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The Cyclopedia of New Zealand [Otago & Southland Provincial Districts]
The Dunedin Drainage and Sewerage Board
The Dunedin Drainage and Sewerage Board consists of nine members, and was inaugurated in December, 1900, as the controlling body of the Dunedin Drainage and Sewerage District, which was constituted by a special Act, passed in October of the same year. A re-election took place in 1902 when the following members were returned; Mr Robert Glendining (Chairman), Dr Mille Coughtrey (Vice-Chairman), Hon, Hugh Gourley, M.L.C., and Messrs R. M. Clark, J. H. Hancock, J.P., William Burnett, J.P., and James Gore. Mr. J. T. Nobel Anderson is the engineer, and has for his assistants Messrs W. A. Smith, B.Sc., and N. R. Fisher, B.Sc. Up to the years 1900 the sewage from the city of Dunedin had been drained into the Otago Harbour, but in that year the city was merged in the drainage district, which comprises an area of 14,000 acres, and has a population of 55,000; and a short time afterwards it was resolved to construct a thoroughly efficient and up-to-date system of drainage throughout the district. The system, now in course of construction, will convey the debris by means of one main interceping sewer and two storm-water outfalls, to the ocean; the chief ocean outfall will be situated one mile to the east of Lawyer's Head, at the reef, known as Bird Island, which projects about half a mile beyond the beach into deep water. The main intercepting sewer is 5 feet 6 inches in diameter, and will deliver the sewage into a large suction basin, whence it will be pumped to the ocean through two conduits. The pumping station is situated at Musselburgh, and affords 100 horse-power, with a stand-by provision for four times that power. In the construction of larger sized sewers and drains the Monier system of re-enforced concrete has been largely used. Those parts of the distric which cannot be connected by combined drain and sewer with the pumping station, are supplied with large detritus tanks, 25 feet in diameter by 40 feet deep, in which the drainage from the locality is to be clarified. These tanks are the largest yet built of the design, their use being rendered possible only by the adaptation of the method of hydraulie elevation, so much used on the New Zealand goldfields, to sewage purposes; an entirely new departure in sanitary engineering. The cost of the new drainage is estimated at £195,000, and, in addition to this, it is proposed to expend a large sum of public money in advancing loans to householders, with the object of assisting them to establish an efficient system of house connections, the present house-to-house drainage being of a very primitive nature. The main works of the Drainage Board will be completed in the early part of 1906, but the house connections will not reach completion till considerably later. The old drainage system will still be refained, chiefly as an euxiliary in times of extraordinarily heavy rain-falls. The present water supply will be insufficient for the requirements of the Drainage Board, which however, is entitled, by a provision in the Drainage Act, to construct water works. There is, therefore, little doubt that the Board's operations will have to include a large water supply scheme for the benefit of those parts of the district which are not supplied by the present system. The chief engineer. Mr. J. T. Noble Anderson, has already made investigations of the Lee Stream district with a view to obtaining the necessary supply at a high level. This district is a silurian formation similar to the watersheds of Manchester. Liverpool Birmingham, and Dublin, which afford the purest supplies in the world. The Board is making an adventurous departure in adopting the newly invented Diesel engines, in place of the steam engines in common use for pumping sewerage. The Diesel engines, which were first used eight years ago by Messrs F. Krupp, of Essen, are worked by the combustion of gasiflied oil fuel, and are therefore internal combustion heat engines. The engines ordered by the Drainage Board are the first of the kind to be shipped for the Southern Hemisphere. The plant ordered consists of two 200-horse-power Diesel engines driving three 27-inch centrifugal pumps, each capable of raising over 17,000,000 gallons per diem; and the combined capacities of the whole plant for storm water discharge is 50,000,000 gallons per diem.