Woronoco Hydro LLC

Woronoco Hydro's forebay and concrete ogee-shaped south dam

The Westfield River has a drainage area of 346 square miles when its is diverted into a 550 foot long penstock and dropped 57.4 feet to the Woronoco power station.  Swift River and Hobbs Contracting purchased the land and facilities from International Paper Co in June 2001. However, hydro was first developed in the early 1870's at Salmon Falls located 5 miles upstream of Westfield and 2 miles below Russell, Massachusetts. 

The Woronoco dam is a low hazard dam because it is anchored on the top of a large rock outcropping that naturally formed Salmon Falls.  The structure of the North dam is only 15 feet high at its highest point but forms a dam approximately 25 feet high and 307 feet long. A south dam (constructed in 1950) is also a concrete structure, approximately 25 feet high and 315 feet long. The dam crest is equipped with pin sockets to support 30-inch flashboards.  IPC did not use the flashboards in recent years because of limited repair budget and inexperienced operators at the hydro plant.  So, IPC dropped flashboards from the project when it renewed the FERC license.  However, Woronoco Hydro intends one day to amend the FERC license to install a flap gate in place of the pin-boards on the dam crest. This design will improve headpond regulation by deflating the rubber dam to lower the headpond impoundment when required to pass floods. Compressed air will raise the rubber dam during normal flows to the historic elevation required to sustain upstream wetland habitat.

South Dam viewed while impoundment was drawn down in 2002

An interim downstream fish passage chute was constructed in 2000 adjacent to the intake trashrack house at the downstream end of the dam. The passage is located in an existing sluice gate previously used to pass ice and trash.  The gatehouse is approximately 40 feet wide enclosing two trash rakes.  The large horizontal timber gate with a hand-operated rack and pinion gear is no longer safe and should be replaced.  Recently SRHOCO repaired existing trashracks, replaced wooden beams with massive steel beams that support the racks, automated operations with a PLC and has begun rehabbing and re-powering two 450 kW Francis horizontal turbine-generator sets.

Bottom of Salmon Falls on the Westfield River from bridge above Woronoco powerhouse

In the early 1880's Horace A. Moses acquired a controlling interest in the fine writing paper mill of the Vernon Brothers.  Five water wheels were operating at Salmon Falls until a powerhouse for generation of electricity was built in 1916 to supply both Mill 1 and 2 with power most of the year.  Moses formed the Strathmore Paper Company in 1911.  Moses used the hydro to power "Strathmore Town," a village housing all the employees and all the mill operations.

Woronoco powerhouse with bridge over the lower Salmon Falls visible on right

There is a single horizontal Francis turbine with a 1,900 KW Westinghouse generator operating full time at Woronoco requiring a design flow of 450 cfs at a net head of 55.4 feet.  Two 450 KW Leffel camelback turbines (with new runners in 1983) were shutdown more than 20 years ago because of leaks in their pressure cases and damage to one runner.  Woronoco's FERC license renewal was issued in May 2002 for 2,700 KW to encourage repowering of T-1 and T-2.

T-3's 1,900 kW generator in cage and exciter for 450 kW generator on left

    Since T-3, the 1,900 kW turbine, uses less than the Westfield River's mean flow, the owners plan to expand capacity by rehabilitation of the two 450 KW units, restoration of flashboards and construction of a new substation.  The previous FERC license included 30-inch flashboards on the dam and a lower tailwater elevation in the powerhouse pool.  Woronoco will seek agency agreement to amend its FERC license to restore the headpond elevation to its original level by installing a rubber flap gate on the spillway section of the dam.  Woronoco also owns a 1,100 kW Kaplan turbine that one day might be used to optimize capacity at between 3,450-3,900 KW.

Historic operations of the site reflects the secondary nature of hydro power production to the Strathmore paper mill during its years of decline.  In the monthly production history recorded below, one can see that the period from 1984 to 1993 is when there was a breakdown lasting from July 1989 until May 1990 during which time the penstock was relined with shotcrete and the generating equipment was reconditioned.  During the following years, energy prices were too low to justify repairing the two smaller turbines.  Then, in June 1993, T-3l was damaged beyond repair.  At that time, new runners were installed to rehab the damaged turbine.  It was nearly two years later when the more efficient equipment was put back on line. From May 1995 until August 1997 the new stainless steel runners plus high flow conditions caused output to jump, even though IPC abandoned the 2 smaller runners.  Finally, IPC closed its Woronoco paper mill.  Hydro generation was not restored until September 2000 when SRHOCO start T-3.  IPC generation history was as follows:

Two Rounds of Re-construction

When purchased in 2001, only one of three turbines was operational. So, major rehab of the station began in late 2001 and T-3 returned to full time operation in February 2002 when construction of a new intake structure, stoplog gates and transducers for the pond level control system were installed.  The hydro served the electrical load of Mill #2 across the Westfield River and surplus energy was sold to WMECO at ISO market clearing prices. However, the load of Mill #2 was not large enough to take more than 10 to 15% of the station output, and it was intermittent since the plant did not operate more than one shift and closed on weekends.  The hydro had to sell its output at higher prices or find a market for its renewable energy certificates (RECs) it was to continue its modernization.

Woronoco forebay and granite dam, visible on right

Fortunately, the Massachusetts Technology Collaborative (MTC) solicited for green energy projects willing to sign 10-year contracts to sell RECs.  Woronoco Hydro proposed a program to restore the 2 low flow turbines in order to stabilize green energy sales over 10 years by a complete rebuild of the Woronoco Hydro facilities, as they were constructed in 1917. The program now underway includes: (a)  reinstallation of flashboards, (b) repowering T-1 and T-2, (c) building new intake gates, (d) an automatic trash rake, (e) a new substation and (f) automation to become a run-or-river project under the terms of its new FERC license..  The result: Woronoco Hydro expects average annual production to increase to 11,075 MWh from the 2000 to 2002 average of 3,463 MWh per year.

 MTC's purchase agreement supports new project financing obtained in November 2005.  So, while Woronoco is looking for a stable long-term contract to sell all of its output, including the generation from the capacity expansion described above, the 10-year REC sales contract secured the financing necessary to refurbish the project.  Woronoco's estimated monthly average production is shown in a Graph in the Woronoco section of Operating Projects. It is also possible that the output of both Indian River and Woronoco could be sold together to a single customer.  For the monthly output of these two projects combined, refer to the graph shown in the section Energy Sales.  The combined output would help to offset the low summer time flows characteristic of the Westfield River.

Installing stoplogs in winter is both a cold and wet job for routine maintenance

Woronoco Hydro is certified by the Connecticut DPUC as a Class 1 REC generator.  This is based on the rehabilitation of T-2 last year and 2006 repowering T-1. plus integration of these smaller units with T-3 under control of a PLC program which will convert Woronoco Hydro from store and release to automatic run-of-river operations as approved by its renewed FERC license. The long-term sale of Class 1 RECs will pay back the financing needed to upgrade and modernize the 90-year old hydro plant.

Example of a section of the 1974 shotcrete lining of penstock to be refurbished in 2006.

Ken Smith, replacing stuffing material in stuffing box to stop water leaks along shaft.

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