.8km long twin tube highway tunnel, completed by two Herrenknecht rock TBMs and a fleet of roadheaders, was built by the Leighton Contractors/Baulderstone Hornibrook/Blifinger Berger design-build JV for the RiverCity Motorway consortium and opened to traffic in March last year 2010.
It is designed for flood conditions that would see water levels higher still than the 5.5m levels predicted for this event but the concern to perhaps close the tunnel was real. As it was the tunnel remained open and continues to be operational as one of few major highway arteries able to offer a safe alternative for travelling across the river during the crisis. To contribute to the emergency status in the city, tolls on the concession tunnel operation have been suspended until 17 January more than a week after the peak of the flood was anticipated.
Brisbane's Airport Link powering ahead - TunnelTalk, Jun 2010
Brisbane takes delivery of second TBM - TunnelTalk, April 2010
Brisbane road tunnels celebrate milestones - TunnelTalk, Dec 2009

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