LIHI Certificate #92 - Pierce Mills Hydropower Project, Vermont
The Pierce Mills Project is the most upstream of the four Projects, located at river mile 15.2. It was built in 1917-1919 by the Twin State Gas & Electric Company. The powerhouse was completely destroyed in the flood of 1927, although the concrete dam was largely undamaged. The plant was rebuilt in 1928 utilizing portions of the earlier substructure.
The Project impounds a 24.7-acre reservoir that extends 1.25 miles upstream to the Great Falls Dam with a water surface elevation at 605.0 feet msl and 24.7 acre-feet of usable storage. The concrete gravity dam is 93 feet long by18 feet high, with a crest elevation of 603.5 feet mean sea level (msl). The dam is topped with 18-inch flashboards. A 37-foot-long intake structure forms the left abutment, with a manually operated bulkhead gate and rashrack. A 6-foot diameter, 246 foot-long wood stave conveys flows from the dam to the powerhouse with a drop in elevation of 18 feet. The powerhouse contains one vertical shaft turbine rated at 271 kilowatts (kW) and a generator rated at 250 kW, along with appurtenant equipment. The Project also includes a substation, and a downstream fish passage facility located in the spillway adjacent to the intake. The bypassed reach at Pierce Mills is about 330 feet long. The Project has a hydraulic range of 90 to 200 cubic feet per second (cfs) and an average annual generation of about 1,337 megawatt-hours (MWh).
|Project Name||Pierce Mills|
|LIHI Certificate No.||92|
|LIHI Certificate Term||February 6, 2017 - February 5, 2025|
|Owner||Green Mountain Power Corporation|
|Location||Located at river mile 15.2 on the Passumpsic River, a tributary of the Connecticut River; the most upstream of the Passumpsic River Projects.|
|Installed Capacity||250 kW|
|Average Annual Generation||1,133 MWh|
|FERC No.||P-2396 issued 1994, expires 2034|