Water supply system for water storage in Australia
Water supply system through horizontal directional drilling
Project name: Mardi Dam and Mangrove link project
Project date: 2011
Products: PE 100 pipes, da 1200 SDR 11, 282 m horizontal directional drilling-method
The 282 m long OD 1200 mm SDR 11 (PN 16) water main pipe was installed by horizontal directional drilling (HDD) underneath the Wyong River as part of the Mardi Dam to Mangrove link project.
The project was constructed by John Holland Group for GWC Water, which is a joint venture between adjoining councils on the Central Coast of New South Wales (Australia). GWC Water administers the 3 rd largest urban water supply system in the state. AGRU worked closely with the local pipe welding contractor, Kenkar Plastics, in putting together a proposal for the HDD drilling contractor UEA Pty Ltd. The original design was a micro tunnel, utilizing mild steel concrete lined pipes. The project has been converted to directional drilling process using PE 100 pipes in order to eliminate the need for deep shafts, to reduce the risks associated with micro tunnelling in alluvial ground conditions as well as provide a reduction in project costs.
The specific complexness of the project was
Production of the heavy wall PE 100 pipe in OD 1200 mm SDR 11 – this comes up to a wall thickness of 109 mm. These pipes were produced in lengths of 11.8 m (to reduce welding at site). 24 pieces had been installed and one pipe piece was kept for contingency purposes. Pipes of this size were special ordered products from AGRU Austria and have never been handled before in Australia.
The welding of the pipes on-site was performed under stringent environment conditions. The welding was performed by the local company Kenkar using hydraulically controlled trench heating element butt welding equipment. The butt welding process was executed according to validated DVS welding procedure and parameters. The qualified welders made 3 joints per day (in total 27 joints). The total preparation of the pipe string (282 m) before installation into the ground took 14 days.
The installation of the PE 100 OD 1200 mm PN 16 pipeline with HDD method was performed first time in Australia. The extremely limited access to exit and enter the site with products and equipment required innovative planning and solutions.
Limited number of calendar days to complete the project which was only achieved by applying PE 100 pipes and the HDD installation method: The pipe was hydrostatically pressure tested to 16 bar prior to insertion into the HDD bore. Installation of the pipe into the bore was completed within 12 hours.
The pipeline links two existing water storage facilities, Mardi Dam and Mangrove Creek Dam.