Hydro-electric power station, recreational lake, irrigation water reservoir & conservator of downstream minimum flow, all-in-one
Opuha Dam is located at the confluence of the north and south branches of the Opuha River, 18 km from Fairlie in the Mackenzie district of the South Island of New Zealand.
A selective tender resulted in Doug Hood Limited being awarded the contract in October 1995 to build the dam for $16M. Construction commenced in 1995.
In 1997, when the dam was built to half design height, the project was delayed 9 months as the result of a series of storms in the catchment leading to overtopping of the dam.
Commissioning began by the end of 1998, and the dam has been operating at full efficiency since April 1999.
Unique features of the project included that it was the first built under the Resource Management Act and the new Building Act, it was carried out to a fixed price, and was a design, build and maintain contract. The project included a variety of complex designs, for example the stepped spillway as a solution to aid energy dissipation.
A lump sum contract to design and construct a 50m high earth dam to contain a lake for irrigation, electricity generation, and recreational use.
The dam required 750,000m3 of fill, a concrete spillway, single penstock, 7.4 MW Francis turbine and generator, and downstream weir for maintenance of minimum flow of 1.5 cumec.
Turbine average maximum energy output is 6.8 MW, and average annual energy output has been 30 Gwh.
The 710 ha lake has 95M m3 of water storage, allowing summer irrigation to 16,000 ha of farmland.
In 2001, the NZ Contractors Federation and Caltex jointly recognised Doug Hood Ltd’s commitment to the contracting industry with regard to the successful completion of the Opuha Dam in 1999.