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14/09/2018
Zinfra deliver for ActewAGL in Hume, ACT
APEN June 2015 digital edition out now

This excerpt about Zinfra is taken from this month's edition of Australian Power and Gas.

 Hume PRS

Needing to deliver approximately 30,000 scmh into the gas distribution networks in the projected growth areas in the Australian Capital Territory and in Queanbeyan over the next 20 years, ActewAGL contracted Zinfra to construct a new five kilometre primary main and a new Primary Regulating Station (PRS) at Hume.

These new facilities will ultimately supply natural gas to approximately 25,000 customers, as well as provide long-term capacity for prospective large consumers, and long-term supply into the Hume-Tuggeranong Interconnection supplying the southern ACT.

The Hume Primary Main Extension (PME) project involved the design, construction and commissioning of five kilometres of DN250 steel high-pressure primary gas pipeline, operating to 6.895MPa, and built and constructed to AS2885.

This new pipeline connects the existing primary network to the new Hume PRS, a separate project delivered by Zinfra and completed in February 2015, and was tied-in to the existing network in three places.

The Hume PME project also required installation of 0.2 kilometres of DN250 steel high-pressure secondary gas pipeline to connect the Hume PRS to the existing secondary network and associated infrastructure supplying the district of Jerrabomberra.

Construction of the pipeline included:

» Open cut construction

» In-service welding to live gas main

» A hot-tap

» Two major water crossings, and

» Four cased bores.

A hot-tap was required to connect the pipeline to the existing primary main at Jerrabomberra Package Off-Take Station (POTS).  To maintain the ability to pig the existing primary main, a hot tap fitting was specially designed with a spherical tee and guide bars.

Pigging pipework was also constructed at either end of the pipeline to allow pig launching facilities to be connected to inspect the integrity of the pipeline.

There were numerous challenges and complexities to the project:

» Development Application (DA) approval - original design included the removal of many trees that was not approved during the DAprocess. The solution, achieved through rigorous negotiation with ACT government agencies, was to relocate the final two kilometres within private land.

» Existing services - multiple existing services, including those for a nearby correctional facility, were at risk when trenching.  

Extensive investigation and stakeholder management, including AC mitigation, surveys, collection of DBYD and private land owner information, and non-destructive pot-holing, meant there were no service strikes throughout the project.

» Proximity to the Monaro Highway - traffic control, including some lane closure at stipulated times, was required throughout the  project.  Zinfra had to carefully manage time and resourcing to ensure the project remained on schedule.

» Subterranean rock - completing the Monaro Highway crossing was complex, with rock slowing drilling to as little as six metres a day.

The project was completed on time and under budget.  Excellent site safety supervision, and a strong culture of safety within Zinfra, meant the project was completed with no LTI or MTIs.