During times of low electric demand, six turbines pump water from Lake Michigan 362 feet uphill to the 27-billion-gallon reservoir, where it is stored. When electrical demand is high, water is released from the reservoir, and it flows back downhill and turns the turbines to generate electricity. Unfortunately, this method of electric generation has a very serious impact on Great Lakes fish.

As water is pumped out of Lake Michigan, fish are pulled in this water. Fish that travel through the pumps to the reservoir are subjected to rapid acceleration and deceleration as well as pressure changes and contact with the turbine blades. Those that survive the passage to the reservoir are subjected to the same conditions on the return to Lake Michigan. A significant number of fish that pass through the pump/turbines are killed or suffer injuries that result in delayed mortality.