Projects

Pillans - Tauranga

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After a winter of severe flooding, Harker Underground Construction was contracted to install a 400m stormwater outlet in the Tauranga harbour.

After only 20 days of pipejacking, Harker installed over 400LM of 2.9m OD pipe through soft, highly sensitive and very fine Tauranga ash using our new TT2550H Slurry TBM. This is the first time a slurry TBM has been successfully used through this ground and is particularly gutsy given the size of the pipe.

The project involved designing and building a completely new state of the art 2.95m OD slurry TBM. Right from the development stage, the separation plant was mostly sourced from New Zealand using Kiwi companies and know-how. The entire system worked so well that it installed up to 40LM of pipe per shift, or 50Tonnes of solid material separated per hour. Line and level were within 30mm of the design.

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This project included a complete re-design of the client's original scheme to stabilise a 10m high unstable bank above the outlet structure. Harker used an innovative soil nail design to reduce costs, shorten the construction time and minimise disturbance and hence reduce the impact on local residents.

Due to site constraints, the entire slurry separation plant and offices were set up in a nearby park, approximately 50m from the jacking shaft. The park was surrounded by residential properties, and despite working some long hours to ensure the project's success, Harker received far more letters of appreciation than complaints.

In addition to the 400LM tunnel the project also included:

  • 500LM of open cut pipe ranging in size from 225 to 1650mm
  • 55LM of 1800mm box culvert
  • 1 x 5m x 5m underground structure
  • 1 sea outlet and associated Reno matting
  • Road reconstruction; and
  • Numerous sumps, manholes and inlets

The project was successfully completed in May 2008, receiving a certificate of appreciation from the Mayor.

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