the turbines and other equipment required about gallons of cooling water from Lake Ontario per hour. Total construction cost was . The turbine hall was almost 300 metres long and was an impressive sight, viewed from the visitor gallery on the west side of the plant where the offices were located. Units 1–4 had one turbine-generator each. The units (5–8) had two turbine-generators per unit—an arrangement called tandem cross-compound—so there were a total of 12 turbine-generator sets in the turbine hall. At the peak of the R. L. Hearn's operation in the 1960s the station employed up to 600 people. Many Ontario Hydro (later Ontario Power Generation) operators, maintainers, technicians and professionals began their careers, and were trained at the station and then went on to work at other plants and Ontario's CANDU nuclear stations. The station at first had four smaller chimneys, one for each of the four boilers. The construction of the four units added four more chimneys. The last three were a bit taller than the first five. The eight short chimneys were a source of air pollution in local neighborhoods and downtown Toronto and also fly ash and other particulates. The station contributed to Toronto's smog problem. The eight chimneys were demolished and electrostatic precipitators were added for the units when the large smokestack was built. The new single tall smokestack was built in response to pressure to reduce smog in Toronto by the emerging environmental movement in the late 1960s. It stands 215 metres tall and was one of the tallest in the world, costing when it was completed in 1971. Air pollution in Toronto from the station was greatly reduced and the area around the plant became known as a good fishing and recreation spot. Conversion to natural gas By the end of 1971, the entire plant was converted to burn natural gas with four units retaining the option to burn coal. In December 1972, Alberta Premier Peter Lougheed called the billion cubic metres of Alberta natural gas the station was burning annually "an appalling waste of natural gas" at the price of about $0.035 per cubic metre, and he charged that Ontario was getting a "cheap ride" at Alberta's expense. The station operated burning natural gas until 1983. Units 1–5 were mothballed between 1978–1979. Conversion to natural gas reduced pollution but increased operating costs and the plant's efficiency was much lower than today's