POSITION AT ARAPUNI.

Thames Star, Volume LXII, Issue 17388, 28 March 1928, Page 5

POSITION AT ARAPUNI.

THE POWER-HOUSE SITE. DIFFICULTIES OVERCOME. CONCRETE WORK STARTED. The chairman of the Thames Valley . ~'" Power Board, and Mr N. C. McLeod, engineer to the Board, accompanied by press representatives, visited Ara- Vf; puni on Friday. Of late there has been an uneasy feeling amon? power-. '■: consumers, particularly farmers, and;-. .; there has been talk of installing oil 'f engines for and reverting per- ; manently to the old method. The /:• possibility of further interruptions in the Horahora supply and the length. . of time that will elapse before the Ara- ' '":'; puni works will be in operation are ", matters of great importance to dairy 4 farmers and industrialists. There ; have been rumours of insurmountable difficulties and it. has been suggested that very troublesome times are ahead for those who are dependent on electric ;.; power supply. It was in order that "\> some reliable information could be * > placed before the Power Board . and ■ v : passed on to the public that Mr. McLeod and the chairman visited the ■ works. They were met by Mr. Dirinie, the engineer for the Public Works I)e-. -f partment, who afforded every facility ' ~ for obtaining information. > As far as the Power House site. isconcerned the Public Works Depart* ment is meeting with success. The ." ; excavating is being done in sections, ; a_nd from that section on which they.. " are now working the water from the v *,: old river channel which caused so ) J much trouble at first has been almost .: r. ; entirely cut off, the flow having been '■ reduced from 4000 gallons to 400 gallons per minute. This has been ac- • complished by putting down a succession of bores along that side of the ;j power house site facing the river and \, forcing through pipes at a pressure of . 1501 b. to the square inch •cement. This cement is forced into crevices of the rock and becomes a solid wall through. ;jf which the water cannot force its way.:, v| The practice is to put down a bore a ■' certain distance and then force cement through the pipe. When the rock ,-' within range of the pressure has - 'been treated the boring is continued ; and the process- repeated. '"' Altogether about 200 tons of cement havei'been used in this way. At one place the- _i| excavations have been made to within :jj a couple of feet of the required • depth, i and in about a fortnight a start will'■>'.;>•' be made with the concrete foundations 7T for the first unit.

Nearly the whole of the water which ;| has to be .dealt with at the present time comes from tat part of the-site :■■:■!s on which excavation has; in the meantime comes from .that part of the site not yet been protected - against the ■ river*'by forcing cement into the ere-, - vices. Plans are about to be put into '..■•;■ operation which-may get rj£ pf.-thj> water altogether. A 'powerful, pump' * is being obtained from Napier and will • be installed on the bank formed where the Waikato returns s to its-old course . after passing through Waitete valley. Materials brought down as the river made a course for itself through the, ">. valley raised the Waikato bed about :i 28ft., but gradually the bed has been ,'; lowering until now it. is only 20ft. above the old level. A high bank has :■ been formed between the stream as it - flows at present and the dead water . X lying between the bank and the big /'■/ dam. With the pump it is expected ; i that the water lying" between the river and the dam will be lowered about i 18ft. As there is an enormous quan-.;. i tity of water to deal with it will prob- ,y~ ably be a month after the pump starts working before there will be much jj difference in the water level, 'but once ■;,::; an impression -i§ made it will become ■ "'S more marked each day. The seepage ~;: from the river now flowing above the power hottse site is negligible. One or two tiny streams come out of the hillside, resembling springs that might be tapped-anywhere. The same thing :i applies to the Arapuni clam. Many people have been wondering /, what the effect of a heavy flood-would be at Arapuni. Until the river takes , \ its final leap over the rocks .into the -..',;, small lake that has been bored-out :j below there can be no effect that could, cause any concern. During recent heavy rain the water over the spill-:. r . way only rose one inch and that was * scarcely noticed. The dam that .has ;?f been, formed al Arapuni is 18 miles j long and averages about a quarter of ""• *a mile in width. This means a sur-; .;; face area for the water of about five square miles, and when heavy rains fall the whole level of the lake is raised so that the flood waters in spread- ;. ing themselves over this area will - lose much of their power and wilt" be slow in attaining their full vlpume" - \ over the spillway. The dam itself is a gravitation dam. That is. it is so constructed that it has sufficient weight and strength to hold nack of '* itself any volume of water it may be = called upon to resist. Some experts consider the dam unnecessarily strong.- --^