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Tunnelling completed on NZ project

The MTBM has recently been used in the Snells Algies Ocean Outfall project in the North Island, where it had a achieved a new world record of 2,021 m for the longest single drive by a Direct Pipe® MTBM earlier in 2020.

After Snells Algies Ocean Outfall, the MTBM was quickly re-mobilised at the Westland Milk Products project.

McConnell Dowell said its project team used its world leading experience to complete the 845 m of tunnelling and install the 832 m steel outer casing for the wastewater pipeline in just over one month, two weeks ahead of the expected constructed program.

“The Direct Pipe tunnelling method was chosen to mitigate the impact of work on the delicate coastal ecosystem,” the company said.

The scope of works included constructing a 60 m long, 6 m wide and 7.5 m deep sheet piled MTBM launch trench; completing the 845 m micro tunnel Direct Pipe drive; installing 832 m of steel casing pipe through the Direct Pipe thrusting technique that remains buried and submerged at the seaward end; and sliplining installation of the HDPE carrier pipeline into the steel casing pipe.

McConnell Dowell said an ocean recovery of the MTBM followed by installation of the marine diffuser will also be required, as was construction of an onshore deaeration chamber and carrier pipe connection.

“To retrieve Piper the MTBM, specialist excavation equipment sourced from Malaysia will be used to expose Piper under the seabed,” the company said.

“A dive team will then disconnect Piper and tow her to Greymouth Port where she will be lifted from the water. 

“Once complete, this project will be the first ocean outfall on the west coast of the South Island and will provide a new ocean discharge point for the treated wastewater from the Westland Milk Products facility.”

The company expects final marine operations will be completed early this year.

For more information visit the McConnell Dowell website.

If you have news you would like featured in Trenchless Australasia contact Assistant Editor Sophie Venz at svenz@gs-press.com.au

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