LIHI Certificate #67 - Stillwater Project, Maine

The Stillwater Project is located on the Stillwater Branch of the Penobscot River in the town of Stillwater in Penobscot County, Maine. The project is located at a former logging and milling site, near the City of Old Town. The site was developed into an operating hydroelectric facility in 1902 by the Orono Pulp and Paper Company. A second powerhouse (now Powerhouse A) was constructed on the south side of the dam in 1932, and by 1942, the original powerhouse was abandoned, with the remains still visible on the southeast portion of the dam. Powerhouse B was constructed in 2013. The new downstream fish passage facility and eel ladder began operations in 2014 and 2016, respectively.

The Penobscot River Basin is New England's second largest river system with a drainage area of 8,570 square miles. The Basin includes the East and West Branches of the Penobscot River, the Piscataquis River, the Sebec River, the Pleasant River, the Mattawamkeag River, the Passadumkeag River, the Stillwater Branch and the main stem of the Penobscot River. The project is located just upstream of the Stillwater Branch’s confluence with the main stem of the Penobscot River. The project is one mile upstream of the Orono project (LIHI #66) and several miles downstream of the Gilman Falls Dam (part of the Milford Project, LIHI #113). With removal of the Veazie Dam in November 2013, there are no longer any dams on the Penobscot River downstream of the Orono Project. Removal of the Veazie and Great Works dams was key feature part of the nationally recognized restoration of the Penobscot River.

The Stillwater hydroelectric project is a component of the Penobscot River Restoration Agreement. The overall intent of the Agreement is to provide enhancements to the Penobscot River's environmental resources, and lower and minimize the influence of the Owner's hydroelectric projects on those resources while maintaining the levels of renewable hydropower generation from the river. The restoration effort is one of the largest river restoration projects in our nation's history. In an unprecedented collaboration, a diverse group of stakeholders worked together to restore 11 species of sea-run fish to the Penobscot River, while maintaining energy production.

The Stillwater Project consists of a main concrete gravity dam, about 1,720 feet long, consisting of 13 sections of various heights. Powerhouse A contains four turbine-generator units with a total capacity of 1.929 MW. Powerhouse B contains three turbine-generator units with a total capacity of 2.25 MW. The Stillwater Project has an upstream eel passage channel in the west channel of the 0.6-mile-long bypassed reach at Powerhouse B.

Project Name Stillwater & Stillwater B
LIHI Certificate No. 67
LIHI Certificate Term June 1, 2020 - May 31, 2025
Owner Black Bear Hydro Partners, LLC
State Maine
Location Located at river mile 2.4 on the Stillwater Branch of the Penobscot River in Old Town, Maine.
Installed Capacity Total: 4.179 MW

Powerhouse A: 1.929 MW

Powerhouse B: 2.25 MW

Average Annual Generation Total: 21,153 MWh

Powerhouse A: 9,764 MWh

Powerhouse B: 11,389 MWh

Facility Type Run-of-river
FERC No. P-2712 issued 1998, expires 2048

The project operates in a run-of-river mode and impounds a 191-acre reservoir. The project provides a minimum flow of 70 cfs in the east channel and 1-2 cfs in the west channel. These flows promote bypass reach habitat for migratory and resident species and to enhance upstream eel passage. This flow regime was developed as part of the Settlement Agreement with consultation from the parties involved including Maine Department of Environmental Protection and the Penobscot Indian Nation.

Waters within the project reach are designated Class B, suited for fish propagation and survival, as well as primary contact recreation. The Stillwater Branch of the Penobscot River is not listed for any impairments. The project owner conducted water quality monitoring following the construction of Powerhouse B which indicated that project operations are not adversely impacting water quality in the river reach.

Diadromous species present in the Penobscot River include alewife, Atlantic salmon, American shad, sea lamprey and American eel. Historically, the Penobscot River supported larger runs of American shad, blueback herring, Atlantic sturgeon, shortnose sturgeon, rainbow smelt, tomcod, and striped bass.

There is no upstream passage for anadromous fish since fish collected at the Orono fish lift are trapped and trucked to a location upstream on the mainstem Penobscot Rive. This is because it was determined to be more beneficial for overall fish restoration of the river basin to concentrate the upstream passage in the Penobscot River mainstem.

The Project does have upstream eel passage via a permanent, flow-through concrete channel which is approximately 6 ft wide and 36 ft long with a bristle-brush floor and provides a 1.5-cfs conveyance flow seasonally. It is located at the small bedrock island about mid-river of the spillway, not far from Powerhouse B. The original eel ladder at Powerhouse A was removed when the current one was installed. This upstream eel passage ladder is operated at a minimum from June 1 to August 31 annually.

The Powerhouse A downstream fish bypass facility is located at the left side of the intake (looking downstream) between the forebay wall and 1-inch clear space trashracks and consists of a low-level entrance and a surface entrance both of which flow into a 2.83-foot-wide bypass flume that discharges into the tailwater through a 36-inch-diameter conduit pipe. Subject to suitable river conditions, the Powerhouse A fish bypass is operated from April 1 to December 31 annually, with a total combined flow of 70 cfs. From April 1 to August 15, the flow is provided entirely through the surface entrance. From August 15 to November 15, the flow is balanced with a 40/30 cfs split between the surface entrance and low-level entrance to enhance downstream eel passage. The flow then reverts back to surface entrance flow only from November 15 to December 31 (or ice-in of the headpond).

Powerhouse B also has1-inch clear space angled trashracks to minimize fish entrainment, and a downstream fish passage facility consisting of a combination of an opening in the flashboards in the forebay near the trashracks (for 2 weeks during the downstream Atlantic salmon smolt migration) and a 4-foot-wide fish bypass opening in the forebay wall. A 4-foot square downstream eel passage facility is installed at the base of the trashracks. Both fish bypasses discharge to a plunge pool that empties into a flume which runs along the west side of the powerhouse to the tailrace. Subject to suitable river conditions, the Powerhouse B fish bypass is operated from April 1 to December 31 annually with a total combined flow of 70 cfs. From April 1 to August 15, the flow is provided entirely through the surface entrance. From August 15 to November 15, the flow is balanced with a 40/30 cfs split between the surface entrance and low-level entrance to enhance downstream eel passage; operation of the fish bypass then reverts back to surface entrance flow only from November 15 to December 31 (or ice-in of the headpond). The double-regulated unit nearest the downstream fish passage facility at Powerhouse B is operated as first on and last off to provide attraction to the downstream fish passage.

The project lands consist of 4.7 acres. Lands under project ownership are limited to those housing project facilities, with no control of nearby shoreline. No lands of significant ecological value exist in the limited project boundary.

Threatened or endangered species potentially present in the project vicinity include Atlantic salmon, yellow lampmussel, brook floater, tidewater mucket, Northern long-eared bat, little brown bat, eastern small-footed bat, big brown bat, red bat, hoary bat, silver-haired bat, tri-colored bat, and several rare plant species. Ongoing efforts to restore river connectivity for the listed aquatic species have yet to confirm the effectiveness of the passage facilities at the project. The facilities are not likely to adversely impact these species, but effectiveness of passage is still under review. The mussel species are not expected to be impacted by normal run-of-river operations. Similarly, the bat species are not likely to be impacted as limited shoreline management activities occur. The project has committed to adhering to the US Fish and Wildlife Service 4(d) rule concerning bat roosting site protection should any construction or tree-cutting occur at the site. Consultation with the Maine Natural Areas Program (MNAP) identified the presence of several state plant Species of Special Concern, in the project area. The species has been previously observed in the area and led to the development of a Sensitive Plant Protection Plan. The plan has helped to preserve critical habitat for the species and MNAP has stated it has no concerns related to project impacts on the species.

Consultation with the Maine Historic Preservation Commission has concluded that no historic, archaeological, or cultural resources exist in the project area. The State Historic Preservation Office and Tribal Historic Preservation Office must be consulted should any potential resources be discovered in the area.

Recreational resources at the project include a canoe portage trail. Public access is provided free of charge.


Certification History

April 26, 2021: The decision to recertify the Stillwater Project became final after the close of the appeals period on April 17, 2021 with no valid appeals filed. The Certification term is from June 1, 2020 through May 31, 2025. The certification includes the following conditions:

March 18, 2021: The Low Impact Hydropower Institute (LIHI) has preliminarily approved recertification of the Stillwater Project for a new 5-year terms of Low Impact Certification.

  • Condition 1: The Owner shall provide LIHI a copy of agency correspondence documenting numerical performance standards that the agencies may establish for upstream eel passage and/or downstream diadromous species for the Penobscot River basin that affect the Stillwater Project within 60 days of publication of the standards.
  • Condition 2: If additional upstream fish passage studies are required at this Project, the plan and schedule for implementation, study results, and agency and PIN comments on them shall be provided to LIHI in applicable compliance statements. Should studies occur, LIHI reserves the right to modify this condition based on study results and assessment of the effectiveness of upstream passage.
  • Condition 3: In annual compliance statements, the facility Owner shall notify LIHI of actions implemented, as agreed to by agencies and PIN, that address downstream passage concerns for alosines and American eel:
    1. At the conclusion of meetings held to address the three concerns identified in FERC’s March 6, 2020 letter, the facility Owner shall provide a summary of the final agreements. This shall include a copy of filing(s) made to FERC addressing these concerns, plans and schedules for implementation, results of studies, and agency and PIN comments on them. Should the Owner not agree to make all requested modifications, the rationale for these decisions shall be provided.
    2. Should studies or modifications occur, LIHI reserves the right to modify this condition based on study results and assessment of the effectiveness of downstream passage.
  • Condition 4: In annual compliance statements, the facility Owner shall notify LIHI of actions implemented, as agreed to by agencies and PIN, that address Atlantic salmon downstream passage concerns:
    1. Any changes made in the current Atlantic salmon downstream passage performance standards established by the Biological Opinion or if formal consultation under the Endangered Species Act ahead of the 2023 deadline is needed. The status of actions undertaken as part of any formal consultation shall also be provided.
    2. If during the term of LIHI certification, the current or new performance standards cannot be met within the existing or any new timeframes established by NMFS, LIHI reserves the right to modify, suspend, or revoke the Certificate.
    3. If, prior to expiration of the LIHI Certificate, the facility Owner receives NMFS concurrence that current or revised numerical performance standards for downstream Atlantic salmon have been met, thus confirming safe and effective downstream passage, the facility Owner may request that LIHI consider possible certification extension pursuant to satisfying the PLUS requirements under the Threatened and Endangered Species Criterion.

This decision is preliminary pending the 30-day appeal window. Only those who commented on the initial application during the 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 by email to comments@lowimpacthydro.org with "Stillwater Project” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 1167 Massachusetts Ave, Arlington MA 02476. All requests will be posted to the website. The applicant will have an opportunity to respond and any response will also be posted. Requests must be received by 5 pm Eastern time on April 17, 2021. The full application and reviewer's report is available below.

If no appeal requests are received and the decision becomes final, the Certification term for the Project will be June 1, 2020 through May 31, 2025.

December 1, 2020: The Low Impact Hydropower Institute has received a complete application for Low Impact recertification of the Stillwater Project. The complete application can be found below.

LIHI is seeking public comment on this 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 comments@lowimpacthydro.org with “Stillwater Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 1167 Massachusetts Avenue, Arlington MA 02476. Comments must be received on or before 5 pm Eastern time on January 30, 2021 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.

February 12, 2017:  The 30-day appeal period ended with no appeals received. Therefore, the Stillwater Project LIHI Certification is final and the effective certification date for the Stillwater Project is June 1, 2015 for a five (5) year term, which will expire on June 1, 2020.

January 18, 2017: On January 13, 2017, LIHI Executive Director Shannon Ames, using authority delegated from the LIHI Governing Board, has issued a Preliminary Certification Decision that the Stillwater Hydroelectric Project (FERC No. P-2712) satisfies the LIHI Certification Criteria.  This certification decision is based on authority delegated from the LIHI Governing Board.  The certification includes four facility-specific conditions, as follows:

  • Condition satisfied 2018. Condition 1.  The Owner shall notify LIHI within 30 days of receipt of USFWS certification of the downstream anadromous fishway and of the up and downstream eel passage facilities as required by the Lower Penobscot River Multiparty Settlement Agreement. This certification requires affirmation that a) the facilities were designed and installed as prescribed, b) the facilities are ready for routine operation as evidenced by approved Operating Manuals and electronic data collection systems and c) one year of testing and any required “fine tuning” has been completed. If such USFWS certification is not received by the end of 2017, the Owner shall provide LIHI documentation as to why the certification has not been received and the plan and schedule to remedy deficiencies identified by USFWS preventing such certification.
  • Condition satisfied 2018.Condition 2.  If the requirement for re-initiation of studies of downstream passage of juvenile alosine species occurs within this LIHI certification period, the Owner shall notify LIHI within 60 days of receipt of such study re-initiation. This notification shall include the study schedule including the expected report issuance date. A copy of the final report, along with agency comment as to whether or not the testing results prove that safe downstream passage has been demonstrated, shall be provided to LIHI within 60 days of issuance of the final report.
  • Condition 3.  The Owner shall notify LIHI within 60 days of receipt of USFWS, NMFS and MDMR acknowledgement that the standards specified in the Biological Opinion for safe downstream passage of Atlantic salmon have been met. Currently, effectiveness testing should be completed by 2018 based on the three-year testing requirement, unless advancement to the third level flow enhancement sequence is found to be necessary. Should this occur, the Owner shall notify LIHI in the annual compliance report as to the new date by which such continuing testing to meet passage standards is expected to be completed.
  • Condition satisfied 2019. Condition 4.  The Owner shall provide LIHI a summary of the results of the 2016 quantitative downstream effectiveness study for American eel, along with comments received from USFWS, NMFS and MDMR as to whether or not the testing results prove that safe downstream passage for American eel has been demonstrated. Also, the Owner shall provide a summary of the annual American eel upstream passage results, along with confirmation that any changes to the passage facilities recommended by the resource agencies have been implemented or are scheduled for implementation. The noted upstream and downstream passage results shall be provided within 60 days of report finalization.

As provided for in Section 4.2.5 of the LIHI 2nd Edition Handbook, the Preliminary Certification Decision, 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 begins on January 20, 2017 and ends on February 20, 2017.  The appeal request must state specific reasons why the hydropower facility should have failed one or more criteria.  Only individuals or organizations that commented on the initial Application Package may file an appeal.  Further information about the LIHI appeal process is available in the LIHI Handbook, available at https://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 Stillwater Project is June 1, 2015 for a five (5) year term, which will expire on June 1, 2020.

December 11, 2015: The Low Impact Hydropower Institute has received a complete application for a new term of Low Impact Certification for the Stillwater Hydroelectric project.  The application materials can be found in the Files section below.

The public comment period for this application closed on February 12, 2016.

January 28, 2011: The Stillwater Hydroelectric Project has been certified as low impact for a five year term, effective June 1, 2010 and expiring June 1, 2015.

August 2, 2010: The public comment period for the application for certification has been closed.

June 2, 2010: Black Bear Hydro Partners has submitted an application for the certification of the Stillwater Project. Public comment period will be open for 60 days.