MR NOBLE ANDERSON’S REPORT.

Evening Star, Issue 12163, 6 April 1904, Page 8

MR NOBLE ANDERSON’S REPORT.

SHOWING THE DRAINAGE SCHEME

AND THE WORKS FINISHED AND IN PROGRESS.

Mr J. T. Noble Anderson, engineer, presented his annual report to the Drainage Board last night. It reads as follows :

. —The Board’s Powers.— This Board have administration of the ■Urmedin Drainage and Sewerage Act, ISOO, and the Amendment Act of 1902, which .aU previous Acts and by-laws drainage and sewerage of the disr it *“ ese Acts, provide for the control oi all covered drains and sewers, and the construction of such new drains and sewers Rs the Board shall'deem requisite, and the Reversion of all sewage matter so that it shafi no longer discharge into the harbor. Up to now there have been no less than eleven different channels for the drainage of the district, and they all discharged into the harbor. Of these the following are by covered sewers:—(l) Frederick street; (2) St. Andrew street: (3) High street; (4) Manor place; (5) Railway Crossing. Kenmngton; (6) Caversham (Cargill road); (7) South Dunedin (Macandrew road), and the most rigid of the Board’s statutory obligations is to divert the sewage and detritus from these artificial channels. My scheme for this purpose was duly adopted by the Board in May, and shortly afterwards obtained the approval of the Harbor Board, which, under statute, was all that was required to enable the works to bo commenced. —The Scheme.— Briefly, this scheme consisted in intercepting all of the covered drains by a main drain, which will run underneath them as CiOse to the harbor frontage as practicable, and then pumping from "it to the ocean. -The interception will be by weirs, placed in the existing channels at such places as shall be above tidal influence, and with one exception—part of George street Fewer —all the existing drains which are of either brick or concrete, and are above tidal influence, that can safely be used, will be utilised as part of this scheme. Economy to Public Bodies.—This means a considerable saving to such of the munici. ahries in the district as have in the past constructed permanent works, because, while the Board are under obligation to j»y interest on existing permanent works, their obligation is strictly limited to such works as the 80->rd’s scheme can utilise. Economy to Private Individuals Due to the System Adopted.—With the exception of their_ designer, I cannot find that any of the engineers who in the past, were asked to report on the sewerage of the City proposed their continuance as part of the sewerage scheme. This extraordinary extrava gance in their proposals was evidently duo to the fact that, having mainly Australasian experience, they had little acquaintance with the methods of fitting existing well-estab-lished sewerage works into a new scheme, and that they under-rated the value of the existing works under two misconceptions. Tiie first misconception was that the old sewers were designed of antiquated and insanitary types. _ They may have fallen into thus misconception by their impression of one of the most important sewers of the City—e.g., High street—and this is the only sewer of ail about which such an allegation could with any shadow of truth be made, and also the most prominent and easy of examination. But owing to the plentiful flow of water at all times in this sewer, and the ease with which it can be ventilated, the departure from the usual modem type in its design by adopting a flat bottom did not cause any real danger, and was a considerable economy. The second misconception was. that since the sewage must be pumped no matter what scheme be adopted, it should of necessity be separated, from the ordinary drainage. The absurdity of this will be seen from the records, which show that the polluted water which the Board are compelled to remove bv pumping will every year amount to no less than 80 per cent- of the whole discharge from the district, excepting only the discharge of the' Water of Leith. "The small extra cost of pumping storm water cannot be compared with the immense cost of installing a separate system, because sych a system would mean the duplication of all existing,drains, private as well as public, bv a separdtg Bbt Bf sewers for the whole district. ”

Irte following figures will indicate howgrave a public misfortune is averted:—The total value of the property, public and private, which would have' been dunlic-ted and practically abandoned is about £200.000. Added to this, there will be a contjnuai economy for all future works. The difference between the _ combined and separate system for new; buildings would average at the least in favor of the combined £5 for each new tenement.

It will be seen that to properly estimate the value of the saving to he obtained by Utilising where possible the old sewers it above all things, necessary that the condition of these sewers should be verv closely scrutinised. The inspection, mea'surement, and full investigation of these sewers was therefore one of the first labors. These sewers have been measured, planned, and reported on by two separate sets of men. The estimate given to the Board in November of the cost of putting these sewers in order was that in the next three years it would cost £IO.OOO. It was expected that by th°n the greater part of these sewers would have been brought into a state to stand at leaSt for the next thirty yars. Appendix No. 3 shows how far this work has been completed. It is encouraging to find this expenditure is so far within*the estimate. —Original Programme.— It was intended that the pumping station and outfall should be the first work done. by this means the heavy pumping which will be required for the main intersewer will be provided in the most economical way. This programme is being carried out without any variation, except that, owing to hj delay of about six months while the scheme was being reported on by the consulting engineers; several matters which were not intended to be commenced until the stress of starting the main works Lad been somewhat relieved could not be longer postponed, and consequently much heavier work is. thrown upon the staff during this first year than otherwise. As an example, the first portion of the main intercepting sewer east of Frederick street, which had been started about the time intended, is relatively to the rest of the works six months ahead, and the same remark applies to all the works of reticulation and branch sawers. Works at the outfall have also been most seriously retarded by the objections which led to the Royal Commission on the Bird Island outfall, and subsequent events are adding to this delay and the cost of these works.

. -As published in May, the scheme consisted of an intercepting sewer at a lower level than the existing drains, which run south-westerly along the city side of the railway, through Athol place and Cumberrand street, _ and thence along the harbor frontage beside the Ocean Bea-ch railway to pumping station at Musselburgh, where it is pufiiped by a rising main to the main ontiall storm water drain and sewer, which flows from Tahuna Park to I awyer Head. ln^storm water drain, which will only be wanted for a few days every vear, discharges at Lawyer Head, while the sewer jrasses by tunnel on to the Tomahawk Beach beside the Lagoon bridge, and thence »long the Tomahawk road to the bluff, and icross by means of a siphon to Bird Island. in addition to thes- main works, which jrere estimated to cost £82.615, there were to be rertain storm water relief drains, to ronm °°’i, aild ! " pt,c tanks - to cost branch sewers to cost £35.100. and reticulation s"wr rs to cost £23,600 These are beimr carried out by day labor, as follo'vs ;—On the main works more than three-quart-rs of the a fferent items have been Started. Of the storm water relief'drains more than three-quarters are completed, approximately about half of this work by contract. J The s°ptic tanks, which were tentatively proposed m December, 1902, were found by the surveys completed shortly after to he easily obviated, and close investigation of

the condition of certain of the existing branch drains showed that Maori Hill, North-east Valley, and the harbor watershed might be efficiently served by branches to the main intercepting sewer, and so save the need of bacterial method of treatment for those areas. The £9,000 expenditure allocated for these tanks will suffice for the additional expenditure for branch drains which this will involve, though the capital expenditure will be the same. The annual expenses will be less, because (he tanks require more care than drains.' Of the new branch sewers, allowing for their increase, fully one-fifteenth part is completed, and of the fresh reticulation sewers more than one-tenth.

—The Detail Survey of the District.—

This work was recommended by Mr Mestayer in 1898. He stated that had such been in existence in Wellington he would have been saved an expenditure of nearly £2,000 in obtaining sufficient information for toe reticulation works. When it is remembered that, as has since been proved in Wellington, the saving in carrying out the works is trifling compared with the continual loss and trouble due to lack of accessible details for maintenance and future operations, such as installing the new tramway system, making fresh water, gas, and sewerage connections, etc., the importance of the work will b-' appreciated. In Melbourne already £IOO,OOO has had to be spent on similar work.

Among the first contracts let by this Board, therefore, was one for the survey a bout one-third of the city portion of tne district. This work was completed in March, 1903. Since then similar work has been continued vigorously by day labor, with the result that the whole of the City has now been so surveyed, and practically all of the suburbs, so far as they are laid out in streets and built over. The work done by day labor has been all plotted to a scale of 40ft to the inch, and the cost of the day labor work compares most favorably with the contract, work, and with the cost of any similar work yet carried out in any of the colonies. It is worthy of note that in Great Britain this work is carried out entirely by tic- Government, arj at the expense of the Government, and it seems hardly fair that a Board constituted as this is should have to carry the whole expense of work which is needed equally for general municipal purposes, for the information of the country at larce, and for the benefit cf every individual who purchases a block of Imd and proposes to improve it or build thereon.

It is a subject of congratulation that this survey was sufficiently advanced to prevent any mishaps from a drainage point of view in connection with the tramways, and to enable the Board to protect themselves against the charge of complicity in risks. In the absence of detailed surveys, the course followed is to design the reticulation work by relying on the permanent street levels. That course was followed in Glenroy, North-east Valley; but, unfortunately, the street levels were considerably higher than they should have been, and consequently i't was found that the drain would have entailed racing several of the sections before they could be drained. The drain was therefore lowered. The cost of lowering the part of the drain (702 ft) laid before the detailed survey was completed was less than £l6; but the incident is worthy of notice as to the value of these detail surveys The Board's by-law came into force "in November, 1902. To prevent loss to vested interests this was more or less held in abeyance for more than twelve months. Meantime a senes of demonstrations and examinations for drainers, and latterly examinations for plumbers, were hold, and samples and drawings of standard pipes, fittings, and appliances, etc., made available to the trade, with the result that to date nearly 200 houses have complied with the Board’s conditions

Towards the end of last year it became necessary to take steps to compel observance of certain clauses, and nineteen cases were threatened with proceedings. In the majority of these cases the builders complied with the by-law. Of those who were fined. I am pleased to state that some showed that they appreciated that the action was painful to me, and was dictated purely from a sense of duty and without any personal feeling.

—Quality of Work.—

Sewerage works are peculiar, even among hydraulic works, as requiring for their success not only the highest class of materials, but the greatest care in the workmanship. Unfortunately these requirements are hardlv compatible with the ordinary easy mode of carrying out engineering works by contract, and consequently everywhere where it has been earnestly desired to have a good sewerage system the work has bad to be carried out by day labor. The storm-water works, with one exception, have been carried out by contract, and although onlv the ordinary standard for hydraulic works has been maultamed, the wages of inspectors on these contracts has equalled 10 per cent, of the payments made to the contractors, and I regret to say that while this contract work is sufficient for its purpose it is not of a class which would suffice for sewerage. The training of local foremen and assistants to the grade required has been coin" on unremittingly since the works “were started some nine months ago, and I have every confidence that my present men, all of whom when engaged here were strangers to me, wiL be able to give excellent°accounts of themselves. It will, however, be apparent that this mode of carrying on the works entails very heavy- work' on all the staff, especially the accountancy. The list of works in hand will show that the amount of accountancy, correspondence, and management devolved on the Board is equal to that which would be done by a score of different contractors if the work were carried out by contract, and the exact cost of any one job cannot be given until all the accounts are presented and the plant accounted for or disposed of on other jobs. Notwithstanding this, so assiduously have the accountants worked that every job undertaken up to January last has been completely accounted for (a brief abstract of these is given in appendix No. 4). This work of apportioning costs is, of conr.-e quite independent of the accountancy for the Auditor-General, which will, I understand, be completed in a day or two for this year.

Taking appendix 4, one item deserves further detail—namely, investigations, etc. The total of this item is £1,464. This certainly seems abnormally heavy, but only about £4lO is chargeable to ordinary investigation works. This is: Ocean current observation by steamer Express, £187; sinkia" trial holes, etc., £223. The balance of the item (£1,054) was spent on two inquiries namely, Messrs Cutler, Reynolds, and Rogers’s report and the Bird Island Outfall Royal Commission.

The works carried out to date are sufficient to dispose for ever of the chief doubts which were cast on the scheme

The first of these was that the velocities I calculated to get would not be attained, ihe Frederick street sewer has abundantly vindicated the accuracy of my estimate, then combating this Objection I showed that the difference of levels which causes speed of flow is the difference of the levels at the surface, and is, under certain circumlil“l e ' S ;, of the levels of the bottom of the channels or well which contains the water; and yet the same bogey is agaiii being raised in connection with the Bird Island siphon, which is objected to because it is alleged that the difference of -evel to cause flow i s only Ift (Ift .OSinl whereas, if the calculation is worked out it will .be found that this difference cannot possibly be less than 3ft. 1

The other objection, also voiced by Messrs Cutler, Reynolds, and Rogers— namely that the deep-level sewers and drains would be almost impracticable—has been also disproved. In dealing with the- Fonburv storm-water aqueduct they considered that it was only practicable to carry it along th e route iny scheme proposed by using a siphon. Whereas by dint of excavating to a depth of through running sand, of the finest and mo t difficult nature, carrying a large body of water, the aqueduct htu been constructed with a uniform grade throughout, thus entirely avoiding the siphon, and at the same time the cost has been well within their estimate.

And the third and last objection was the heavy cost of the engines and annual charges under the combined system. The first cost of the engines and pumps is less than my estimate. Few realise how great are the economies in fuel and attention of modem types of engines. Both the contractors for the Dumus and the oil encines have adeed

to the economy trials which I specified, and which are considerably better .than I cared to promise when preparing my estimate. To give an idea of what the economy is, the engine contractors’ guarantee is equivalent to a charge for fnel of £l5O per annum on the assumption that English prices of Can obtained. The colonial price will be considerably heavier, but my estimate allowed more than 'our turns this amount, and the consulting engineers’ . - mate on an expenditure of £1,580 per annum on coal.

—Pumping Station.— ~ e ngine 3 are in duplicate, each of the three cylinders Diesel type, with a guaranteed economical load of 120 brake horsepower on the pump shaft, but capable of U P t0 L ls ? brake horse-power, or a total of 300 brake horse-power (probably over 400 i.h.p.) The pumps are in triplicate, each capable of raising up to 15 million gallons daily against a head of 25ft, or i 18 gallons against a im u ’ an< *. not to require more than 100 b h.p. on the shaft. The arrangement is that either engine can drive any one of the pumps, or, in an emergency, both engines can drive all (hree pumps, consequently a flood provision for 54 million gallons a day is secured. The engine-house has been designed as per the accompanying perspective view in the Tuscan style of architecture, somewhat! after the Art Gallery in Princes street, Edinburgh.

—Suction Well.— This is made of considerable capacity for several reasons. Chiefly to facilitate the accumulation of solid matter, where it would better liquefy in still water than in the flow of the main sewer. Incidental to this it will form a receptacle for detritus, which may to advantaga be used to reclaim land. The chief point in- its design is, like a septic tank, to avoid, any current or disturbance, as much as possible, and to cause no nuisance by volatile effluvia rising into the air. These results could be most economically obtained by a circular basin of considerable size. As, however, the Board decided that in the event of any disagreeable effluvia arising it should be covered, this design had to be abandoned, and in place of it a rectangular tank (120 ft x 30ft) has been designed on the well known septic tank system, and the portion- nearest to the building will be covered by a light Monier arch, which, if required, ca:f be easily extended to cover the whole well. —The Works.— The following works are in hand, but practically completed;—

1- Repairs of Maclaggan street sewer (finished except for new junction at Town Belt). 2. The Forhury intercepting drain (lj mile finished). 3. The Frederick street sewer (finished except for connection to the detritus tanks). 4. Caversham portion of drains on the Fmt (finished except for flap valve at outlet). 5. Dividing well at Tahuna Park. The following works are in hand, and being vigorously pushed ahead 1. Frederick street detritus tanks. 2. Repairs to Caversham main drain, Main ' South road. 3. Repairs to sewer under York place. 4. Construction main intercepting sewer be* tween Frederick street and Leith. 5. Main intercepting sewer east of the Leith. 6. Construction! of Monier pipes for main intercepting sewer between pumping station and High street. 7. Construction of hardwood pipes for rising main, from pumping station, Musselburgh. 8. Excavation of engine bed and suction well, Musselburgh. 9. Construction of combined drain and sewer from rising main to Lawyer Head. 10. Construction of Monier plates for combined sewer. 11. Tunnelling for sewer to Bird Island

under Lawyer Head. 12. Construction of straining frame on Bird Island above high-water mark for aerial tramway. 13. The pumps were shipped by Messrs Gwynne and Co. last month from London. 14. The. engines were expected to be shipped on the same boat as the pumps, out owing to some deiay wid probably only be shipped next week. 15. Making drainage connections for the electric tramways.

In conclusion, it is my duty to thank the Board, but more especially the Works Committee, for the untiring patience with which they have considered and dealt with every detail as it occurred and was brought before them. Some idea of the weight of the task may be gathered from the fact that before they decided some nine months ago on the scheme voluminous reports andj some 156 drawings were considered, and during the short interval since then practically all the works described as undertaken or finished in this report have been considered in closest detail by more than one member of the Committee. At times the work of this Committee has entailed almost daily meetings.