The commissioning of the new crossing was completed on May 9 and the temporary aerial crossing of the river that had been constructed in March was decommissioned and dismantled.
The February 16 floods washed out the Pohangina River Bridge, leaving NGC’s 8 in. high pressure gas pipeline that was attached to it suspended in floodwaters. Gas supplies were restricted to residential and essential users until February 20, when NGC was able to resume full supplies east of Ashhurst by recommissioning the existing, damaged pipe to half its normal operating pressure. Use of the existing pipe ceased on March 3 when the more robust temporary aerial crossing commenced operation. About 100 metres of the aerial crossing was suspended from a cable approximately 6 metres above the river at centre span. See The Australian Pipeliner, April 2004, Page 36 for more information on the aerial crossing.
The new crossing is located about 60 metres downstream of its former bridge location and involved the installation of 540 metres of 8 in. pipe. About 144 metres of its length is encased in concrete and is laid in a trench 4-5 metres under the river bed.
Inglewood Engineering was involved in the construction of the emergency aerial crossing and the installation, including trenching, pipelay and testing, of the new permanent crossing.
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The construction of the new section of pipeline took approximately six weeks including the river crossing, pipeline realignment and tie ins to the existing line. Inglewood Engineering had an average of six men on site, peaking to twelve during the pipe pull. During installation, the pipe was floated across the river and into position. Despite the wild weather that led to the damage of the original pipeline, the weather during construction was mostly fine with the river back to normal summer flow.
“Inglewood was proud to be part of the successful emergency management team that ensured that full gas supplies were restored as soon as possible. The emergency and the tough conditions associated with it brought the best out of the whole emergency response team,” said Dallas Chadwick, Managing Director of Inglewood Engineering.
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