A HALF-MILLION SCHEME

Dominion, Volume 12, Issue 174, 17 April 1919, Page 8

A HALF-MILLION SCHEME

There is no more important utility to any city than its water supply. On that supply being at least adequate at all seasons of the year depends not only the wants of the people for such everyday, needs as drinking, washing, and cleansing (in every sense of the word), but, what is vastly important, the hygienic condition of the city. Our drainage system (the Shone) is one of the 'best, but it depends on an unceasing and plentiful supply of water. It does not take a seer to determine that Wellington ie a rapidly growing centre. If there be any doubt on that point let the doubter .endeavour to secure a six-roomed house at a reasonable rent. Wellington is probably at the present time in the van oi growth as far ag the chief centres are . concerned, arid it is therefore most important that its executive officers should exercise foresight when considering an extension of the water supply syst.mi. It is therefore fitting that.one of tho last works Mr W. H. Morton (City Engineer) should report upon before leaving on his tour should be the water supply of the future, It will bo seen that Mr. Morton has not ouly taken in.the needs of Wellington City as it stands to-day (including Miramar, which Wellington already supplies, and Onslow, now a part of the city) but he takes in the whole of the area which may one day have, to be served by the one scheme, an area which includes Eastbourne,.. Hutt, Petone, and Karori. The report is as follows:— • . . . ■~ "In accordance with instructions 1 have to report having considered the present'capabilities of the Wellington water supplv system, and the-possibilities of extension to meet further rcquiwnents of the city and such adjoining districts as may in future become incorporated with tho city or require to obtain an adequate water supply from the city sys-1 tern. Owing to the advisability ot con- j sideriug the extension of the system I to adjoining districts the preparation ot all the necessary data to enable a reliable estimate of the cost and a clear decision as to what works are at once essential could not be prepared. I have, therefore, to ask that this report be taken as'tentative, with a view to ascertaining the probability ot adjacent districts coming into the scheme, and at the same time giving an approximate indication of what works aro essential to the whole of the districts herein considered and of the order in which they should be undertaken. Inspection bae been made and rough data obtained ot the following sources of additional supply :-(l) Additional storage at Wainm-o-niata. (2) Orongorongo River. (3) Hut River, above the junction with, the I'mUratahi Biver: (*) Akataniwa River, (a Whakataki River. It at once.bcco.ite. evident that sufficient water is easily obtainable from the above sources or supply to meet any possible growth of the population of the City of Wellington and its suburbs for many years to come. "The present population of tho cilj and suburbs likely to bo supplied may be taken as follows-.-, .. . Ponu- ■ lation. 1918. 1. City of Wellington 77 000 • 2 Borough of Miramar ]W 3. Borough of Karori l.;«" i. Borough of Onslow ■• *< MV 5. Borough of Eastbourne and ■ districts on eastern side ot harbour -. ""• 7 ', m 6. Borough of Pctone ',400 7 Borough of Lower Hutt WUU : Hutt Valley (north of Lower Hutt) s'm5 ' m -I estimate the population of the above districts in twenty-five years will be as follows-.- intimated

Population. 1943. districts on eastern side ot ffitlt&^er^ Hutt) ■ ' . T tal ~ 198,000 "The* supply from Wamui-o--mmmsi out any. increase « ' eviipova . out making an -V, aUo :™ is capabie of determine what ihi - l«» hc i, occurred m ■»? 8 ""' r lv sunulv from are hereafter retcrred to, 1 iw■= esU . | cases taken only U , mated discharge of bucli s ™ d stor s , w&w « at watani -°- oure o supply herrinbefore referre*. rfestimatetobeasfollows-.-^^^ per day. 1 AVainui-o-mata, future supply to be obtained from addi2. Orengorongo River, Scheme ..^^ tl)hcme"B'"I"'""""-''""'"' *i»,m 3. llutt River übove its junction with the Pakui-atohi i River *. r ),Ot)U,(il]ll 4. Little Akatarawa River *3,300,000 5. Whnkatiiki River »J,H7,0C0 tl ; or '120 days. ''Two-thirds of estimated summer (low. "It will boecon, therefore, that by tho adoption of any one of the above schemes the present- maximum daily supply of .'.VlOO.flflO gallons from Waiinii-o-mata can bo increased considerably. It is only.

necessary to decide what provision should now be made and to select one or more of the new sources of supply abovo enumerated to provide the requisite quantity of water. The inquiries made concerning the additional sources of supply before mentioned necessitate the following remarks "concerning each:—

Existinq and Proposed Additional Storage at Wainui-o-mata. "There appears to be a suitable site for a dam below the existing reservoir capable of storing 800,000,000 gallons. A dam in this position would require to be built in concrete, and if on investigation by sinking shafts, a suitable foundation is procurable, it should be of the gravity type, curved upstream, and with the level of 'the waste weir the same as that of the old reservoir in this locality. It would, however, be necessary to construct a new tunnel through the Waiwetu hills at a much lower level than that now existing in order to make the whole of the water to be stored available for use. The height of the dam above the stream at the po:nt suggested would be about Soft. Without sinking shafts it is impossible to determine to what depths the foundations would reciuire to be taken, but natural abutments (if suitable rock are easily discernible. The length of the dam would be approximately 775 ft. Except for a few weeks at tho end of a very dry summer tho (low of the Wainui-o-mata River is at present greater than the draw-off, and for the greater part of the year there is a srong stream going over the by-wash. There >:ai>, therefore, be no doubt that the stream is capable of supplying, duriiif winter months, the additional quantity proposed to be stored. Assuming a minimum daily flow of gallons find proposed storage totalling 940,000,000 Kallcns. ,the population thnt could be supplied would bo approximately 140,000. To this must be added the population to b<; supplied from the Karori reservoir, and this may be set down as 10,000 of u total population of loli.OOO, can be supplied with seventy-four gallons of water per head per day from present sources I of supply with additional storage.

Orongorongo River. "The suggestion to connect tho Orongoronjro River with the Waiuui-o-muca waterworks system is not of recent date, but was under consideration during the period that Mr. B. Loughrcy was City Engineer. As far as I can gather it was then proposed to connect the two etreams by means of a tunnel near the source of tlie Wainui-o-mata River. It is now clear that the additional amount of water to be obtained by a connection so made would not be sufficient to justify (lie expenditure owing to the small catchment area of thu Orongorongo above tho place at which the connection was to be made.

"Schonio A.—l have previously pointed out 1-jiß value of this river for obtaining additional supplies of water l'or the city, and the first proposal was to drive a tunnel opposite Georco's Creek, immediately above the new reservoir at AVainui-o-iiiiita. The catchment area that would bo added at this spot would be slightly larger than the Wainui-o-mata, and conseiiuenlly the flow of water into the Misting reservoirs could he doubled. This proposal would necessitate tho construction of a tunnel 161 chains in length, and as onlv two adits would be available the cost will b3 heavy and tho rate of progress slow. It would, however, greatly mihano.e the value of the existing works at Wainui-o-mata, and it additional storage as proposed be provided at Wainui-o-mata, the quantity of water that could be supplied daily for 120 days would bo 13.800.000 gallons-sufficient for a population or approximately 180,000 at 7-1 saltans per head per day. "Scheme U.-Owing to the great length of tunnel required and the fact that it could be provided with only two,adits, further investigation lias recently been made, and it is found that this river could be lapped much further down stream, at i. point about thirty-two chains above a tributary known as Turoro Creek and at a height of about 1308 ft. above sea level. . ! "Bv a selves of tunnels totalling about 101! chains in length water can be led into and along the valley of tho Catchpole Stream through the Wainui-o-mata V.'illev into GoHan'e A'alley/aud then over a low saddle to the road along the eastern harbour front, and thence along the 'Day's Bay road into l'otone, and ic'iiing up with tho mains of the city. Thin main would be available tor the wliolo of the residential districts situated on the eastern side of Port Nichol"Tho catchment area of the Orongoron"o at tho point at which it is proposed to be tapped in this scheme is about 28 square miles, from winch I estimate a minimum daily discharge ot £458,400 gallons per day. Of this quantity 4,300,000 gallons could be made available for city requirements without incurring risk of .claim for compensation to owners of property below tho intake. An inspection of this river at tho proposed intake has been made on several occasions, and under normal conditions the quality of tho water, so far as colour is concerned, appears satisfactory, but I am informed that after floods it is discoloured by tho deposits of rock, clay, etc., from landslips, which appear to bo of frequent occurrence. It is also evident that a large volume of water flows through tho shingle of tho river bed, and a casual examination can give no accurate idea of the quantity of water in the river. Owing to the largo quantity of shingle brought down by the river during floods it would be inadvisable to attempt the construction of an impounding reservoir. A submerged weir would be necessary, however, to raise the water sufficiently to obtain the necessary head at the intake, and steps would require to be taken to prevent shingle obtaining access to the mains. It would l>o advisable to ascertain the depth of the shingle in the bed of tlie river in order to determine tho depths I to which the necessary cut otf wall of I the weir would require to be taken. Tho level of the proposed weir would be ; about 380 feet above the sea-

Hutt River. "The Hutt Biver above its junction with the Pakuratahi River has a catch- ■ inent area of about 32 square miles, and is mostly, it not all, forest reserve. It is heavily timbered, and appears in every respect suitable for water supply purI poses. Tho level of the stream at its junction with the Pakuratahi is about COO feet above sea level, sufficiently high to permit a main to Iμ constructed through the Hutt Valley, Lower Hutt, and Mono, ami along the Hutt Bond to the city, and discharging into tho old reservoir at Karori. This reservoir would ' then become most valuable as a uervice ' reservoir. Some alterations would pi-ob- . ably be necessary to the existing mains : leading from Karnri Bwcrvnir in order ' that the supply to the higher levels of the : gravitation system abovo the level of Tho Terrace and above Aro Street in the vicinity of MitehcUtown and Mortimer Terraco may bo maintained at a satisfactory pressure. Arrangements would require to bo made with the boroughs through which the proposed niain would pass, and should the authorities , concerned bo desirous of entering into I negotiations with the City Council for a '; supply from this source, or from any , I other source of supply that may be tie- . j termined on from the Hutt Bivor dis-

Irict, close consideration of their present and future ■requirements must bo given before such negotiations can bo satisfactorily concluded. The principal objection to Iliis source of supply is the heavy expenditure clue lo the length of the main which would be required, and the construction of a tunnel 100 chains in length through the hills on the eastern side of the Hutt Biver Gorge, between Mangarna and tho l'akuraiahi River. A submerged weir similar to that described for the intake proposed at Orongorongo would require to be"built across the Hutt River to provido a suitable intake for the main.

Akatarawa River, "The Akatarawa River is a tributary of the Hutt Kiver, juuctioniiig with the latter about two and a half miles above the township of Upper Hutt. It has a total catchment area of about 12 square miles on the western side of the Hutt River. At a point about two miles from the Hutt River two streams, the Akatarawa and the Little Akatarawa, join. In view of the settlement which has taken place along the Akatarawa above the junction with the Little Akatarawa, I am unable to recommend it for consideration, and am of opinion that any supply from this locality must be drawn from the Little Akatarawa, which has a catchment area of about 20 square miles. The level of the streams at a suitable point for the construction of ii weir would be about 390 feet above si-a level. This level would not be sufficient to deliver water to the Karori Reservoir «i may be done with the supply from the Hutt River as herein previously suggested, but would be only slightly below the level of the existing "reservoir at Wainui-o-mata. The construction of tho main from this 6ource of supply would present little difficulty as compared with tho supply from the Hutt River above the Pakuratahi or the Orongorongo.

Whakataki River, "This stream connects with the Hutt Biver from the western side just above the Moonshine. It has catchment area of about 19 square miles, and has a tributary called the Wainui, which conveys the water from a considerable portion of the catchment area which is settled and would require to be purchased. There is a suitable site for a dam immediately below the junction of the Whukataki and the Wainui, the level of the stream at the point referred to being about 334 feet above the sea. The length of m.iin from this source of supply is considerably shorter than would be required by the adoption of the Hutt River or Akatarawa schemes.

Proposed Now Mains. "The existing 30in. main between Wai-nui-o-mata and the Wajivetu tunnel would require to be continued into the city through a new tunnel through the Waiwetu Hills; thence along l'etone Esplanade and the Hutt Road to the northmi end of Tinakori Road, along Tinakori Road to the south-west corner of tho Botanical Gardens, where it will be reduced to 27in. inches in diameter; thence through a tunnel under portion of the Botanical Gardens, Boundary Read, and private property in i-pproximately a straight line to the foot of Norway Street; thence along Aro Street to Willis 'Street, where it will be reduced to U inches in diameter; thence along Webb Street, Taranaki Street, Wallace Street, <Howard Street, Tasman Street, John Street into Adelaide Road, where it will be again reduced to 18 inches in diameter; thence across Adelaide Road and along Riddiford Street, Hospital Itond, through the Town Belt to Wellington Road, joining the existing 12in. main at the corner of Wellington Road and Kilbirnie Crescent. Connection would be made to principal existing mains on Tinakori Road and to pumping stations for Wadestown, Kelburn, and Northland, Brooklyn, and the district now known as Onslowwhich is about to bo incorporated with the city; also, to existing mains . from Karori Reservoir at Aro Street near the junction of Holloway Road, and again a* the junction of Willis Street, Hanson Street, and Adelaide Road. The route above proposed will be expensive, but is believed to be the best that can be suggested in order that the new supply may benefit the whole of the city,' and to avoid further congestion of the mains in the central portion of the city. It will also tend to cheapen tlie cost of pumping to W'adestown, Northland, Kelburn, and Brooklyn, and further, the main will bis constructed on solid ground throughout instead of on the filling in the reclaimed areas of the city.

Alterations to Existing Mains. "The existing 2tfn. diameter main to be connected to-tile proposed new dam at AVainui-o-mata through ,I'ne new tunnel through the Wniwetn Hill* already referred to. The existing 21in. main to bo continued i-rom its junction with the existin" 24in. main at the western i.»!o of the Waiwetu Hills to the upper rcservoir at Wainui-o-mata. This tunnel would then accommodate only the proposed extension of the '21in. main. Tins work will be beneficial in ensuring Hiefilling of the. Bell Koad Reservoir iitull times without assistance from the Karon Reservoir, and would result in pressures being kept nearly uniform-throughout the. city at all hour?. , The existing Bell Road Eeservoir is not used to its fullest capacity during the summer months, owiii" to the level of the ground which had to be selected for the construction of same. This, however, only applies during the summer mouths, ami the difficulty is obviated by bringing into tiio city an additional supply from Karori. It will ne seen that the construction of the mains proposed will cost n-considerable amount of money. It has,' however, to bo remembered that the .scheme put forward has the object of being sufficient-to'sup-ply the whole of tho city at the end of twenty-iive. years, when the estimated population for tho city alone is expected to reach 150,000, or practically doable the present population. "After careful consideration, I am of opinion that the most economical supply of water to the city is still to bo obtained from the Waitiui-o-mata. district, and this is the most suitable, having regard to levels and length of mains. If the new ressrvoir is built and 3,000,000 gallons obtained from the Orongorongo as proposed, it will Iμ seen that a supply sufficient for a population of 180,000 person* at 74 gallons per head per day is obtainable. In the estimated population of Wellington and suburbs for 1913, the total is set down nt 198,000, which includes a population of '12,000 in the Hutt Valley. After full consideration, I am of opinion that unless specially desired, no provision should at present be made for a supply to Petone, Lower Hutt, or the Hutt Valley. If these districts were omitted the estimated population of the adjacent districts likely to bo incorporated in the city may be taken at 156,000, so that ample provision is niado in the above scheme. In thu event, bowever, of a'supply of water being required for Petone, Lower Hutt, and the Hutt Valley, this can 'be obtained from the Little Akatarawa and could bo joined up with the city supply at Petone. Tho Akatarawa caii be relied upon to supply a sufficient quantity of water for these districts, and it' joined up with tho city syslem the supplies to all parts would bo available from the two different sources. As before stated, the Little Akatarawa can be relied upon to supply about 3,300,(!00 gallons per day, without storage, and if connected with the Wainui-u-mala-QrongoroiißO scheme, a total daily,-supply of 17,100,000 gallons would be provided, which at 7-1 gallons per head per daj would be sufficient for a population ol well over 230,000 people. I havo not estimated the cost of connecting the Akatarawa stream with .the. proposed additional Wainui-o-mata scheme, as it seems improbable that such additional supply is likely to be desired by the residents of tho Hii'tt Valley for a considerable time, and such would probably be the last work lo be undertaken. I am, however, satisfied that it would bo tho most economical to undertake if the Wainui-o-mnta-Oro-ngorongo scheme were required to be extended in order to embrace the supply U the whole of the Wellington district as previously referred to. Estimates ior WainuNo-wata-Oroiigoronno Scheme, "I estimate the cost' of constructing a new (lam as previously described at Wainui-o-inata, the provision of additional storage from the Oroimorongo, the provision of a new 30-iiich main iind iiltorations to existing mains, to be as follow.:- £ New dam at Wainui-o-mata to hold SOO.nfiO.ooo 120,000 Now ,10-inch main through the city to reduce to 18-inch at Kilbirnie, including cost of new tunnel through Botanical Gardens to Norway Street 108,000

Extending existing 24-inch main from (lie west cud of Waiwetu inline] lo the proposed new dam ill. WaiiiUiWi-iiiala 30,000 llxtendiiii; existing 21-inch main ' from west I'mi of Waiweu lunticl to upper Wniniii-o-niata licservoir 3,1,000 New tunnel through the Waiwotu Hills lo accommodate- tho new 30-ini'li and extension of 21-ineh xiiiiins 18,000 Alterations to existing mains ... 3,000 Cost of purchasing private property, way leave-?, etc.,. new road construction, caretaker's quarter.* 7,500 New tunnel between George's Creek, Wainui-o-mata, and tho Orongorongo with 21-inch pipe through same, headworks, etc.... 80,000 .£•191,500 Ten per cent, for contingencies and engineering 49,150 Total '. <£510,G50 "With reference to the estimated cost of the work proposed, I desire to point out that notwithstanding the expenditure which' has taken place, during the last fifteen vears in connection with the extension of the city water supply, no additional rate hos been incurred. As a matter of fact, the rate for water supply has been reduced. The work which has been done during that period lias been in every respect beneficial, but the growth of the city and its extension by '.he incorporation of adjoining districts makes it necessary that a much greater jirovision "half be made ahead of present renin rcments. 1 am satisfied that the proposals herein made are the most economical that can be brought forward for consideration for supplying the estimated Dopulation. it may ba considered that, ttio allowance of 74 gallons per head per day is more than is necessary. It is. however, in my opinion, useless to Lase the supply on any lesser allowance. Ir, will be noted that its.greater supplies have been made available the demands have increased. The growth of parka and gardens (both public aud private) necessitates that the increased allowance should Iμ provided for. I have now only to point out that the total cost would be spread over a considerable time. It may be some years before the work is completed, unci therefore it would not ijn necessary to raise money for the whole of the work, but authority should be grantod if possible, and the money to be raised from time to time as occasion reauires, It will be necessary to determine which works should bo at once undertaken, and after full consideration, it seems advisable that the new dam at W:iinui-'o,-niata and the alterations to existing mains should be constructed first, and that the tunnel into the OroiiEorongo could wait until such works are completed. It should be rememberml that additional mains are required p.s well as additional supplies, and that it is not advisable to extend the districts to be supplied from the city system until provision has been made for increasing both supplies and delivery mains. In conclusion, I have to acknowledge tho assistance given me b/ tho Government Statistician in connection with the estimating of the future population of the districts referred to in this report."

The position of the foregoing report, is that it lias been considered by the City Council in committee, approved, nnd ordered to be printed. Its formal adoption as a work to be prosecuted will depend on its approval by the ratepayers at the loan poll concerning this and other works.