LIHI Certificate # 91 - Silver Lake Project, Vermont

Silver Lake Project, LIHI #91
Project Name Silver Lake
LIHI Certificate No. 91
LIHI Certificate Term February 6, 2017 – February 5, 2027
Owner Green Mountain Power Corporation
State Vermont
Location Located at river mile 0.25 on Sucker Brook in Goshen, Liecester, and Salisbury, Vermont.
Installed Capacity 2.2 MW
Average Annual Generation 3,993 MWh

(2011-2016 average)
Facility Type Seasonal storage/peaking facility
FERC No. P-11478 issued in 2009, expires 01/31/2039

The Silver Lake Project is located in the Green Mountain National Forest in the towns of Goshen, Leicester, and Salisbury, in Addison County Vermont. The facility was originally constructed between 1916 and 1923 for electricity generation. The original development began construction in 1916 and was completed the following year. The Goshen Dam was added in 1922-1923 to create the Sugar Hill Storage Reservoir. The project is owned by Green Mountain Power (GMP), the first energy utility certified as a B-Corporation.

Project works include two storage reservoirs: the 74-acre Sugar Hill Storage Reservoir impounded by a 60-foot-high, 680-foot-long earthen dam and the 110-acre Silver Lake, impounded by a 30-foot-high, 257-foot-long buttressed concrete wall with an earth backfill dam. The single powerhouse is located approximately 5,200 feet downstream from the Silver Lake dam and includes one 2.2-MW turbine generator unit. The project then discharges into a 450-foot-long tailrace into Sucker Brook, which then empties into Lake Dunmore. There is a 11,700-foot-long bypassed reach from the Sucker Brook diversion dam into the tailrace of the powerhouse.

A new intake structure is being constructed at the Sugar Hill Storage Reservoir during summer of 2021 to address FERC dam safety requirements. GMP is consulting with FERC and resource agencies as appropriate for this work.

The project operates as a seasonal storage and peaking facility. Silver Lake is maintained as a stable reservoir for recreation in the summer and to enhance conditions for resident trout species. The Sugar Hill Reservoir is operated as a seasonal storage reservoir in accordance with a rule curve for water surface elevation. The project’s operations plan was developed based on historical and forecasted data to arrive at the rule curve, which is designed to protect smelt spawning, improve habitat, and account for springtime precipitation. A minimum flow of 2.5 cfs is maintained in Sucker Brook between Goshen Dam and the Sucker Brook Diversion dam and the bypassed reach. This flow regime is based on recommendation from US Fish and Wildlife Service (USFWS) and Vermont Agency of Natural Resources (VANR).

Waters within the project reach are designated as Class B cold water fish habitat. The project owner conducts dissolved oxygen and temperature monitoring when drought conditions occur and maintains a continuous minimum release of 2.5 cfs conservation flow during summer low-levels.

The Falls of Lana, a natural water fall downstream of the project, has historically precluded access for migratory fish to the project area. American eel have been known to ascend these falls but none have been observed in the project reaches. The area from the Project tailrace to Sucker Brook’s confluence with Lake Dunmore provides a short riverine stretch where landlocked Atlantic salmon, brook trout, rainbow trout, and lake trout can access spawning habitat. There is a small section between the natural barrier of the Falls of Lana and the Silver Lake Powerhouse tailrace that species can also access, and landlocked salmon have occasionally been observed in this reach by project staff. To prevent fish from moving past the tailrace and entering the Silver Lake powerhouse, the project maintains a vertical fish exclusion rack and screen device at the tailrace. Furthermore, the project operates the turbine in the powerhouse at a reduced capacity or goes offline completely during smelt spawning season in the spring.

Resident river species include brook trout, brown trout, rainbow trout, sunfish, rock bass, and minnows. The project does not hinder the free movement of trout for successful completion of their lifecycles. Starting upstream, the Sugar Hill reservoir outlet includes 3-inch clear spacing trashracks, which would not prevent the species from entering Sucker Brook as there is no generating unit at Sugar Hill which could pose a threat to the trout. Species residing in Sucker Brook would then be able to pass either over the Sucker Brook Diversion Dam spillway (when adequate flows are provided,) or through the 4.5-inch trashracks (again, no generating unit is present which could harm the fish). The Silver Lake intake currently includes 2-inch spaced trashracks.

The project lands consist of 350 acres within the Green Mountain National Forest, and landcover consists of a mix of deciduous forest, mixed forest, and evergreen forest habitat, with several small areas of developed open space. A 3.5-acre wetland is located at the south bay of Sugar Hill Reservoir where Sucker Brook enters. The wetland is dominated by low diversity annual plant species. The project delays winter drawdown activities until January to help mitigate impacts to the wetland and other aquatic species that seasonally use the shallow mud areas. Additionally, a 1.8-acre emergent wetland is found upstream of the diversion dam as well as various wetlands along Sucker Brook. The 2.5-cfs conservation flow requirement and reservoir management practices include several measures to minimize the amount of time the wetlands are inundated.

Threatened or endangered species potentially present in the project vicinity include the Northern Long-eared Bat, Indiana Bat, Tri-colored Bat, and Eastern Small-footed Bat. The project is not expected to have any impact on the listed species based on consultation with VANR. The project owner adheres to tree cutting and removal restrictions which mitigate impacts to potential bat habitat and roosting locations. This also includes surveying and reporting requirements for identifying potential roosting locations.

Project structures are eligible for listing on the National Register of Historic Places. The project operates under a historic properties management plan which was developed with Vermont Division for Historic Preservation and US Forest Service. The plan provides provisions for management of project resources and mitigation of any adverse impacts on said properties.

Recreational resources at the project include a boat ramp, parking area, a handicapped-accessible trail to the boat ramp, handicapped-accessible fishing access landing, and overlook access to the Falls of Lana. Public access is provided free of charge.

Compliance Status

The Certificate includes the following facility-specific conditions:

Condition 1: The facility Owner shall submit to LIHI copies of all correspondence with VDEC regarding their ongoing review of the operations records within 60 days of receipt. LIHI reserves the right to include any recommendation that may result from that review as a condition of re-certification.

Condition 2: The facility Owner shall provide to LIHI copies of all correspondence related to the water quality monitoring requirement to confirm effectiveness of the baffle structure if, and when the appropriate drought conditions occur over the term of LIHI certification and shall submit either a statement that no monitoring was required or the monitoring results and any agency comments on those results with annual compliance submittals. LIHI reserves the right to include any recommendation that may result from that review as a condition of re-certification.

Condition satisfied in 2023. Condition 3, added in 2022:  The facility Owner shall report to LIHI on a quarterly basis starting in July 2022 until all dam-safety related work is completed and the project resumes operation.  The reports shall include a brief summary of project status, any consultation with VANR that occurred, and copies of all correspondence with VANR in the prior calendar quarter.  Any environmental upsets related to the LIHI criteria shall be reported as soon as possible after discovery but no later than 10 days after the event.  LIHI reserves the right to suspend or revoke the Certificate if significant environmental impacts related to the LIHI criteria occur during the remainder of the project.

2024: No material changes or compliance issued were identified. The project remains in compliance based on the annual review. For Condition 1, the project reported no change in status. For Condition 2, the project reported no drought conditions in 2023 that would trigger monitoring.

2023: No material changes or compliance issued were identified. The project remains in compliance based on the annual review. For Conditions 1 and 2, the project reported no change in status due to the dam safety work.  For Condition 3, the project reported that dam safety work had been completed and submitted the quarterly update report for 4th quarter 2022 noting that no upsets had occurred. On April 28, 2023 the project submitted documentation of completion of dam safety work, thus satisfying  Condition 3.

2022: No material changes were identified.  For Condition 1, the project reported continuing to develop operations data. For Condition 2, the project reported no water quality monitoring due to impoundment drawdown for dam safety work and although drought conditions may have occurred, the project maintained run of river operations during that time.  Condition 3 was added in response to a compliance issue resulting in a 2021 VANR notice of alleged violation for discharge of sediment that occurred during the dam safety work. A Sediment Monitoring Agreement was developed with VANR to minimize impacts of the construction project. The project developed a water management plan and submitted quarterly update reports required under Condition 3 and reported no upsets had occurred. The project thus remains in compliance based on the annual review.

2021: For Condition 1, baseline operations data continues to be developed for submittal to VDEC. For Condition 2, with agency approval monitoring was not conducted due to the ongoing dam safety work. The project remains in compliance based on the annual review.

2020: The project reported a need to address FERC dam safety matters resulting in an approved extended drawdown of the Sugar Hill reservoir for work planned in 2020 and 2021. For Condition 1, baseline operations data is being developed for submittal to VDEC. For Condition 2, monitoring was not triggered by drought conditions. The project remains in compliance based on the annual review.

2019: Annual reporting for the current Certificate has not yet taken effect.

Certification History

January 1, 2022: The LIHI Certificate term has been extended in accordance with Revision 2.05 of the LIHI 2nd Edition Certification Handbook issued January 1, 2022. Refer to the facility table above for the new term.

February 12, 2019: The decision to recertify the Silver Lake Hydroelectric Project is final. No appeals were received during the appeal period which closed on February 10, 2019. The new certification term for the Project is from February 6, 2017 through February 5, 2022.

January 11, 2019: On January 10, 2019, the Low Impact Hydropower Institute (LIHI) preliminarily approved the Silver Lake Hydroelectric Project for a new 5-year term of Low Impact Certification. 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 “Silver Lake Hydroelectric Project” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, 329 Massachusetts Ave, Suite 2, Lexington, MA 02420. 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 February 10, 2019.  The full application and reviewers report are available below. If no appeal requests are received and the decision becomes final, the Certification term for the Project will be February 6, 2017 through February 5, 2022.

November 12, 2018: The Silver Lake Hydroelectric project has been granted another extension of the current certificate term. The new expiration date is March 31, 2019.

November 6, 2018: The Low Impact Hydropower Institute has received a complete application for a new term of Low Impact Certification for the Silver Lake Hydroelectric Project (LIHI #91). The Project is located on Sucker Brook in the towns of Leicester and Salisbury, Vermont. LIHI is seeking public comment on this application.  Specifically, we are interested in knowing whether you think the Project meets the LIHI Low Impact Certification Criteria, as revised in the 2nd Edition Handbook.  Please review the program and criteria in LIHI’s revised Handbook and then review the Project’s 2018 application materials below. 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 “Silver Lake 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 on or before 5 pm Eastern time on January 5, 2019 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.

June 11, 2018:  The Silver Lake Hydroelectric project has been granted another extension of the current certificate term. The new expiration date is December 31, 2018.

November 3, 2017:  The Silver Lake Hydroelectric project has been granted another extension of the current certificate term. The new expiration date is March 31, 2018.

December 16, 2016: The Silver Lake Hydroelectric project has been granted an extension of the current certificate term. The new expiration date is November 6, 2017. See extension letter for explanation below.

September 9, 2012: The Silver Lake project has been certified as low impact for a five year term, effective February 6, 2012 and expiring February 6, 2017.

April 6, 2012: Public comment period on application has closed.

February 6, 2012: The Central Vermont Public Service Corporation has submitted an application for the certification of the Silver Lake project. Public comment period has been opened.

Certification Files

2018 Recertification

2012 Certification

Key Documents