The station was originally built in 1928, both turbine runners were replaced in the 1960’s, both generators were rewound in the mid 1980’s, and the main transformer and associated electrical equipment were replaced in 2006. One runner replaced in 2016. The station has an installed capacity of 9.5 MW at a gross head of 24.9 meters.

Located 120 km east of the town of Fort Frances, the station is a run-of-river plant. Operation pertaining to levels and flow are governed under the Seine River Water Management Plan. The plan specifies the rule curve elevations and flow requirements for the Seine River, including storage dam operations at Raft Lake which is the primary storage point on the river. The station is subject to a minimum flow of 2.5 m³/s at all times, and an instantaneous minimum flow of 10 m³/s during the period from April 15th to June 15th.

The Calm Lake station consists of a powerhouse and a concrete gravity section containing the spillway. Each generating unit is provided with two head gates, which are operated by an electrical screw hoist. There is a sluice gate on the spillway, fifteen bays of stop logs on the spillway, and a hydraulic log lifter for log handling. The head pond operates between the minimum elevation of 382.2 meters and maximum elevation of 382.75 meters.

Calm Lake is connected to the IESO grid on circuit M1S.