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Sat August 08 2020

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New micro boring record set

30 Jul New Zealand contractor McConnell Dowell has set a world record in the use of Herrenknecht’s Direct Pipe micro tunnelling technology.

The world record for the longest single drive by the micro tunnel boring machine (MTBM) was set on Watercare’s Snells Algies wastewater pipe and outfall project.

The record set this week by project team and the MTBM, which is called Piper, surpassed the previous New Zealand record by 92m.

Piper had been named by students from Snells Beach School, who provided their handprints to decorate the machine with the intent to “help her on her journey”.

The closed-faced Herrenknecht machine bored through challenging geological conditions and a curved alignment on what was considered an ‘essential’ project during the Covid-19 lockdown.

“This record achievement demonstrates the depth of skill and experience we have in our tunnelling teams, as well as our dedication to working through challenges to deliver another world-class project for our customer,” says McConnell Dowell project manager Brent Whiting.

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The project is split into three distinct operations involving a trenched dig and lay section, the Direct Pipe drive and marine dredging for the final marine pipeline.

Over 4km of DN630 HDPE pipe has been laid through traditional trenched dig and lay, primarily along public roads. The design incorporated six air valves and seven scour valve chambers.

The outfall section consists of 2,021m of trenchless installation of a 1,220mm-OD steel pipe, which is linked to the seabed section of 258m of DN 335 HDPE pipeline.

Upon breakthrough, the MTBM was driven into a pre-dredged trench off the coast at Martins Bay. The machine will be separated from the main steel pipe and lifted to the surface using an in-house designed pontoon that will also be used to transport the MTBM to a local harbour where it will be lifted out using a straddle carrier.

The project is the first phase of Watercare’s three-stage scheme to supply the Warkworth, Snells Beach and Algies Bay communities with wastewater services designed to cater for population growth. The scheme will improve water quality in the Mahurangi Harbour and deliver an upgraded wastewater system.

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