SEWAGE OUTFALLS

New Zealand Herald, Volume LXXII, Issue 22209, 9 September 1935, Page 12

SEWAGE OUTFALLS

Sir,—A momentous decision involving an expenditure up to two millions and affecting not only our generation, but succeeding ones, now rests on the ratepayers. The problem is, shall our sewage be taken (possibly as # temporary expedient) to Motukorea and there be treated before discharge, or shall it be conveyed; to Manukau Heads and then be discharged directly into the Tasman Sea, thus solving the problem for all time? Mr. Watkins, in his exhaustive report, deals with both these outfalls, and arrives at a conclusion which is not convincing. In his own words, he admits that "disposal by dilution in the Tasman Sea yould afford a particularly satisfactory solution of the sewage disposal for the southern area," but adds, "it is extremely unlikely that any project of this nature could be seriously considered for many decades to come, having in view the enormous expenditure." He therefore decides on the Motukorea scheme at an estimated cost of £1,360,000, against £1,900,000 for the Manukau lEteads scheme, although the inference from the above quotation from his report is that the latter scheme must eventually be adopted with the result that work done and the huge expenditure incurred in making the main sewers gravitate toward Motukorea will be practically wasted. Hei provides in his estimates for £350,000 on account of treatment works at Motukorea, whereas at Manukau Pleads the whole volume of sewage could be discharged into the Tasman Sea without any treatment and, consequently, without any expenditure whatever. It will be remembered, when the Orakei outfall was decided oi>, that elaborate tests were made to show that the currents would disperse the sewage so thoroughly that, it would be rendered innocuous. It is not necessary to stress the point that this prediction was far from being fulfilled. Yet once again th-a same prediction is made in regard to the sewage when discharged at Motusorea. Will this second prediction share the' fate of tho first? Mr. Watkins, later on i:a his report, states that "a 1 estimates are based on preliminary investigations and surveys,," but admits that "the figures given are only approximations and, therefore, would bo subject to amendments upon completion of detailed surveys and working plans." Surely by this admission the value of Mr. Watkins' estimates is gravely discounted. It is perfectly evident that the clear course to pursue is to have a detniled survey made of the Manukau Heads scheme and accurate estimates thereby made possible. If the cost of that scheme is then found to be altogether too high, even for a permanent solution, a similar survey of the Motukorea scheme can then be put in hand. It would be a fatal mistake to rush heedlessly ahead with what, after all, may be only a temporary expedient, when no proper survey has been made of the Manukau Heads scheme, which everyone competent to give an opinion admits will provide a permanent solution of the whole problem. Therefore, before we go further, let us insist upon an accurate survey of the Manukau Heads scheme. The Long View.