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50,139 h.p. The latter, however, has not a capacity sufficient to supply all this, so that; Waikaremoana and Arapuni have to be increased to each carry a portion of the load to the north-east and north-west of Palmerston North. To provide for all contingencies of the scheme it is proposed to make the Waikaremoana development 40,000 h.p., as above, W t aikato Development. For the Auckland and Main Trunk district supply, and for the bulk of the Taranaki supply, two alternative sources have been selected -namely, the Arapuni Gorge and the Aratiatia Rapids, on the Waikato River. Of these two the Arapuni is the better one, provided our investigations prove the construction of the big dam required to be practicable. It also has the advantage that it is fortyfive miles nearer the main market in Auckland, whilst at the same time it is not much farther from the other market in Taranaki. The transmission-line south to Taranaki and the Main Trunk districts does not have to cross the same amount of undeveloped country as from Aratiatia, but will everywhere traverse country that is in process of development along the railway routes. It is to be expected that the loads along the routes of these transmission-lines will develop rapidly as the heavy sections of railway thereon require electrification, and the settlement increases with the improved conditions. The scheme of development proposed is to build a dam in the gorge of the river, raising the water-level about 140 ft., and diverting the river into an old parallel channel at a higher level. Some 60 chains from the dam this old channel approaches within. 8 chains of. the existing channel, and at an elevation of 165 ft. above it. Here a low weir will be built across the channel, and the water required for power will be taken through pipe tunnels to a power-house on the present river-bank. From observations made during the low-water flows in 1915 it is estimated that we could ultimately install a plant capacity of 162,000 h.p. in this station. To fill its function in the universal scheme outlined in this report a plant capacity of 96,000 h.p. is required. At this stage the development becomes an exceptionally economical one, and the cost to supply on to the main transmission-lines as in the other cases is estimated at £1,078,700, or £10-78 per horse-power. If the scheme were ultimately extended to its limit it is likely that the whole plant capacity of 162,000 h.p. might be installed for £1,426,707, or £8-78 per horse-power. Partial developments of this source would, be relatively more expensive owing to the cost of the large dam having to be incurred from the inception, but it is estimated that even a partial development of 37,500 h.p. can be put in for £20 per horse-power. The Aratiatia Rapids also afford a very good, source of power, and up to a limit of 66,000 h.p. can be developed in successive stages without unduly loading the earlier stages of development. The limit of 66,000 h.p., however, is not sufficient to fit in with the scheme of distribution herein proposed, and. another scheme of development has been adopted. This necessitates building a dam at the head of the rapids which will back the water right into Lake Taupo, drowning out the Huka Falls. With this scheme a fall of 175 ft. becomes available, and with the regulation afforded by the storage, in Lake Taupo the plant capacity can be, increased to 135,000 h.p. The development will be a fairly economical one at the ultimate stage, though owing to heavy cost of dam it will be somewhat expensive at earlier stages. Unless exploration work proves special difficulties to exist at Arapuni it is unlikely that Aratiatia will prove a better source for generation. i Primary Transmission System. The main transmission-lines are shown on* drawing E 116, and will be of the suspension type, carried for the main on ironbark poles, though steel towers will have to be adopted in some cases where special construction is necessary. It will be seen that the various lines have been duplicated and interconnected in such a way that practically every substation is supplied with alternative supply in case of one line breaking down. The lines have been laid out to serve existing markets in the most economical way, whilst as far as possible at the same time the routes best calculated to serve prospective railway and special development loads have been adopted. The scheme provides for a total length of 1,112 miles of main transmission shown on drawing, also for 309 miles of branch mains at lower voltage to supply disconnected main substations. The configuration of the country is not so suitable for transmission as it is across the Canterbury Plains, where the lines can practically everywhere follow roads. A considerable length of the main lines in the North Island will have to go across country, and provision has had to be made for the extra difficulty of patrol under these conditions. A substantial type of construction has been decided upon, and depots and linemen's quarters at frequent intervals have been allowed for. The total cost of the main transmission system is estimated at £1,795,240. Primary Substations. The main substations connected to the main line will transform down the power to 11,000 volts for distribution to the local substations and surrounding districts. At these stations it will also be possible to cut out sections of line which may develop a fault, and transfer the load to other circuits leading in the same direction, thus adding greatly to the flexibility of the system. Most of the stations will have alternative supplies from either direction to give extra security in case of temporary breakdown of supply on any one circuit. They have been arranged to give supply to the various local authorities and power-users with the least expenditure in the secondary distribution system. The complete main substation equipment is estimated to cost £838,808.