Project Description

On the Presumpscot River there are eight hydroelectric facilities between Sebago Lake and the Atlantic Ocean in Portland, Maine.  The Gambo project is the fourth hydro project downstream of the Sebago Lake outlet.

The Gambo Project has been used almost continuously for hydroelectric generation since its original construction (c. 1850). The site was originally developed as a sawmill in the 18th century by Jonathan Lovett, and was later part of the Oriental Gun Powder Mill until c. 1904. The current dam was built in 1912 by E.I. duPont de Nemours Company, which used the site to manufacture wood flour for dynamite until 1950. Between 1950 and 1960, the site was owned by the Town of Windham, U.S. Small Business Administration, and the Commercial Chemical Corp; but was not known to have been used. In 1960, Mr. Lawrence Keddy began to use the site to provide power to his Little Falls steel mill. He also sold some of the power to Central Maine Power Company (CMP). S.D. Warren (later renamed Sappi North America, Inc.) purchased the Gambo Project from the Commercial Chemical Corporation on October 18, 1974 and the John Phinney property on the Gorham side of the River in 1978.

Project Name Gambo
LIHI Certificate Number 139
LIHI Effective and
Expiration Dates
 September 5, 2017 – September 4, 2022
Owner Sappi North America, Inc.
State Maine
Location Windham and Gorham, Cumberland Counties
River mile 18.6
Presumpscot River
Installed Capacity 1.9 MW
Average Annual Generation 7,000 MWH
Facility Type run-of-river
FERC No. 2931

The Gambo Project operates in a run-of-river mode and consists of the following features:

  • a 300-foot-long, 24-foot-high reinforced concrete dam, consisting of a 250-foot-long overflow section with a height of 133.8 feet USGS; one-foot-four-inch-high wooden flashboards on the spillway section of the dam;
  • a 50-foot-long canal intake structure, and a sluice gate structure;
  • a 737-foot-long, and 15-foot-deep concrete-lined intake canal;
  • a 47-foot-wide by 78-foot-long reinforced concrete and brick powerhouse containing two vertical Francis turbines direct-connected to generators, each with an installed capacity of 950 kW for a total rated generating capacity of 1,900 kW;
  • a 300-foot-long, free-flowing bypass reach between the dam and powerhouse tailwaters;
  • a 3.3-mile-long impoundment extending from the Gambo Project dam upstream to the tailwaters of the Dundee Project, with a surface area of approximately 151 acres and a normal surface elevation of 135.13 feet USGS.
  • an 8-mile-long, 11-kV transmission line;
  • an upstream passage for American eel; and
  • a reported average annual flow at the dam of 760 cubic feet per second (cfs).

Gambo Powerhouse

Gambo Dam and Spillway

Certification History

March 5, 2018 – The 30-day appeal window closed for the preliminary certification decision of the Gambo Hydroelectric Project closed on March 1, 2018 with no appeals to the decision received. The decision is therefore final and Dundee is LIHI Certificate #138. The Certificate term will be September 5, 2017 – September 4, 2022.

January 30, 2018 – On January 24, 2018, the Low Impact Hydropower Institute (LIHI) preliminarily approved Low Impact Certification for the Gambo project with the following conditions:

Condition 1. The Owner shall notify LIHI when the modifications to the Project to improve upstream eel passage are completed and submit copies of MDMR and USFWS comments related to whether these modifications are sufficient, and/or if additional effectiveness testing is required to confirm that eels are safely passing upstream at the Project.  If additional testing is required, the schedule and final results along with agency comments on the report, agency recommendations for modifications, and plans and schedule for any needed modifications to shall also be provided to LIHI.

Condition 2.  The Owner shall update LIHI on the following activities in the annual LIHI compliance statement:

  1. The status of Condition 1 above.
  2. The status of upstream and downstream anadromous fish passage activities at the Project and at the Saccarappa Project. The updates should include summaries of agency and stakeholder consultation and recommendations made, any changes in the fish passage plans from those described in the LIHI application, and any changes in passage requirements or the timing of implementation at both Projects.  LIHI reserves the right to suspend its certification if the agencies do not determine that safe passage at the Project is being provided and that such passage needs have not been waived.
  3. A summary of any consultation with MIF&W and/or USFWS related to state or federally listed species identified as possibly occurring at the site that could be impacted by construction activities or non-routine operations or maintenance activities. This would also include impoundment drawdowns that would expose a significant portion of the river bottom, among other non-routine activities. A summary of the relevant triggering activities and the measures implemented during the year to protect such species shall also be provided.

The reviewer’s report is attached at the bottom of this page. This decision is preliminary pending the 30-day appeal window. Only those who commented in the initial application 60-day comment period are eligible to file an appeal. Such appeal needs to include an explanation as to how the project does not meet the LIHI criteria. Appeal requests can be submitted to comments@lowimpacthydro.orgRequests must be received by 5:00 pm Eastern time March 1, 2018.

September 7, 2017 – On September 7, 2017, the Low Impact Hydropower Institute (LIHI) received a complete application from S.D. Warren Company d/b/a Sappi North America for the Low Impact Certification of the Gambo Hydroelectric Project, FERC No. P-2931, located on the Presumpscot River in Maine.

LIHI is seeking comment on the Gambo application for certification. 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 comments@lowimpacthydro.org with “Gambo Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 329 Massachusetts Avenue, Suite 2, Lexington, MA 02420.  Comments must be received at the Institute on or before 5 pm Eastern time on November 7, 2017 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.


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