Tannery Pond Hydro

The facility is licensed by the Federal Energy Regulatory Commission. It is known as Tannery Pond Hydro, FERC L.P. No. 8895-MA . The project is located on the Millers River in Winchendon, Massachusetts. It consists of an existing 248 foot long by 10 foot high, concrete capped, masonry gravity dam founded on ledge. The crest of the spillway is at 936.95 NGVD. The left, southerly abutment consists of a concrete, monolith pinned to the ledge. A series of cast iron brackets spaced at 6 foot intervals supports 30 inches of flashboards and an access catwalk. The top of the flashboards is at 939.45 NGVD. The right, northerly abutment contains a 10 foot wide by 8 foot tall flood gate. The gate is operated vertically by a back geared Rodney Hunt gate stand. The dam impounds Tannery Pond which has a surface area of 9 acres with a storage capacity of 47 acre-feet and a normal surface water elevation of 939.45 feet NGVD.

A reinforced concrete, 34 foot long by 16 foot wide powerhouse is located adjacent to the northerly dam abutment. A short forebay with a stoplog structure and trash racks leads into the waterbox. The waterbox contains two hydraulic turbines, which discharge vertically beneath the powerhouse. A 25 foot wide by 425 foot long tailrace conveys the water back to the Millers River. The powerhouse is interconnected to the 13,800 volt, Massachusetts Electric Company's distribution line on River Road. A short, 125 foot long, transmission line runs from the road to a wooden pole adjacent to the power house. An air break switch on top of the pole controls the flow of power from the arial line to a 6 inch conduit which is attached to the pole and is buried beneath the parking lot. The conduit then runs to a 13,800 to 480 volt station transformer.

The powerhouse contains two turbine/generator units with a total installed capacity of 189 kilowatts.

A) Unit Number One: Rodney Hunt Francis turbine.

It is a model Type 80, Hi Test unit with airfoil adjustable wicket gates, at 14 feet it produces 142 horsepower, Rodney Hunt Francis turbine

It is a model Type 80, Hi Test unit with airfoil adjustable wicket gates, at 14 feet it produces 142 horsepower, rotates at 184 rpm, has a hydraulic capacity of 105 cfs and will make approximately 97 kilowatts at the generator leads.

B) Turbine Two- Leroy Somers Tube turbine

It is a model Hi H automatically adjustable semi Kaplan which at 14 feet net head produces a maximum output of 96 kilowatts while consuming 122 cfs and can regulate down to a minimum of 31.5 kilowatts while consuming 49.4 cfs.

The station hydraulic capacity would be 227 cfs which occurs approximately 15 % of the time.

The lead machine would be the Semi Kaplan which would operate between 49.4 cfs which occurs approximately 60 % of the time and 122 cfs which occurs 22 % of the time.

The lag machine would be the Francis machine which would operate up to the combined hydraulic capacity of 227 cfs at 15 % of the time.

This plant is currently interconnected with the Massachusetts Electric Company. An interconnection study was conducted by Mas. Electric and the metering and telephone poles were installed and paid for by French River Land Company. The metering and protective relays have been calibrated every year since the date of installation.

Tannery Pond Hydro was re-activated in the spring of 2004. The basic equipment was installed in 1998 but the site was never completed for commercial operation. Celeste, Will, Warren and Bill Fay aligned the generator and gearbox, installed a tachometer controlled relay, a disc brake on the high speed generator shaft, debugged the control system and commenced operations in late May of 2004, just in time to miss the Spring runoff. Bill Munch designed the original control package and did much of the work of de-bugging it.

Will Fay inspecting the new disc brake on Unit One. Note Woodward governor and pump in background.

Close up of the new disc brake

Installation of 22,500 volt air break switch.

Bad picture of welding on top of 40 foot pole.

Overview of Unit One. Note protective relays, Minco temperature relay and tachometer relay in left cabinet. Large fan was used to cool the gearbox during the summer months.

Unit Two ready to be lowered through its cylinder gate down onto its seat.

Send mail to: cfay@frenchriverland.com with questions or comments about this web site.
Last modified: 10/06/08