From the magazine

Trenchless to help Unitywater build big

Queensland water utility Unitywater has a message for no-dig drilling companies: get your forward-order books ready, as there are some crucial sewerage infrastructure projects on the tender horizon.

With population numbers rising, Unitywater has set in planning several large projects to maintain the provision of sustainable high-value sewerage and water services to customers.

Engineers from Unitywater’s Infrastructure Planning and Capital Delivery division have identified trenchless construction methods as the best option for a number of upcoming sewerage infrastructure projects.

“We find that trenchless drilling reduces cost and disturbance to the natural environment,” said Unitywater Executive Manager Infrastructure Planning and Capital Delivery Simon Taylor.

“This form of construction optimises operational efficiency. One of its biggest advantages is the reduction in construction impacts for customers and residents, because there aren’t the large open trenches associated with other sorts of drilling.

“No-dig also meets Unitywater’s strategic focus to enhance customer value.”

Mr Taylor said the drilling method did present some challenges.

“We recognise the major challenge to the successful installation of large diameter sewer mains using trenchless techniques is the ground conditions,” he said. “This means we are very careful and considerate when selecting contractors to work with when we take opportunities like these projects to market. Experience certainly does count.”

Project designers KBR and drilling consultants Bamser are working closely with Unitywater to optimise the design, specifications and contract documents relating to the three upcoming sewerage infrastructure projects.

Investigations are underway to examine ground conditions, access restrictions, achievable vertical and horizontal alignments and the size of drill rig required, taking into account proposed lengths and pipe sizes.

Successful contractors will be expected to carry out detailed geometric design of the trenchless sections.

“This work provides an exciting opportunity for drilling companies with an eye towards their forward-order books,” said Mr Taylor. “We look forward to working with the successful contractor in constructing these critical pipelines within our sewer network.”

Tenders are expected to be released in early 2016, with consideration currently being given to bundling the first two projects under a single Design and Construct contract.

Overview of proposed projects

Nicklin Way, Caloundra

The project will upgrade a sewer rising main on Nicklin Way.

Initial designs favour a combination of open cut and horizontal directional drill (HDD) construction methods to install 900 mm diameter pipe.

Approximately 800 m of HDD is anticipated over two sections located at Sugarbag Road (400 m) and Seagull Avenue (465 m).

Mountain Creek

The Mountain Creek project will see the construction of roughly 3.5 km of 900 mm outside diameter 100PE rising main from north of the Mooloolah River through to Kawana Sewage Treatment Plant.

A combination of HDD and open-cut construction methods will be used.

North Street, Caloundra

The North Street project will involve the construction of a 600 mm gravity main in North Street and First Ave to relocate an existing sewer and decommission a sewer pump station located in the Caloundra Waterfront Holiday Park.

Preliminary designs indicate microtunnelling techniques in three sections:

  • A 550 mm outside diameter sewer and 105 m microtunnel crossing under Bowman Road;
  • A 650 mm outside diameter sewer aligned beneath Caloundra Waterfront Holiday Park;
  • A 752 mm outside diameter sewer located beneath Park Place.
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