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The Jackson Mills Project is located on the Nashua River approximately 700-feet downstream from the crossing of Route 3 (Main Street) in Nashua New Hampshire. The area in the vicinity of the project is urban in character and typical of an old New England manufacturing city. The Nashua public library is located on the south bank of the river. The former powerhouse on the north bank currently houses a restaurant, which contains some of the features of the old operation. The new powerhouse was constructed adjacent to the old powerhouse with the turbine inlet located beneath the restaurant.

Project Name Jackson Mills
LIHI Certificate Number 54
LIHI Effective and
Expiration Dates
January 31, 2015
January 31, 2020
Owner City of Nashua, NH
State New Hampshire
Location Located on the Nashua River, approximately 700 feet downstream from the crossing of Route 3 (Main Street) in Nashua, New Hampshire.
Installed Capacity 1.0 MW
Average Annual Generation 4.4 GWh
Facility Type Run-of-river
FERC No. 7590

The land uses along the north side of the river to the east of the restaurant are predominantly industrial and to the west they are commercial. On the south side of the river the land usage to the east of the library is predominantly urban residential with commercial uses lying to the west. Along both banks above and below the dam the vegetation consists of planted ornamentals and those types typical of disturbed ground.

The 180-foot long by 33-foot high dam is a gravity-type masonry structure with that includes an eight foot high pneumatic crest gate and concrete-faced stone gravity-type abutments.   The top eight feet of the dam are a pneumatic crest gate. Upstream and downstream fish passage is provided at the project by an Alaska steep-pass fishway and a stainless steel bypass pipe. The 40-acre impoundment has a normal maximum water surface of 116.6-feet NGVD. The Project operates in a run-of-river mode. The powerhouse which is located at the north dam abutment houses a 1 MW turbine generator.

The Nashua River has a total drainage area of 529 square miles, with 88 square miles being in New Hampshire, and 411 square miles in Massachusetts. The net drainage area available to the Jackson Mills Project is 410 square miles as 119 square miles are intercepted to supply water to the Massachusetts cities of Boston and Worcester.

For thousands of years, the watershed has been used by humans. Today it retains much of its agrarian and early industrial past while actively participating in the high technology economy of the late twentieth century. The watershed’s classic New England villages now shelter those who create our current age, while its waters, wetlands, and forests still shelter many of the species that have been here since the retreat of the glaciers.

Thirty years ago the rivers of this watershed were polluted by industrial and residential discharges. The Nashua’s restoration has been a model of how communities can recover a natural resource.

The facility is operated as a fully automated run of river project. At times of non-generation, the project is licensed to release an outflow equal to an instantaneous minimum of 207 cfs which is .50 cfs for the 414 square mile drainage are above the project site. When inflows fall below 207 cfs, inflow is equal to outflow.

Construction of the Jackson Mills Dam was completed in 1920. The dam is designed as a gravity-type stone masonry spillway, with a concrete cap and a concrete extension and concrete-faced stone gravity-type abutments. The height of the dam is 33 feet and the length is 180 feet. The crest elevation is 115.6 feet and the project is run with one-foot flashboards for a total hydraulic elevation of 116.6 feet.

A semi-Kaplan Turbelec turbine is installed in the powerhouse. The generating unit consists of one single-regulated propeller-type turbine. The installed capacity of the unit is 1,000 kW.

Certification History

August 19, 2016:  On July 18, 2016, LIHI issued a Preliminary Certification Decision that the Jackson Mills Hydroelectric Project (FERC No. P-7590) continues to satisfy the LIHI Certification Criteria.  Notice of the preliminary decision to certify was posted on the Institute’s website and sent to the New Hampshire stakeholder email distribution list on July 19, 2016.  LIHI provided a 30-day appeal period for commenters to request an appeal of the preliminary decision. No requests for appeal were received within the  30-day period.

The Jackson Mills Hydroelectric project is now deemed certified by LIHI.  The effective certification date for the Jackson Mills Project is January 31, 2015 for a five (5) year term, which will expire on January 31, 2020.

This Final Certification Decision includes two facility-specific conditions, as follows:

  • Condition 1.  The Owner shall complete the water quality sampling at the facility that is being conducted in concert with NHDES. All results from this monitoring program should be forwarded to the LIHI upon its completion no later 120 days after LIHI certification. The owner shall also send LIHI documentation of NHDES’ interpretation of the results.  If the water quality results continue to indicate, as they did in 2010, that operation and maintenance of the Project is not a contributing cause to any violations of any applicable water standards, this condition is satisfied. If water quality issues are discovered, the Owner shall provide LIHI with a resolution plan reviewed and approved by the USFWS and the NHDES.
  • Condition 2.  The Owner has been proactively working with the USFWS and NHDFG in meeting their upstream and downstream fish passage concerns. Site visits, meetings and agreements with State agencies have occurred in recent months.  The owner shall continue these agency interactions and, no later than 45 days after LIHI certification, send LIHI documentation verifying FERC’s approval of actions taken since February of 2016.

July 18, 2016: LIHI Executive Director Michael J. Sale, using authority delegated from the LIHI Governing Board, has issued a Preliminary Certification Decision that the Jackson Mills Hydroelectric Project (FERC No. P-7590) satisfies the LIHI Certification Criteria.

As provided for in Section 4.2.5 of the LIHI 2nd Edition, the Preliminary Certification Decision to certify, along with the Application Reviewer’s report and (if prepared) report of the Executive Director, will be posted on the Institute’s Web page for 30 days.  Notice of the posting will be provided to all individuals or organizations that commented on the initial Application Package.

Any Commenter may submit a letter to the Executive Director requesting an appeal within the 30-day period, which ends on August 19, 2016.  The appeal request must state specific reasons why the hydropower facility should have failed one or more criteria.  If an individual or organization did not comment on the initial Application Package, they may not file an appeal.  Further information about the LIHI appeal process is available in the LIHI Handbook, available at http://lowimpacthydro.org/certification-program-html/.

If no appeal is requested within the 30-day period, the Executive Director will issue LIHI Certification for the facility and post a notification of certification on the Institute’s website.  Once final, the effective certification date for the Jackson Mills Project is January 31, 2015 for a five (5) year term, which will expire on January 31, 2020.

October 30, 2015: The Low Impact Hydropower Institute has received a complete application for a new term of Low Impact Certification for the Jackson Mills Hydroelectric project.  The application materials can be found below in the Files section.

The public comment period for this application closed on December 30, 2015.

July 10, 2015: The Jackson Mills Hydroelectric project has been granted an extension of the current certificate term. The new expiration date is December 31, 2015. See ExtensionLetter_20150709 for explanation below.

July 21, 2010: The Jackson Mills Hydroelectric Project has been certified as low impact for a five year term, effective January 31, 2010 and expiring January 31, 2015.

March 31, 2010: The public comment period has been closed.

January 31, 2010: Essex Hydro Associates has submitted an application for certification of the Jackson Mills Hydroelectric Project. A public comment period will remain open for 60 days.


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