The TBM, called Blanche, set the world record when she reached 1,496.48m – the longest-ever stretch of pipe laid by the system.
Direct Pipe is a Herrenknecht trademarked tunnel boring machine (TBM) that combines microtunnelling and Horizontal Direct Drilling (HDD) into one machine. In one step, the borehole can be excavated and a prefabricated pipeline installed. Direct Pipe is generally used in Europe to install pipelines under rivers and other large bodies of water.
Blanche is working at Watercare’s Army Bay Wastewater Treatment Plant, Whangaparaoa. The McConnell Dowell project team monitored progress as she approached 1,495m, the previous record set in Texas in 2017. The eventual length on the project will be 2km.
Project manager Chris Powell said that the record was attained “by achieving the right balance between pipe strength, thrust and the operation of the 34 tonne TBM to maximise its capabilities”.
Powell added: “This is the first time the Direct Pipe system has been used in New Zealand. As a consequence we weren’t constrained by traditional applications and were able to use the Direct Pipe system it in ways not explored before. We set some pretty high expectations, we learnt much and achieved a real global step-change in how this new tunnelling technology can be used.”
He said that the benefits of Herrenknect’s Direct Pipe system include the ability to install long pipelines in a single drive, safely with speed, all of which reduce environmental impacts. The benefits make it ideal for working in small or sensitive spaces such as the Shakespear Regional Park, where the site is located.
Herrenknecht Asia pipeline expert and area sales manager Ben Hayes congratulated McConnell Dowell on using the method to achieve a world record. “The hands-on site team have been particularly impressive in their ability to adapt and overcome hurdles encountered – along with the support of Herrenknecht site personnel with their considerable trenchless technology expertise – to ensure an efficient and safe execution with a technology that was essentially new to them.”
The project team has developed the system so it can achieve drive speeds of up to 30m a day.
The scope of Watercare’s NZ$31m project includes constructing 2.9km of new gravity-fed wastewater pipeline – 2km of onshore pipeline installed using the trenchless Direct Pipe system, and 900m of marine outfall that will run along the seabed. The project also involves upgrading the existing ultraviolet disinfection facility, electrical controls and standby generators as well as building a new pump station.
Construction to upgrade Watercare’s third-largest wastewater treatment plant began in August 2017 and is scheduled for completion in early 2019.