This project formed part of the Gold Coast Water pumps and pipes project – a program aimed at delivering approximately 80 kilometres of water mains and several pumping stations to the Gold Coast area. The HDD crossing of the Coomera River formed a part of the proposed northern extension of the Pimpama-Coombabah trunk recycled water main
The ground conditions varied between high plasticity clay, sand, silts and gravels. The geotechnical information supplied by the client was very accurate and enabled the drill muds to be managed effectively through the continually changing ground conditions.
Due to the salt water conventional walkover locating systems could not be used. UEA utilised its own Digital Control Incorporated “steering system” to undertake the pilot bore. The first bore was used an exploratory as well as providing a 100mm drill fluid return line. The hole was pre-reamed using the D300 x 500 and a tail string installed in place as the ream continued.
The pipe weight was approximately 40 tonne. With the pipe required to be filled with water to create neutral buoyancy and prevent the pipe lifting in the hole and cutting through the surface the finished pipe weight for install was nearly 90 tonne. During the pullback pressure never exceeded 20 tonne at any time.
For more information about this project or UEA Trenchless, please send enquiries to Steven Hopkins.