Effluent At Moana “Inoffensive”

Press, Volume CVIII, Issue 31871, 26 December 1968, Page 10

Effluent At Moana “Inoffensive”

Effluent from oxidation ponds at Moana, on the shore of Lake Brunner, would be quite inoffensive, although it might increase the weed problem in the lake, said Mr G. L. Evans, consulting engineer to the Grey County Council.

Mr Evans said that some residents had asked that effluent from the ponds be pumped back to the swiftly flowing waters of the Arnold River, but the extra expense was not considered to be justified. If a definite need was proved for discharging the effluent into the Arnold instead of into the lake, the council was prepared to do it.

“We know that the lake is polluted now,” said Mr Evans. “The water is not fit for drinking.” He said there was no night-soil collection at Moana, and residents and bach owners used septic tanks and soak pits for sullage, or they buried their sewage in the ground. In the course of time it seeped into the lake.

Mr Evans said the sewerage system would cope with practically all of the present subdivided area of the town, plus two areas of future subdivision. It was designed to be adequate for 30 years, serving a peak population of 380 persons. He estimated the present peak population at 150.

The ponds would have a total area of an acre and a fifth. They would be built on swampy land to the east of the township and the effluent would be discharged through a pipe extending at least 200 ft into the lake, at least 2ft below the low water mark.

Mr Evans said the ponds would be capable of being expanded after 15 years or as demand required. The material discharged into the lake would be an inoffensive type

of effluent. It would contain phosphates, nitrates and other fertilising elements, but in very small proportions. “These could have an effect on weed growth,” said Mr Evans, “but weed is already a problem in certain areas.”

He said the scheme had been approved by the Ministry of Works, the Health Department and the Local Authorities Loans Board. “Nobody can prove it’s a bad thing,” he said, “and we are prepared to deal with any problems as it arises.” It was proposed to call tenders early next year. The cost of the scheme was estimated at $38,000, plus $6500 for the future extension of the ponds. Mr Evans said that al-

though the ponds would be closer to the nearest dwelling than was usual in New Zealand, their location in relation to the township was comparable with overseas practice. A Christchurch resident Who is a ratepayer at Moana, Mr R. F, Smee, has been told by the Minister of Health (Mr McKay) that some degree of pollution of the lake is unavoidable. “But this does not mean,” said Mr McKay, “that it will necessarily be detectable other than by biological and chemical analysis of the lake water.

“I am sure you will agree that the degree of pollution envisaged is preferable to the existing situation with drainage nuisances and the result-

ant dangers to health being present on individual properties.”

In another letter, Mr Smee has been assured by the Nelson district health office that “there will be no significant change in the quality of lake water to fishing grounds or weed growth.”