THE DRAINAGE SCHEME.

New Zealand Herald, Volume XLV, Issue 13673, 14 February 1908, Page 3

THE DRAINAGE SCHEME.

HARBOUR BOARD ENGINEER'S REPORT. FAVOURABLE TO THE PROPOSAL. The report on the City Council's drainage scheme, which was prepared in August last by tha engineer to the Harbour Board (Mr. W. H Harrier), has been printed and circulated amongst, the members of the Board in accordance with the resolution passed at the last meeting of the Board. The reportwas prepared' for submission to a special meeting in September last, but- the meeting wa- not held, and consequently the report did not come before the Board.

The report gives the results of the recent float experiment:;, which, as already slated, arc favourable to,the; drainage outfall scheme, proposed by Mr. Midgley Taylor. Referring to this scheme Mr. Hamer says:—

The City Council's proposals—a scheme which proposes to improve the existing condition of things by divertirig the sewage which is at present discharged at numerous points on the south shore of the harbour to an outfall carried well out. into deep water. end to a point, as fax removed a,s is reasonably expedient from the city, and so cleansing the foreshow immediately under the noses of the public at. the entrance to the should be welcomed and supported. These foreshores, when bare,-are exposed dining a largo portion of the year to a hot sun, winch evaporates the polluted 'moisture from the mud, giving rise -to noxious exhalations generally over the waterfront, calculated to encourage the propagation cf disease. It is probable., that wide dispersion, due to the existing sewer outfalls being situated well apart, and the consequent thorough dilution of the sewage volume, has so far saved the city from serious.. risk of epidemic; but only a portion oi the city is at present linked up with the existing drainage, and with lite population rapidly increasing, and the general desire to connect all new buildings with a modern system of sewage disposal, it is not difficult to imagine conditions of overtaxing Nature's remedies-, with detrimental results. Even at present it cannot be gainsaid that the polluted state of the mud upon the 'foreshore .is a- menace to the public health.

The objections urged against the proposal of discharge of sewage into the harbour are summarised as follows: —

(a) The pollution- to sumo extent of the i waters of the harbour. ci-jMScially localised ! nuisance in the region of the outfall, and the : spoliation of beaches now enjoyed by natives and pleasure parties, (b) The obstruction of waterway by the sewer crossing' the foreshore, and blocking access to Orakei basin. (c) The possible silting up along the lino of the tea outfall, and the deposition of sediment around about the mouth of the outfall, and in the still and shallow areas, (d) The effect upon the oyster and fishing industry. In dealing with these objections Mr. Hanicr says that with all other conditions favourable the proposition of the City Council) "appeals to me as preferable to the present system," and that "it is hardly conceivable that the possible nuisance will be as serious as that tolerated for years past along the waterfront." He advises that provision for purification, if necessary, should be retained as a safeguard clause in any agreement. The other objections are not regarded as serious, but it is stated by Mr. Hamer that stringent stipulations will be necessary in regard to the dredging of the sites about the sewer outfalls. ■...'. .;; .., The .conclusions...arrived at" by Mr." Hamer are summarised . as followsl. That the objection to the propsed outfall at Okahu 12ft below L.W.S.T. would be ■ much less' than the many'existing outfalls and their present insanitary conditions. 2. That the sewage controlled at about this point, and discharged at proper periods of tide, would be sufficiently diluted to if; inoffensive, except immediately at the point of discharge, where no sewer can be other than unpleasant. 3. That there would be no contamination of adjacent shores. 4. That the stiller waters of the inner and upper harbour would be unpolluted, and free from present objections. 5. That 'if the petition of the City Council be approved by the Board special provision should be insisted upon as to the screening of the sewage before its discharge, and the regular periodical removal by the city authorities, of any silt that may be deposited at the mouth of the outfall. 6. That •the point of discharge! finally chosen should not interfere with navigation to and from the Orakei Wharf or ■ elsewhere, and that a beacon should always be maintained by the Council at the end of the pipes. Finally, it is recommended that the charts and sections with these remarks should be submitted to the engineers for the Council for their information, and, notwithstanding the opinion expressed herein, that they should be asked k> consider as an alternative the question of cost of a scheme of clarification of effluent, for, setting out with the experience and knowledge gained in foreign harbours, it would seem desirable for the people to willingly undertake a moderate extra burden for the purpose of preserving as pure as possible the fair waters of this favoured harbour. In an addendum dated February 1 Mr. ! Hamer says:"Since writing the foregoing report . further floats have been set free from the site of the proposed outfall. ! Only one has been found, and that lying , outside a boatshed, with the suspended weights removed. Mr. Midgley Taylor has recently considered the question upon the site, and has dealt with the points raised in his report."