The Sludge Decision

Press, Volume CIX, Issue 32032, 5 July 1969, Page 12

The Sludge Decision

The Christchurch Drainage Board has confirmed its scheme to dispose of sludge from the Bromley treatment station. This week the board rejected an alternative scheme proposed by persons who oppose the board’s plan to buy a large block of land on which to spread and farm sludge. Ratepayers have now had an opportunity to learn why the board prefers the farming scheme to the lagoon scheme advocated by the objectors. The economics of the two plans and the limited life of lagoons were persuasive factors in the report made by the board’s chief chemist Members were apprehensive, also, of pollution of the Estuary by water discharged from the lagoon, and cited experience with the lagoon method of disposal in Auckland.

But are these arguments conclusive? Contrary to Mr C. H. Russell’s belief, the Auckland Regional Authority has not faced a public outcry against smells from its lagoons. When an Auckland lagoon was first used nine years ago vegetation rotting on the bottom of the lagoon caused a nuisance; but it was short-lived. The Auckland lagoons are not aerated to prevent smells; the sludge is aerated to facilitate its distribution. Nor does the evidence of Auckland experience suggest that discharge from the lagoons—returned, in fact, to the oxidation ponds—will foster the growth of weeds in the Estuary. Harbour pollution was a serious problem in Auckland before the lagoons came into service; it was the result of industrial waste and, sewage being discharged into the Manukau Harbour. The problem has since disappeared. Apparently the board is satisfied the lagoons cannot be satisfactorily cleared and re-used indefinitely. A decision on this point turns largely on how and where the sludge may be used most profitably. If the price of the land proves higher than the board now expects, the farming scheme will look less attractive. The board is undoubtedly relying on the Christchurch City Council’s being ready to zone the land so as to prevent an increase in price. The council will have the unenviable task of considering objections already lodged against a proposal to change the present zoning from “ rural ” to “ sludge “land”. It will have to weigh these objections knowing that the preferred scheme may stand or fall by the value of the land as determined largely by its decision on zoning.

In general, it must be agreed that the efficiency of a public service outweighs claims for private gain; it is, however, possible that private use of the land would offer the greater benefit to the communityprovided that the public service could be efficiently discharged by other means. The Drainage Board’s decision this week was based largely on the technical considerations canvassed in the report of its chief chemist, on which it rightly places great reliance. Until the present uncertainty about the cost of the land—and therefore about the economics of its scheme—is resolved, the board would be wise to keep its mind open to alternatives.