MR CARRUTHERS AND MR BRAY.

Globe, Volume VIII, Issue 907, 22 May 1877, Page 3

MR CARRUTHERS AND MR BRAY.

The following are Mr Bell’s remarks upon Mr Bray’s letter, referred to in our report of I lie" Drainage Board yesterday : It cannot be considered in any way remarkable that the figures given on the sections refer to the tops of the drains and not to the bottoms, as sewers are usually made with the tops in a continuous line, so that alterations in size occur by stops as it wore in the bottoms ; there are of course occasional exceptions to this rule.

The plan does not show the levels of every drain, consequently Mr Bray is mistaken when lie says the fall shown of the outfall drain is only 4ft. Sin. in the whole length of the drain, the total fall is 7ft. 9in. In regard to the datum used for the levels Mr Bray complains that the one in question is an unknown datum. The datum he is accustomed to use, is, I presume, high water mark; this is an uncertain and, to a great extent, an arbitrary datum, and extremely inconvenient to use when the levels of works or sections may both rise above and descend below it. No one will understand better than Mr Bray the objections to this, and on account of them the datum used is a long way below high water level. Mr Bray’s remarks on the depth of the sewers below ground, and the desirability of now or hereafter connecting the water closets with them or not are merely his opinions as against those of Mr Carruthers, and we have had already evidence that opinions are apt to be divided on this subject both here and in Europe, but I believe I am justified in saying that Mr Carruthers thought that sewers close to the surface arc very inefficient, and that the smaller ones if laid at flat inclinations would be sure to become choked. It was represented to him that the sewage of Christchurch being extremely dilute, the gradients of sewers might be kept flat, but he thought that there was no knowing but that in a few years the sewage might be ot a very different character, and it then the flat laid sewers were found to become choked, the ex. pensc would be enormous in keeping them clean. These considerations, of course, determine that areas arc capableoi being drained by gravitation to the Estuary. It may be remarked that the area as at present to be drained by simple gravitation, and Mr Bray observes is so small, might have been enlarged by Mr Carruthers if the present outfall drain had been built at, say, the inclination but about 2ft. Gin. lower. As regards Mr Bray’s remarks with reference to the Edgeware road district, that it might bo drained to the high level system by a drain laid at sft. per mile and 3ft. Inflow the surface, it is to be observed that if the main drain is only oft. Inflow the surface, the side drain leading into it, and which ought to be laid at from 10ft. to 10l t. per mile, would come up to the surface in no distance olf from the main drain. Consequently, to drain the whole district, all would have to be parallel main drains at the same inclination, and the previous result applies to this case, that Mr Carruthers considered that shallow sowers laid at flat inclinations would bo unserviceable. The whole of the question is therefore as to the efficiency of surface as against underground drainage, and Mr Carruthers adopted the latter as applicable to any case that might arise, and he avoided the former as being a temporary measure likely to become superseded. In regard to flushing waters, Mr Bray seems to have considered that water used for this purpose would have to bo pumped. It is, however, neither usual nor necessary to do so. By taking the pumping sewer up Ollivier s lane to the outfall drain, "tho necessity for the Ferry road storm overflow is not obviated, as Mr Bray seem.' to infer, because the great body ol water in storms could not be conducted in the pumps, but must be allowed to flow away down the Ferry road. In regard to the preference to lie given to water closets or to the pan and tub -ystem, tlic question is again merely the difference of opinion as between Mr Bray and Mr Carruthers. On this subject also there it considerable diversity of opinion in Europe, but tlic gist of the discussion on the subject has been repeatedly published in the Christchurch papers, and was given in Mr Carruthers’s report.