FERC No. 2485
Key features of the Northfield Mountain Pumped Storage Project are the upper reservoir dam, intake channel, powerhouse, and tailrace tunnel.
Upper Reservoir Dam
The crest of the upper reservoir's Main Dam is at elevation 1010 feet msl. There are three dikes known as the North, Northwest, and West Dikes, and are constructed in a similar manner and to the same crest elevation as the Main Dam.
Upper Reservoir Storage Capacity
Per the current FERC license for the Northfield Mountain Pumped Storage Project, the upper reservoir may operate between 1000.5 feet msl and 938 feet msl, which equates to a useable storage capacity of approximately 12,318 acre-feet. The upper reservoir was constructed to accommodate an elevation of 1004.5 feet msl as approved by FERC in 1976. In addition, the reservoir retains useable storage capacity down to elevation 920 feet msl. Located southwest of the upper reservoir is the intake channel that conveys water to the powerhouse.
The underground powerhouse contains four reversible pump/turbines operating at gross heads ranging from 753 to 824.5 feet. The electrical capacities of the units are as follows: Unit 1: 267.9 MW, Unit 2: 291.7 MW, Unit 3: 291.7 MW and Unit 4: 291.7 MW, for a total station nameplate capacity of 1143.0 MW. Historically, the total station capacity was 1,080 MW (270 MW/unit); however, Units 2, 3 and 4 recently underwent efficiency improvements with the replacement of the turbine runner, and rewind of the motor-generator.
When operating in a pumping mode, the approximate hydraulic capacity is 15,200 cfs (3,800 cfs/pump). Alternatively, when operating in a generation mode, the approximate hydraulic capacity is 20,000 cfs (5,000 cfs/turbine).
Water flows between the Powerhouse and the Turners Falls Impoundment via the Tailrace Tunnel.
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