DRAINAGE OF THE CITY OF WELLINGTON.

New Zealand Times, Volume XXXIII, Issue 5346, 16 May 1878, Page 2

DRAINAGE OF THE CITY OF WELLINGTON.

MR. CLARK’S REPORT. The following is the report of Mr. Clark, C.E., on the drainage of the city of 'Wellington and the disposal of the sewage, as presented to the City Council : Wellington, May, 1878. Gentlemen, —1. I am honored with your instructions to inquire into tho subject of the drainage of your city, and I now beg to submit my report. The city of Wellington occupies an area of 1526 acres, and has about 50 miles of thoroughfares made and projected ; its population, on the 31st December, 1877, was 17,334, and the fleglstrar-General now estimates it to be 19,037 ; only four years since, I am informed that the number was not more than half the present, which is a remarkable increase. 2. Of the above area, 78=1 acres have been reclaimed on tho margin of the bay, giving a depth of 8 to 12ft of water immediately in front of the city along the Custom House-quay, and it is in contemplation to reclaim a further portion of 50 acres along the Te Aro shore. This area has been reclaimed by material brought from the adjacent hills, and its level as finished is 4 feet above high water-mark. The rise of the tide is said to be 4 feet. The flat area on the margin of the bay is encompassed by high hills; excepting towards the south, where the Adelaide-road is carried along a valley w { th a rise of 40 feet in the first mile. 3. -The mortality in the city during the year 1877 was 335, or at the rate of 19‘5 per thousand; in the province of Wellington, exclusive of the city, the mortality was but 12*8 per thousand. These figures prove-that the climate is naturally one of great salubrity, but that in ‘Wellington there are causes in operation to which the deaths of 117 persons were directly attributable during the year 1877, that being the number in excess of the average of the country districts. Moreover, one-third of tho deaths were from diseases of the zymotic class, and therefore preventable.

4. Under such circumstances, with a thriving population where want is scarcely known, these causes must be sought for in defective sanitary arrangements, and in an insufficient or impure water supply ; one or both of these causes being present, diseases of the zymotic class find their appropriate habitation, and the result is found in the tables of mortality.

5. The drainage works at present constructed are very insignificant, and consist chiefly of small pipe drains, with a few timber sewers which are In some cases uncovered; all of these, intended to convey rain water only, are nevertheless used foe the conveyance of sewage: a fact easily detected when passing the gratings in the channels where rain water admitted. Nor can this be matter of surprise when it is remembered that there is really no other outlet whatever for the discharge of the water supply after use in the houses, and when it has become filthy.

0. The removal of fcecal matter is done by contract under the supervision of the Council; how imperfectly will be seen from fche following figures ' The number of shops and dwelling-houses at the end of 1877 was 3334, exclusive of Government buildings and other public institutions, such as churches, schools, police and constabulary barracks, the hospital, asylum, gaol, and college. The contractor, however, reports that for the year ending 30th March last the soil had been collected from 1893 premises only, at a total cost to the occupiers of £1897. Thus, supposing that the premises had all been iu existence at the beginning of the year, about one-half of the number would have more than one year’s accumulation of filth stored on the premises. This may not be exactly true, but it indicates that a large mass of deleterious matter is constantly present in the midst of the population. 7. The water supply distributed amounts to about 324,000 gallons daily. Taking the number of premises as before at .. 3334 The full water rate is paid by .. .. .. 2631

Leaving the number of those who do not have the water laid on to the premises at .. .. 703 Of these it is estimated that SSX houses are beyond, reach of the water mains; but there remain 352 habitations, representing about 2500 of the population who drink the water obtained from wells, creeks, etc., etc.

It is not necessary to pursue this part of the inquiry further; measures have been taken to increase the quantity of the water supply, and the drainage inquiry has for some time past occupied the attention of the Council.

8. For effecting the desired improvement, a scheme lias been proposed by Mr. D. Climie, which comprised in its leading features the construction of a main sewer extending along Lambton-quay from the of Charlotte-street (where it would be,4£ feet above high water), Willis-street, Manners-street, Courtenayplace, and Kent-terrace to Drummond-street f in the Adelaide-road- Here it would pierce the hill between Wellington and the sandy isthmus lying between Evans and Lyell Bays. The gradients of this main line of sewer commence at its upper end at 1-800, and gradually become less. In Kent-terrace, at Pirie-street, it is 1-900, and the depth 19 37 feet; from thence to Drumaiond-street. a distance of 47 chains, the gradient is 1-1200, and the depth has become 44 feet; this as an open excavation would be deep and expensive, and probably would be more economically constructed in tunnel. From this point a further distance of 120 chains would be in tunnel, the fall being continued at 1-1200, and arrive at the margin of the isthmus at a level of 14‘4 below h'gh water-level; here it is proposed to lift the sewage, by pumping, 28 feet, or to 11‘0 feet above high water, an elevation “sufficient to discharge the effluent water when not required for irrigation.” For the purpose of irrigating the 400 acres of sandy area which there exists, and is suitable for the purpose, a further lift of 8 feet would be required. 9. In addition to tbe sewage, Mr. Climie proposes that a certain portion of the rainfall, amounting to B-l Otha of an inch in ‘24 hours over the entire area, should also be admitted, and the remaining portion of the rain water should escape by existing channels into the harbor. 10. It will be seen from the above description that the arrangement comprises the pumping of all the sewage of the entire area, including that on the hill-sides as well as the flat reclaimed land, all of which would bo received into the main sewer above described. This, briefly, is Mr. Climie's scheme. It was submitted to C. N. Bell, Esq., C.E., of Christchurch, who did not approve of it, and considered that, where so large a portion of the area lies at a considerable elevation above the leveVof the land on which it is proposed to utilise the sewage, an attempt should be made to intercept as much of it as possible to prevent a necessity for pumping the entire quantity. 11. It must be here stated that Mr. Climie in his report, in the paragraph headed “ alternative pumping station,” points out that “if the committee would allow the pumping station to be erected at the west end of Pirio-street, the sewage from that part of the city south of Vivian and Ingestre streets would not require to be lifted by steam power, for it could be discharged through the tunnel to the outfall by gravitation,” and ho points Out that the saving in first cost of machinery and buildings would be from £2009 to £3OOO, and in the annual working charges from £7OO to £BOO. As arranged this would be from about onethird of the entire area.

- - Mr. Bell had other objections to urge to the scheme proposed, but the one alluded to is the most prominent. .

12. I have had the opportunity of discussing the subject with both gentlemen, and my inquiries into the best means of obtaining the desired economy—which Mr. 801 l considered should be extended beyond the area alluded to by Mr. Climie’s alternative pumping scheme—have thereby been considerably facilitated. 13. I may mention that Mr. Cllmie had several alternative proposals as to the ultimate disposal of the sewage, but the one X have alluded to above is, I believe, the one he finally recommended ; while the one reviewed by Mr. Bell was intended to discharge the sewage at Island Bay, which is at a greater dis- 1 tanoe from the city, involving a longer tunnel, and with a smaller area for utilisation of the sewage. 14. Speaking generally of these proposals, I think Mr. Cllmie is correct in his selection of the outfall at the isthmus whereon to dispose of the sewage ; and also in his proposal to exclude the bulk of the surface water from the sewers :■ but I think also that Mr. Bell was quite correct In insisting on the desirability for Intercepting the sewage from the higher levels as far as practicable. 15. Adopting so lar the views of these gentlemen, my inquiries have led me to an entire re-arrangement and construction of the scheme in its main features, and with a view to extend the area to be drained to the extreme limit of the city. The accompanying plan and sections Nos. 1,2, 2a, and 2b. will show the arrangement proposed by me. 16. The lower levels of the city will be drained by a sewer (plan 2) commencing at the city boundary, near the Hutt-road and Wades town, at a level of Bft. over high water-mark, , proceeding through private land at the back of the houses on Thorndon-quay, which will be drained'into it, at a fall of 1-600 to Lambton-qnay at Us junction with Sydney-street, where the level will be lit. above high water; thence with a gradient of Bft. per mile to the junction of Custom' House-quay with IVillis-street,^where the depth will be Oft, below high water, and a gradient of 1-800, with a gradient of Btt. per mile. It will then proceed along Willis-street, Old Custom House-street, and the margin of the bay at the back of Mannersstreet and Courtenay-plaoe to the east of the gasworks. A further extension of the reclamation is here proposed ; and on a portion of it, or on the present vacant spot of land at the end of Cambrldge-terrace, it is proposed to place the pumping station, and into the pump-well the above described sewer will dis.charge. From Willis-street the inclination will be , Oft. per mile, and the level of the invert of the sewer, where, it falls into the pump well, will be 3ft. below high watermark. 17. The area now in course of reclamation, extending from Lambton quay to Custom House-quay prolonged, will, X am informed, be chiefly oecupled by the railway sheds, &c., where surface drainage only will be required. ■ The proposed new raUway station, the Government Buildings, and those blocks adjacent thereto which will bo occupied by buildings, can all be drained into the Lambton-quay main sewer. 18. From the pump-well a cast-iron rising main, 24in in diameter, will be laid along Cambridge-terrace and Adelaido-road to Drummond-street, where it will bo 28ft. over high-water level. The pumps will therefore be required to lift the sewage from the well Oft, below high water mark to 28ft. above it, or 37ft. The discharge from the iron main and a higher intercepting sewer, presently to bo described, will be received into a length of sewer of 11$ chains, and continued by a tunnel 1$ miles long, with an inclination of SJft. per mile, to the sandy isthmus, which it will reach at a level of 22ft. over high-water mark. This level will be sufficiently high to command the entire area of 400 acres for irrigation without further pumping. 10. For the purpose of intercepting the drainage from the higher levels-aided by Mr. Baird and his staff—l have boon able to lay out a very good lino of sewer, which is shown on the accompanying plan No. 1. Commencing at Drummond-street, at a level 2Stt. above high water, it passes through the block of land bounded on two sides by Adolaideroad and Tasman-street, along Sussex-street, street, thence crossing to. and along Haining-street and Martin-street. Crossing private property again it then proceeds a short distance along Ingestro-street: here It again crosses private property, Garnett and Ghusnce streets, to and along a portion of wiiusstreet: again crossing private property and Mannersstreet it enters tho lull side below Boulcott-streot; through the hill it proceeds in a tunnel 25chains in length, and comes out to the day in the valley at the back of Wellington-terrace, chains from the Club, in front of which it passes: thence through private property, and crossing Aurora-terrace, Bolton, and Bowen streets, it readies Sydnev-streot throughitlio gardens of the Government Buildings, it crosses HlUstreet to Molosworth-streot, along which it proceeds for a short distance, when it again crosses private property and Murphy-street: and finally it reaches Fitzhorhert-terrace at a level of , 66ft. above highW The totai length of tho sewer so described is nearly

three miles, and it will intercept the sewage from an area of about 400 acres. On plan No. 1 the position of another intercepting sewer is indicated, extending from' Brumraoud*street;to and parallel with Clyde and Oriental-quays. (Plan 2c). :By the section of the sewer, plan No. 2, it will be seen that, withgthc exception of the tunnel, there are no especial features to make it an expensive work; along its entire length, with (he same exception, it is well situated for receiving the drainage of the various localities through which it passes. It will in some cases pass under buildings, but iu no single instance, I believe, will it be necessary to pass under a dwell-ing-house. The line has been carefully levelled : it is, however, quite possible, when the buildings on the route are put upon the plan, that some further improvement may be made, and any objectionable interference with private property be modified or avoided, sufficient has been done to prove it to be practicable, and very desirable for the efficient and ecouomical drainage of the area which it will intercept. -v- I have thus briefly described the scheme which has been before the Council, together with the one which I would propose to substitute for it; and I will n £ w proceed to consider the present circumstances as affecting the further working out of the details. The plan and sections as prepared by Mr. Climle have been handed to me, and I have caused the levels from the sections to be transferred to fche plans for more convenient study, I have walked over a very considerable portion of the area, more especially that portion where the intercepting sewer above described is situated, and I am impressed with tho fact that, without a more complete and detailed plan of the city, showing the position of the natural creeks by which the surface water has hitherto escaped together with the position and character of all the buildings and the levels of the surface in all the blocks bounded by the streets, it would be quite impossible for an engineer to lay out the details of the system of sewers properly and to the interest of the community 21. Every person who knows 'Wellington will be aware that, excluding the reclaimed area, the street levels give but very little indication of the surface bounded by them. It need scarcely be pointed out that the sewers aro required to occupy tho lowest elevations which can be given them, with due regard to the work they have to do; and it is therefore necessary to ascertain where the elevations are sUua-ivl At »aj the 4 jo itioiia uf thy natural creeks have been approximately sketched on the plan No. 1, and an examination of these will afford sufficient evidence that the street levels alone are Insufficient ; the surfaces of the streets not being arranged with reference to drainage requirements. 22. To procure a map of the entire city area, with all the information upon it which is required, would occupy far. too long a time to admit of its accomplishment during my visit. I have therefore requested that two of the blocks into which the city is divided by the streets may be surveyed, and. the information I require put upon them. This has been done, and plans Nos. 3 and 4 are the blocks referred to. These are sufficient to illustrate what is required; they however are insufficient to enable me to lay out the main sewers even upon these blocks, for that will be dependent upon other blocks which are not so surveyed ; but within these areas, by arranging the minor drains for individual- properties, the principle I am now endeavoring to describe will be apparent. 23. These plans show distinctively the various classes of buildings; the dwelling-houses as distinct from shops and warehouses, outhouses, privies, and drains are all separately indicated.,. ■ : An examination of the levels as indicated by tho figures will convince any person who can understand the subject, that to drain r all the properties direct into sewers laid in the streets would be impossible. Any attempt to do it .would increase the cost of the entire work enormously, and destroy Its *efficiency. It would be an attempt, not exactly to make water run up hill, but an attempt to convey it in defiance of levels, which must be.both, difficult and costly. 24. What; is shown on these block plans with reference to the minor sewers and house-drainage arrangements, is equally„ true with reference to the entire area to be drained; and it is therefore evident that, until the plan is prepared, the complete scheme for the drainage of Wellington in all. its details cannot be given. My first recommendation, therefore, is that no time should be lost In making the plan. 25. It' is evident that very many of the minor sewers shown on the plans 3 and 4 are best placed at the backs of the houses, where the lowest levels are found; and doubtless in laying-out some of the larger or main sewers this will be found to bo the case with them also, necessitating their being carried through private property. The power to do this is, I believe, given to the Council, and it is Very necessary . that it should extend to the buildings also, making due compensation for any damage that may be done thereto. ...

26., In the plans 3 and 3, and also in'the intercepting sewer before described, page 4, : which goes through a length of nearly three miles, chiefly, in private property, several buildings are. passed under, but in no single case will it be necessary to go dwellinghouse, It is, therefore, evident that-what would naturally bo objected to (though it need be no actual cause of danger) by proprietors and tenants, will not often occur, as it will bo generally possible to avoid it.

27. After construction, all that will be required will be an occasional visit from >n*inspector, who should at proper times have access. to ..the. premises for that purposes. At the various angles, and' at distances of about 300 ft. apart in convenient positions, “ man-holes” and ** lamp-holes” will be constructed. ; (Plan No. V). These are covered up, about 12in. to ISin. below the surface of the ground; beyond the removal of the surface soil for the purpose of removing obstructions la the sewer should they occur, no damage will be done to any garden or yard in which they are placed. Their use is to prevent the necessity for disturbing the ground at all other places. ! 23. According to my experience,, when the pipesewers are properly laid, if due attention be given to protecting the inlets to the sewers fay 'gratings and traps, so as to prevent the . intrusion of such things as old kettles, broken crockery, &c.; then it is impossible to cause a stoppage in a pipe-sewer which conveys the house drainage from an area fairly supplied with water, : 1

29, With regard to the damage which may possibly be sustained by buildings here In Wellington, where they are nearly all of wood, there is not the slighest danger or difficulty. 1 It would be far otherwise wore the houses of brick or masonry, and the foundations laid in soft ground fullof water but, here, except in the reclaimed land, where I believe piles arc used, the foundations are laid in perfectly sound strata. There will therefore be no difficulty whatever in carrying out any of the works which are necessary for the main and minor sewers required for the drainage of the city of Wellington. L ' 30. I may now allude further to some of the principles which are involved in: works of this character;— ,

I recommend that tho rain water, (except in a modified quantity, and where it cannot readily be excluded) should not be admitted to the sewers.

First, with reference to the area from which the sewage will hare to be xmmped. It xs.evident that if this be confined to a. quantity, represented by the water-supply, when it has done its duty for manufacturing or household purposes, its amount will be tolerably well defined. If on the contrary rain water be admitted, not only must the pumping power be sufficient to lift tho large quantity that occasionally falls, but the sewers must ba enlarged to receive it, entailing not only greater cost in construction and annual working charges, but also to some extent inefficiency ; for it is better that a pipe shall bo constantly running, 'filled to half its capacity during the dry periods, than that the same stream should be spread over a larger surface in a larger sewer capable of conveying the water of storms. 31. Another object attained in excluding rain water is, that the road gritjfrom street surfaces is thereby excluded. This is the most difficult of all matter admitted to the sewers to remove by running water. . 32. When the area is so perfectly .flat as is the reclaimed portion, to avoid an unnecessary lift in tho pumping operation, and depth to the sewers, and at the same time extend the benefits of the drainage system as widely as possible, veiy careful consideration is necessary in fixing the inclinations to be given to the sewers, in order that. their self-cl causing action may be insured without sacrifice of 1 economy. If the road grit be excluded, then it wilt be possible to give a somewhat flatter gradient to the sewers than could be done with safety if it be admitted. Guided by experience, I have arranged the levels of the system and the inclination to the bambton-quay sewer, so as to receive the drainage from the houses built along tho Thorndon-quay to the commencement of tho Hutt. road, at the furthest limit of the city area. V 33. With regard to the area which will be drained by gravitation, one of the above objections to the admitting surface Water, viz., the increased quantity to be pumped, does not apply; but the other does apply with greater force. . To increase the area which can be drained by gravitation, the intercepting sewer (described at page 4) Is laid with the smallest gradient consistent with its efficient. action—nearly three miles of pipe sewers, with inclinations varying froml-500 to 1-C6O, and of sizes within the capacity of pipe sewers ; both sizes and inclinations could of course be increased in this case to receive the surface water, but I shall endeavor to show that it is not desirable to do so.

34. The quantity of road-grit which is scoured from road surfaces is very great; it may be roughly estimated at the quantity of road, metal which is put upon the roads, part of which is dispersed by wind as dust, and afterwards washed into the natural channels by rain, Another and larger portion is scoured from the road surfaces and side channels, and during heavy, storms-. as in Wellington, the hills are precipitous, coarse particles are displaced, which, with less velocity in the water, would remain undisturbed.. 35. Every gully or inlet for. storm water to the sewers requires a rather expensive l work, such as is shown on plan No. C, consisting of a pit to arrest the grit and prevent its entrance to: the sewers, and with a trap to prevent the escape of sewer air near the foot--paths where they are placed. To ba efficient those gully-pits must be of large size, for they not only speedily become" filled with road gilt in, times of rain, but during windy and dry weather they also accumulate „dust in considerable quantities, allot which has to be removed by baud labor: and if they be not kept clean and free from deposit they are of no use whatever/ 30, Another and; by no means an unimportant reason for not admitting the storm water where it is intended, as in this case, to utilize tho sewage by irrigation, is that the sewage for agricultural purposes is very considerably reduced in value, as the farmer has then to receive the greatest bulk of fluid when it Is not only valueless to him, but precisely et the time when it is most difficult to dispose of it. Sewage farms.; where this has to be done, arc seriously reduced In value from this circumstance. „ 37. It is, however, necessary to consider careiuuy how the surface water, if not admitted to the sewers, is to be disposed of. ... . The plan No. 1 shows approximately the position oi the natural creeks by which the drainage area » "r tersected. I am informed that the actual sou whicn forms the bed of these creeks has been sold with tne land, yet the proprietors thereof have no right to appropriate the channel to other uses. These rights oz the public for this purpose should be carefuujr served. It is not intended when tho sewage works are carried out to put them to any other use I than conveyance of rain water, and this will, in q*^ 5 ?» be the same as it hasbeoniaall time. These chape or creeks should be continued in tho future, asin past, for the conveyance of rain water. Th«y require from time to time to be cleaned, thev y also, where it is necessary, be straightened ana in proved for the convenience of properties. 38. When roads have to be crossed the City Coim* ell will of course be responsible for the construction of proper culverts for the purpose; and wM stream arrives at the fiat reclaimed land at th ot tho hills proper drains must be constructea conveying tho water direct into tho harbor hy shortest route. The drains for this crosang the reclaimed land will not exceed 10 to 15 length from tho foot of the high ground to the marm of the bay. They way be laid to a level of abpuw v« above low water et tho lower end, and general an inclination of I-200fch to l-250th, at which incuna tlon a 12-inch pipe will be sufficient to drain an a l ®* of 00 acres, the rain, falling at tho rate of m ** hours. . • / , , __ At the crossings of the streets In tho awa* where the surface water therefrom would be aamujeu Into these pipes, gully pits must be provided, bet tw would require no trapping, as nothing but SU Y*:® water would be admitted. Manholes at interval t facilitate cleaning, &0., would bo also required, anti provision for this portion of tho work will bo xuado m the estimate. . 30. The existing pipe drains bolero alluded to WOtd then boused solely for tho purpose for which are Intended. An examination $f their number

condition Is; however; necessary before deciding upon the works to be taken la hand for the removal of rain water, and it will only ;bo necessary to reconstruct them, when it is proved that they are'inefficient for the purpose. '' " ' ■ «■ ' 40. Arranged as above suggested, all the'road-grit from the higher levels will be discharged into the harbor, and it is probable that to preserve the depth of water dredging may be necessary. The cost of removing silt, &c., from gully pits and sewers cannot bo estimated at less than Os. ,to 7s. per cubic yard; the cost of dredging the same material and its disposal would not exceed Is. For this reason it Is better to discharge the road-grit into the harbor and remove itin the manner here indicated. 41. I have thought it necessary to dwell at some length on this part of the. subject, in order that it maybe understood ; and 1 may add that on so broken anti undulating a surface as Is the greater part of the city of ‘Wellington, there would be some difficulty in collecting the surface water, except from the road surfaces, in any Other way. On the road surfaces I observe the side-channels are now being constructed with asphalto concrete, which appears to make a very useful channel, at once cheap and efficient, and suitable for preventing scour when on steep declivities. 42. In recommending that surface-water shall bo excluded from the sewers, it may be understood that this especially refers to roads and all other places where loose sand or similar material is present; the water from roofs and paved surfaces, when it cannot otherwise be easily disposed of, can be admitted into the sewers, and the dimensions given to them will bo sufficient to admit of this.43. The uses to which sowers are generally applied are—lst. The removal of the water supply after it has become filthy. 2nd. The removal of excreta. 3rd. • The removal of subsoil water: and 4th. The removal of surface water. In Wellington, however, it is proposed that this lasts use.shall not be required of them, or only to a very limited extent. With reference to the third use of the sowers, that of removing subsoil water, very .little will here bo required, the hill surfaces affording very dry sites for houses. In a few places in the Ade-laido-road district the ground is of a swampy character: in such places It will be sufficient to cement carefully the lower part of the pipe-joint, leaving a small space at the top to be stuffed with clay. This will be quite sufficient to secure the drainage of the subsoil in all wet places, and no other especial provision, will be required. In the reclaimed area I am informed the water rises with the tide: it would therefore be useless to admit it Into the sewers, and every possible care must be taken to exclude the salt water, by making the tubes perfectly tight when they are laid below high water-level. 44. The chief uses of 'the sewers In Wellington will thuaboconflned-to tho-twafirst-mentioned, of which the removal of the water supply is the most considerable.

The total area of the city, as stated in paragraph 1, is 1520 acres, but excluding several areas not to be built upon, it may be estimated at 1476 acres, including the reclamation area now in progress, and a further extension of the Te Aro area of 50 acres; and of this amount it is estimated that pumping will bo required to remove the sewage } from 611 acres. ■- 5 The density of population varies considerably with different localities.. Thus

the population'located on the area-shown by plan No. 3,.exclusive of the streets, is estimated at 512 on acres, or about 78 to the acre. This, however, is considerably in excess of the general average, which is usually taken at 47 to the acre for.towns, and 82 for suburban areas. Assuming the .higher number, the population would amount to 1476 x 47= 60,372 for the entire area or the city, and 511 x 47== 24,017 persons on the area from which the sewage will require to be pumped. [ I s : ; 1 , 45. Taking the water supply at 50 gallons, or 8 cubic feet pec head of the population, and assuming that half of it will ho delivered during 4 hours of the day, the tnttTimnm quantity flowing per minute from the entire town to the outlet will bo at the rate of 1166 cubic feet per minute; and per acre *79 of a cubic foot. To allow for a portion of the rainfall, if 1 cubic foot per acre per minute be taken as the maximum quantity to be providedfor in the sewer, this will allow for lin. of rainfall per day: over nearly one-fourth of the area, whilst the sewage is at its maximum flow; so considered, the discharge from the sewers will be at the rale of 1476 cubic feet per minute from the entire area; and 511 cable feet per minute from the lowlevel which will require to be pumped. ' 46 After careful examination. I have fixed the pumping station to be near the present gasworks, whore coals can be conveniently landed, and water for condensation obtained in any quantity. '■ The position and depth of the sewers, as before described (paragraphs 16and 32), will command the houses on the flat surface to the commencement of the Hutt-road, a total distance of 2 miles 28 chains, while the houses in Wadestown at the higher level will he drained into the intercepting sewer. 47., It is probable that apprehension may arise as to a nuisance which will be caused in the neighborhood of the pumping station ; this, however, may bo en- ' • tirely avoided. I annex a' sketch (plan No. 5), which indicates the pumping arrangement where the sewagewill be received into a cohered well, and from thence raised to & sufficient height to flow over the land on which it is proposed to utilize it, without, further pumping. Most persons are familiar with the action of small force-pumps worked by hand ; the water drawn from a well, passes- through the pump-barrel, and forced into the raised cistern without any surface of the water being'exposed In the operation. In the same way here, the sewage will be received in the covered well.'lif ted therefrom, and forced through an Iron pipe to the .end of the tunnel, which takes it to the isthmus. No surface of the sewage will be exposed ; and the only connection between the pumpwell and the outer atmosphere will be through the air-flue, (shown on the plan) to the boiler-furnace and chimney-shaft. ' In no other way will the sewage well communicate with the outer air.. The means are thus available for constantly purifying the air through a furnace, which will effectually prevent any nuisance rising in th«> neighborhood of the pumping-station. It is nob intended that the ’diagram. No. 6, shows the precise arrangement which win Ihe followed; hut it illustrates in a convenient way the principle which will be followed in designing the pumping arrangement. 48. To lift the quantity of sewage 511 cubic feet per minute as a maximum during four hours'of the 1 day to a height of 37ft., and to overcome the friction through a 24-inch rising main to the tunnel, a distance of 7l£ chains, 42-horse-power effective will be required; this will be most conveniently arranged in duplicate: engines of 25 horse-power with a .spare boiler. ' , , ~ 49. The principal work for the removal of the sewage will be the tunnel; this is shown on plan No. 6, and will require a heading to be driven, the extreme * dimensions of which will be 6ft. 6in. high by sft. 6in. wide; for 4ft. Sin. in height this will be lined with cement-concrete 9in;ln thickness; when discharging, a maximum quantity of 1500 cubic feet per minute, it will be running 3 feet deep with a mean-velocity of 160 feet per minute. ■When discharging 250 per minute the depth will he 1 foot, and velocity 110 feet per minute. \ ‘ The rock through which the tunnel will be driven it is not expected will require lining for the roof, but , in the estimate provision is made for lining one-fourth ■ of its length with 4&-inch of brickwork or cement-, concrete blocks. 50. , Flan No, 6 also shows the other sewers required; of these, an oval sewer 4 feet 6 inches by 3 feet 9 inches from the Adelaide-road to the 'end of . the tunnel, and a sewer along Old Custom House-street to the pumping station alone will require to be of brickwork or concrete. The remaining sewers are all stoneware pipes, to be laid in concrete, or puddle where suitable clay is available. There being no plan on which the details of the scheme for draining the city can be laid out, I am .. unable to do more than give the few main lines already yreferredto ; for the rest an approximation only as r to length and sizes can be given. 51. The length of streets at present formed Is 301 miles, and. there remains to be formed lOf miles, 50 miles in all, which will probably represent the length ; of sewers to. be! constructed, when the population ' extends over the entire area. Ac present, however, ' the length of the existing streets, 40 miles In addition .to the mains, maybe assumed'as the length for immediate or early construction, ■; ~ The sizes of these sewers, except In a very few cases, will not, I believe, exceed Din. in diameter, while a very large portion, may be 61m , only. If to the estimate, the cost of 40 miles of 9!n. pipe sewer he added, lam . of opinion it will cover all that will be necessary. 52. I have now to consider the one remaining use of the sewers alluded to in para. 43, the removal of feecal matter. , ' ' Very considerable objection is, I am aware, frequently urged against the removal of excreta by house drains and.sewers; and it Is not unusual to find even well-informed persons advocating the “ pan system," or some other mode of removing this offensive matter by hand-labor and cartage; this is always an expensive and disgusting operation, not only to those who are engaged in it, but also to all persons who come within its Influence during removal. ■ ! . In Wellington, the removal of the excreta is under the supervision of the City Council, anti during twelve months, March, 1877-78, the total coat was £1897; this effected the removal from about one-third of the total number of dwelling-houses only; from the remaining number it does not appear to have been . removed at all. K 63. The objection to the nse of the sowers for-this purpose probably proceeds from two causes:—lst. The apprehension that they will become mbreoffen- , sive if they are made to receive this matter. 2nd. The expense of constructing and keeping a watercloset in good order. ■ With reference to the first of these objections, the sewers are considered in the light of ccas-pits and an inevitable nuisance ;, and the pipes which ’ form the house drains, it Is urged by some, act similarly to the gas pipes, except in the latter .case,' illuminating gas Is conveyed into the house for a useful purpose ; and by, the other, malarious gasses find access which engender fevers, &c.; hence it is careful persons consider that by keeping as much filth as possible from the »ewers.they thereby prevent nuisance from arising. As applied to cess-pits this is undoubtedly true; and if the sower with which the house drain is to bo connected be an "elongated cesspool/' it would, if actually connected with the house, be true of* this also. Bat the case as between a cess-pit and a properly-constructed sewer or drain is widely different. : 1 ' . The former means stagnant filth stored for months, and in a state of active decomposition. If the cesspit be, as it too often is, a hole dug In the ground, and the soil be an absorbent one; the nuisance will be .less* for a large portion of the fluid will ho absorbed, ana a period of months or possibly years may elapse during which .comparatively a small amount of nuisance will be experienced. But the operation, however slowly it may proceed, is surely saturating the soli with filth ; and any person who has seen such, a soil removed fer a house-foundation, or cellar, or other purpose, would require no other evidence of the danger, unseen though it he, which the presence of suchamassof putrid matter must engender near to a human habitation. , 54. Water-tight cess-pits, though they avoid this danger, are also, from the nature of their contents,' and the decomposition which is set up in a few hours, the source Of great nuisance and In the highest degree '■\>m are'an Improvement on both, doe to. their urn alter size and more frequent removal: ont they alio are most offensive, owing to the days and weeks during which the filth Is stored before removal; and , tbo cost of this removal amounts to a not Inconsiderable tar, which lalls equally heavy on tbo poor as on the more affluent of the population. The sewers, on the contrary, remove immediately on its production all the filth put Into them without band-labor; and If a liberal quantity of water, saytwenty gallons per head of the population, be dally supplied for all domestic purposes. It is quite sufficient to remove completely all the solid fceccs or other matter which should find access to the scwers. Jn about two hours It will boremoved cnt '™'y beyond the limits of the city, and before decomposition can take place, 65. With regard to the 'second objection to theremoral of fcccal matter; by house drains paragraph 7% viz., the espouse Involved In the,construction and maintenance of a water-closet In good repair, there Is more weight. Cheap closets, as they are often ' fired, with valves, and moveable pan traps, do get out of repair in course of time; this, however,-does, not apply to the simple syphon trap which Is usually fired under the others, and Is really sufficient in Itself, re-

qulting only a liberal mo of Water. ( , : ; . ; -It Is, however, necessary that- a' separate water clstern should be used In connection with this arrangement(. between thp,closet pipe and the house-service, . as no direct connection should on any account bo permitted. For such'an arrangement the cost Of the .cistern and fittings wlilbo about £4,' exclusive of the Water and drain pipe# outside tile closet, and for that

sum all that is really necessary can bo obtained where the water is supplied by constant service, ajid no storage of water be required. 63, When, however, a separate charge is made ior ■ water for the closet (as la sometimes the case on ac count of the great waste entailed.by their imperfect construction), which would press heavily on the poorer class of tenants, it Is quite possible, by another and * even more simple arrangement, to cause’ the ordinary-house-slops and other drainage fluids, from washing, cooking, &c.. to effect the removal of the foecal matter, and at a cheaper cost, by an arrangement requiring no plumber's work whatever, and which it would be difficult to put out of order. The arrangement is shown in plan No. 0; it is there supposed to be fixed in close proximity to a house of the poorest description. , , The water tap for the house supply is shown at T, and the sink or trap Into which all the house slops are peured Is beneath it at S. Beneath an ordinary privy seat a small tank is constructed of brickwork or concrete, it has a sloping bottom arid is lined with cement, the length is about 3ft., and it will contain ton or twelve gallons of water. At the lower end of this tank, which is about 16in. wide, a circular cost-iron socket is fixed 4in. in diameter. which communicates with the bouse drain. This socket is closed by a wooden plug, P, with an iron handle extending above the seat. Water can cither be admitted* from the tap T through the grid and trap S, or the ordinary house* slops poured - into the grating at S will in some cases bo sufficient. The small tank thus becomes filled, and. can overflow through the pipe provided for that purpose. . - j : After one or more uses of the place the plug may be lifted by the handle, and the entire contents of the 'tank will be discharged through‘the’house drain to the sewer. Nothing more is then required:but to replace the plug in the socket and refill the tank. 57. To prevent stones, bricks, and improper subotances of that nature from entering the house drain, an ordinary ** dip’* trap is ■ constructed outside the closet, and when obstructions occur, r which such matters would cause, they can easily be removed by , lifting the cover. The quantity of water which is usually available where it is V laid on" from any public source, if it bo made to pass through such an arrangement as is above described, is'abundantly sufficient to keep it in perfect order. There is no plumber’s work or expensive fitting of any kind liable wear out, or derangement; it can bo built by an ordi- 1 bricklayer, and Is cheap ; the entire work as shown in the sketch would not exceed £3, in addition to what is usually provided, » It is not of course absolutely necessary that the water-tap T and sink S should bo fixed in close proximity to the closet as shown in the sketch. - They may.' bo at any convenient distance that may be desired, : provided the. requisite fall be-given to the house-, drain.- ’ i T. 58. The use of this form of closet will not I believe require any enforcement. The comfort, cleanliness, and the absence of a payment amounting to £1 10s. to £2 per annum for the cleaning of ccss-plts, or pans, will bo quite sufficient to ensure its adoption by a Large majority of the population. t -.*■ i -I have here dwelt at some length upon a subject which may appear to some persons triviabibut really it is of the greatest .importance, with a; hope that those who,have,opposed the removal of excreta by the sewers will perceive that it . can „ be accomplished without entailing any nuisanco, and that the comfort of efficient arrangements fori the-purpose; can be . 'extendedto the poorer class of inhabitants, and with - benefit to the health of the entire. community. 59. In the foregoing portion of this report it is assumed that the point of outlet for-the sewage and itsmltiraate disposal will, bo the sandy isthmus lying between Evans and Lyell Bays. This land will:have to be acquired under the Municipal Corporations Act t ; of 1576- and its i Amendment of *1877, clause 7,which . empowers the Corporation to take land for such purposes.’’ . ' - : This sandy area comprises about 400 acres, and is the property of J. C, Crawford,Esq. Its position and; character make it especially suited r for . the purpose, there being no. single habitation oh it, and entirely nnsnUed as it is to cultivation without such aid as that "works here contemplated will abundantly furnish. From the levels which have for the,purpose, it has been ascertained.that4f .-the sewage be delivered at the end of the tunnel at a height of 22ft. over high water, it will be 1 sufficient to carry the ; sewage over the entire area. The/tunnel* is, therefore, arranged to terminate at this level. i r . CO. Some protection from the wind will be required- ; for the future vegetation, and also for the preliminary operations oharranging the surface, as the sand is of a character to be easily blown away by the wind. One. of the first proceedings will therefore be: to plant several belts of quickly-growing shrubs, trees, &c., such os gorse, crossing the area. v ‘ >v > : After obtaining further levels, a plan and sections will be made, showing the most economical mode of arranging the surface, the positions of the;** carrier” channels for. the sewage,' drains for'effluent water, &c. The process of levelling and forming the surface r will then be a gradual one. As the “carrier" chan-7 nels are formed in the sand and; the sewage admitted 1 ' to them. It will be quickly absorbed, as in'ah ordinary:water filter. 1 On the deposit left vegetation will quickly arise, fixing the sand, and forming: a.permanent carrier channel, from which the sewage will be made [to flow over a few acres formed and prepared to receive it. As deposit accumulates it .will: bo turned in, and the surface cropped'with suitable grass or vegetables. Successive areas, will be similarly dealt with, ■ , ■■■*■■ . ''After* a time the effluent water will'collect in the ditches, which must then be formed; to j convey it? away to the bay or to the. sea—being continually moist there will be no difficulty in'protecting these 1 ' with vegetation also. . .. ••• *."'•■■ , 61. In a very short , time the land will be highly productive, and the Council will probably let it for a term of years on . such .conditions., as will insure,the entire area being brought into use,-and the whole"of - the sewage utilized. This will be accomplished if the rent be made sufficiently easy to. induce ! competent persons to engage in it, and. the term of first occupation .be sufficiently extended to make it profitable* to them. ; J ' ■'

In the estimate I have included a sum of £2OOO for the purpose of forming a principal carrier and drains, together’with the forming of a portion of the area whereon'to commence the' utilization of the sewage ; the further works for the purpose being accomplished under the conditions I have alluded to.

62. As intimately connected with-the; subject of drainage, though not necessarily a part of my inquiry, I would suggest, for the consideration of the Council, whether the tramway now in course of construction may not be utilized for the removal of the solid filthy such as sweepings and rubbish from the city; it extends nearly to the upper end of the proposed tunnel, which, if enlarged to pass an engine and trucks through it, might by an early train In the morning be made to carry away from the city these matters which would, In connection with sewage, further improve the area for the purpose of cultivation; all that would be required would be to enlarge the tunnel, and the laying of 1J miles of tramway,-—as, however, this, is not strictly a subject for my inquiry,'! have hob included any estimate for this additional .work. 63. Having now discussed the principle on which I recommend the drainage works for this city should be constructed, I proceed to notice the character and cost of the works. :'

Where coals are expensive, as in Wellington, it is economical to adopt the most perfect kind of machinery, even though the first cost may be increased, to avoid the continued expense of an unnecessary consumption of fuel. In the estimate which follows, this has been considered ; provision is made for compound engines working at a.high rate of expansion, calculated not to consume more than 31b. of coal per horse-power per hour.'. Two '25: horse-power engines and three boilers are provided, and pumps of the reciprocating class ; the engine and boiler-house will be substantial brick buildings ;• the chimney, also of brick, wi;l be 70ft.- high! -. : i 64. The greater part of the material required for the sewers will be stoneware pipes. To ensure durability and proper action, these should be of the very best quality; no soft pipes should under any circumstances be used. The material of properly burned and glazed pipes is indestructible, and entirely non-absorbent, the glazed surface affords no foothold.to rats, which avoid them, while in brick sewers they are occasionally troublesome and destructive.

- The pipes should not only be of good material, but their shape should be as nearly perfect as possible, straight in l their length and truly, circular, each spigot end 'fitting accurately- into the socket of the: adjoining pipe without “lip ” or irregularity of level at the junction. The joints should be made with good Portland cement, so as.to bo watertight, and any cement which may be forced into the interior of the pipe in making the joint should be at once carefully wiped out. ~ j 05. The plpes should be laid ihstraight lines, and where any deviation from the straight line occurs, a “man-hole" should be constructed. *

These “man-holes", also form junctions for other pipe sewers r the arrangement is shown on plan No. 7. One of these “man-holes" is provided, for every 250 ft. In length of pipe sewer.. , Their use r is to facilitate the examination’of-the : sewers before they are brought into use; also, the examination and cleansing, should it be required in the future. CO. The pipe sewers should be bedded in 6 to Sin. of concrete, or good puddle carried high enough just to cover them.. Every care should be taken to get out the bottom of the trench with regularity, so as to preserve a uniform thickness of concrete beneath the pipe; its rise being to prevent any displacement or irregularity of settlement of the pipes when the weight of carts comes upon them, f 67. The junction pipes for house drains, &c.,‘ should os far as possible bo inserted when the pipe Is laid ; the end of the branch; when not immediately used, being carefully and securely stopped with a suitable stoneware plug and clay, to>preveht the entrance of the surrounding soil. An occasional half-socket pipe, may also bo inserted with advantage where junctions are likely to be required. This will admit of a length being taken out generally without breakagethere' is' always some risk that the pipe line when disturbed for the purpose of making connections will not be replaced with the same solidity and accuracy as when originally laid. Special pipes are made by some manufacturers to overcome this difficulty; they are somewhat more expensive, but I have found with care competent ; workmen: can, with the arrangements I have alluded to. above, do all that la necessary. *' ' ' 68. It is, however, important that only qualified workmen In the employ of the Board should be permitted to make the connections with the public sewers, and that not only the material, hut the workmanship to the private drains which are to be connected with the public sewers should be subject to official inspection and approval. Those tradesmen only who have proved their competency to do the work, and who hold licenses from the authorities, should be permitted to undertake.the house-drainage; work. i

09. Those sewers which are so largo as to exceed the pipe sizes can either be made in concrete or brickwork f cement, not lime, should be used in either case, with hard.‘non-absorbent material. (Plan No. 0.) The brickwork should be of the very beat quality. Where any spaces or broken ground at the back of the brickwork occurs - in the construction of the sewer, it should be filled in entirely with concrete and shingle, back to the solid ground; it shonld not be refilled with the original soil, or the sewer will crack and probably get out of shape. l - The size of the biggest sewer required la not large—-9-incli werk will be sufficient ; but it should bo backed with concrete, and a thickness of 0 inches up to the'springing of the arch is included in the estimate. The interior shonld be rendered with cement up to the same level, and the work in the arch carefully pointed. - 70. When water appears in the trench, It la necessary to lay a drainpipe in concrete or shingle to carry it oif, so as to insure good work, in the invert. The extra expense will be more than repaid by the quality of the work obtained. As the brickwork sower shown in Plan No. (I will bo constructed below Ipwwatcr level at the present margin of the bay, a considerable quantity of water may bo met with. When the sewer Is completed this water shonld bo excluded by carefully stopping the pipe ends with cement, and filling in the A sumphs' r used during construction with cement concrete. 71. So constructed, the work and estimate are as follows For two 25 horse-power engines and three hollers, pumps, engine and boiler-house, with chimneyshaft and pnmp-well complete, and houses for workmen ; 1673 yards 24Jn. Iron pipe laid In Adolaide-road, with and connection with pumps; l 376 yards concrete or brickwork sewer, 4ft:,oln. x Bft. Sin., from Adclaidb-rbad to end of tunnel, withmanholes. Tunnel, 2200 yards long ; lower portion lined with concrete Din. thick; roof lined lor one-fourth its length - with -I Jin. cement blocks; flvo working shafts -lor ventilation, three, to be filled sip and, two retained for .ventilation, with lining, and protected by wall at top. 1 chain open sewer, and small tank at

south-east end of tunnel. Interce'pting-h1?Ii level : sewer from Drummond-atreet -to .north boundary,of the city area,- 2 miles 76 chains In length (os described in paragraph 19 ami plan No 2) Lower lerelscwer from pumping station to north boundary of the city, , 2 miles 26 chains in length, described at paragraph 16 and plan 2a. Man-holes at 250ffc; apart on above sewers, i Ventilators, 800ft*; apart on above- sewers. Intercepting high level sewer towards eastern boundary, approximate length, U miles. Low lev Q^ along Clyde-quay to Hay-street, 48 chains long, with nian-holes and ventilator* at above distances. Three miles of 12in. pipe for . carrying surface drainage across the flat area with gully-pits and man-holes (para. 33). Approximate length of sewer to complete the drainage of the city, estimated at 40 miles 9iu, pipe (para. 61). Carrier channels * or gation on the sandy isthmus (para. 61). The total length of sewers, &0., included in the works abovedescribed, is 62* miles. The estimated cost of the above work is £131,000, adding thereto the survey or the city, with 10 per cent, for couvi-iusation contmgencies. engineering, &c., it will amount to £145,000. 72. The annual working charges nre estimated as for a consumption of 1 ton of coals pit* day;—3uo tons per annum at 32s per ton, £584; oil, tallow, and waste, £130; Establishment One engineer at £5 per week and residence, assistant engineer at £3 per week ana residence, one laborer at £2 per week total per week, £lO ;• total per annum. £520 repans and depreciation, £2oo'; complete total, £1434. • Total annual .chargeslnterest on £14°,320 at 6 per, cent'., £8720; ’ working expenses, £1434 ; total per annum, £10,154. .' ' • r A\>A*u.« This is exclusive of the cost of land (par. j 0) for the. utilisation of the sewage., which I am unable to estimate. The purchase of this area at .its fair value there can be little doubt is an investment which.will* in the future bo highly remunerative, and beyond the loss of a few years; interest at:the commencement of. Its use as here proposed should not bo considered as* a burden on the income of the Corporation. f • • 73. The annual value of premises for assessment in"Wellington,.at the commencement,of the present year. Was £207,605/ and, at the. rate of increase during 1877, will, at the end of . the present year, amount to £239,000. •-’- 1 • C-' M A rate of 10d. in the pound per annum on tmsyalue : would yield £IO,OOO. . ~ There is, therefore, every reason to expect that the burden, on the ratepayers ' for-this'purpose will not : 1 exceed-this amount; and if from It ,w‘e deduct What*, should bo the annual expenditure, for removing nighty soil under, the ‘present, system (para., 6) once a-yoar* only, it would reduce the amount about;£6Goo. js 74. Without a-proper-plan for-the'purpose, I am,) unable to go further into 1 the details of the) scheme .which should bo adopted for the drainage of wdlmgton. «■ The, course which! T now recommend’to-be-pursued is to carry out the heavier works which I have described,—viz , the: tunnel, .-pumping station, ; and the main sowers, while (the survey is in progress. These works would occupy probably about twoyears, while the survey would; require but nine months,; Sufficient time wouldthusbe available for completing the scheme on the plan, and laying the pipe sewers m those portions -of* the city. f where they are most ur-. gently •required ; the whole being brought into operation when’the tunnel; which- will' probably occupy, more time than any of the other works; is completed?; and the remainder can be as they become necessary,. • ... , • ■ ' ; *' 76. It may be useful if I now append a few; remarks’ on the flushing'and ventilation- of;the seweft; the construction of house-drains; and further legislation which may be required. r.,K i 1 - In a surface so irregular and broken as thaf of Wel;lington, when-carrying out these works various expe-,. dients will be necessary to overcome obstacles; these" •will chiefly assume the form of; tunnels and! syphons to cross hills.and hollows.*. ‘ v ' Tunnelling is" fortunately not very expeusive/andthe ground jis notltolrequire timber. After the hill is pierced (as shown on section Nck.2), the pipe must-be laid,,in its bed,of concireto/ahd" covered up, with about *a* foot" of'earth tp prevent breakage or disturbance f by workmen passing over it.. The ends of the tunnel-may then be closed, and only--in case, of obstruction will it requjrp further Attention. In "crossing rivers, hollow places. ,or roads that have been excavated through' hills/ syphons will [occasionally benWessary; one of these bccur&in the same line„ of sewers as the above, and .the arrangement is shown, on plan No. 0. -- The greatest pressure, in this case, is 7ft,. which'stonowaro pipes -aro able to bearj above 10 feet, iron pipes will bo required. > «■- : ••• u •- A sluico-vaivo should: be provided,'in the well at the; lower end of the pipe which may be opened by a chain , from, above.- should' occasion require, to empty the' syph6n'.' ,, ‘ * i- ; If a few inches of between the iix’et and outlet of the pipe isewee .to f the, wells be given, sufficient wilb be obtained to keep the.syphon free from deposit' F As a further security for this/it is usual to fix a'smair pit and grating in the line of the pipe at its junction, with the descending we 11..; This is not shpwn, on,the sketch. _ With the opportunity of .cleaning the wells out from f below, they may '.bo con-' structedof pipies the size of the sewers , •■ / / Flushing is an operation which is often considered • as absolutely, necessary to the proper condition and action of the sewers, as it is affirmed that they are unable* to'discharge without some such aid the matter which‘finds, access to thorn. This, however, is not the case where there, is an abundant water supply for domestic purposes; and the sewers are so constructed as "hot to' allow of its leakage into the surrounding soil.. There is no tendency to deposit if, as is here 'intended,- the*road surface-water is excluded; for then the material which, constitutes deposit in sewers, viz,, road-grit, is also excluded. The ** raanholes u at ; all'' times'bW- used for the purpose if needed, and no further .special s arrangement for the fluabing/ofthe sewers-is: required. Solid , refuse, .which must ,be removed, !n the dust cart; or by the’'’ scavengers^'should hot find access 1 to the sewers. Every inlet* except tho watoi'Cleset pipe, which is rttapped/iwili? bo protected by an lirpn grid and trap, and it will be impossible to* put.such substances into the' s'ewere io ipterfere'with theirproper action. 76.. ,The area :of the city Is Intersected: in several places by natural streams, and of these the Tinakori; stream is capable of :being intercepted arid diverted into the two principal 'sewers herein described, viz., the intercepting and low-levcl sewers which extend to the northern boundary of the city/ Advantage should be taken of this circumstance to provide the means .of flushing these sewers. : ; As. explained in paragraph 32, tbese sewers are laid with the [lowest possible fall, and it is very desirable that an occasional flush shall r be given to.them; -all that is necessary will be a small' •dam and a 9-in. pipe (which may also act as a sewer to the locality through which it passes), witha means ofadmitting or shutting off the water from the,sewer;as occasion may require. ' ; -,

77. In 'every : system of sewers provisions for perfect ventilation must be made. Every cubic foot of fluid; which is admitted will displace-a similar 'quantity of air. If no provision be made for escape, the air in the sewer would be under, pressure. and tend to force' its way through every imperfectly trapped;inlet; which may bo .existing,; and should such inlet be within the house, the - atmosphere thereof would be vitiated.- It ii’explained below- that direct communication between the houses and the sewers should not, except in the case:of water-closets, be made. The usual- means of ventilation is shown in Hhe plan No. 7. A small brickwork box is ; constructed 'in' connection with a “ man-hole," at or near the centre of the street. The air in escaping, a basket 1 of.charcoal;; and afterwards tnroughan iron grid fixed at the level of the street surface. The charcoal is Intended to, render the air inodorous/ The 'arrangement also pro-’ vides-thab any water which may enter the grid shall pass on with the current in the sewer, but the rbadgrit will be arrested, and will require occasional removal. These ventilators sKofild be flxecLat con-* yenient places about 800 ft. apart.; ; n‘ 78 v A more active ventilation- has in some cases been attempted by'connecting the sewers-with-the furnace or chimney of manufacturing establishments, the proprietors of which may be willing to permit lt.Undoubtedly a more rapid change of the air of the sewer wonld thus be. effected,'as the draught would' be promoted by the heated chimney. Another means which may be adopted is to take a pipe from a “ manhole" situated near to a wall—not,that of a dwellinghouse—and to affix a vertical pipe thereto of any convenient height; free eacape of the air may thus be obtained.- ■ - • ■ * ;

Practically, however, if the sewer be properly constructed, so thatho stagnation occurs in the flow of the sewage, and its removal be effected before decomposition takes place, all that is actually required is a free passage forthe inlet and • outlet of the air at the streetjurface. -V .. . ;

: 79. The usual points in a house to which the drain-' age requires to be carried are—lst, kitchen'-sink; 2nd; water-closet; 3rd/stopcock in the paved yard, where water may he drawn for washing carriages, &c; 4th, where after use it can be removed; 6th,t the ; stable ; and oth, rain-water pipes. In the Ist and 6th cases the pipe can be brought down on the wall of the house, aha should terminate, a lew inches, above the trapped opening, as is shown in,plan No. 8; - in 3,4; and 5 a similar grating, and trap placed in the yard surface, or in the stable, will receive the water. For all these cases it is impossible that the sewage gas can enter the house, as they have no direct connection with it. The second point, viz./, the water-closet, is the only one having a direct connection. In this'ease if the soil pipe be'carried for its full size up to the top of the house, ;and a< syphon trap be fixed at its lower end, the ventilation t of the pipe will.be perfect, and the danger of gas entering the ’ house will be reduced to a minimum. 1 The arrangement is shown on plarirNo. 8.- The principle is simple, if the proprietors of houses will only insist on its being carried put. i -■ AU : ' 80. When there are 'several branches to the house drains f ifc is desirable to'carry them all to one point, as shown at TP on the plan. This should bo trapped by a similar arrangement of dip-trap, and, if carried up to near the surface, can be readily opened for ln- ; spection. ’lf this be done, no further trapping at the of the house drain with [the public-sewer will, be required. ) A direct communication , from this trap to some convenient wall, where a ventilating pipe (not near to a window) can be fixed, is jdesirable, as it removes all chance of. pressure within the pipe, and ensures a. perfect ventilation.- Stackpipes are commonly used for this duty, but this Is not to be recommended, as at the time the staclcpipo is discharging rain-water downwards it does not readily admit of the .upward escape of j,the air which is then necessary. , 81. The points whore.drains are generally wanted are at the back of the house, and where it is conveniently practicable, 'very great economy in the house drains, as well as efficiency,' will, bo obtained by placing the public sewer there also. J : This arrangement, or what Is called “back drainage," is most economical and applicable where the houses are in continuous rowsj or nearly so; in that case the for conveying the house drain under; the house, which is always undesirable, is avoided. Wellington, at present, contains bat few localities of this character. Flans 8 and 4 illustrate the principle recommended, ' t : 82. All the minor drains In the scheme are assumed to be Oin. in diameter. For a very large portion of the length Oin. would be amply sufficient to carry all that will bo required of them. (Paragraph 51.) 83. As It is probable that some further powers -will be required by the Board when carrying out these works I would recommend for consideration those clauses of the Public Health: Act of; England, 11 and 12 Victoria. 1848, which refer to the construction and maintenance of sowers and the construction of private houses, sections 43 to 40 inclusive, by which power is given, to take works through any place or land what-, ever, making compensation for damage. 84. In Wellington there are at present but few cellars : their construction is, however, on the increase. And In order that damp unhealthy houses should not bo erected, it Is very important that their construction should be subject to proper regulation. Sections 51 to 64=of the, above Act provides for these regulations, and empowers the Local Board to fix the level of the collar ana Idwost floors of houses to bo erected. The depth is regulated by that of the adjacent sewer, and must ho such as the sewer will effectually drain ; 2(b. or 3fb. above the invert will generally be sufficient to keep the cellar dry. The possession of the general scheme for the city will'thus enable the Board to reuglate.the depth of collars, These clauses also refer to the proper construction and management of cesspools, privies, &c. ■ 85. The rating clauses also are worthy of consideration. ; The special district rates give the power to the Board., to. levy rates on districts especially benefited-' by any particular drain. ? . The' power td lovyprivate Improvement rates have found to be very useful and acceptable to rate- 1 payers. .These rates are for the purpose: of recouping' the Board for any works and necessary improvements to private property which the owner may be unable or unwilling to do, and tho Board have executed. In these cases the outlay Is secured as fa first charge on tho property, and provides that principal and interest shall bo repaid in a limited number 'of years. ** It Is also desirable that the Council should'have the power to'diwet that the private drainage o( f^grpup

of B<rfenH’-houses should .be, drains , ; operation, thlswill fie'evident from an*, the plans 3 - seen that m mo** the premises oau only be drained by a sewer commou to several; of My thAbiick drainage before described; 'in theae'casesrthe Council- should have the power to direct the couree-to bo adopted; and also to prevent disputes^which'would, otherwise arise—the settlement 6! the lust proportion of the expenses incurred ; for this purpose, a c ause should be inserted in the Act, a suggestion for which is given below (1.) If it appear to. the Council that a group or block of contiguous, buildings, or of adjacent, detached, or semi-detached buildings, may be drained, more economically or advantageously in, combination than, separately, and a main sower, or some branch thereof, shall bo within 200 ft. of any such group or block of buildings, it shall be lawful for tho Counc,! to order that such group or block of buildings he drained and improved by a combined operation : and if the owners of such buildings or premises neglect or refuse, daring twenty-eight days after such order or notice to that effect has bcen deUi-orcd to such owners, or left at such houses, buildings, or premises, to begin to construct such drains and works aforesaid, or thereafter fail to carry thorn on or complete them with all reasonable despatch, it shall be lawful for the Council to cause the same to be constructeu or altered and made, as the case may be, and to recover the expenses to be incurred thereby from such owners in the manner hereinafter provided. - C2.) Where, under the authority pf this Act, two or more persons are or may be directed by the Council to do, or join in doing any acf, or to pay or join in paying any sums of money, costa, or expenses, it sliall be lawful for the Council to apportion the matter to bo done, or the sums of money, costs or expenses to ,to bo paid- between such persons in such manner as the Council considers just and 1 reasonable, ami to recover the same in the manner hereinafter provided. i ' - ■ :"WV. Cpajijc, 1 . u (Member of the Institute of Civil Engineers.) * For the purpose of. illustrating this report, the following plans have been prepared:—No. 1. General plan of the city, showing, position of the .main sewers^ 'pumping station, tun-’e!, &c., -Sic., laid 'land for the Utilization 1 of. tho sewage.,: No. 2.. Section of highlevel’intercepting sewer., .No. 2a* Sectio;: ot lowlevel sewer. No. 2b.. Section of ' Adelaide-road tunnel, Ac, No. 20. 'Section ot intercepting and 1 • low-level sewer ’east: of Adelaide - road Nos. 3 and i. Plans of blocks of tho city at enlarged ■scale, illustrating arrangement of sewers, back drainage, &o. " No.' 8. Diagram showing arrangement of pumps and pump-well. No. 0. Sections of sewers and • tunnel, guliyrpits, syphon, Sen. . No. 7., Plan of manholes, lamp-holes, and- ventilators. No. A Diagram showing arrangement of house drainage,. No. 9. Plan - “of closet for the' poorer description ot property.