WAIRARAPA HYDRO-ELECTRIC BOARD

Dominion, Volume 13, Issue 279, 19 August 1920, Page 8

WAIRARAPA HYDRO-ELECTRIC BOARD

ENGINEER'S EEPOUT ON WAIOHINB SCHEME. (From Our Special Correspondent.) Carterton, August 17. A meeting of the Wairarapa i'lectrio Power Board waß hold at Carterton to-day for tbe purpose of receiving the report of Mr, 11. P. Toogood (engineer) upon the Waiohinc scheme.

The engineer stated that he had tubniittcd 'plans in sulUcient detail to allow the whole proposal to bo critically examined by the Public Works Department. Mr. Bolnic-s, recently tngineer-in-Ohief of the Department, visited the site during tho last week he held office, and considered the proposal quite Bound from an engineering point of view. Since the change in the control of the Department, Mr. Furkert had been unable to glvo time to go cloßely into the scheme, but he had been consulted from time to timo.ns the work proceeded, and'the general engineering principles involved had been diHCUßacd. It remained for Mr. Furkert to visit the site, which he would do us soon as the opportunity offered. Since the previous report the investigations caused the engineer to amend the proposal in. two directions, as satisfactory rock was not found at the upper Bite, and it had to bo abandoned. Coming down stream fifteen chains, satisfactory foundations were found, but the borings showed that tho bed rock.was 30 feet below water level, The discovery that the rock bed was fifteen feet deeper in the gorge than olsowhere in the river made it necessary to alter the dam desigu, and the engineer proposed to lower the height by fifteen feet, making tho dam 115 feet above present water level at the Jam site. This discovery also made it necessary to add to the estimates to provido tor deeper foundations. The lowering of . the dam would reduce tho power en drought conditions and would necessitate starting up the stand-by' plant a littlo earlier. It did not greatly effect average summer conditions, as WO cubic feet per second could be relied upon, which would give 1000 k.w. continuously, or with storage 2000 k.w. on 50 per cent, load factor. The rock on which the dam was to to founded had been approved by Mr. Holmes, as tar as he was able to inspect it, as quito suitable. No rißk would bo accepted in regard to leakage, and at least 10 feet of rock would be cut away from both sides and bottom to ensure perfect bond between concrete and rock. The water would bo taken from the impounded area througli screens placed in tho fore-bay. It would then pass through a tunnel 6 feet in diameter and 570 feet in length, to a surge chamber 15 feet in diameter, and of sufficient height to take all the surge caused by rapid shut down. From tho surge chamber the water would enter the pipo lines. The pipe lines would consist of separate riveted mild Heel pipes for each unit. The- diameter of the nines would bo 44 nches. and they would be 200 feet in length The powerhouso would bo flood proof, so that a floodrso of 25 feet would not rrcvont he wo king of the plant. The capacity of the Plant for the present would be !M0 kw. in two unita oach of WW k.w. Provision would bo made in tho powerhouse and tunnel for an additional unit of 1000 kw. to enable the station to devLn the full average summer water sups when So demand reached that point. The engineer's estimate, excluding all electrical machinery, which has already lieou provided for in the electrical engineer's report, was £116,000. and included a Bneclal contingency allowance of £9100. ' A diversion tunnel has been proposed U» out off tho water and allow the foundations to be excavated. Another method which appeals to the engineer, and w 11 she--ten tho time required for the work, to provide five pipes, each five feet in diameter, to carry the smaller floods past the foundations during construction. Those pipes will be built into coffer dams, and will bo provided with valves, which will ultimately become the scour valves for tho dam. A sum of £15,000 has boen allowed in the estimate- for coffor dam, •pipes, and valves for this purpose. The onglneor considered that the borings were sufficient to indicate the foundations below water level, but they should be extended. , . , , Tho board decided to proceed with further borings, and to submit the report to the engineer of the Public Works Department for approval in accordance with thl Act.

It was also decided to meet Jfr. Furltcrt, enginecr-in-chicf, nt the Waiahlnc, on a date to bo arranged, and to invite Jlcaarn. A. D. Jl'Lcod and G. R. Sykcß, M.P.'a, to attend.

An option for n. period was givon tho board by llio W.F.O.A. for a section of land near the railway station, Carterton, nt, £275. A further offer from Mr. W. Tf. 'Wilton, of two Boctlona In Broadway, Carterton, nt £450. was not entortained, being on tho wrong Ride of the railway for tho bonrd'n purpoßos.

Tho trenaurer reported thnt the expandlturo to datn had been ,C 853 9s. Id. Accounts totalling .£842 93. were ipassed. for payment.