The ongoing infrastructure works in Canterbury, New Zealand’s ambitious Central Plains Water Enhancement Scheme is centered around a 55m-high dam and affiliated storage and diversion canals. Up to 60,000 ha (148,230 acres) of land will be irrigated by the project. The Rakaia and Waimakariri Rivers would be connected the 280 million cubic meter-capacity reservoir via a 56km-long headrace canal.
The overall water scheme is currently in Stage 2 of its development.
LINING THE HEADRACE CANAL
International geosynthetics manufacturer Solmax has supplied 600,000m2 of high-density polyethylene geomembrane for the headrace canal. The barrier solution will optimize the canal’s flow and prevent loss of vital water to seepage.
One of the primary goals of the project is to give the region’s farms 100% water dependability.
The geosynthetic installer’s work on the headrace canal has involved the excavation of 3 million cubic meters of soil. The cut and fill construction utilizes a slope gradient of 2:1 (H:V) with a specially designed key anchor trench. The HDPE geomembrane is protected by 900,000m² geotextiles, used as underlay and overlay, depending on the section of canal.
Some invert sections require liner ballasting, the installer reports.
The scope of the headrace canal works have also included 13 bridges and 5 off-take structures. A special termination detail was utilized to seal the liner to the structures. A #316 marine-grade stainless steel batten bars and neoprene rubber gaskets were fixed with epoxy anchors at 150mm centers to provide a continuous compression seal between the concrete structure and the HDPE liner.
A crane was utilized for deployment for the terrace section where limited access and safety had to be considered. The narrow cut reduced excavation and saved on construction cost.
- Learn more about Solmax’s HDPE geomembranes at www.solmax.com
- Follow the headrace canal and overall Central Plains Water Enhancement Scheme at CPWL website: www.cpwl.co.nz
CPWL has shared a flyover of the works on its website.