CHRISTCHURCH DRAINAGE.

Globe, Volume XXIV, Issue 2600, 7 August 1882, Page 3

CHRISTCHURCH DRAINAGE.

The following letter appe’r* in thi* morn ing’s issue of the “ Pros* Sib, —It has been my misfortune throughout the intere»ting controversy on the drainage question to have arrived at conclusions on one most important point of the question wholly opposite to the view* yon so fairly and ably advocate. I refer to the admission of water closet excreta to the «ewer». I read with much pleasure in your leading article of August 4th instant, your recognition of the valuable services of the Drainage Board, when you *ay —" They have initiated, with great skill, an elaborate system of underground drains for removing the house slops and liquid sewage.” But, with your permis sion, I will give reasons for dissenting from the concluding portion of the sentence, which states that ‘‘they are so pleased with their work they want to spoil everything by admitting excreta into the sewers.” I understand your objection throughout your articles to be founded for the most part on the writings of [certain medical sanitarians, who view with alarm any system for removing the «swage of town* which admit* of sewage gases being forced by back atmospheric pressure into dwellinghoueos. For my part, I at once agree with those writers on the gravity of the danger to be apprehended under conspiring circumstances from this cause, and the necessity which exist* for making provision against it. My present object i*, in chief, to point out in plain terms the wide difference existing between the construction and surrounding circumstances of the drainage systems in large town* in England which have called forth the adverse criticisms referred to, and the pipe sewer system designed by the late Mr Clark for the city of Christchurch. It is well known to all of ua who have lived in large cities, in London to wit, whether expert* or laymen, that the sewers there are of large capacity throughout all the loading streets, for the reason that they have to convoy storm waters as well as house sewage and must, consequently, be of great size to quickly carry off the heavy downpours of rain water which are of frequent occurrence. Further, they must be of sufficient size to admit workmen to pass freely through them for the purpose of cleaning out the deposit* of road grit which, notwithstanding the catohpits, is continually being carried by storm-waters into them. The only sewers in the Christchurch district at all of the character of the ordinary sewers referred to are the outfall portion of the sewage sewer on the Bast belt and Drain road, and the storm-water sewer which, draining the heart of Sydenham, passes under the railway, and thence along Madras street to the river Avon at Madras street bridge } and the Ferry road storm-water sower which, draining Waltham, passes along the Gasworks road to the South belt, thence down the Ferry road, where it join* Bell’s creek, thence for some distance as an open sower until it discharges into the river Heathoote near the Christchurch quay. I particularly desire to draw your attention to the fact that the last named sewers are not designed to carry drainage from houses, although temporarily this obnoxious duty is forced on them by reason of the house slops of a large district finding its way for the present along the street side channels into them. These two sewers are occupied by flowing liquid contents it may be to the extent of one half more or less of thrir capacity, the remaining space (except in flood time) being charged with offensive odours arising from the sewage matter. These liquid contents, although “only house slope,” &0., are of thofoulestpossibledesoription. Chemists call it the worst form of sewage matter. My own experience has never led me into fouler London sewers, where the contents were largely composed of the proceeds of all the water closets of densely populated districts. As no house connections are permissible with these two sewers, no sewer gases from them will bo forced through water-closet traps into our houses.

The speciality of Mr Clark’s scheme is that the storm waters are carried by street side channels into the two storm water sewers referred to (and into the River Avon), whilst the house sewage is to be convoyed separately from such storm water through underground pipe sewers to the pumping station. Hence the plan adopted here is termed the “ separate system.” This "separate” system should bo the delight of the medical sanitarians of the “ Lancet,” for it leads up to a realisation of the conditions which they so strongly and wisely in their aims, if not in their proposed methods, contend for, to wit, the exclusion of sewer gases from our houses. I have shown that the two largo storm water sewers are occupied in the space above the water line by gases in like manner as the large common sewers of London or elsewhere, although no water closet excreta is passed iato them. I now desire to show that the 9in sewage pipes of the “ separate ” system which receive the house connections are not open to objection on the score of being "gas reservoirs” in the sense applied to the large sewers. Take a London street » quarter of a mile long, witn a 4ft by 2ft Sin egg-shaped sewer. The space above the water line may, under ordinary circumstances, be equal to, say 4000 cubic feet, charged with sewer gases. If the house connection enters the sewer above the water line, then whenever a sudden atmospheric pressure occurs, the tendency to some extent is to send the gases up the house pipes, and, if the traps are imperfect,_ they may find their way into the house. This is a condition of drainage which, as I _ understand the case, the " Lancet ” is waging war against. The principal vent for the gases is through the street ventilators. When the house connection enters the sewer below the ordinary water line, the atmospheric pressure on the sewers will not affect the house drains.

Next consider the case of a 9in sewer pipe in a Christchurch street. The space above the ordinary water line may be equal to only 100 cubic feet iu the pipes a quarter of a mile long, and as the house pipes enter below this line, dread of harm from atmospheric pressure is dissipated. It amounts to nothing. These pipes also are provided at regular intervals with ordinary street ventilators. When these pipes oome into general use and are running at, or nearly at, full bore, there will bo little or no space in them fo gases to occupy. Further, if, as Mr Clark states, the sewage matter i i the pipes “ will not stop for a moment ” in its passage through to its destination, and the time "occupied in its journey from the most distant part of the city will certainly not bo mt-e than three or four hours,” what time is there tor dooomoosition to set in P

Observation specially directed to the subject when resident in London led to the conclusion, in conjunction with other observers, that sewer gas was actually introduced into dwelling houses through the medium of rain water pipes, which are there universally connected with the sewer pipes. The rain water heads are often in close proximity to upper floor windows, and I have been informed of oases where the occupants sometimes had to close such windows on account of bad smells. Here, in Christchurch, such an evil cannot possibly occur, because our rain water pipes are not connected with the 'sewer pipe system, but discharge into open channels, thence to the street channels, and so on to the storm water sewers.

The other two points at which sower gas may enter a houso under the old arrangement are at the sink and at the water-closet. The arrangement laid down by Mr Clark for making sink connections leaves it physically impossible for any sewer gss to enter a house at this point, as anyone can see who will examine the matter for himself. Concerning tho water closet, it can easily be constructed bo as to be perfectly clean and innoxious. But why it should be commonly placed so as to be, or to appear to be, a menace to the health of a household I do not understand. In ninety-nine oases out of a hundred it can be placed at a reasonable distance sway from the main buildings, and when attached to the dwelling the entrance and ventilation can bo so managed that tho atmosphere of the one shall be completely out off from the other. Only that space forbids, I would willingly have quoted the testimony of scientists to tho dictum that for 11 economy and completeness, with the absence of nuisance,” no other practical system for the removal of sewage matters can compare with that of water carriage. That the sewer pipes as laid down can convoy away wateroloset dejecta, as well as house slops, we have Mr Clark’s emphatic statement, “to omit this use of them is to forego one of their most valuable advantages 1” Finally the chemist adds his evidence that “ tho house slops are the worst form of sewage matter.” The articles in “ The Lancet ” are valuable contributions to sanitary literature, but a

careful perusal of them tide by side with Mr Clark’* aoheme lead* to the conclusion that the evil* to be apprehended from the introduction of sewer gae into our Christchurch house* are either non-existent, or can readily and absolutely be avoided. Yours, &0., Feedo. Jokes.