Kalgoorlie DN800/DN900 Horizontal Thrust Boring
Project Summary
Kalgoorlie, WA
Trenchless Technology
Water Corporation
- Completed
January 2009
May 2009
Project Overview
The overall project involved Water Corporation’s Construction Branch constructing a DN800/DN900 MSCL water main to improve Kalgoorlie’s water supply infrastructure.
We were contracted to install all the road and railway under bores for the project. These had to be constructed ahead of the pipe laying crews to ensure no delays occurred and impact on the local community was minimised.
Our scope of works included obtaining all necessary stakeholder approvals, traffic management, excavation and management of pits, installation of rail and road under bores and temporary backfill and compaction of affected areas. Our previous experience in completing bores under railways proved beneficial, with the approval process being streamlined and completed well ahead of the allocated timeframe.
The hard ground anticipated and the possibility of rock required consideration of the appropriate trenchless methodology. We elected to use thrust boring for all installations due to its flexibility and cost effectiveness in these ground conditions. It involved boring a DN1050 steel casing into position, sleeving, then grouting the MSCL pipe inside the casing.
Using our Auger Boring equipment and specialised rock heads, we were able to drill through hard rock under various roads and rail crossings without any impact on the existing asset, a significant benefit for the client.
Significant achievements and benefits
This sewer installation needed to be completed across Whitfords Avenue and Wanneroo Road without disruption. Our trenchless experience allowed us to mitigate the risk to the client of construction impact on these two major roads.
There were 2 sections to this project. The first involved the installation of 1,060m of DN600 vitrified clay jacking pipes constructed over 12 drives. The second involved the installation of 362m of DN500 vitrified clay jacking pipes over 5 drives. The entire service was installed successfully with a high degree of accuracy, given the significant number and length of drives necessary.
Seventeen reinforced concrete thrust and receival pits were constructed using 4.2m caissons that were formed, poured and sunk into position on site. This kept exposure to acid sulphate soils (ASS) management to a minimum and reduced the impact on the surrounding neighbourhood.
Nineteen type 6 plastic lined access chambers were manufactured in-house using our approved design. This was a cost effective option for the Water Corporation. It also enabled us to have full control over scheduling of the chamber fabrication to suit project requirements.
A 300m section of work extended from Whitfords Avenue to Hocking Road, through a proposed bush forever site. It was also an ASS risk area. By using trenchless techniques, we kept the construction corridor to within and sometimes well below, the allowance 10m width.
Construction of this 1.4km trunk sewer was through environmentally sensitive and built up areas. Installation was achieved with minimal impact and enabled two existing pump stations to be decommissioned.
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