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Volume 9, 1876
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Art. IV.—On the Draining of Towns.

[Read before the Wellington Philosophical Society, 4th November, 1876.]

The subject of drainage comes before us, in almost every town, either as a question of system or of clarification at the outfall; in England, both of these aspects of sanitary work have of late received a great deal of attention, and many of even the most lethargic towns have been stirred into action by injunctions served upon them by River Conservancy Boards.

The consideration thus bestowed upon drainage has necessarily caused a more methodical grappling with the subject; and the author having been actively engaged for several years upon drainage works, submits to the

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Society the following practical considerations, which may be of use in improving the healthfulniess of New Zealand towns.

It is proposed to glance at the various systems that should be before the mind of a person who wishes to consider the most judicious manner of draining a town or district.

Two prominent divisions are first noticeable: First, we have the midden, pail, and dry-earth systems; Secondly, the water-carriage systems.

The midden system is that which has been the first usually adopted. The old-fashioned midden, with a fixed receptacle-trench cut into a porous soil, which is continually absorbing the moisture from the accumulation of the filth, presents the most loathsome combination of bad management. The trench, or pit, is often not covered in, and, when it is, it has still oftener no ventilation except through the seat of the closet.

When no provision is made for the slop water of the house, it is cast out into a channel, which only too often conducts it on to the public street, afflicting the passer-by with disgusting stenches.

When the midden trench is abolished, and a receptacle, such as a tub or pail, substituted, that can be removed weekly or fortnightly, or as occasion might require, then the first requirements of sanitary laws are attained.

A. The various kinds of pail systems, and also the results of the adoption of them in towns, require closer consideration.

The simplest method is, perhaps, that practised in Rochdale and Warrington, in England.

Rochdale has a population of 18,552 persons. It has some 5,600 closets, with pails and ash-tubs, both of which are removed weekly by carts, the whole system of collection being carried out by the Corporation, and under the management of Mr. Alderman Taylor, to whose paper before the Society of Arts I am indebted for these particulars. The refuse is manufactured at the depôt into manure, mortar, cement, or fuel. The collecting of pails is so well managed that the number of omissions has not exceeded thirteen per week. The whole of the refuse collected from an area of 4,000 acres is utilised, and defrays most of the cost of collecting. The death-rate has diminished as the pail system has supplanted the middens. From 1870 to 1875 it averaged 23.57 per 1,000, whereas previously, from 1864 to 1869, it averaged 26.22.

Another kind of pail system is that known as the Gough Absorbent System. Here the pails or containers, are provided with a lining of three or four inches of ash-tub refuse, mixed with a little soot, charcoal, gypsum, etc., and are removed weekly with the ash-tubs.

This system has been in use for several years in Halifax, Woolwich,

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Sheerness, Aldershot Camp, and Halstead; at the last-named place, the Surveyor asserts that it pays for collection. In Halifax, in Yorkshire, it has been worked for five years by the Grough Company; at first, at the rate of 5s. per closet per annum for a period, and then 12s. per closet, including the collection of ashes. The Corporation offered an additional subsidy of 50 per cent, when the contract ended, in order to induce the Company to continue the working of the system. The Town Corporation, however, have now purchased the plant for £3,500, and work the system themselves. Some 3,000 closets are in use, representing 18,000 of the inhabitants. The population, in 1871, was 65,510, when the death-rate, which had been rapidly increasing, amounted to the alarming height of 31.5 per 1,000; but it has now been reduced to 24.1 per 1,000. The raw manure is sold at 11s. per ton at the Gough depôts. The Gough Company also make a more portable manure, like leaf mould, which is sent out in bags to any part of Yorkshire at £4 per ton, including bags and carriage; ashes, charcoal, soot, and gypsum being added to form this manure.

The price of the closets, in duplicate, with license to use them, is 40 shillings.

At Manchester and Salford, the pail closets have a cinder-sifter attached to them. The sifter is so arranged that the fine ash falls into the pail, while the cinders fall into a bucket, to be used again as fuel.

In Salford, the patent of Mr. C. Morrell is used, the builders purchasing the working closet from the Sanitary and Economic Manure Company, the cost of application, either to new premises or the reconstruction of old closets, varying from £4 to £6 10s. per closet, including apparatus. About 1,000 closets are in use. The collecting per 1,000 is done by two and a-half horses and twelve men. The annual quantity of manure collected is 3,900 tons. The total expenditure for this is stated to be £1,117, including manufacture, so that, when the manure is sold at 5s. 6d. per ton, the expenditure is recouped.

The earth-closets invented by the Rev. H. Moule are largely used in establishments such as schools, barracks, hospitals, and also in the village of Halton, in Buckinghamshire, and at the Broadmoor Asylum they have been used for seven years.

Other forms, invented by Dr. Bond, Messrs. Moser and Gibson, are worthy of mention, and have each their advantages.

The Moule Earth-Closet Company states that three pounds of earth is required for each person per diem, but four and a-half pounds is probably the usual amount used.

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From, particulars stated by Messrs. Taylor, Mason, and Pearce, the following table has been constructed:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Cost per Head. Coat of Manure, per Ton.
For collecting Ash and Manure. Do., including Manufacture of Manure. Raw. Manufactured.
s. d. s. d. s. d. s. d.
Rochdale 1 3 2 9 ½ 4 6 *11 10
Halifax *2 0
Salford 3 3 4 4 4 2 ½ 5 7

In estimating the amount of pail sewage to be removed, one pound may be taken for each individual per diem, or three and a-half hundredweight per annum, and five hundredweight including ash and refuse. About ten tons of pail sewage appears to be necessary to produce one ton of manure, with five or six per cent, of ammonia; so that 62 persons would produce one ton of such manure, and, in such a concentrated form as this, it would be sure to command a market.

In these dry systems, the slop water is taken from the sinks by four or six-inch pipes into the road drains; or, where there is a garden, it should be conducted into a blind drain composed of open-jointed porous pipes two inches in diameter, to form a mode of intermittent filtration, a system which has been found to be most efficacious in dealing with water-carried sewage.

The first outlay in the adoption of one of these dry or pail systems is not large, which forms the great inducement for towns to adopt them; there is also the benefit of an easily manufactured manure that might be made to cover the cost of maintenance.

B. In the second division we will consider the various kinds of water-carriage systems.

The first use made of this method of removing sewage was to conduct the whole into cess-pits, or vertical shafts, lined when necessary with bricks laid without mortar. This was only an enlarged phase of the old midden pits, and open to the same objection. They require to be emptied periodically, causing an intolerable nuisance; and sometimes, as in the case of Sevenoaks, Kent (population 4,250), tho whole town was drained into two or three large cess-pits, which overflowed when surcharged by storm water. The subsoil was thus contaminated to such an extent, that almost all towns in England similarly sewered into cess-pits, are endeavouring to abolish them.

[Footnote] * Approximate.

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The following Table shews the Outlay upon Sewerage Works and the beneficial effects arising from them, and it also shews the varying Cost per Head of Population.*

* See Inaugural Address Society of Civil Engineers.

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Population in 1861 Population in 1875. Average Mortality per 1000 before Construction of Works. Morality in 1875 per 1000. Saving of Life in one year. Total Outlay on Works up to 1874. Annual Cost of Maintenance. Cost of Works per head of Population. Proportion of Pail Systems, etc., in use. Mode of Disposal of Water-carried Sewerage.
£ £ S. D.
Banbury 10,238 11,718 23.4 19.66 43 ½ 6,000 5 10 3 Irrigation.
Cardiff 32,954 73,000 33.2 21.26 869 76,000 400 20 10 Drained direct into Bristol Channel.
Croydon 30,229 63,000 23.7 21.71 136 77,000 1,100 24 5 Irrigation and Filtration.
Leicester 68,056 95,064 26.4 26.02 36 41,000 1,500 8 7 3,500 Middens 3,660 Ash Pits 3,000 Pails Precipitation by Lime.
Salisbury 9,030 12,902 27.5 24.3 41 15,000 700 24 9 Drained direct into River Avon.
Warwick 10,570 11,001 22.7 19.1 39 ½ 23,872 1,187 43 4 Irrigation.

[Footnote] * Mr. Baldwin Latham, M.I.C.E., has attempted to estimate the pecuniary saving effected during thirteen years, since the completion of the Drainage Works of Croydon:—2,439 funerals, which would have cost £12,195; 60,975 cases of sickness prevented, £60,975; value for the labour for six and a-half years of 1,317 adult persons whose lives were extended, £166,930. Total, £240,100.

[Footnote] † The cost of land for irrigation not included.

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There are two methods of dealing with water-carried sewage: either the whole, together with the rainfall on the streets, can be conveyed by sewers to the outfall, which is the “combined system,” or it can be kept separate from the rainfall by a double set of pipes—one for the sewage and one for the rainfall, which is called the “separate system.”

The General Board of Health, in England, recommended the latter system, and that the sewer be laid at the backs of houses in order to avoid laying the house-connections under the dwellings from back to front, any leakage from which would render the house unhealthy.

The great advantages are, that pipes can be used to a far greater extent than by the former method, both for the sewers that take the house and yard drainage, and for the drains taking the road drainage. The sewers have then to carry off a regular daily flow, and so can be of much smaller size than they would be if they were to take the rainfall also. The road drains can also be smaller, because they can have as many outfalls as convenient into the nearest watercourse without polluting it and causing a nuisance. In fact, most towns would require only nine-inch pipes laid in the greater portion of the drained area. There is also a regular quantity discharged at the outfall, and, when it is necessary to clarify or deodorize, there is a much more convenient form of sewerage to be dealt with thereby effecting a great saving in the cost of treatment.

In all the best-drained towns of England, the sewers are laid in straight lines, with shafts at their junctions, and at regular distances apart. These shafts are man-holes and lamp-holes, or man-holes and ventilators alternately, both the man-holes and lamp-holes acting also as ventilators. When it is required to inspect a sewer, a lamp is lowered down a lamp-hole, and a man goes down a man-hole, and, by looking along the sewer, can tell whether it is clear or not. If it is not, he places a flushing-board in the man-hole above the blockage, and in a few hours there is sufficient accumulation, and the board is drawn up, and the rush clears away the deposit or obstruction in the pipe.

When a householder finds there is something wrong with his drains, and reports it to the authorities, the public sewer is first inspected, and, it it is proved to be clear, a trench is cut down to the house-connection, and the pipes cleared with rods. A great saving is thereby effected in the maintenance outlay, for, before any expense is incurred at a blockage, it is ascertained to be in either the public or private portions, and all uncertainty and useless excavation is avoided.

The Town Surveyor should be able to refer at once, when necessary, to the block plans sent in when the house-connection pipes are laid, and on which the position of the drains are shown. In some towns, sections, showing their falls, are required by the authorities.

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It is to be hoped that in this country the local authorities will be empowered to lay the whole of the house drains, as they are most important portions of a drainage scheme, and, when left to builders or jobbing workmen, are seldom laid properly, and with cement joints when they pass under houses.

The most efficient means of keeping sewer gases from the interior of houses, is to have the sink and soil pipes discharging upon the grating of a small receptacle outside the house, and which is connected with the sewer, or the soil pipe can be continued up to the roof, so as to form a ventilating shaft. Nothing short of complete disconnection will stop the gases. They have been proved by Dr. Fergus, at the meeting of the Social Science Association, in 1874, by experiments, to pass through water-traps. Traps are also constantly getting choked and out of order; but if there is a disconnection of the sink-pipe, any sticks or brushes that have been forced down the pipe by servants are at once intercepted.

The chief defects of a water-carriage system are always in the faulty workmanship of the house-connections. Gas and Water Companies take care that they have the laying down of the house-connections in their hands; and so should that department of work be as carefully done for the sewers as for the gas or water.

Flushing arrangements are required in every town to clear those pipes that have low falls, and are liable to have deposits during the ordinary flow through them. Chambers are built specially for this purpose with penstocks, worked by chains or screws or self-acting counterpoises. It is stated, in the First Report of the Health of Towns Commission, that, on the occasion of one trial, a length of two and a-half miles of sewer was cleaned by one flush, with a four-foot head of water, and carrying 21 yards of sediment away. The cause of sediment is nearly always the road sand that has found its way into the drains from the gullies.

Charcoal baskets have been used to a very great extent in the ventilators to absorb the noxious vapours rising from them, but they are now falling into disuse, as it has been found that free circulation of air through the sewers has a much greater beneficial effect.

The streets and roads are provided with gullies to catch the flow of water along the channels. They are usually four feet deep and three feet by two feet in plan, and are well trapped if they are connected with sewers; but, on the separate system, the road drains would not require that precaution.

In connection with this subject it may be stated that the high proportion of the deaths in New Zealand towns, due to zymotic diseases—viz., dysentery, diarrhœa, enteric and typhus fevers, cholera, etc.—show plainly that there

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is a fearful loss of life that might be prevented by proper sanitary measures. In 1873, the annual death-rate per 1,000 on the population of 68 of the largest English towns, due to the above cause, was 3.6, while in the rest of the country it was 2.9. In 1875, the corresponding death-rate of seven New Zealand towns, referred to below, was 8.63, while in the country districts it was 3.17.

In Wellington, there would be a saving of 32 lives each year if the mortality was lowered to 23.1 per 1,000—the average of English towns in 1873.

But the most startling fact is, the difference between the proportionate healthiness of the town and country districts in New Zealand compared with that of England.

In England, in 1873, the death-rate of 130 largest towns was 23.1 per 1,000, and in the rest of the country 18.4, giving a proportion of 1.27 deaths in the large towns to 1 in the country. Now, in seven of the largest New Zealand towns the average death-rate was 25.91, and in the rest of the country it was 13.31, or 1.96 deaths in the towns to 1 in the country.

If the New Zealand towns were as healthy, relatively, to the country districts as the English ones are, then their death-rate would be only 16.9, and the saving of life would be as follows:—

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Number of Lives that would be saved in One Year.
1875 Estimated Mean Population. Proportion of Deaths per 1,000 of Population. If the Death Rate was the same as in average English Towns. If the Towns were proportionately as Healthy to the Country Districts as compared to England.
Auckland 13,084 35.77 166 247
Thames 8,259 18.16 10.5
Wellington 10,956 26.01 32 100
Nelson 5,805 27.39 26 61
Christchurch 10,611 20.44 18 144
Dunedin 19,153 22.24 102
Hokitika 3,461 21.38 15.5
25.91 302 680.0

In Wellington, I may remark in conclusion, the present mode of construction of sewers is highly objectionable, inasmuch as they are of wood, and cannot be prevented contaminating the subsoil; neither are they so durable as pipes, and are therefore more costly in the long run. They have flat inverts, and so present the least scouring power, and are liable to be infested with vermin. I exhibit a diagram shewing the increase in depth of the same quantity of water in three figures—square, circular, and eggshaped sewers, all having the same area.

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The pail system can never compete in completeness with water carriage, but it would be better than the present one in Wellington. For some portions, such as the suburban and hilly parts of this town, it would be specially advantageous, with water carriage for the remaining parts.

An outfall for the reclaimed and adjacent portions of the town could be formed as far beyond Pipitea Point as money would permit, and the Te Aro end provided with an outfall towards or at Jerningham Point.

The discharge of drains from even a pail system town would not be desirable to have poured into a bay opposite it.

Wellington would do well to protect with jealous care the beautiful bay that is its pride and source of prosperity.