From the magazine, HDD

AXIS of power

The Vermeer AXIS guided boring system is being used to install part of the new Yarra Park Water Recycling Facility, which is being built in the parkland surrounding the Melbourne Cricket Ground (MCG). The facility’s design and build operator chose the Vermeer AXIS in order to achieve pinpoint, on-grade installation accuracy with minimum site visibility and minimal environmental impacts.

About the Yarra Park Water Recycling Facility

Constructing the water recycling facility in Yarra Park is a key component of the Yarra Park Master Plan (YPMP). The water recycling facility will produce Class A water by means of sewage treatment. The majority of non-potable water produced will be allocated to Yarra Park, with a significant amount also allocated to the MCG and the remainder to the Punt Road Oval.

The works will assist in providing a sustainable water supply for the future maintenance and upkeep of the park, enabling it to maintain its important role within the collection of inner urban public parks.

The vast majority of the development associated with the water recycling facility to Yarra Park will be located below ground, and hence will not be visible within the Yarra Park landscape.

The water recycling facility will incorporate a substantial below ground treatment plant measuring 25 by 31 m and ranging in depth from 4-8 m. The levels of the below ground plant will provide for storage and maintenance, the processing area and equipment, tanks, office and an amenities area. The underground plant will be covered by topsoil and turf.

Project scope

The main physical components of the water recycling system include:

  • Diversion and transfer of raw sewage from Wellington Parade South, with underground pipes of supply and return wastes
  • Underground sewage treatment plant
  • Treated water delivery to storage tanks irrigation reticulation to Yarra Park, the MCG and Punt Road Oval.
  • The project is being jointly funded by the Melbourne Cricket Club, who are contributing $A16 million, and the Victorian Government, who are contributing $A6 million. The contract for designing, building and operating the facility was awarded to Tenix.

An environmental approach

The construction impacts have been minimised due to the importance of preserving the trees in the area, as well as to minimise impacts on the heritage-listed park. Throughout the construction, the MCC wanted to maintain the aesthetics of the existing parkland, and maintain parking facilities for people attending MCG events as well as other stadiums in the area. For this reason, Trenchless Technology was a natural fit for the project.

Infrastructure installation with the AXIS

The Vermeer AXIS guided boring system was chosen to deliver keyhole pipeline installation. Due to the fact that the pipe being installed was at a depth greater than 8 m, a shaft was erected to position the boring machine for the installation. It was important the rig chosen for the task was compact in size and flexible enough to set-up in a restricted area.

Because the project was one of a highly environmentally sensitive nature, it was evident waste removal from the bore path would need to be dealt with in a responsible manner – no easy task given the depth of the bore. The AXIS power supply and waste removal functions via remote cabling and a closed hydraulic loop and vacuum system. This means the drill cuttings are transferred with a vacuum system through cabling to a vacuum unit above ground. This prevents leaving residual spoil in the excavation, which could be a hazard to the environment and to personnel undertaking the drilling process. This drilling by-product can then be disposed of from surface in a clean, safe manner to the appropriate disposal site.

The AXIS’ ability to drill through rock and alternative geology was an important consideration in rig selection. The AXIS’ retractable cutting head and ability to change cutting heads for conditions encountered during the bore meant avoiding the inconvenience of extra excavation and changing to alternate tooling. This meant a cost-saving to the client and faster turnaround time for installation.

Drilling conclusion

A pilot bore of 340 mm diameter extending 28 m was constructed from the launch shaft. Upon completion, a polyethylene pipe was inserted into this bore. The solid geology encountered permitted the withdrawal of the drill rods and insertion of the product pipe.

How the AXIS guided boring system works

  • A launch pit and exit pit are constructed.
  • A pipe laser is set-up in the launch pit at the required depth and grade of the installation.
  • A levelling frame and rack are lowered into the launch pit.
  • The drill head is lowered next, and contained within the drill head is a camera connected to a monitor on the operator console.
  • With the camera viewing the laser beam on the target, the operator can accurately monitor the target grade and make adjustments if the drill head moves off course.
  • At the front of the drill head, the cutter bit rotates to cut through the soil. The displaced soil is vacuumed out through a hollow section in the drill head and subsequent drill casing to a vacuum storage tank.
  • After the drill head is bored in, it is uncoupled from the carriage assembly. The carriage assembly retracts to its most rear position and is now ready for the first section of drill casing.
  • Rotation and thrust from the carriage assembly resumes as the first drill casing is pushed through the hole. This process is repeated with numerous sections of drill casing until the drill head reaches the exit pit.
  • The product pipe can then be installed using the pipe jacking method.
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