Nelson Evening Mail THURSDAY, AUGUST 19, 1920. HYDRO-ELECTRICITY

Nelson Evening Mail, Volume LIV, Issue LIV, 19 August 1920, Page 4

Nelson Evening Mail THURSDAY, AUGUST 19, 1920. HYDRO-ELECTRICITY

SPECIAL interest attaches to a recent meeting of the Wairarapa' Electric Power Board held at Carterton the other day, and it is well in view of the forthcoming developments in this district to observe Carefully what has been done. Air T. V\ Moore, act-ing-chairman, presided, and the engineer, Air H. F. Toogood, presented

his report upon the investigation work at the AVaiohino. The ,engineer, according to the Post report, stated he was in a position to report definitely on the proposed development of the Waiohlnc River for electric power. Plans in'sufficient detail were submitted to allow the whole proposal to he critically examined hy the Public Works Department. Mr Holmes, recently Engineer-incChief of the Public Works Department, visited the site .during the' last week lie held office, and lie permitted the engineer to say that the proposal was quite sound from an engineering point of view. Owing to the change in the head of the Department, Air Fnrkort had been unable to give time to go closely into the whoje scheme, but he had been consulted from time to time as the work had proceeded, and the general engineering principles involved bad boon discussed. It remained for Air Fnrkert to visit the site, and this he would do as soon as opportunity occurred. Since the engineer’s last report the investigations had caused him to amend the proposal in two directions. Satisfactory rock was not found at tho upper site, and it had to; 1)0 abandoned. Coming down stream about fifteen chains satisfactory foundations wore found, hub tho borings showed that bedrock was 30ft below water level. Tho discovery that tho rockhed was loft deeper in the gorge than elsewhere in the riven; made it necessary to alter the (lain design, and it was proposed to lower the height by loft, making the dam 1.1.0 ft above present water level at the dam site. This discovery also made it necessary lo add to tho estimates to provide for deeper foundations. The lowering of tho dam would reduce tho power ii) drought conditions, and would necessitate starting up tho. stand-by plant a littlt? earlier. 11l woulcf not greatly affect average summer conditions, as 140 cubic feet peri second could he relied upon, which will give 1000 k.w. continuously, or, with storage, 2000 k.w. on 50 per cent, load factor. The drainage area of tho river above the darn was to square miles, and the expected highest flood discharge was 27,000 cubic foot nor second. The total spill-way allowed was 220 ft by 12ty deep, and with this height of water, floods up to 30,000 cubic; feet iter second would

ho safely accommodated. Hie rod; in which the dam he founded j had been approved by Mr Holmes, ns j far as he was able to inspect it, as| quite sniable. No risks would be accepted with regard to leakage, and, at least ,10ft of rock would he cut away from both sides and bottom to ensure a perfect bond between the concrete and the rock. The dam proposed was designed on the arch principle, which was an improved method o) construct-j lion already adopted in .vv /('aland at the M’anorburn dam m Central Ota go. The water would be taken from .the impounded area through screens placed in the fore-hay. It would thou pass through a tunin'! bit in diameter and 570 ft in length, to a surge chamber ,15ft in diameter and of sufficient height to take all toe singe caused by a rapid shut-down, from the surge chamber ; the water would enter the :pipo line, which would consist of separate rive tied , mild stool pipes for each unit. The pipes will be 4 t indies in diameter and 220i:t in length. The power-house would be Hood-proof, so that a Hood, ol 2oit ■would not prevent the working oi the plant. For the present the capacity of the plant would he 2000 k.w. in two Units, each, of JOOU k.u . Ji o\ i»siou would be made in the powerhouse and tunnel for an additional, unit of 100 k.w. to enable the station to develop the full average suminei water supply when the demand had reached that point. 'Hie engineer’s estimate, excluding all electrical machinery, was £ 116,0U0, which included a speeia I contingency allow tvneo ol £9100.,. A sum of £15,000 has been allowed in the estimate for coffer dam, pipes, and valves for the diversion of tho river during construction. -On completion of tho work, the valves would remain as permanent scour valves. The engineer considered that the borings had been sufficient tp indicate the foundations below water level, but recommended that they should l>e extended. The ■engineer considered’ the scheme out, . The board decided that the engineer should continue the borings, and that, his report should be submitted to the Public Works Department for approval, in accordance with Power Boards Act. The treasurer reported expenditure to date to bo £853 9s Id. Accounts totalling £212 9s were passed for payment.