PROGRESSIVE SEW PLYMOUTH.

Taranaki Daily News, Volume XLVII, Issue 7798, 14 April 1905, Page 2

PROGRESSIVE SEW PLYMOUTH.

COMPLETION OF THE WATER SCHEME. A MAGNIFICENT KUI'I'LY. Justified by the mucked progress of the town and district, which gave and continues to give foundation for j unbounded confidence in their future .prosperity, the Now Plymouth .Borough Council in 190ZI, backed up bj a vote of the ratepayers, embarked upon a progressive policy of municipal works to bring New Plymouth into line with tlie other substantial towns of the colony. Loans were flouted for the carrying out oj a pretentious water scheme to provide for all requirements for many years to come, an extension of drainage works to modernise the town in this direction, and an up-to-date municipal electric lighting schome tor the town. The most important and pressing of these was the water scheme, as for j eats past the supply from the old reservoir, ranging up to 250.0(H) gallons perVlay when the pumps were working at full pressure, has been in* adequate for the nei'ds of an expanding commuiyty. The shortage of water has 'been seriously felt during the last few months, ami the completion of the new scheme, which will ensure a magnificent- supply of one million gallons per "day, is a notable event in the history of the town, and as such was suitably celebrated on the occasion of—the opening ceremony on Thursday afternoon.

GENERAL O UTLINE. The scheme, which will favourably bear comparison with those of the leading towns in New Zealand for suitability *nd efficiency* has beet carried out on the lines mapped out by Mr it. L. Mestavei\ M.LC.E, of Wellington, whose admirable plans were, adopted by the Council. The credit for the successful carrying out of the work', however, may , with fairness be given to the liorough ! Engineer, Mr E. ilurvey Gibbon, who, although taking up office after the scheme was inaugurated, appliod himself to it with energy and skill, and spared neither time noV trouble to turn out the work in a highly satis*' factory manner.

To entirely supersede the antii united method of pumping-, the scheme was devised on the gravitation basis, which, though a little more costly to inaugurate will reduce the working expenses to a minimum.v The source of supply is 'in the upper reaches of the Waiwakaiho river, about seven miles from the town, and the spot selected is, an ideal one, an illimitaable supply, of beautifully clear water flowing over a rocky river bottom, being available. Even in the driest summer the stream is little nfTecte(\ a fine' strong* volume coming down from its mountain source to empty into the sea.

The river is tapped at this spot, and the water conducted by uravitotion through a concrete tunnel which is ingeniously bored for a distance of over three-quarters of a mile under hill and dale to the pipe head, wherp. the pipe line commences. From this junction over two miles of massive 15 inch .pipes are laid, connecting with two modern iilters. from which the water emerges purified to be stored in the huge reservoir a couple of chains distant. Tlio filters and reservoiraarte t conveniently situated on a borough reserve at the intersection of the Mongorei and Junction Roads, only about four miles outside New Plymouth. Large mains lead from this storage base to the town. The river at ihe intake works is 390 feet, übove the town, so that with a graduul down fall (though the upper portion of the country is undulating) there is no nece.^ity whatever for pumping, and u splendid pressure is assured.

Tile scheme is of course a costly undertaking, and the work having so many distinct features lias been divided into several separate contracts while the Council have carried out the laying of mains Incidental to the scheme by day labour. Tho amount allocated 011 loan was £24,000 for the whole of the project, but with extra work necessitated and contingencies, (lie original amount will be exceeded by about £>*1,325, including £BOO lincc authorised for the erection of a caretaker's* cottage nt the reservoir sito. The Council have struck.a loan rate of lOd. —lntake Works and Tunnel.— This portion of the work, presenting some interesting features from an engineering point of view, is certainly the most striking part of tho scheme. The contract for the tunnel and intake works was let on August 15, 1903, to Messrs McWilliftms & Andrews l , the former being well known in connection with tunnel work' on several big undertakings. The contract price was £5595 3s, and through various cause*, principally tha large amount of extra work that the conditions rendered imperative-, the contractor is twelve months be-' hind time specified for the completion of the co|i(,rapt. The contractors hud |t severe tasU set them in boring at a considerable depth underground, and driving for over three-quarters of a mile through all classes of formal ion. In one locality the tunnel burrows in the bowels of the earth under hills which Vise from 100 ft to 120 ft above the average level. Again a swamp bed is excavated under, and at another point the tunnel pitrces its way directly under tho Mangamahoe stream. It will be recognised lhait. the undertaking taxed the skill of tho contractors, but' under the supervision of the Borough Engineer whatever difficulties presented themselves were met with resourcefully and successfully combattod. When boring, all kinds of formation wore met with, clay, boulder beds, sand patches, hard grit and swamp bed being alternately encountered. To tho layman it is wonderful that tho tunnel could have been put down in such excellent manner, being as straight as a die-, without a flaw in the levels at any point.

In the. l concreted sections the dimensions of the tunnel which is built in the form of an archway, with a hollowqj flooring pf concretp, are 3ft 9inclies in wjdth by'Sff 3 inches in height. The concrete walls vary from 1 - inches to 9 inches in thickness, and the workmanship is good, durable and strong in paoh setdion, Of course whfm the formation is hard and stably no concrete is necessary, as ior instance in tho granite beds, where tho boring i(,solf forms a strong natural tunnel, Evon should there be any subsidence at any uf these points the tunnel could be repaired without much difficulty, though ino fall can be anticipated. Originally some 2fi chains of concrete wbrli had been provided for in t'ho plans, but as operation,s' progressed the formation was lound to be. too yielding in places for a water course, and it was deemed necessary to strengthen the walls. an additional 934 feet t»f ■c,inC!Y!t|! iunjiel||iig wai pu|. la. no risk of instability being taken throughout, thp total length of 'the lil chains of tunnelling. At a short ; distance from the Walwakalho river intake tile tunnel passes under the bed of the Mangamahoe stream, and is built especially strong in this section,

Tij e Q' (Joncptp work totals J 300 cubic yapds. The greatest depth- of the tunnel .below the surface is 120 ft, and the least depth (where it passes under the swamp), l(rft, The height of tile rjveja|, the intake js iGit above water |ovel jn the reservoir. ' ''' Tin; l'epivspntative of the Daily News watj the tivst person other Lhan thu oflicialif tp inakp the dark underground journey through (.lie completed tunnel, ami inspected the work with curiosity and interest. Thot'e is no soakage into the tunnel whatever and on its journey to 'die pipe he»d the \vtiter can in no way be contaminated from this source.

Th« openings to the tunnel ar« the intake chambers, the manholes on each side of the Mangainahoe, and the pipe head chamber. ■The intake lisylf is a culvert runiiing several feet out into the Waiwakiiiho I'iver, it is on a level entirely submerged at I ho lowest known water and in winter time the rjver ui-pi-sionally rises 10 Mi' 12 feet above (.lie present mark, The culvert leads to tho intakq ehapilier, which is lit ted with a 1 argij strong vail sluice if. regulate the Inflow of wa'tor, and a wrought, iron serecn contrived to prevent timber and debris from entering tli« tuuircl The solid relaiyipg; way

at which the controlling sluice is placed is • built up to the highest, | flood level ol the stream.

As previously indicated the amount due for extra work beyond that spccilied in the original contract, will be considerable, totalling about £IOOO or £I7OO, but against this the Council will lia,ve, if enforced, a good proportion of tile sum named as lines for non-coinplotion of the contract, to time. —The l'ipe llead.— The starting point for the mains which le.id to the Miters and reservoir is a chamber technically known as the pipe head. A tJquare concreted chamber lends down to llif underground tunn-.1, "about, 40 feel under the surface at this point, and contains the apparatus for regulating the pressure into the 13 - inch main, etc. There is a large wall sluice for shutting the water off altogether from the tunnel in case oi icpairs being necessary to any of the otl'er valves. Provision is made for clearing out the sediment from the tunnel by a ti-inch sc u ur. valve. The tunnel will have a steady even flow when working regularly. but ill . the early stages tile .scour valve will lie brought into requisition to thoroughly cleanse the structure. The chamber will also |j'ei've as a medium for eiiteiing tile ('tunnel when any repairs or inspecItkm is advisable from this end of I the underground channel. —Day Labour

The l."i.inch steel rivetted main which connects with the reservoir site was laid by the Council under the day labour system. 'llio pipes, which show excellent workmanship, are strong and adequate, anil were supplied by the well-known firm of Mephan, Ferguson and Co, of Melbourne, who have a branch at U'angantii. The country which intervenes between the jiij>o bead and the reservoir site is uneven, but the work of laying the main, at times under the suriac:-, and again crossing a ravine ou supports, ii well carried out. The distauce is over two miles'.

—Filtering- Gear.— The importance of supplying the people with water as puro as the mechanical methods wiil,l ensure, has been well studied by the establishment of modern filtering goal*. Two Ulters are installed adjacent to the reservoir. They arc Known as Mather and Piatt's single contact gravity patent, and are capable ol tillering iv maximum of one million giilions of water pen <lay of 21 hours. The filters; circular in shape, are 12ft in diameter and lift high, tind in appearance resemble huge vats. From the lli-inch main leading from

the tunnel, the water connects up with the (liters by a tapered 12-inch pipe, a GJuch pipe connecting with each. The, water first (lows into an outer chamber encircling the lil-

ter, and enters into a sort of tank through a number of portholes. The filtering medium is graded quartz, specially imported from Germany, and the water issues through this and emerges, purified of any suspended matter, into the pipe which replenishes the reservoir. The litters

are each tilted 'in H n automatic valve, to regulate the flow Suto the apparatus, and filtrate valve, re-wash valve, washout inlet valve, washout discharge valve, and mechanical agitating gear or rake to stir up all the dirt and sediment which accumulates on top of ihe filtering medium.. and the water thoroughly scours the apparatus, the affluent making its escape by means of a 1.1-inch scoOr pipe. This pipe leads to a series of manholes, which drain into an adjacent swamp. The lilUts are of the latest and most, efficient type for dealing with a big supply. The tender for their supply and installation was secured by Messrs Palmer and Co., engineers, of Wellington at £2207. A portion of the plant was' cast in AVellington and the balance imported. Messrs Newton and Koxon, engineers, of New Plymouth, undertook the. work of erection for the Wellington firm, and have completed it ia first-class .style. The foundations were put in by Messrs Pikett and Spencer. The ■ steel spiral pipes, used for connecting up", -were manufactured ) )v - Messrs Ferguson and Co. t —Tho Keservoir.— '

The reservoir is admirable designed and cou.structo.l. It is a vast oljlong... excavation, built of concrete throughout and lined with Yal de 1' lvl ' rs asphalt which lends a sijlemdid finish to the internal walls. Tho dimensions are Soft (iiri by 125 ft, at the water level, 11 (ifi 'j )V 72a floor measurement, and the depth measuring from the W all plate is .1 Jit, the water-line .being at the 1(1 it mark. The floor und walls are substantially constructed. The bottom and battered walls ore 9in. in thickness, and tho vertical' walls vary ,eel (o 0110 10o <- through. 1 ho hhole is protected by an arched tool in two sections, .supported in niLr™ 1 ' 0 , hy fOUi " llmssi ve concrete pillars and turned urchvs. The roof is the lattice girder principle, the rooting material being galvanised uon, which is lined underneath with rimu sark;ng. This makes „ splendid covering in all weathers. From the floor of the reservoir to the ton o. the roof is 21 feet, and the summit is eight feet above the surface of tho ground. Ventilation isi well secured by four louvres at each end of the structure and what is Known as a "lantern" ventilator at the crown Of each roof, running nearly the whole length. Some idea of the size ol the 10sorvoir will be given by ,the fact that it is designed to store one million gallons of water. Viewed in its empty state the reservoir bears a striking resemblance to a large underground ukating rink. The water, after passing through the filtering process at the filter site, a couple of chains away, is convevod to tho reservoir by a 15 inch nuiin, and enters by u specially contrived inlet chamber. This chamber is fitted with an inlet valve, regulated by an automatic float, whiph rises when there is sufficient water in the ri>servoir and shuts o(T the inflow. The stream empties into a concrete weir, and' Thence down tile face of the concrete wall. The huge tank can lie completely filled in 24 hours. At the other end of thg resevvrfir is situated the outlet chamber, which is the real check 011 tho water supply. in this chamber is the 12 inch service main, the fountain head for the other subsidiary mains, A scour pipe is also placed in position at i'hih point, ft will only be necessary to clean the reservoir out very occasionally, and the scour pipes will convey the affluent a way. At the back 'of the scour valve is the overflow pipe, 'installed for use in the event of the automatic ;nlet valve bjccomjng out of order, and obvjatjng any floodage at the site. Thp overflow and all waste v ater at the reservoir and lilteis is drained to an adjacent swamp, by means of a series of manholes, with whiph steel spiral rivetted pipes are connected. ; Tilt reservoir is a very fine one of ' its class, and the contractors, Messrs Pike(j. ami flpcncer, of New Plymouth, are to bo eongratainted on ' the splendid work from start to (in- > ish. The tender price was £3")3<i ;is <■ (id, and the contractors were almost up to 'their fime. <

—The Mains,— Thq aeiual eo.st of the whole of the pipes laid by the Council, including l«ying and jointing, is £9187. From the reservoir to the junction of the Avenue and Old Hospital lioarlt a liJin. majn Is laid, and from thence i 9iu. pip(i conveys th« water along the Hospital Jioivd (p the existing tOin. main at the old reservoir gate.

Returning to the Avenue Road a lOin, main is carried towards town, crossing Messrs Saxton's and dordan's property, and coming out on the Avenue Road again bv Mr CliU's property, At this point the lOin. malfi supplies a (iin. main, whiqh junctions with the existing (iin. pipe, by the High .School, and a 9in. main which crosses over to {he Victoria Koivd, following ;ha(. down as fa(' as ilil) Hoad. after it has been gradually reduced en route to a (iin. main it connects up with the present service pipe at the foot of Stamlifch 1 till. The next extension of mains will probably lie iji t|iu direction of the breakwater. —Electric Power House.—

The tunnel, as indicated, will not only supply the reservoir, hut also provide tho water to drive the turbines in connection with the electric light power house, soon to be put in hand. Tho power house site is most advantageously idiuuti'd on the river Hat, ab))iit "JO plains distant from (hp,'pipe head. The structure will he erected on a level section owned by the borough, and, calculating from the pl]ie head level, therein a sheer drop of 12(1 feet, leading to the site. Twenty-one inch mains are bring laid, and a good deal of trouble is being experienced In this work on account of tho steep declivity. This cliff will prove of great lienoht, however, in view of the line prossure that will be generated by 'the water rusMug 'dqwu-wu, •