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The Cyclopedia of New Zealand [Canterbury Provincial District]

[introduction]

The Christchurch Drainage Board was constituted by special Act of Parliament, “The Christchurch District Drainage Act 1875,” to provide for the drainage of the City of Christchurch and surrounding districts. There were originally eight members on the board, but by an Amendment Act of 1880, Sydenham was constituted a separate electoral district, and sent a member to the board, the number being thus increased to nine. The members of the board are:—Messrs. John Deans (Riccarton, chairman), W. E. Samuels (Northeast Ward), C. Palairet (North-west Ward), R. Pitcaithly (South-east Ward), Dr. B. M. Moorhouse (South-east Ward), R. M. Tayler (Sydenhan), C. Burgess (Avon), G. Melntvre (Heathcote), and J. Down (Spreydon). Mr. E. Cuthbert, M. Inst. C.E., is engineer, secretary, and treasurer to the board. The Christchurch Drainage District extends from the sea to about eight miles inland, with an area of 32,000 acres. Before the drainage works were put in hand the district was undoubtedly unhealthy, as was shown by the death-rate, which, however, has been so considerably reduced since the present system has been brought into operation that the city now ranks amongst the most healthy in the Colony. A very large number of sewers have been constructed by the board, the ordinary surface drainage which is collected by storm-water sewers, natural creeks, drains and side-channels, being discharged into the Avon, Heathcote, and Styx rivers. The system of sewers for the removal of sewage proper was designed by the late Mr. W. Clark, M. Inst. C.E. The sewers vary in depth from three to thirteen feet below the surface and are provided at intervals with man-holes, ventilators, and flushing tanks supplied by artesian wells. The district served by the system of sewers embraces the city of Christchurch and portions of the suburbs of Sydenham, St. Albans, Linwood, Ricearton, and Spreydon. The length of sewers proper in connection with the pumping-station equals nearly thirty-five miles and a half; length of storm-water sewers, fourteen miles and a quarter, flushing tanks supplied by artesian wells, and of rivers and open drains, 123 miles. There are all under the jurisdiction of the board. The whole of the sewage on the north side of the Avon converges to a point on the bank, where it is passed through a cast-iron syphon under the river-bed to the sewers on the south bank, from which it flows into a very large tank at the pumpingstation at Linwood. The plant at the pumping-station consists of two compound surface-condensing horizontal engines of fifty horse-power each. There are four pumps altogether, two being attached to each engine, and each is capable of throwing 3000 gallons per minute, and there are three Lancashire boilers fitted with Galloway tubes. It is usual to work only one engine and one boiler at the same time. From the enginehouse to the sewage-farm on the sand hills. a distance of two and a half miles, there is an iron main along which the sewage is forced. On arrival at the farm it is distributed by carriers over a considerable number of paddocks laid down in English and Italian rye-grasses and is there treated by surface irrigation. The liquid passes over the land and percolates through the sand, where it is caught by effluent water-drains by which it is discharged into the Estuary. By this means the sandy loam has been fitted to bear excellent crops of grass, which are cut twice a year for hay, and on which stock thrives splendidly. The operations on the farm have given most satisfactory results. The revenue of the board is derived from rates made by special orders on the various local bodies within its jurisdiction, under the Rating Act of 1894. The amounts of these rates at present vary from 3/4d. in the £ on capital value, and one shilling in the £ where annual value assessment is adopted, to 3/8d. and sixpence respectively, and are based on the expenditure of each of the sub-districts. These are collected by the local authority and handed over to the board, the revenue from this source being from £19,000 to £20,000 per annum. The Christchurch Drainage Board has a loan of £200,000 bearing six per cent, interest, out of which the various drainage works, including station and plant have been provided. The loan matures in 1926, and the payment is provided for by an annual sinking fund.