Responding to drought in remote NSW: the Merri Abba Bore Pipeline

Following recent droughts and the drying up of its lake, for the town of Lake Cargelligo, located in remote central-west New South Wales, the construction of the Merri Abba Bore Pipeline project was identified as crucial to the town’s water supply.

By transporting up to 6 ML/d of groundwater as an alternate water source into the Lake Cargelligo water treatment plant, the Merri Abba Bore Pipeline project is designed to guarantee the town’s water resource throughout future drought situations.

The project was supported by Lachlan Shire Council, through funding from the Australian Government’s Strengthening Basin Communities Program, and from the NSW Government’s Country Towns Water Supply and Sewerage Program drought emergency works funding.

Construction of the approximately 35 km, 100-300 mm diameter Merri Abba Bore Pipeline began on the 7 September 2011 after being identified as crucial to the town’s water supply. At the time of writing, the project was scheduled for completion in January 2012.

Scope of work

The scope of the project included construction and installation of a bore and pipeline network with associated instrumentation, valves and fittings at each of the three production bores, as well as testing, demonstration and commissioning. This included operators’ training and use of operations and maintenance manuals for the entire project.

Construction of the pipeline was awarded to Mitchell Water, who subcontracted construction of the pump stations, tanks and water treatment.

To deliver the project, Mitchell Water designed, supplied, installed and constructed:

  • Pre-fabricated concrete buildings at each bore site and at the reservoir site to house the associated electrical equipment;
  • A pipeline from each bore to the 75 kilolitre (kL) balance tank;
  • A balance tank at the high-lift pump station (HLPS) site;
  • High-lift pumps, pipework and associated instrumentation, valves and fittings for the HLPS;
  • The HLPS building;
  • A pipeline from the HLPS to a reservoir;
  • A 165 kL concrete tank reservoir;
  • A pipeline from the reservoir to a connection into the existing pipeline from the Lake Cargelligo pumping station;
  • A spray aeration system to oxidise iron, and a potassium permanganate dosing system to oxidise manganese at Lake Cargelligo water treatment plant;
  • A fit-for-use water reticulation system to supply non-potable water;
  • High-voltage power transmission lines to supply power to the system;
  • All electrical, control and telemetry equipment; and,
  • Construction of all civil works associated with above.

The project involved testing, demonstration and commissioning of the pipeline, the bore network and all telemetry upgrade works. These were carried out in conjunction with Rad-tel, the telemetry service provider, and Lachlan Shire Council.

The relationship between Mitchell Water and the Lachlan Shire Council has been described by Mitchell Water Project Manager Wayne Slimmon as “corroborative and a good working relationship”, with the completion of the project as the collective aim of the partnership.

Challenges of working in remote NSW

“The remote location of central-west NSW has made working on the Merri Abba Bore Pipeline a different experience to other pipeline projects for the 36 employees on the project,” says Mr Slimmon.

“The remoteness of the project meant transport and logistics posed tough challenges. Sourcing equipment such as parts for machines and general building supplies was made difficult by the fact that no major freighting companies service the township.”

A safety requirement needed throughout construction of the pipeline was that one lane of the Lachlan Valley Highway had to be closed each day for the laying of the main pipeline.

At one stage, rock blocked the pipeline route. “A 30 m section of the main pipeline was constructed through rock that had to be drilled with an airtrack drill before the rock breaker could remove it,” says Mr Slimmon.

A 1 km section of the main pipeline was constructed though a cultural site under an Aboriginal heritage impact permit.

“The only area allowed to be disturbed was the trench width, and the top 400 mm of material was to be stockpiled for sieving at a later date for artefacts,” says Mr Slimmon.

Other challenges included sourcing accommodation for the project in the tourist town of Lake Cargelligo. This meant that in many instances, the accommodation had to be juggled around
pre-existing tourist bookings.

Future plans for Mitchell Water

Mitchell Water is simultaneously completing the 148 km, 63-250 mm diameter East Loddon Stock and Domestic Pipeline Project, and the 40 km, 63-110 mm diameter Mount Hope Stock and Domestic Pipeline Project, both located in northern Victoria.

In addition to this, a further two projects are planned, with formal agreements pending.

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