GasNet’s subcontractor McConnell Dowell was making good progress with the construction of the pipeline with days that sometimes saw in excess of six kilometres of pipe laid. However, this progress was soon halted when on March 25 2004 Severe Tropical Cyclone Fay hovered off the coast of north Western Australia. When the Bureau of Meteorology indicated that TC Fay would impact the construction area and Camp 2 (approximately 220 km from Port Hedland, the main construction camp at the time of the cyclone) within the next 48 hours, the decision was made to evacuate the workers on the pipeline. On March 27, TC Fay crossed the northern coast of Western Australia near Pardoo (150 km east of Port Hedland) as a category 3 cyclone. Torrential rains resulted over a broad area of the southern Great Sandy Desert with recordings between 400 and 600 mm in a 48 hour period at the Telfer Mine Site.
The rain from TC Fay cut access to the recently established Camp 3 (approximately 340 km from Port Hedland), the pipe stockpile on the Telfer Road (approximately 380 km from Port Hedland) and extensive sections of the pipeline Right of Way. The main road access to the Telfer Mine via Marble Bar was also cut for an extended period following the cyclone.
The level of water in this area had not been seen before, so no accurate assessment could be made on how long this inundation would last. A subsequent hydrological assessment was conducted with the results indicating that whilst the surface water may dissipate by the end of November 2004, it was unknown when the saturated soil profiles would dry.
Waiting and hoping that the ground conditions would return to a state that would allow normal pipeline construction techniques was not considered the best option for the fastest completion of the pipeline. GasNet and McConnell Dowell had dealt with the temperature extremes of the desert and now needed to implement a solution to tackle the extremes caused by TC Fay. Both parties, together with Newcrest Mining took action to complete construction around and through areas of the RoW still inundated with water. Safety, environment, land access and existing design conditions had to be reviewed and new/additional approvals obtained to enable works to recommence.Article continues below…
The solution was to re-align the pipeline route in one area and to build a platform that was high and dry and would allow for pipeline construction activities to recommence through another inundated area. Following the grant of environmental approvals by the Western Australia Government, approximately 40,000 cubic metres of rock was placed along the RoW in a section approximately 15 km long to form a temporary working platform (TWP). The TWP allows pipeline construction equipment to access the RoW to string, weld and coat the pipeline. The pipeline trench is then constructed through the inundated areas using excavators on swamp mats.
The pipeline is then wrapped in a protective wrapping, placed in the trench using excavators with slings and weighted down through the water, using sit on pipe weight saddles. All this work requires specialised construction techniques and skilled operators to ensure that the pipeline is laid to the same safety and quality standards as the rest of the Telfer Pipeline Project.
At the time of TC Fay, pipeline construction had reached approximately KP 250 with lower and lay, and KP 430 with front end clear and grade activities. At the time of writing this article the construction of the TWP was largely complete. It is anticipated that the construction of the pipeline through the inundated areas will be conducted in the last week of September to early October 2004. The conditions encountered during the construction of this pipeline have been extreme and the actions taken have been both ingenious and dramatic. These actions have enabled the project to now forecast a gas supply date of late November 2004.
Once a pipeline project like this has been successfully completed, the difficulties encountered along the way are often forgotten. What won’t be forgotten on this project are the invaluable experiences learnt by GasNet, McConnell Dowell and Newcrest Mining in delivering a project of this magnitude through Australia’s harsh and unpredictable environments. The Telfer Pipeline has thrown almost every extreme at what is GasNet’s first major project outside the state of Victoria. By the end of this year the Telfer Pipeline will be another quality asset behind GasNet’s name. The experiences gained through this project only add to GasNet’s abilities and further demonstrate GasNet’s unwavering commitment to delivering successful projects to its customers, whatever the extremes.