Island Filtration Plant
There have been four water facilities of different types constructed on Toronto Island on the same site.
The first of these consisted of an infiltration basin constructed in 1874. It was about 823 metres long (perimeter 1932 metres) and 4.3 metres deep with a filtration capacity of 20 500 cubic metres per day and a volume of 60 500 cubic metres. The basin was connected to the John Street Pumping Station 3.2 kilometres away on the city side of Toronto Bay by means of a 1200 millimetre wooden pipe across the Island and a 900 millimetre cast iron pipe across the Harbour. Use of this basin was discontinued after about five years when its capacity was reduced by silting and became too small for the increasing population.
The second plant was a 182 000 cubic metre per day slow sand filtration plant constructed from 1909 to 1911. This plant continued in service until 1968 and was maintained ready for operation until 1975. Currently, two of its filter basins are used for lagooning filter backwash wastes.
The third plant, a Ver Mehr mechanical drifting sand filter plant with a capacity of 273 000 cubic metres per day, was constructed during the First World War and went into service in December, 1917. This plant continued in use for 60 years and was kept ready for operation until 1981.
The present plant, a modern, high rate, direct filtration plant, was constructed from 1975 to 1977 and placed in service in April, 1977. It was designed to supply 273 000 cubic metres per day with a design filter rate of 11.7 cubic metres per hour, but included hydraulic spaces for high rating to double that capacity. The plant has been successfully operated at a capacity of 409 000 cubic metres per day. This resulted in decommissioning of the drifting sand plant in 1981 and establishment of a 409 000 cubic metre per day nominal capacity.
In 1966 the Island plant was changed from a year-round operation to summer only peak control and operates from about May 1 to October 1 each year.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.