FERC No. 1889
Key features of the Turners Falls Hydroelectric Project are the Turners Falls Dam and associated impoundment, a gatehouse, a power canal, two generating stations (Station No. 1 and Cabot Station), and a bypassed reach. Each feature is described below.
Turners Falls Dam
The Turners Falls Dam consists of two individual concrete gravity dams, referred to as the Gill Dam and Montague Dam, which are connected by a natural rock island known as Great Island. The 630-foot-long Montague Dam is founded on bedrock and connects Great Island to the west bank of the Connecticut River. It includes four bascule type gates and a fixed crest section which is normally not overflowed. When fully upright, the top of the bascule gates are at elevation 185.5 feet mean sea level (msl).
The 493-foot-long Gill Dam connects Great Island to the east bank of the Connecticut River, and includes three tainter spillway gates. When closed, the elevation atop the tainter gates is at elevation 185.5 feet msl.
Turners Falls Impoundment
Turners Falls Impoundment extends upstream approximately 20 miles to the base of TransCanada’s Vernon Dam in Vernon, VT. To provide storage capacity for the Northfield Mountain Pumped Storage Project, the Turners Falls Impoundment elevation may vary, per the current FERC license, from a minimum elevation of 176.0 feet msl to a maximum elevation of 185.0 feet msl; a 9 foot fluctuation as measured at the dam. The Turners Falls Impoundment is not a level pool; rather, it is sloped between Turners Falls Dam and Vernon Dam. The slope of the water surface profile steepens as the magnitude of flow increases.
The gatehouse is located on the west of the Connecticut River. It forms the abutment for connecting the Montague spillway with the shoreline and is equipped with headgates controlling flow from the Turners Falls Impoundment to the power canal. The gatehouse houses 14 gates controlling flow to the power canal.
The power canal is approximately 2.1 miles long and ranges in width from approximately 920 feet in the Cabot forebay (downstream end of canal) to 120 feet in the canal proper. The power canal has a design capacity of approximately 18,000 cubic feet per second (cfs).
Station No. 1 and Cabot Station
FirstLight has two hydroelectric facilities located on the power canal, including Station No. 1 and Cabot Station. Station No. 1 operates under a gross head of approximately 43.7 feet, and has an approximate total electrical capacity and hydraulic capacity of 5,693 kilowatts (kW) and 2,210 cfs, respectively. Cabot Station is located at the downstream terminus of the power canal. The powerhouse houses six vertical, Francis type, single runner turbines. Cabot Station has a total station electrical capacity of 62.016 megawatts (MW) or roughly 10.336 MW/unit. The station has a total hydraulic capacity of approximately 13,728 cfs or roughly 2,288 cfs/unit.
The canal bypasses approximately 2.7 miles of the Connecticut River. Fall River, located near the head of the bypass channel, discharges into the bypass reach. Station No. 1 discharges into the bypass reach approximately 0.9 miles downstream of the Turners Falls Dam.
Fish Passage Facilities
The Turner Falls Project is equipped with three upstream fish passage facilities, including (in order from downstream to upstream): the Cabot fishway, the Spillway fishway, and the Gatehouse fishway. Each of these facilities is associated with the Turners Falls Hydroelectric Project.
Fish passing through the Cabot fishway enter the power canal; from there, they swim 2.1 miles upstream to the Gatehouse fishway. Fish bypassing the Cabot fishway move upstream via the bypassed reach where they will ultimately encounter the Turners Falls Dam. Fish arriving there are passed upstream via the Spillway fishway into the upper terminus of the power canal, below the gatehouse. Here, they rejoin fish that have passed to this point via the Cabot Ladder. From the upstream end of the power canal, all fish are passed above the gatehouse via the Gatehouse fishway. The Gatehouse fishway delivers fish into the Turners Falls Impoundment to continue their journey up the Connecticut River.
The Connecticut River Atlantic Salmon Commission (CRASC) establishes an annual schedule for the operation of upstream fish passage facilities at the Connecticut River dams. The schedules are based on the projected movement of migratory fish and may be adjusted in season to address actual observations.
Downstream Fish Passage Facilities
The downstream fish passage facilities are located at Cabot Station, at the downstream terminus of the power canal. Assuming no spill is occurring at Turners Falls Dam, fish moving downstream pass through the gatehouse (which has no racks) and into the power canal. Downstream fish passage facilities at Cabot Station consist of: reduced bar-spacing in the upper section of the intake racks; a broad-crested weir developed specifically to enhance fish passage at the log sluice; the log sluice itself, which has been resurfaced to provide a safe passage route; above-water lighting; and a sampling facility in the sluices.
In addition to downstream passage facilities at Cabot Station, a guide net is installed below the Northfield Mountain Pumped Storage Project tailrace to reduce entrainment of emigrating salmon smolt into the Northfield intakes during pumping operation. The CRASC also establishes an annual schedule for the operation of downstream fish passage facilities at the Connecticut River dams.
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