It utilizes three large pipes have been run 5 kilometres (3 miles) into Lake Ontario, to a depth of 83 metres. The water at that depth is a constant 4°C, its temperature protected by a layer of water above it, called a thermocline. The water is piped to a filtration plant and then to a heat-transfer station on the lakeside. Here the chill is “transferred” to another closed loop, consisting of smaller pipes that supply the towers of the city's financial district. Built at a cost of C$230m ($200m) over four years, the system is run by the Enwave Energy Corporation.