POWER DEVELOPMENT.

New Zealand Herald, Volume LXV, Issue 19916, 9 April 1928, Page 6

POWER DEVELOPMENT.

WAIKAREMOANA PROJECT. PLANT AT THREE LEVELS. : '■ - ' \ti"l i " TUNNEL UNDER THE LAKE. FIRST STAGE READY IN 1929. [BY TELEGRAPH. —OWN COREESFONDEKT.) WELLINGTON, Saturday. It is now likely that the first develop, ment of the Waikaremoana hydio-eleu-trie scheme will be supplying current to-the Mangahao system (that is, to Wanganui and to Wellington province as well as Hawke's Bay) by June of next year, probably some months before Arapuiti will bo supplying current. Bar accidents," the Waikaremoana works and the transmission line to Napier can be completed by that month. When the other two developments are complete, some of the water will be used three times to turn turbines. Forestalling Arapuni. A suggestion that the Arapuni area might benefit by the earlier completion of Waikaremoana, through the urgent construction of a transmission line north to the Waikato, does not seura to have met with much encouragement. The drainage river of Waikaremoana is the Waikare-taheke, a tributary of the Wairoa. The No. 1 development in its present form involves no physical interference with the lake, though in certain contingencies the lake may be drawn on. No. 1 collects some water from the Wai-kare-taheke, by means of a weir and open race, diverts this water into Lake Kaitawa (which, by a simple earth dam, is raised in level by 10ft.), further conveys the water by an 11 chains tunnel to the su'ge-chamber, and shoots; it down* pipe-lines to a power house on Lake Whakamarino, a drop of 645 ft. Lake Whakamarino, at the foot of the' drop, is not exactly a lake, but it will be built up—when the No. 2 development is undertaken—in the same manner as Kaitawa—that is, by simple earthen dam-walls—and will be of greater superficial area than Kaitawa. No. 2 development means that the used water from No. 1 wi'ii riot be allowed to fall • back into the bed of the Waikare-taheke, the river from which it was taken, but will be conserved by means of the enlarged Lake Whakamarino, and will be carried ou partly by open cut, but mostly by means of a 112 chains tunnel to a point where the engineers can give it another fall down pipe-lines—the drop this time will be 369 ft.—to a power house on tho bank of the Waikare-taheke. From this power house, which can be called No. 2, the twice-used water can escape back into the parent river. Fuf.ure Tapping of tho Lake. Triple use of tho water will not bo achieved until No. 3 development is undertaken in tho years to come. It will be seen from the aboVe that No. 2 comes in at. a lower altitude than No. 1. But No. 3 does not follow in that order of descent. No. 3 is higher than either of them and represents a first use of the water, for il taps the lake itself. Normally Waikaremoana overflows at its outlet only for part of the year, but it has also subterranean outlets or fissures some of which have a constant flow. The engineers design ?s to seal these fissures, drive a tunnel under the lake, then sink a caisson to the ficor of the l&ke, snd, behind I'.he protection of the caisson hole through to the tunnel. (In similar way Lake Coleridge has recently been tapped for extra power.) From this tunnel mouth pipe-lines will convey the water to No. 3 power house at Lake Kaitawa, a drop of 430fi. As No. 3 development belongs to tha future, no exact data are yet obtainable about, its sub-lake tunnel—which replaces the idea of an open cut current, in 1125 --but some interesting comparative figures of the three schemes may be presentee. Altitudes and Main Points, First of all, compare altitudes. Ap' proximately, the water surface of Waikaremoana is at 2015 ft.; Lake Kaitawa water surface (which may be taken as indicating approximately the position of 3 „P°\ ver bouse) will be at, 1689 f.; Lake Whakamarino water surface and 3\ r o 1 power nouse will be at 900 ft.: and No'. %rPn Wer rl] ouse ' tho lowest, will be st K /v numerals of the power 2 and 3 > no* correspond with those given in some of the older charts. The numerals in this article represent the order in which the developments will be undertaken, not the order in which the three power houses will ultimately stand in the Waikarrtaneke Galley. The following; table summarises some of the main facts:— Length Full * it ~ Water DevelopPipeline Drop, ment. " Feet. K.V.A. *£•2 •• 1500 3T.3 40.000 No> 3 •< 3000 430 50,000 totals .. 6355 U44 150,000 It will be seen that No. 2 will require not much more than half the pipe line needed by No. 1, now in hand. But i>iO. will require a tunnel 10 times as Jong as that of No. I—ll2 chains, as against 1.1 chains. Cheaper by Avoiding Big Dams- „ \By the time No. 1 development, is completed, probably not later than June, 1929, it will have cost approximately three-quarters of a million : that is for headworks, open race, tunnel, surge chamber, pipe-lines and power houses. The three-quarters of a million does r.ot include cost of transmission and distribution. Compared with other hydro-elec-tric works, it would seem that a very great deal has been secured for (he threequarters of a million. In being able to dispense with dams such as have been made at Arapuni and Mangahao, Waikaremoana is very fortunate, for the earth dams are comparatively a bagatelle. So Waikaremoana should generate, its power relatively cheaply. In Hie absence of big dams, the surge chamber and pipe-lines and power house represent about 80 per cent, of the cost. It should be added that in the first place only half Fne capacity of the No. 1 development will, be generated. The 60.000 k.v.a. means three sets of 20,000 k.v.a. each Two are being installed, . and there is room for the third. In the first place, there will be water enough for one and a- . half (30.000 k.v.a.), rendering immediately available, as stated, half of the full load of No. 1 development. The present position of the works at No. 1 development may be summed "P as follows:—Head works, including surge chamber, about 95 per cent, completed; pipe-lines, about 60 per cent.; power house building, 65 per cent.; . outdoor sub-station, 50 per cent. The Waikaremoana works are copnected by a 35-mi!es road with Wairoa. but as the deficiencies of the Wairoa .River caused the development of a port at Waikokopu, with connecting railway, carriage of heavy material has mostly involved haulage from the latter" p'ace The road section of the haulage would not have been practicable had not the Public Works Department, taken the road in hand, and (with a contribution from the County Council) largely remade it. Bridges have been rebuilt or strengthened—even the big Wairoa River BriogJ at Frasertown haa to be stiffened—[Here has been constant maintenance « the road surface. The biggest gross loaa involved in tht haulage is 34 toni.