BOROUGH ELECTRICAL SUPPLY

Taranaki Daily News, Volume LI, Issue 209, 25 August 1908, Page 4

BOROUGH ELECTRICAL SUPPLY

AX IMPORTANT REPORT. | ADDUimAL iL.S.NEL GIVING IUU-H.P. . 5 instructed by the Borough Council, .the borough engineer, .Mi 1 . A. il. Kendall, jast night prcscnu'it i!k- following eport concerning the best nietliud oi producing additional water-power for th; .electric su[>plv system:— , 1 have hail till- pleasure of conferring with the elc.-lrieal engineer, anil have gone very carefully into this, mutter, anil have arrived at the following conclusions, :

in the lirst place, the capacity of the' present tunnel has, with its present construction under the Mangamahoe river and apart from the construction ,of a dam iu the Waiwakailio river, .which would only prove of service tor a limited time, almost reached its limit, and, considering the rapid strides wliicn are being made iu tlie consumption oi current lor light and power, any balance of power that is left in the water .supplies which the prr-.ellt tunnel call .deliver may be quite ignored, especially in view of the I act that auxiliary supplies, or the storage of water iu bulk #t or near the pipe head or other loca- | tion, is now absolutely imperative.

mSSiIiLK SCHEMES. Storage of a reserve from the present supply appears to be out of the question, as the day load at the power-house and consequent Consumption of water .will leave a margin for collection that >ill very soon be found to be insufft.cient to supply the ever-increasing demands owing to the expansion which is Jbouud to continue in the use aud consumption of current. There is no doubt .that something can be done to help in 0, small way at any rate to give extra .water supplies 'by making that portion of the present tunnel which lies under the Mangamahoe river of an internal area equal to its other parts; but this .will be much more dillicult and costly co carry out at present than at a time iwhich I will shortly point out, and the increased supply will still be inadequate. fThe construction of a dam across the iWaiwakaiho river would also be of sonic assistance, but again a costly matter and with limited advantages; and for these reasons 1 would recommend that the present tunnel be not interfered .with at present, especially in view of .the fact that the water supply for do nftstic and fire purposes and so much pf the lighting aud power of the town depend on its existence. Recommending such a policy therefore means that auxiliary water supplies will have to be provided in other ways, and the only other way which I feel every confidence in recommending ,to your Council after repeated visits io Mangorei for this purpose (both alone and when I had the honor of being accompanied by the chairman of the. Electric Light Committee) and after persistent and determined efforts—.which I feel have been successful—to master all the details of the surrounding country, is in the construction of another tunnel in a location some few chains further to the south than the present tunnel, and in what should prove much better country than was found in the track of the present tunnel, as in no part of its length would it lie .under any swamp or ground of a swampy nature, so far as surface appearances go. I would also recommend this tunnel to be larger in size but not-' in length and with a rather steeper gradient than the present tunnel.

THE XEW TUNNEL SCHEME. By constructing an open-race for the present and then commencing the new liuinel at a point approximately some twenty chains south of the present pipe head ami continuing in a direct line to jthe .south-east corner of Mr. King's farm, and to a place of deep water immedi atelv below Kaipi Island, there will. Without any dam in the river, be possible an increased head of at least fifteen fwt greater than at the present intake, and the main advantages o-f t!rJine of route will be in addition that this tunnel, not being immediately necessary for domestic water supplies., can, so soon as the Mangamahoe rive; - is reached, be so constructed as to be capable of receiving the whole of the contents of that river either temporarily or permanently, and thus enable jthe alteration to the crossing of the .present tunnel under this river to be

readily carried out, after which the river can again be allowed to run its former course if desired, and the tunuel continued as far as the Waiwakaiho river, ami the necessary supplies taken therefrom: or in lieu of this, t>r indeed at any future lime in conjunction with other methods, the waters of the Mangamahoe can, by means of a dam immediately below the proposed new crossing, be impounded, and. owing'to the favorable configuration of the surrounding country, an extensive reservoir so formed in the valley of this river as to .very materially increase the pressure that will be available for use at the ipower-house. INCIDENTAL ADVANTAGES.

The collection at the proposed ue v lAliingamalicc crossing of the waters tit itliat river by the new tunnel (which ca i J>e so constructed and used at its outlet as not to interfere iu any way with the town's water supplies) will then enable any work required in the ilangamahou river'below this point to be readily and economically carried out in a dry riverIbed.

The proposed location of the auxiliary supply and tunno! will make extensive reservoirs possible either in the Mangamahoe Valley or between the two tunnel outlets south of the present pipe head, and until clams in the rivers are found necessary in the future no easements will be required from anyone other than Jlr. King, who has, I believe, been at all times most willing to render any help or assistance required or necessary.

The one great point in the scheme which I recommend is the ultimate water supply which will be available by .the arrangement I point out; the work tan either be taken in. hand and the. whole completed at once, or the tunnel jean l>e put through at present and the .more extensive reservoirs and dams constructed later on as the need comes nearer.

AYliat 1 would propose with regard to the present Maugamahoe crossing is the making of the tunnel of one continuous bore and size, and the present invert ard also a properly formed sump near the pipe head 'being fitted with valves and outlets for the purposes of scouring periodic-ally the leaves and (more especially) silt which should be collected in such a manner. THE INCREASE OF POWER.

■The velocity of the water in the present tunnel is veiv low, the discharge being only about 17UUft per second, white the available horse-power is little more than :tOO. In the tunnel which 1 propose the area would approximate ,4tU*t, and tin* velocity without dams or reservoirs' near the intake would not be less than 130 ft per minute. The discharge, not less than 5500 cubic feet •per minute, would give an available horse-power of 1U0(», 300 of which would be required for an electric tramway service when the size and importance of the borough warrants such advancement, and 300 horse-power would be available for the present and immediate future needs of electric light and power extensions. 1 consider my estimates of the |>ower that will l>e available from the new tunnel of the size and inclination given as very moderate and capable of very considerable expansion •when all the possibilities of the proposed scheme* come to be made use '!.

I as additional poWer will, if required. >« i found in storage reservoirs near the | Albert Road, in the Mangamahoe Yal.ley, and, finally, a dam across the Waiwakaiho River. The proposed tunnel would be about ten chains shorter than the present one. THE COST. 1 have not included any details >f Costs at this stage, which will, however. Uc represented" by Additional casements from Mr. King; new pipe head works: open race about 30 ehains; improved screening chamber at present •pipo head, which will largely prevent and almost completely cure tin* pre-ont .trouble from leaves, etc., finding their •way to the turbines; tunnel about chains; valves and sluices at the Mangamahoe: alterations to the. present Ma.ngainahoe crossing; intake. ;»ates, and chamber- (;ind iu connection wish this F take this opportunity of *titi:rr that the inlak" -hould. a* far as p"-ible. !>" made to have the opening f;n*tn-- <lo\yii stream); reservoir at a later d.'le 'j

•hold at least 2,000,000 cubic feet of .water near the Albert ltoiul; dam and reservoir in the .Uangauiahoe Valley.