Rakaia hydro scheme gets second wind

Press, 5 July 1978, Page 21

Rakaia hydro scheme gets second wind

By

MIKE HANNAH

Plans for a 500 MW power project on the Rakaia River, which received a damp reception two years ago, have recently resurfaced in a modified form. Members of the Southern Energy Group, private engineers who originally devised the scheme, have received $lO,OOO to prepare a feasibility study of a 47MW power station which could lie about 20 km downstream of the Rakaia Gorge. The grant comes from the Central Canterbury Electric Power Board and covers a more detailed study of the power station, canal system and irrigation races which comprise the first stage of the initial project. The door is still open for other power supply authorities, such as the Ashburton Power Board, to contribute to the scheme at a later stage. This first phase is estimated to cost almost SBOM over a five-year construction period, allowing for inflation and inter* est charges.

It does not involve the raising of Lake Coleridge, an integral part of the original scheme. Five power stations are proposed in the whole project, and Mr Bob Morris, chairman of the Southern Energy Group, is optimistic that the whole scheme be accepted and constructed by the year 2000. In the first phase, however, only a diversion

canal, running parallel to the existing riverbed, a single power station and the main irrigation race would be constructed. Another power station of 50MW capacity could be constructed on the canal before the raising of Lake Coleridge would have to be considered, says Mr Morris. When the scheme was first suggested in 1976 it failed to gain the interest,

let alone the support, of the Ministry of Works or the then New Zealand Electricity Department. Mr Morris says the scheme now planned has the interest of the M.W.D. and the Electricity Division. Water would be drawn off the river at the 230 m level opposite the Highbank power station, some 10km downstream of the Rakaia Gorge Bridge. A diversion canal would sidle across the river terraces until it reached the plains. The canal would be about Bkm long, 15m wide at the bottom, and 7m deep, with a maximum capacity of 170 cu. metres per second. At the top of the terraces an irrigation race would branch off and a short power canal would run 600 m to a headpond and a penstock intake. Penstocks would run from the intake structure to a powerhouse on the river bank below, and a tailrace would carry the water back to the Rakaia River.

Mr Morris expects the feasibility study to take about three months to complete. This will then be presented to the Government committee on small hydro schemes and an application made for Government funding to carry out the next stage; About $150,000 would be needed for investigations to show whether the scheme was viable. An environmental

impact report would be prepared and water rights applied for, but the work could be funded by two grants of $75,000, so that if the project did not appear viable it could be halted before the second half of the investigations began. The concept study already prepared is not binding on any of the parties that contributed to it, but, as Mr Morris points out, there has been a lot of co-operation up to this stage. The Southern Energy Group prepared the original report for the New Zealand Energy Research and Development Committee and was funded to the tune of $20,000. The group itself has spent $20,000-$30,000 on its investigations and, says Mr Morris, “We’re very much on the debit side at this stage.” Not surprisingly, he expects the private engineering companies represented in the group to receive the scheme contracts.