ELECTRIC POWER

Nelson Evening Mail, Volume LXVI, 21 February 1935, Page 10

ELECTRIC POWER

MARLBOROUGH WORKS TROUBLE AT HEADWORKS STORAGE CAPACITY GONE* lii view of the- recent remarks in Nelson regarding (he Mar'borough hydroelectric scheme the following from the "Express” of a meeting of the Power Board yesterday could be read with interest. During (lie past few months the rapid silting-up of the dam at the electric power headworks at Waihopai has been causing concern to ihe Power Board, and while in_ Wellington last month a visit was paid by the manager-engineer |Mr G. F. Mac Lean) to Mr F. T. Kissed, the chief electrical engineer for New Zealand, for the purpose of ascertaining whether any likelihood existed of the district being brought in under a major Government electrical scheme. The problem was referred to at yesterday’s meeting of the Board, when the following report was submitted bv Mr Mac Lean : “During the past few months it has been noticed that the lake at the headworks has been tilling rapidly with rubbish and practically all our storage has disappeared. A few chains up •from the dam there is only Bft of water, and at the dam the depth has been reduced to 17ft. During the time we were working at the bottom of the small spillway We could not do any dredging, and the silt and rubbish completely covered the screens at the lower level. This did not worry ns during the summer loading, but should they block up during the winter months wo would require to run the stand-by plant to assist the hydro station. We have now dredged a Dole 50ft deep as far as the crane will reach, and the lower screens are again clean. To overcome the difficulty it is advisable to have a steel flue made for another intake similar to the two put down some two years ago, and I would recommend that the material be ordered for this immediately. The cost for this flue erected should be approximately £2lO, plus a. small amount for extra exchange ; the estimate being bascd on the cost of the last job.

STAND-BY PLANT “During dry spells experienced since our plant has been in operation, it has been noticed that the lowest river flow has been capable of maintaining a conslant load of only 350 k.w. Our present stand-by plant can take 420 k.w., making 770 k.w altogether. Our heaviest peak load has been 1200 k.w., which means that our storage capacity has now disappeared, and if wc have a serious drought, we will be short of power. It does not seem practical to attempt to clear the silt out of the lake. The only possible way v r ould be to have a sluice-gate in the dam but as this rvould probably get blocked up with logs and rubbish it would not be much good, unless wc had a stand-by plant large enough to take the load v. biic the gate was being cleared. We experienced great difficulty in keeping the diversion tunnel clear during the final stages of the headworks contract, and we were actually delayed some ten weeks to enable this to be done. This t'cuble would recur every time the gate was opened for any length of time, and as it would be necessary to low'er the lake level to reduce the quantity of mud by any great amount, the danger would be that we would probably run out of water before it could be cleared. To get over this difficulty we would require more sfand-by plant to carry the load in case of accident. Allowing for an increase of load it would not be advisable to put in less than 550 k.w. extra stand-by plant ,which would o-ive us 350 at the headworks and 980 k.w. at the stand-by station.’’ The engineer went on to say that he had talked the whole matter over with -Mr Kissel] and, barring getting a supply from some other source, the only thing to do was to start negotiations for a larger stand-by plant. Mr Barker: And pay the 25 per cent, exchange? Mr Mac Lean: I suppose so. The plants are not made in New' Zealand. He added that if the stand-by plant was added, the transformer capacity would also have to be increased. The necessary new transformer would bring tlie approximate cost of a new stand-by up (o £19,000. The chairman (Mr H. J. St,ace): In round figures, say £20,000. Mr Stace went on to say that he did not expect she meeting immediately to adopt the idea of going in for a new stand-by plant, but be wished to impress upon members that the matter was urgent. "I want you to come to a decision, if possible, at the next meet- i ing,” lie added.

j “TIP IN THE AIR” | “As far as Marlborough is concerned i it looks as if we have been left up in the air again, and will lmve to do the best we can,” the chairman declared at a later stage in reporting that the letter forwarded to the Waimea Power Board after the last meeting suggesting that a conference of all power boards in ilie northern portion of the South Island he called for the purpose of discussing a major power scheme, had merely been received. The reason, he had since been informed by the Waimea Board’s chairman, was that at the present time tlie Public Works Department and a certain company were investigating a suggested scheme in the Cobbe valley. The result was that they would not be able to consider the request just then. Mr Stace, added that tie understood that the Cobbe valley scheme was now to be gone on with. Of course, lie added, an election was coming off, and there was the possibility that the Cobbe scheme would not lie gone on with. Mr E. S. Parker: How about raising our dan: ? The manager-engineer: If we raise K ten feet w e still have five feet of silt at the top of the lake, and in six months the position would be as bad as over. Mr Parker: \\ hero are we goinc to get the £20.000 from? .Mr St ace: That is a matter to be de-

cnlod ;if. Hie next meeting. He added tiiat tile position had been brought about largely by the change in the country around the headworks. The scrub had been cleared from the hillsides, and the country was shiftin'*. Not only flint, but during the past summer they had experienced some extraordinary cloud-bursts, which had brought down tons of rubbish. He was not going into the wliys and wherefores —it had just happened. He desired them all to think it over during the month, and discuss it at the next, meeting. However, it would be necessary to do something about the screens, anil he would move that the engineer be iiw'rncted to lit. on third one. This was seconded by Mr Nees. In reply to a question, the engineer stated that it had taken seven years for- the dam to sill up from a. depth of 60 Feet to eight, feet. He added that with the present Diesel plant it was costing |d a unit, to produce a supply current, and at the headworks it cost about l-10d. added to which was Ihe cost of distribution. Including wages , and everything it was costing about 1 66d per unit to supply the whole district. The motion was carried.