KWIS Recycled Water Pipeline Package 1



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Overview

The Kooragang Industrial Water Scheme (KWIS), near Newcastle, will provide 9ML per day of high quality recycled water to users in the Kooragang Island area to replace the use of drinking water in industrial operations. The scheme involves the construction of a new Advanced Water Treatment Plant and a water delivery pipeline approximately 7.5km long.

Background

Three HDD shots traverse sensitive conditions for water treatment plant

In February 2014 UEA Trenchless completed its work for Hunter Water Corporation as part of the KWIS project. The Division’s task was to design and construct 2.92km of DN400 PN16 fully-welded PE pipe from the new treatment plant at the Steel River Estate at Mayfield West, to midway along Cormorant Road, Kooragang Island.

UEA Trenchless had to take into account the multiple stakeholders to be impacted by the construction process as well as by the pipeline’s ongoing operation in the future. Affected parties included (but are not limited to): Hunter Water Treatment Alliance, Newcastle Coal Infrastructure Group, the Steel River Community Association and Newcastle Ports Corporation.

During planning, design and construction, all potential stakeholders were kept informed, were involved and were notified of proceedings in a timely and professional manner, largely due to the close working relationship and strong communication between UEA and Hunter Water Corporation.

Solution

The scope of Trenchless technology performed by UEA on this job consisted of:

  • Three Horizontal Directional Drill (HDD) shots  of 470 metres, 610 metres and 460 metres,  including one under the Hunter River
  • One Guided Bore installation, including a 600mm steel casing installation
  • A 56 metre steel  casing installation for the Hunter River crossing
  • Slip lining of approximately 600 metres of existing 500mm cast iron mains
  • Conventional open cut works including fittings, final connections, flushing and testing

Project challenges

The three HDD shots each had their own difficulties with the ground conditions being significantly different for each.

Bore 1 was 610 metres in length and approximately eight metres deep and positioned beneath a sensitive mangrove area. The ground was water-charged, due to the close proximity to the Hunter River. Therefore, a suitable mud plan had to be developed to ensure the bore opening was maintained at all times.

The pilot bore was tracked using a ParaTrack 2 system that allowed constant/real-time location of the drilling head. The pilot bore was completed in three days and the hole reamed to size with a tail string in place. Once the ream was complete, the pipe was pulled directly into place with no problems. Lessons learnt from installing Bore 1 helped increase efficiency during the installation of Bore 2 – a 470 metre shot in identical ground conditions

Due to their close proximity to Cormorant Road, the first two pipe installations were performed at night.

Riverbed bore

Bore 3 was a 460m shot under the Hunter River. The material encountered here was soft rock and therefore completely different to the first two bores situated less than 1,000 metres away.

On the southern side of the river there was a 28 metre elevation difference from the natural surface to the design bore depth. Difficult ground conditions at the start of the bore required a  56 metre steel casing to be installed. The casing was keyed into the rock – at a 22 percent angle – to ensure the product pipe was protected and returns could be maintained for the duration of the HDD installation.

This work was completed using a conventional thrust boring machine on an elevated rail. After the HDD rig had installed the product pipe and it had been centralised within the case, the area between the product pipe and case was filled with grout. Once the casing was installed the pilot bore of the HDD crossing could commence. Drill returns were maintained for the duration of the pilot bore thanks to the installation of the case. The D300 HDD rig was then mobilised to the other side of the bore so that back reaming could commence. The hole was reamed straight to size and pipe installed without any issues.

A steel case was required by the RMS for the road crossing under Tourle Street due to the high traffic volumes and future road or bridge widening. The casing was installed using a Guided Boring Machine (GBM) followed by the Thrust Borer. The GBM is capable of installing a pilot bore on grade with a +/- 25mm tolerance in displaceable ground conditions – ideal for this crossing. The area was heavily water charged  and therefore required dewatering spears to be installed. The order of program was changed to enable the trenching crew to perform works in the same area and take advantage of the dewatering process.

The slip lined section was 600m of 400mm PE, installed inside an existing 500mm CICL pipeline.

Challenges for the civil crew installing trenching and connections included the problem of groundwater; contaminated ground; buried obstructions, including metal slag sculls

Environmental protection

Managing the environmental issues was a high priority for all stakeholders and contractors. One area of the project was within a potential Green and Golden Bell Frog habitat. This required an independent environmental study over multiple nights to identify any frogs and move them if located.

A frog fence was installed to separate the frog habitat from the construction zone. All water removed during the dewatering process had to be tested and handled in line with the environmental guidelines for the project. The newly-installed main was pressure-tested, swabbed, flushed and it ultimately passed water sample testing without issue and was connected to the Treatment Plant ahead of schedule.

Overall crews, subcontractors, suppliers and Hunter Water worked in partnership to make this project a success.

Further information

For specific information about the KWIS Project, or for general information about how Trenchless Technology could assist your project, please email us at enquiries@uea.com.au.