Dam Site For Benmore Power Project Chosen

Press, Volume XCV, Issue 28267, 3 May 1957, Page 8

Dam Site For Benmore Power Project Chosen

(New Zealand Press Association) DUNEDIN, May 2. The site for the Benmore hydro-electric scheme has been decided upon and a huge earth dam will be built across the Waitaki river about one mile below its confluence with the Ahuriri. Capable of generating 486,000 kilowatts, the new project will be the biggest engineering job tackled in New Zealand and the earth dam will be one of the largest in the world.

This lower site is about 10 miles below Gooseneck, where the proposed concrete dam, with a generating capacity of 332,000 kilowatts, might have been built.

The site now decided upon allows the water of both the Waitaki and the Ahuriri to be used for power generation.

No official announcement has yet been made, but it is believed that the Minister of Works (Mr W. S. Goosman) will soon make a statement about the site and when work will start. When completed, Benmore will be the main station in the hydroelectric development of the Waitaki basin.

The earth dam, which will have a concrete core, will be faced with concrete or stone on the Upstream face and will provide engineers with problems considerably different from those encountered at Roxburgh. Besides being a considerably bigger job than Roxburgh, the work will be of greater diversity and spread over a larger area. It is likely that fewer men and more machinery will be used. Now that the location of the dam has been fixed, it will be necessary for the Government to use its available authority to take the land required. To Cost £26 Million It is likely that Benmore will cost more than £26 million and take about eight years to complete.

The scheme is part of the major development of the Waitaki area to produce 1,500,000 kilowatts of power.

There is still a considerable amount of design work to be done on Benmore, but once the Government decision to go ahead is made known a start on some of the associated projects will soon be made.

There would have to be a town to house the construction crews, and roads and essential services would have to be provided. Ministry of Works engineers have been engaged for some time sinking shafts and bores and driving tunnels into the hill by percussion and rotary methods: The object is to prove the quantities of materials available and to find the depth of rock bottom at the dam site. Present indications show the average depth of the shingle is about 50 feet. Preliminary Work

Nearly 100 shafts have been sunk on sites over an area of about three miles, extending towards the Kurow-Omarama highway from the dam site. The site of the camp, which was on the north side of the highway, has been shifted to the southern side, close to the Otematata stream. There have been 40 or 50 men

engaged in investigation work at Benmore, and from their information a nucleus design team of six has been able to provide preliminary reports and plans for the Minister. More detailed recommendations have recently been made by Ministry of Works engineers. Once the official word is given, the design team will be increased and will eventually contain about 30 people, the peak size of the group employed on the Roxburgh project.