The NGEP has facilitated the extension of natural gas networks to thirty-four towns in country Victoria. The program is with one of the largest gas infrastructure projects undertaken outside Melbourne in more than a decade. It is subsidised by $70 million from the Victorian Government’s Regional Infrastructure Fund.
One of the projects arising from the program, the reticulation of five South Gippsland towns, was awarded to Multinet Gas. The five southeast Victorian towns included in the project are Lang Lang, Korumburra, Leongatha, Inverloch and Wonthaggi, making natural gas available to approximately 10,000 residents as well as to commercial and industrial users.
The SGNGP is the largest and most complex of all the natural gas projects under the NGEP, costing approximately $55 million and sourcing its gas primarily from the Bass Gas Plant, Lang Lang and Victoria’s principal transmission system. Total length of pipeline, including supply and distribution mains, equals approximately 290 km, with a maximum allowable operating pressure of 10,200 kPa.
Multinet Gas appointed Alinta Asset Management as the project manager responsible for the construction, operation and maintenance of the new gas network.
Construction characteristics
Construction and testing of the transmission pipeline was awarded to Delco Australia in March 2007 and commenced in April 2007. It was completed (including reinstatement) in December 2007. The supply and distribution mains were contracted to Tenix and Champ Constructions respectively. Construction works on the grid and distribution mains commenced in mid-2006 with construction of the total project due to be completed at the end of 2009. The project also involved the construction of two city gate regulator stations located at Lang Lang and Korumburra with an option of three more future city gates as required. Delco and Champ Constructions were the facilities and regulator station constructors.
Approvals and planning
The SGNGP project was awarded to Multinet in late 2005. Following that, the Alinta project team met a rigorous timeframe in completing the approval process from a number of State Government authorities to allow construction to commence on the transmission pipeline. This involved extensive planning, field engineering and design. The 66 km transmission pipeline was installed in a permanent 7 m wide easement with construction taking place on a 20 m wide right of way (ROW) on approximately 121 private properties. The route was selected taking into account agricultural impact, erosion and landslip whilst minimising inconvenience to landholders where possible.
Preliminary works included:
* Detailed flora and fauna, and cultural heritage studies;
* Preliminary selection of the pipe route and desktop study;
* Detailed risk assessment in accordance with Australian Standard AS2885, and background and survey results of the privately owned properties; and,
* Detailed engineering, design, and route selection survey.
Legislative and other approvals were sought from a range of Government Departments including the Department of Primary Industries, Department of Sustainability and Environment, Aboriginal Affairs Victoria, the Department of Environment and Heritage, local councils and local authorities.
Construction
There were a number of issues overcome during the construction of the 66 km transmission pipeline by Delco.
Some of these issues included the discovery of cultural heritage artefacts along the right of way during the construction phase; the discovery of giant Gippsland earthworm colonies; delays due to inclement weather which resulted in an amassed days of lost productivity during construction and reinstatement phases; and, the added complexities associated with the design, construction, and reinstatement of the significant section of the SGNGP that has been constructed through hazardous mountainous terrain in extended periods of adverse weather conditions and heavy rainfall.
The terrain and sensitivity of native species and waterways, coupled with exceeding regulatory specifications, were the drivers necessitating the preparation and delivery of procedures and methods surpassing the standards set for many pipeline specifications previously. The stringent criteria on person, plant, and environment warranted a cohesive effort on the part of the construction contract, client, and regulatory body to minimise the impact of the project and ensure design and safety compliance.
Key features
Anderson “˜Barnacle’s’ Hill
The most hazardous area for construction was between the Bass River and the Regulator Station at Korumburra City Gate. This 18 km section of the route consisted of undulating dairy pasture with slopes ranging between of 10 per cent and 20 per cent encountered on a daily basis by all of the working crews. While intermittent sections of relatively flat ground provided some relief in this 18 km section, the average percentage slope along the section was 17.5 per cent with a maximum occurring at an area affectionately known by the crew as Barnacles Hill. The encountered slopes at this location were in excess of
49.2 per cent (26Ëš).
The section was flagged as a difficult and hazardous area requiring special construction techniques that not only delivered the desired end result, of a safe and operating pipeline with assured integrity, but also ensured the construction was carried out in a safe and efficient manner, and subsequently the environment in which the pipeline was laid was reinstated in a manner that would require no “˜rework’ and returned the land to its original condition. The achievements of the contractor in this 500 m section alone can only be described as outstanding.
Bass River
The Bass River section was constructed by way of a 225 m long Horizontal Directional Drill (HDD). This water catchment is an integral component of the Melbourne Waterways Authority and, subsequently, great attention was paid to these works under the discerning eye of the Victorian Department of Primary Industries. Weeks of planning, design review, and geotechnical study allowed for a successful drill, back-ream, and pull-through of the pre-tested
pipeline string.
Worm Creek
The Giant Gippsland Earthworm was found present at a location affectionately known as “˜Worm Creek’. The works in this area were considered sensitive, hence the HDD method of construction was employed to minimise the impact to the native species. The drill was engaged up to a depth of 5 m below the hard invert of the creek where bedrock and bluestone was found from a depth of 2.5 m. Somewhat unexpectedly, this 195 m drill took two weeks to complete due to the exposure to rock. However, it was finished with the desired result and a successful completion of works was achieved with minimal impact to the environment.
Little Ruby Creek
This watercourse is part of the West Gippsland Waterways Authority and is considered specifically sensitive due to close proximity of the majestic Strezleki Gum population. The works were again constructed by way of HDD, however due to the step incline of the banks and subsequent depth at hard invert of the creek, the drill was required to be deep and constructed over a minimal span of 68 m from entry to exit, in order to avoid impact to the Strezleki Gums. The size of the excavated holes at each end of the HDD was large enough to lose an excavator in! The works were completed effectively under constant surveillance and in consultation with Monarc Environmental.
Korumburra city gate regulator station
Korumburra houses the most significant regulator station of the project. At this location, the transmission pressures of the SGNGP fed from the Bass Gas Plant are reduced to distribution pressures and subsequent supply to Korumburra, Leongatha, Inverloch, and Wonthaggi.
The greatest construction challenges at this location – as has proven true along most of the South Gippsland ridge lines – is exposure to the environmental elements and subsequent rock exposure at minimal depth. However, the Korumburra city gate can boast the most scenic location of the Multinet assets.
This Multinet facility is due for commissioning in early 2008 and will be instrumental in delivering the natural gas by way of the distribution network to the commercial and domestic population of South Gippsland.
Construction relationship
The design and engineering application was carefully planned and executed for this project. As a result of being fast-tracked and with many demands on construction, stemming from expected seasonal change and a succession of regulatory approvals, the need for a transparent and shared working relationship on site between client and contractor was embraced. This resulted in a cohesive client/contractor association and an excellent finished product.
Key personnel integral in delivering the quality project for Alinta Asset Management and Multinet Gas comprised Debbie Jackson, Brian McCann, Paul Haber, Ken Wernicke, and Liz Veneziano. The management team for Delco, namely Mel Whyte, Theo Keonen, Greg Kirsch, Jeff Shepherd, Jim Cummins, Mick Wardale, and Robbie De Waal, ensured the quality in execution of the pipeline and associated facilities.
The achievements of Delco in delivering the pipeline on time, to specification and safely have been recognised by Alinta as significant. Delco’s safety systems, control and performance in this hazardous environment have been outstanding as recognised not only by Alinta but by the Victorian Department of Primary Industries, Energy Safe Victoria, Melbourne Water, the West Gippsland Water Catchment Authority and other consultants engaged on the project by Alinta.
Safety statistics
* Manhours recorded by contractor 100,000 + * Lost time injuries (LTI) 1 * Medical treatment injuries (MTI) 1 (same as LTI) * First Aid treatments (FAT) 4 * Near misses 4 (same as FAT) * Rainfall 840 mm * Number of rainfall days 134 * Number of work days 276
Pipeline details
* 66 km of 150 mm (6 inch) nominal diameter linepipe to API 5L X42 specification with 4.8 mm and 6.2 mm wall thickness respectively * HDD Crossings 35 * Open Cut Crossings 40 * Elevation at Lowest Point 28 m * Elevation at Highest Point 275 m * Trench breakers installed 1,134