Conowingo Hydroelectric Generating Station is a “run of the river” hydro plant operated by Susquehanna Electric Company a subsidiary of Exelon. Located on the Susquehanna River in northern Maryland, Conowingo has been providing electric power to the regional system since 1928. At the time of construction between 1926 and 1928, the Conowingo hydro station was the single largest generating station ever built in one step and used the latest technology, and the largest turbines and generators ever produced.
The original plant had seven turbines providing 252 megawatts (MW) of output. In 1964, an additional four units were constructed which added 260 MW of capacity to the facility bringing the plant capacity to 512 MW. In 2001, Unit 3 overhaul was completed and included turbine replacement and generator upgrades which resulted in an additional 12 MW. A similar overhaul on Unit 1 was completed in May 2002 and on Unit 4 in January 2004 increasing total facility capacity to 548 MW.
Water flow of the Susquehanna River provides the fuel to turn the 11 turbine generators. Because water is used to turn the turbines, Conowingo can be used to "jump start" the electric distribution system in the event of a system failure.
There are 52 crest gates, which act as safety valves when river flows exceed the approximately 85,000 cubic feet per second (CFS) capacity of the generating units. When manually opened, each of the two regulation gates can spill 4,000 CFS and each of the 50 remaining crest gates can spill 16,000 CFS.
The 14 mile long Conowingo Pond behind the dam and the tailrace area provides numerous public recreational facilities and activities including boating, fishing and bird watching. The plant is located about 4 miles upstream of the Chesapeake Bay.