WAIRAU OR WAITAKERE?

Sun (Auckland), Volume II, Issue 586, 12 February 1929, Page 12

WAIRAU OR WAITAKERE?

NORTH SHORE'S WATER SUPPLY

FILTRATION SCHEME SHELVED

The proposal to augment the North Shore water supply by diverting the Wairau Stream into Lake Pupuke has been definitely shelved by the North Shore Water Board following on an adverse opinion from the Department of Health.

This decision was made yesterday, after a discussion on the Health Department s opinion regarding the scheme recently put forward by Mr. W . H. Dufaur, representing Candv Filters (New Zealand), Ltd. The scheme was to impound the waters of the W airau Stream during winter and, after chioriruuion. deliver it into Lake -Pupuke, the level of which would be maintained by this means. The board decided the question would not be pursued further during its present term of office which expires at the end of April. A letter was received from Dr. H. Chesson, medical officer of health, who stated he had conferred with Dr. Mak-g-ill, advisory medical officer, and had discussed all aspects of the suggested scheme with other officers of the department. “GROSSEST POLLUTION” “The department does not favour the use of a lowland surface water from an open valley in which farms, vegetable gardens and residences are located, and which is intersected by loads,” said Dr. Chesson. ‘‘Water from such a scheme as the “Wairau, which is dependent entirely on the washings of the countryside during heavv rain, must inevitably be liable to the grossest pollution. "Whether it is practicable to obtain sufficient water from this stream' during heavy rainfall and store it to provide an assured adequate supply for the present and future needs of North Shore boroughs is an engineering question, although we feel somewhat doubtful, but as regards its wholesomeness untreated, we have no hesitation in condemning it. RESPONSIBILITY DISCLAIMED “We are fully aware that it is practicable by modern methods of treatment to convert polluted water into a reasonably wholesome water, and the means suggested in Mr. Dufaur’s report may possibly achieve this result, but that cannot be guaranteed by my department. The whole question depends on the adequacy and efficiency of the plant installed and the staff in charge of it.

‘‘ln view of the estimated low cost of the proposal as compared with the Waitakere scheme, my department does not feel disposed actively to oppose its adoption by the board, but as any approval carries with it a proportion of responsibility, and we cannot accept responsibility for the installation or management of the proposed works, official approval cannot be given, and if the board adopts the scheme it must accept the fully responsibility. ‘‘The department would reserve the right to interfere at any time should the interests of the health of the community seem to require it. It would rest with the board to supply to the public a wholesome water free from all pathogenic organisms and containing no bacilli coli in 100 c.c., or other evidence of unpurified contamination. LAKE WATERSHED ‘‘Regarding the question of. acquisition of land in the Wairau watershed, it would seem little use acquiring less than the entire watershed, if any is acquired at all. As to the watershed of the lake itself, in view of this being the reservoir for the proposed scheme, and an important factor in the purification system, and in itself forming a considerable portion of the supply, there can be no departure from the precautions at present required; namely, that no new residences can be erected in the lake basin unless the drainage

therefrom can be directly connected with sewers outside the basin, and that an area of approximately four chains, more or less, from the water margin, according to local configuration, be kept free from human or animal use; also, that the powers now conferred on the board by the Act and regulations for maintaining the purity of the lake water be strictly enforced. “The department cannot agree to the contamination of the excellent water naturally in the lake by the admission of unclarified water, even though chlorinated, and would certainly require that clarification of the Wairau water should be secured by filtration or sedimentation, or both, combined with chlorination. PUBLIC SHOULD CHOOSE “Should the board desire to go on with this scheme,, the department is of opinion the community should be given the opportunity to express its views by placing before it the two schemes, namely; (a) The initially unpolluted water from Waitakere, and tb) the admittedly polluted water from the Wairau, depending entirely on treatment and storage in the lake for its safety. ‘‘The public could then choose between paying the higher cost for the purer upland water, or the lesser outlay on the treated washings of the farm lands of the Wairau Valley. The public should certainly be consulted, with the alternatives clearly placed before them.” The questions submitted to the Health Department were answered briefly as follows: (1) The department would not agree to the lifting of any of the restrictions on the use of the lake basin or watershed. (2) All water must be efficiently clarified by filtration or sedimentation, or both, and chlorinated to the extent of being free from B. Coli in 100 c.c. before admission to the lake. (3) Unless the entire watershed of the Wairau was acquired, little would be gained by purchase of any portion other than such as is necessary for the installation and protection of the sterilising tanks, filters, races, intake and other works. (4) The board must take full responsibility for ensuring the safety of the supply, and at this stage the department cannot detail further safeguards which circumstances may render necessary, except that it would be necessary to prevent the installation of septic tanks, the burial of nightsoil, and the

keeping of pigs in the Wairau Valley, or the discharge of *ny household drainage into the stream or its tributaries, or any other matter which may

cause dangerous pollution of the water. The chairman, Mr. E. Aldridge, said the estimated cost of the Wairau scheme, £47,000. as proposed by Mr. Dufaur, did not allow for the purchase of any land in the Wairau Valley. It was decided to defer consideration of the scheme during the term of the present board.