Emergency pipeline cost blows out
News
damian.george@stuff.co.nz
The estimated cost of building an emergency water pipeline for Wellington has shot up by $15 million.
The cross-harbour pipeline, between Wellington and the Hutt Valley, is one of two options being considered to ensure the city continues to have a fresh water supply should it be hit by a natural disaster.
The other, which is expected to cost between $60m and $70m, involves sourcing water using bores from the Waiwhetu Aquifer under Wellington Harbour, near Matiu/ Somes Island.
But it is still to be determined whether the site holds suitable drinking water, with analysis of test results to be completed next month.
Wellington’s water is piped from the Hutt Valley along State Highways 1 and 2, but could take months to repair if the pipelines were damaged in a large earthquake. That could leave parts of the city, particularly the eastern and southern suburbs, without water for up to 100 days.
Greater Wellington Regional Council had set aside $101m for the cross-harbour pipeline in its 2015-2025 Long-Term Plan.
But in its new estimate, it has put that cost up by almost 15 per cent.
‘‘Our current plan continues to provide for [the pipeline], at an estimated cost of $116 million,’’ the council said in its draft plan.
‘‘Since then, we have identified that harbour bores, which connect directly to freshwater sources, might be a more cost-effective solution.’’
A Wellington Water spokesman said the revised cost estimate was largely due to inflation over the past three years.
Testing of a first possible source in the aquifer last June revealed there was enough water for an emergency supply, but it would need significant treatment. The drill site was about one kilometre off the Miramar Peninsula.
Wellington Water said the harbour bore option could not only be a cheaper alternative to the pipeline, but also a more resilient one.
It expected to make a call on the best way forward before the end of July.
‘‘The options are being assessed against a number of criteria including resilience, cost and impact on the environment,’’ a spokesperson said.
Early indications from the Matiu/Somes Island test site were positive because the aquifer was thicker there than at the first drill site, but the water quality was not yet known.
Further analysis of the aquifer was being done by GNS Science.