Cost of fluoridation put at $250,000

Press, Volume CXIII, Issue 33279, 17 July 1973, Page 1

Cost of fluoridation put at $250,000

The cost of fluoridation of the Christchurch city water supply would be about $250,000 and the annual costs $42,350, the City Council was advised last evening in a long report from the City Engineer (Mr P. G. Scoular) and the chief city health inspector (Mr A. P. Millthorpe).

On the recommendation of the health committee, the Royal Society, as an independent organisation will be in-

vited to prepare an up-to-date analysis and report on the advantages and disadvantages of fluoridation. Chlorination or some other sterilisation would be necessary at some time in the future and if steps were taken to fluoridate the supply provision should be made for chlorination also, the officers’ report said. The capital cost of chlorinating equipment would be about $150,000, and the annual costs about $15,000. Pumping stations Christchurch had 22 primary pumping stations, each with a number of wells to varying depths to artesian aquifers, the report said. Artesian water was available throughout the whole of the city area except Sumner and the hills. If fluoridation were to be undertaken, equipment would have to be supplied at each pumping station. The present daily flow varied between 9.5 m gallons in the winter and about 30m gallons in the summer, and the annual total flow was about 5500 m gallons. Consideration had been given to the possibility of reducing costs by not fluoridating at times of peak demand — usually early summer evenings — but this was unlikely to be practicable. Equipment to introduce a solution of sodium silicofluoride into the main would cost $6960, making $153,120 for the 22 sets.

Main alterations To this there had to be added the cost of installation, additional space, structural alterations and alterations to mains and supply pipes to ensure uniform distribution of the fluoride. These costs were estimated to be about $97,000. The daily average of 15m gallons required 2501 b of powder, allowing 60 pet cent fluoride availability from the powder and a dose rate of one part per million. Natural fluoride content I varied between .05 and .1 parts per million. Superphosphate contained; about 2 per cent of fluoride salts, and whereas phosphate salts were absorbed by the soil the fluoride salts were not, and were leached or washed into and from the ground. It was not normal for water supply catchments to be topdressed with superphosphate, but this was not the case in the Wairaakariri catchment, the officers said. The Catchment Board said that about 500 tons of superphosphate was applied each year in the 600,000-acre catchment. This might increase to 800 tons, but was unlikely to exceed 1000. Source of water The Department of Scien-' tific and Industrial Research; had confirmed that the greati

bulk of the city’s water supply came from leakage from the Waimakariri River, and the time taken for the water to reach the city wells varied, depending upon distance and depth, from 10 to 30 years. “It is possible that the quantity of natural fluoride reaching the water supply will vary in the future,” the report continued. “The amount is not likely to be significant. However, because of this possible variation, the large number of wells, the complexity of flow in the reticulation, the wide variation of pumping station output, which depends on adjacent mains pressure, and the large number of dosing points, routine testing Would need to be more extensive than that in more simple water supply systems. “For these reasons also the matter of indemnifying operating staff against claims arising from accidental variations in rates of dosing should be considered.”

Three reservoirs The city had three main reservoirs holding a total of about 15m gallons. They were used for emergency storage and for providing pressure. The turnover of water in them was low because they had to be kept as full as possible against any emergency. Because of this, it would take a considerable time to fully dose the water in the I reservoirs. The officers said there was some technical argument on whether fluoridation accelerated corrosion of water j mains. No consideration had; been given to this in estimat-; ing costs. Most primary schools had* their own private borehole j supplies and were not on city water, with the exception of school dental clinics which must have high pressure water. Unless there were deliberate steps it would be many years before all primary schools were connected to the public supply. Supply pure ! On the future need for I chlorination, the report said i the city was fortunate in having an extremely pure source of water. Risks of chemical pollution existed, but risks of bacterial pollution from the water as it came from the ground were virtually nonexistent. “However, the risk of bacterial pollution once the water is above the ground and in the reticulation is not insignificant, and it has been evident for some time that in due course it will be necessary for the city to chlorinate or otherwise sterilise its water supply to guard against accidental contamination.” The committee said a large collection of pamphlets, brochures, books and articles on all aspects of fluoridation had ■ been assembled for the benejfit of councillors.