AWMA were engaged to design, manufacture, supply, install and commission water control gates, stopboards and electrical equipment for the $385 million Central Plains Water Enhancement Scheme Intake Gates Project located on the South Island of New Zealand.
Stage 1 required 18 months to complete and was delivered on-time. It involved opening up approximately 20,000 hectares of farmland for irrigation in the Canterbury Plains area bordered by the Rakaia and Hororata Rivers. An intake at the Rakaia River will direct water into a 17km long gravity fed headrace, or canal. A network of underground pipes will distribute water to shareholders downstream of the headrace.
AWMA designed, manufactured and installed a variety of water control equipment along the headrace canal that runs around the islands foothills to irrigate and supply environmental water for New Zealand’s largest irrigation scheme.
Engaged by Fulton Hogan/John Holland Joint Venture on behalf of Central Plains Water Limited, Stage 1 involved AWMA supplying;
- Twin 5m x 6m Radial Gates
- Four 2.5m x 2.5m top sealing fixed wheel Intake Gates
- A 2.5m x 2.5m hydraulic drive headrace Undershot Gate
- Ten various sized top sealing Penstocks facilitating offtake isolation
- Isolation Stoplogs up to 5m W x 5m H with lifting frames
- Associated Instrumentation, SCADA, Controls and Electrics
- Walkways and Platforms
The Radial gates are designed to withstand flood and sediment loading totalling 1.2 MN and designed for flat pack transportation and reassembly on site. The Headrace control gate is subject to 7.5m head pressure and required to control flows into the main supply channel with flows up to 33 cumecs and velocities up to 7m/s.
Design considerations include low whole of life costs during the 50yr design life, gate loadings (debris, wind and mud), flow velocities, earthquake compliance to NZ1170.5, material selection, isolation of dissimilar metals, reduced maintenance requirements, inclusion of self-engaging lifting frames to minimise operator risks, SCADA integration and operational flexibility. Designs were also developed in accordance with AS4100, AS4991, AS1657, AS1418.1, ASS3990, AS1170.0 & 70.2 and NZ1170.5. Full design reports were prepared with certification to Environment Canterbury (ECAN) requirements.