LIHI Pending Application - Passumpsic River Hydroelectric Projects(FERC Nos. 2396, 2397, 2399, and 2400)
Central Vermont Public Service (CVPS) Applies for LIHI Certification for Passumpsic Projects
Arnold Falls Dam
Portland, Maine (February 6, 2012) – The Low Impact Hydropower Institute (LIHI) announced today that Central Vermont Public Service (“CVPS” or“Applicant”) has submitted an application for certification of the Passumpsic River Hydroelectric Projects. CVPS owns four FERC-Licensed Projects on the Passumpsic River, a tributary of the Connecticut River. Maps and figures in the Applicant’s LIHI filing show the locations of the Pierce Mills (P-2396), Arnold Falls (P2399), and Gage (P-2397) Projects in the Town of St. Johnsbury, and the Passumpsic (P-2400) Project in the Town of Barnet. All facilities are located in Caledonia County, Vermont. All Projects were most recently licensed simultaneously in 1994, and are operated in run-of-river mode.
Pierce Mills Powerhouse
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 verticalshaft 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).
Arnold Falls Powerhouse
The Arnold Falls Project is located approximately 5.5 miles downstream of Pierce Mills, at river mile 9.7. It was built in 1928 by the Twin State Gas & Electric Company following the 1927 flood which did extensive damage to a "small and old station" on the north bank of the river. The falls bear the surname of Dr. Jonathan Arnold, an early settler and entrepreneur who constructed the first sawmill there in 1787 and a gristmill the following year. The Project impounds a 7.2-acre reservoir that extends about 2,200 feet upstream with a water surface elevation of 574.7 feet msl and about 10.8 acre-feet of usable storage. In 2009 the existing timber crib dams were abandoned in place and replaced with a reinforced concrete gravity dam immediately downstream of the timber crib dams.
The North Dam is 180 feet long by 18 feet high, with a dam crest elevation of 573.00 feet msl. It is topped with 18-inch hinged steel flashboards. The South Dam is 65 feet long by 15 feet high, with a crest elevation of 572.0 feet msl, topped with an inflatable flashboard system. The intake is 20 feet wide with trashracks and a manually operated bulkhead gate.
The powerhouse contains one vertical shaft turbine rated at 335 kW and a generator rated at 350 kW. A substation is located adjacent to the intake. The downstream fish passage facility is located in the sluiceway of the spillway adjacent to the intake. The bypassed reach is about 300 feet long. The project has a hydraulic range of 150 to 262 cfs and an average annual generation of about 1,274 MWh.
Gage Powerhouse
The Gage Project is located approximately 2.5 miles downstream of Arnold Falls at river mile 7.2. It was built in 1919-1920 by the Twin state Gas & Electric Company. The dam was destroyed in the flood of 1927, although the powerhouse was largely undamaged. A concrete dam was constructed in 1929. The facility is significant because it is among the very few genuinely low head stations featuring an open channel and generating units in an open pit setting. The powerhouse is also among the limited number of such buildings constructed entirely of steel and concrete, without the brick facade typical of the 1920's powerhouses. The remains of the first hydroelectric station in St. Johnsbury, reportedly built in 1898, are tied into the north abutment of the dam and support the cableway tower.
The Project impounds a 15.2-acre reservoir extending 3,400 feet upstream with a water surface elevation of 539.9 feet msl and 13.8 acre-feet of usable storage. The concrete gravity dam consists of a three sections: (1) a north section which is 176 feet long by maximum height of 13 feet with a crest elevation of 534.2 feet msl and topped with 6-foot-high flashboards; (2) a center section 30 feet long, with a crest elevation of 542.1 feet msl; and (3) a south section which is 43 feet long by 18 feet high with a crest elevation of 538.9 feet msl and a 6 foot wide sluice topped with 1-foot flashboards. The dam is equipped with a 51-foot wide headgate structure with four headgates.
The power canal is 90 feet long by 44 feet wide by 16 feet deep and conveys flow to the powerhouse via an integral intake with an inclined trashrack. The powerhouse contains two vertical shaft turbines rated at 365 kW (Unit 1) and 522 kW (Unit 2), and generators rated at 300 kW (Unit 1) and 400 kW (Unit 2, along with appurtenant structures. A substation is situated adjacent to the power canal. The downstream fish passage facility consists of a sluiceway in the spillway adjacent to the canal headworks.
The bypassed reach at Gage includes a 2-acre plunge pool and about 120 feet of riffle habitat. The project has a hydraulic range of 170 to 700 cfs and an average annual generation of about 3,040 MWh.
The Passumpsic Project is the furthest downstream of the four CVPS Projects on the Passumpsic River. It is located approximately 1.7 miles downstream of the Gage Project, at river mile 5.5. It was built in 1905-1906 for the St. Johnsbury Electric Company. The powerhouse was completely destroyed in the flood of 1927. Portions of its foundation and those of its associated power canal remain buried on the other side of the existing canal. The plant was rebuilt in 1929 in the location of the Chase leatherboard mill water wheel, which was also destroyed in the flood. The building behind the powerhouse (not owned by CVPS) is the remainder of the former leatherboard mill.
The Project impounds an 18.3-acre reservoir which extends 4,600 feet upstream with a water surface elevation of 521.0 feet msl and a usable storage of 18.4 acre-feet. The concrete gravity dam consists of two sections: (1) a south section 122 feet long by maximum height of 10 feet, with a crest elevation of 519.98 feet msl and topped with 1-foot-high flashboards; and (2) a north section 126 feet long by maximum height of 10 feet, with a crest elevation of 519.98 feet msl topped with 1-foot flashboards. The dam is equipped with a 27-foot wide headgate structure with two gates.
The power canal conveys flow to the powerhouse via an integral intake with an inclined trashrack. The canal is 19 to 22 feet wide and 87 feet long. There is also a sluice and a 24-foot long overflow spillway.
The powerhouse contains one vertical shaft turbine rated at 708 kW and a generator rated at 700kW, as well as appurtenant equipment. A substation is located adjacent to the power canal. The downstream fish passage facility consists of a sluiceway in the spillway adjacent to the canal headworks. The bypassed reach is about 350 feet long. The project has a hydraulic range of 195 to 460 cfs and an average annual generation of about 2,349 MWh.
Passumpsic Dam
Public Comments
We encourage public comments on this application. Specifically, we are interested in knowing whether you think this Project meets our LIHI criteria. Review the program and criteria in greater detail and then review the Project’s application. Comments that are directly tied to specific LIHI criteria (flows, water quality, fish passage, etc) will be most helpful, but all comments will be considered. Comments may be submitted to the Institute by e-mail at info@lowimpacthydro.org; or by mail addressed to LIHI, 34 Providence Street, Portland, ME, 04103. Comments must be received at the Institute on or before April 6, 2012 Eastern time to be considered. All comments will be posted to the web site and the applicant will have an opportunity to respond. Any response will also be posted.