MUNICIPAL ENGINEERING

Evening Post, Volume CXIX, Issue 33, 8 February 1935, Page 18 (Supplement)

MUNICIPAL ENGINEERING

FEW towns in New Zealand suffer so many natural disadvantages from a road con-

_ ' struetion point of view as Wellington. Nature must indeed have been in a perverse mood when, with careless abandon, she shaped the rugged yet beautiful hills on which the city of Wellington has been built. To suggest that these hills would some day be dotted with houses served by an adequate system ofV well-graded roads must once have been considered sheer idle talk. Yet today this, and'more, has been achieved. Indeed, the. city is widely acknowr §?£ t0 remarkable for the small amount of difficult grades in so hilly a terrain. Of the 242 miles of legal roads in'the city, only 19 are unformed- Of the remainder, A\ miles : are wood-blocked—a form of construct tion which has given the city years of faithful service* and which:is only, now abandoned be-' cause: of its high cost. . Thirly-eight milea are of first-class bituminous concrete,^including a portion of the famous*2B-mile,marinef drive, 52 J miles are surface-sealed, and "the balance, '128 miles, are ofimetal or gravel}' which is gradually being,treated by. modern'"'surfacing' methods. The.five.trafficr tunnels,.'ofwhich : Some'inter-' *$$&. P aJti<iulars are given below, are a unique. feature of the roading system :— .Width at Vehicles Tunnel. Length. .Road Level. per _ Chains. ft. in. 10 hour Day. Karon 3.75 .25 6 -1840 . Kilbirnie Tramway 19.25 12 0 363 Mt. Victoria 31.00 27 0 3400 Northland '4.5 24 8 274 Seatoun ........... 6.0 26 0 820 When it is considered that nearly 7000 vehicles per 10-hour day use these tunnels in preference to longer.and more hilly routes, their economic value is apparent. Of bridges Wellington has relatively few, the most notable being the Kelburn viaduct, completed in May, 1931, at a cost of approximately £22,000. This important link in the access to the western suburbs replaced an old wood and steel structure which, for the conditions pertaining 30-odd years ago, was efficient and well designed. Other reinforced concrete bridges over 25ft

of this was to extend the original board's control to a number of roads in and surrounding Wellington, the funds for the construction and maintenance of which were obtained by special levy on motorists within the district. With the advent of the Main Highways Board this levy was abolished and funds were obtained from general motor taxation. ADOPTION OF BITUMEN. This programme of paving was not entered upon without very careful consideration by the City Council, which sent the late Mr. Morton on a tour of the United States of America, England, and Europe, to study modern road construction. _ His report* dealt with all forms of construction, and gave in detail his reasons fdr adopting bituminous instead of Portland cement construction. In. spite of considerable controversy,at the time, bituminous construction was adopted, and has.fully justified itself. ;In May, 1928, a report of considerable importance was presented to the council—that of the Access Commission. The recommendations .contained therein were that access should be provided for the eastern suburbs by means of a traffic tunnel through Mt. Victoria and approach roads. The western suburbs were to be reached by (1) constructing a main road from Bowen Street through the Bolton Street Cemetery to Tinakori Road, via Sydney Street; (2) widening Glenmore Street from Chaytor Street to the Karori Cemetery; (3) the acquisition of the Kclburn-Karori cable tramway, and certain developments in connection therewith; and (4) the construction of a road from the junction of Durham Street and Aro Street to Glenmore Street, via Norway Street and a short tunnel. ACCESS TO SUBURBS. As part of this programme to provide rapid access to the western and eastern suburbs a number of notable works have been carried out, the most important of ;which, the Kelburn viaduct and the Mt. Victoria tunnel, have already been referred to. The latter, which, with attendant works, cost approximately £150,000, is unique in the Southern Hemisphere in having artificial ventilation for the elimination of objectionable fumes, notably carbon monoxide.

provements will be made to the approach roads to the Mt. Victoria tunnel, and .another route will probably be provided to the western suburbs, as well as an alternative route out of Wellington via Khandallah. When these works are completed Wellington will be provided with a fine system of arterial roads from which, as increased: population demands, improved Subsidiary roads will be developed. MEETING THE DEMAND FOR WATER. Early residents of Wellington drew their supply of drinking water from wells, springs, and_ running water, or from tanks and barrels storing collected roof water, in. the same manner as in many a rural community even at the present time. With closer settlement, there could be. only one result, where reliance was placed on surface wells and local surface water, and James Hector, M.D., F.R.S., reporting on.these existing supplies in February, 1871, refers to "the misery and suffering entailed, especially on the children, from the prevalence of intestinal worms." His report contains the analysis of 34 sources of local supply, including wells, streams, and tanks, located in different parts of the town, and calling attention to the high percentage of oxidisable organic matter, concludes that "no water collected within the crowded parts of the city, either from wells or house-tops, is safe or proper for human consumption." In the same report, which was submitted to a special meeting of the City Council on March 3, 1871, by the City Surveyor, together with his own report on a proposed water supply for the city of Wellington, Dr. Hector refers to the diminished flow from natural springs, "owing to the reckless clearing of the hills which is in progress-round Wellington Harbour," and supplies interesting notes relating to the geology of the district ,At this meeting, the City Surveyor (Nicholas Marchaht,; C.E.), recommended the taking of

pipe bridges across tlw Waiwetu and Hutt Rivers. Water was to have been brought into Wellington on Anniversary Day, January 22, 1884, and in preparation the mains were filled on January 20 and 21 as far as Petone, when a burst occurred in the long tunnel and another on the Petone beach, and on the 22nd a heavy flood swept away the dam. The early years of this scheme were further marred by a free-for-all fight about the design and construction of this, for that period, very large undertaking, consequent upon the discovery of Certain defects in the head race, the repairs to which coincided with a disastrous fire in the city. .-,■.'.. In 1900 the City Engineer of the day, Mr. Rountbwaite, A.M.1.C.E., once more faced the problem of increased supplies and recommended additional storage provision at both Karori and Wainui, and the replacement of the water race by the extension of the 30in pipe to the Wainui dam, this last work being carried out in 1901. NEW RESERVOIRS. The need for the additional storage was endorsed in 1902 m a report on the water supply brought down by Messrs. Mestayer and Ferguson, and in November, 1904, a comprehensive ■ report by Mr. W. H. Morton, City Engineer, called for the construction of new storage reservoirs at Wainui and Karori, purchase of the Karori catchment area, extension of the 30in pipe to the proposed new Wainui reservoir, provision for supply of water to the recently added suburban areas of Brooklyn, Island Bay, Kilbirnie, Roseneath, and Kelburn, and for considerable extensions to the city's reticulation system. The estimated cost of these works was £132,000. Again, in 1910, Mr. Morton, as a result of the increasing difficulty in maintaining a safe storage reserve at Karori, reported in favour of duplicating the old 24in main from Waiwetu Hills to the city and the, construction of . a 2,000,000 gallon service reservoir which, with

in length are on the Hutt Road.at'Kaiwarra (44ft) and Tawa, Street, Island Bay; (45ft). The gullies at Everton Terrace and \Hobson> Street are spanned by timber and steel bridges, 105 ft and 96ft in, length respectively. " TAR-SEALING PROGRAMME. As early as 1900 -the matter of tar-sealing the streets was discussed, the then City Engineer, in common with many others of that time, considering that one of the advantages of this formof construction would be a relief to "the nervous systems of those of us who have to do business daily in and-about our streets," by reducing the noise. However, the chief factor influencing the vast improvements made in Wellington's roading. system daring the last; fifteen years has been-the advent of mechanical transportation. ! Some idea of the volume of. traffic carried by'the city streets .may be conveyed by the fact that Jervois Quay carries 12,000 vehicles, almost exclusively imechanicalj per 10-hour day. • Greater-speeds demanded better .surfaces and wider ■ streetsj } involving; high'capital, expendi-; ture whjch xouldvbnly he -tact. by 'means. ; of loans^Thus. in 'paving: loan was raised; followed; in -1925;, ahdan 1927 : hy' fur-, ther loansi :<-:-^'■•>,■'^ f:^- .•..;',■•"■■' 7<. ■: \- -'': " : An,interestingidevelopmerit 'in11924' was the' formation^ of-the; City and Suburban. Highways. Board,-which has been; responsible fpir the paving of some 45; milesbf rpads in and: around Wellington., This'body/really grew'out\of the old Hutt Road Board-by means.of ati amendmentlto the Hutt>Road;Act of 1917. ■'. The effect;

On the opposite side of the city improved access to the western suburbs has made practically a complete transformation. Glasgow Street has been realigned and widened by massive concrete walls; Plunket Street has been treated in a similar manner, and more recently Upland Road. The latter, by its aesthetic treatment, shows that a concrete wall can, by consideration in design, be made to enhance the beauty of the hillside. The depression has had its influence on the development of the suburban roads. Many of . these have been regraded and realigned, and in some cases completely reconstructed. The expenditure on works^necessitated for the relief of unemployment by the W.C.C. under this heading has amounted to over a quarter of a million; pounds Avithin the last few years." Another interesting feature of the depression has been the variation in the volume of traffic in the city. The percentages as under are in each case based upon the; previous year:—l93o-32, 11.25 per cent, decrease; 1932-33, 1.65 per cent, increase; and 1933-34, 6.44 per cent, increase. - Street-widening loans have Tendered possible improvements to several city streets. However, this work must of necessity, proceed slowly as new buildings are erected. . J ; FUTURE DEVELOPMENTS. The future will see further developments in Wellington's roading system, but it is doubtful whether such vast changes in so short' a period of time will take place as have.been,witnessed during the last few years. No doubt certain im-

the water "from the Kai Warra Warfa River, tapping it hear Baker's Hill, 410 ft above the sea level, and conveying it-into the distributing basin by a tunnel cut for this purpose through the ridge that separates the stream from the Polhill Gully." , ; v ;

bridges over the Wainui, was estimated to cost £80,000. The new main increased the amount of water conveyed from Wainui by 237 million gallons in the first year of its operation. In the same report, Mr. Morton proposed that the Government should be approached with,a view to setting apart the Orongorongo watershed as a waterworks reserve. : .•..:> \- ~. In 1917 and again in 1919, unusually,, dry weather severely tested the city's available supplies, and in the latter year Mr. Morton reported in favour of the construction of a huge reservoir in the lower Wainui Valley, a tunnel through to tap the Orongorongo, and considerably increased main capacity, the works to cost £540,000. This scheme was modified—principally on account of the unexpected depth at which suitable dam foundations existed—to become what is known as the Orongorongo scheme, a 21in steel main being constructed from a weir in, the Orongorongo through a tunnel two miles long to the Wainui Valley, and thence through to the Karori Reservoir. This huge task was "completed in 1926. . EFFECT ON POPULATION. ;. The street reticulation and the construction of the high level service reservoirs at Karori and Onslow, fed by gravity through.this 21in main, initiated a period of very rapid development.:in these /reas, the population in Karori increasing from 2857: in 1926 to about 6500 in 1931. - In 1921 the city absorbed the Miramar Borough, which has been supplied through a meter on the borough boundary since 1912 ? and dur-

It was further proposed to construct a dam'in the Kai Warra jWarra—the : present Lower Karorj dam—to store 35,06b,000 gallons, which was considered sufficient, in conjunction with the dry-weather flow, to' supply a population of 47,000 with 30 gallons per head per day. '■/■■.":■ THE QUEST FOR SUPPLIES. Alas for men's plans! An actual minimum yearly rainfall of 28 inches, instead, of the estimated 42 inches, and a dry period consumption, which gradually increased to 80 gallons per head, proved most upsetting, and since those days Wellington has very seldom for any'length of time been able to sit back and congratulate herself upon an entirely adequate water supply. Already in April, 1878, we find the council somewhat optimistically instructing the surveyor to "report upon all available sources from which can be obtained a water supply which will be af all times adequate and reliable," and after submitting-data ..to Mr. Clark, C.E.,; the first Wainui development .was recommended and carried at a '■■■'poll on August 20 1879, by.: 1099 votes to 388. This scheme pro' vided ; for a dam at Wainui with a head race extending nearly to ,the- junction with Moore's Creek and a 30in pipe through the Waiwetu Hills, thence a 24in pipe to the city, including

ROADS, WATER SUPPLY, SANITATION

ing the last two years necessary additions to service storage at Wadestown, Karori, Brooklyn, and Seatoun Heights and to reticulation, together with the preparation of a scheme for using Hutt Valley artesian water as a temporary measure of relief, bring the history of Wellington's water supply to date. Bigger works will be faced in the future as the city reaches still further afield for new supplies to quench its ever-growing thirst. This will be satisfied ultimately only when the head waters of the Hutt or its tributaries have been added to the contributions frpm, the Wainui and Orongorongo Streams. THE VITAL PROBLEM OF SEWAGE DISPOSAL. The introduction of an adequate water supply m Wellington was accompanied by a demand for a modern water-borne sewerage system, and many were the schemes to this end advocated by experts and others. It was not till 1890 that finality was reached, when Messrs. Cuthbert and Ferguson submitted their report on the sewerage of the city of Wellington. They were asked to advise on six schemes previously submitted to the council and generally as to the best means of draining Wellington. The more important of the schemes submitted to them were a report by Mr. D. Climie, dated January, 1877, one by Mr. W. Clark, dated May; 1878, and one by Mr. H. P. Higginson, dated April, 1890. The schemes referred to all provided for sewerage on the separate or partially separate systems which would eliminate the whole or at least the major portion of the rain-water, and favoured the distribution of the sewage on the land between Evans Bay and Lyall Bay. In this connection Mr. Climie reports that he had selected a site on the low land at the south-west corner of Evans Bay, and that "the proprietor of the land, J. C. Crawford, Esq., has agreed to convey the sewage, at his own expense, from the

ward, • crossing the, sandhills and passing the JVhramar golf links, then around the foreshore till it discharges into the sea at "Hine-te-Taka." _ Sewage from parts of Wadestown, Highland Park, and the Tinakori Roddivwaters^d^Kelburn, Taitville, and parts of Brookl^|e|chP3 the intercepting sewer by grawry; asi^^a&tVie sewage, from the city areas lying tqf'th&^iouth as far as the Island Bay 'divide.^S-'-S^; The sewage from the lpw^lytog areas ;t&jcihe north, including the busihessVareas of itfjelcity and also Oriental Bay, Roseneaffijetc^i^lurlped into; the same intercepting server ffom^lfiftepa stations known as^ ejector ;staHonsr^vhic|t^are connected- to two castiron rising: :ina)ns>*one delivering into the interceptor;it ;nead%id the other,at Buckle Street :The sewage;reaching these stations is1 forced through these ■rising mains by ejectors located in pairs and operated by compressed air supplied through a system of pipes from the Clyde Quay mimpin--station. The steam for working the alr-com-pressmg engines at Clyde Quay is generated by the burning of the city's refuse at the destructor. Inere are thirteen more ejector stations scattered through the eastern suburbs of Hataitai, Kilbirme, Ly.all Bay, Miramar, and Seatoun supplied mth air from a modern compressing plant in the old Miramar power station. DECREASE IN DISEASES: *aonnrtr? 97'? ,Was necessary to *™*? a' further 4.(52,000, and the works were completed:'in 1899 at a total cost of £175,000. The resident engineer in his final' report drew^attention to the marked decrease in zymotic diseases under treatment at the hospital, including the following figures recording cases.of, typhoid feverftreated there:—lß93, 96 cases; 1894, 104; 1595, 78----1896, 85; 1897, 62; 1898, 4L ;'' '"' The main sewerage scheme functioned very well for about thirty years, when the^ rapid increase in population drew v atteririon st¥' lack ofi capacity in certain parts, though untihthe pre-

outfall; to a; part of his property, where he will utilise it as manure." ... The scheme finally submitted by these engineers was fundamentally that proposed by Mr. Higginson, the main departure being in connec-: tion with the route of the tunnel through the ridge to Kilbirnie and the use to be made of the existing drains in the city. '-':■ Thirteen years had elapsed from the date of the first printed report on die main drainage of Wellington, so it cannot be said that the city entered lightly .upon this important v development. '■■. > ■■.-.■ .•■ . ■ : SOUND ENGINEERING. Sound engineering knowledge and practice characterised the inception and the execution of the sewerage system, and Wellington's reputation as a very healthy city owes something to' those whose names are so closely connected with the undertaking, namely, Messrs. Higginson, Cuthbert, Ferguson, and Mestayer. A brief outline of the scheme as carried out will be of interest An intercepting sewer commencing at the junction of Dixon Street and Willis Street traverses Willis Street, Ghuznee Street, Cumberland and Stepney Places, Vivian Street, Cuba Street^ Abel Smith Street, Martin Square, Sages Lane, Tory Street, Buckle Street, Sussex Street, Rugby Street, King Street, Drummond Street,.and Adelaide Road to the Government House- grounds, where it enters a tunnel which comes.out above the Kilbirnie Recreation Ground. Thence the outfall section, on a uniform gradient, traverses Crawford Road, Childers Terrace, and Queen's Drive, and turns east-

sent time nip major additions of alteration^ havel been required. • ' .' '-'■ ■> '■>"■ Additional ejector stations have beeflv constructed and two additional- engines installed at the Clyde Quay engine : room-and motor compressors at Miramar, but expenditure on sewerage was for many years confined to the reticulation of the suburban areas ladded .to^the city from time to time, together with the'construction of septic tanks for treating the sewage of these areas before discharging it into the harbour or the sed or, as at South Karori,,into the stream. ...■''■ SUBURBAN[FLOODING. T^ ? The culverting of the old watercourses and streams in the city proceeded hand in hand with the growth of-the population, but in the suburban; areas where the development has been much more rapid, flooding andr its ■ attendant troubles have in recent years committed, the city to heavy expenditure at Miramar, Seatpunj Kilbirnie, and Island Bay. At these, piades the increase in storm-water run-ofiF due to construe-, tion of impervious roads, paths; roofs,' etc., has been very considerable, the old: channel iieing quite unable to cope with the sudden concentration of flow so. produced. The effect of building and road improvements in adding to the volume of storm-water to be dealt with will be reflected in extensions to and replacements of existing storm-water drains for some years to come, and already the ultimate population of 75,000 provided for in the main sewerage system has been reached, so that new works cannot be put off for long.