LAKE COLERIDGE.

Press, Volume XLIX, Issue 14760, 2 September 1913, Page 4

LAKE COLERIDGE.

■ # ■ ■ ■■■ . VISIT TO THE WORKS. STATEMENT BY THE , MAYOR. Last week-end the Mayor paid a visit of inspection to the Lake Coleridge works, and at the meeting of tho City Council last night ho gare a most interesting account of the present stato of tho works. Hβ said that by the courtesy of Mr L. Birks, Assistant Government Hydroelectrical Engineer, and Mr Kissel, engineer at tho works,' he was sho%vn over tho whole of the extensive works at Lake Coleridge. Tho day of the visit was fine but very windy. That might havo been the cause of the disturbed appearance of tho placid waters of the great lake, but it suggested to him that the mighty power pent up in tho lake was eager to be exerting its energy in a manner that would be beneficial to tho peo'plo of Christchurch and surrounding districts. THE INTAKE.- J At the intake end of the tunnel there J was not much to be'eeon abovo ground, except what had already been described. Practically all that could be done had , been.'- until tho arrival of tho gates to prevent the water entering the tunnel. Theso gates were due to arrive this week. The tunnel at that end was now l"i chains in, and still in solid rock. At the central whaft there was quite a littlo village of huts, and a large staff of men, otherwise there was not much to interest the visitor, us all the works are 200 feet below tho surface. THE OUTLET END. Tho work at the outlet end liad made great progress since his Inst visit. The party entered the tunnel and walked its entire length as fa r as completed, 73 chains. The tunnel inside was quite dry and in places dusty. It was lit up with electric light the whole length. The two extreme ends were now within iiftecn chains of meeting. Barring unforeseen circumstances, it was confidently anticipated that the two ends would meet by the end of October. Several lengths of lining had been comploted. Tho finished tunnel wae "D"' shaped; the width ut the bottom was Bft, and it wn s Bft high at the crown. One-third of the lining would be completed by the end of this month. HEAVY WORKS. At tho outlet end. some heavy con creto and - reinforced concrete works were well forward. Extraordinary precautions had been taken to ensun safety and reliability. A hiifjo surge chamber was in course of constructioi of reinforced concrete: that pit, oi chamber, is D-shaped. 32ft in diameter and about the same depth. The bot torn of the surge pit would be 27ft be low tho normal level of the lake, ant tho water would rise, in the nit to the samo level as the lako. The water frorr the tunnel enters the pit on the straight side of the D, and tho nipes conveying tho wnter to the power-house entered from the opposite side. Eacl; pipe, was protected by three gates, s<: that if by any chance ono gato became fixed there were two other« to fall back On. The flow of water'into, the pipes could b<» regulated from the powerhouse. Tim surge pit served two useful functions; first, it held a sufilcifit simply of "water to meet any sudden demand for power. ft would be 6een how important tl;o pit was, for it would toko a considerable time for an inorensod simply to arrive from tho tunno!. It also filled the useful purpose of a '"safe-tv valve. :, Should it for iiiy rotPon bentne ne<*e.°sarv to stop thfl flow of water, the pressure on tho rt'vip* 1 would he enormous, but the nit would t »-f'i;r>vf t,he presFf - * , . Provision was mode for two firirKtior-.M pipes ivhenpver the 'lomand for additional power warranted it. ELABORATE VUKC MTTION'-S. Extraordinary care had been taken to secure tho pines in the sttrgo pit, and to make the union of the pipes and tjb.o tunnel doubly secure huge angle iron rings were firmly attached to the pipes at short intervals,'and the whole embedded in reinforced concrete for 15ft. In addition to the tliree gates mentioned there wore two others at the top end, and ample provisi6n tyas made for trapping shimrle. drift wood, or any other foreigu matter. All the concrete supports for the double pipo lino were rinished. THE PIPE LINE. The pine line wus a very interesting piece of engineering skill. The pipes Trc-ro mode of boiler .eteel,- and at the bottom end the plates were Sin thick. Each pipe -was £2m in diameter, and capable of carrying sufficient water to develope 5000 horse-power each at the power-houeo end. Those pipes wei-v (lirided by a V junction, forming four 56in pipes lending to the turbines, etc. The pressure on tho pipes was 2001b par eqnnro inch. 6O that it would be seen there wos. n bursting pressure of no less than 10,4001b in each of tho large nines. But in that as in everything about tbo worjis, a very lavgi; factor of safety had been provided for. It would be interesting to note.thnt there was nn enormous Wl pressure on the pipes in a drop of BTOft in half a mile and the pressure was no less thnnJWO tons, «nd that pressure was all in the direction of dract'ji the pijvps away from the tunnel.' " To prevent that the precautions tnfcon at the surge pit was related at regular intervale down the nine lino, where the pipes were "anchored" to enormons concrete anchors. THE POWER-HOUSE. Tho power-house building was now t-aking chape. It was composed entirely of reinforced concrete, roof as well a« walls, rrtkl was fireproof. It was 184 ft long by 75ft wide, and 35ft high. At the present time the walk were up to the window-sill level. Tho most difficult work, namely, the foundations, which were below the water level, were all completed. Looking over the building it was now passible to form some idea of the general arrangement. The water would enter the bnildin,c by four 36in pipes, being branches from the two 52in pipes leading down tho hill side. These branch pipes paused under the floor into the bneement of the power room. Hero the thrust of the pipe line tvas also taken ui> by substantial concrete blocks. The pipes turned up through the main floor to the turbines. The building was largo enough to hold six turbines, giving a maximum output of 2.600 h.w. each, orul a nominal full load of 2.100 h.p. Those turbines run at a coeed of 000 revolutions per minute. Of thoso three wnro included in the present contract. The turbines were coupled direct to largo generators, the foundations of wliich wrre already in and complete. An idea could easily be formed of the of thoso by the size of the foundations. After the water bad passed through th« tnrb'nes it dropped down by & eteel draft tube through the basement floor into a deep pit, where it was conducted in a concrete tunnel onfc to the riverbed, passing over a weir on its way, so , that the miantity passing away could be accurately measured and recorded. THE PLANT. From the generators, the power was conducted to the switch chamber, over which the special gallery for the switch hoard will be plaoed. From the switch chamber the current flowed to the largo transformers, of which there were six each of MOO horse power capacity, to be installed, and th°nce on tho transmission lines to Christchurcb. Duplicate sets. The whole arrangement of the power house, and indeed everything connected with the works, was designed to provide a duplicate set, or a stand-by set. The method carried out was that every operation involved in the generation

and transmission would be drawn from | the alternative sources, namely a UOU j h.p. water-driven exciter, a largo storage battery, and a motor-driven exciter operated by the power from the generators. The switchboard and switch genr bad been designed so that the plant could bo operated on as & whole, or as two absolutely separate and independent sources of power. The duplications extended to pipo' lines, generators, exciters, switching apparatus, transformers, transmission lines, sub-station, and distributing cables to tho main cojisumens, and as a further precaution, nnd to guard against the untamed attacks of Mature, the transmission lines wero k«pt several miles apart. From a very careful inspection, considering tho limited time at his disposal, thero appeared to be nothing left to chance. He was naturally, very pleased with what he had seen, and that he had identified-himself with what ht> believed would be a great boon to the people of thifilcity. Humanly speaking, it would seem iniposs'blo for any serious breakdown to occur. TRANSPORT JHFPTCULTIES. Tho , matter of transport was one that wns causing son'e anxiety, as the works" required a regular supnfy of forty tons of coal per vrcek. nnd the same ive?ght of cement each nook. J t was a "pictnresquo scene on Monday-moruin? to view from the Downs road, above Hororata, no fewer than six traction trains puffing away laden with goods of .■all kinds for the power scheme.