Harrington Park, New Jersey (January 6, 2016) – On December 30, 2016, the Low Impact Hydropower Institute (LIHI) received a complete application from Green Mountain Power Corporation for the Low Impact Certification of the Essex 19 Hydroelectric project, located at river mile 17.6 on the mainstem of the Winooski River in the townships of Essex Junction and Williston, Chittenden County, Vermont.

Project Name Essex 19
Owner Green Mountain Power Corporation
State Vermont
Location Located at river mile 17.6 on the mainstem of the Winooski River in the townships of Essex Junction and Williston, Chittenden County, Vermont.
Installed Capacity 8,050 KW
Average Annual Generation 42,924,800 KWh (2010 – 2014)
Facility Type Modified peaking
FERC No. 2513

The 8,050 kW Essex 19 Hydroelectric Project consists of a 495 foot-long concrete gravity dam consisting of a 66 foot-long by 50 foot-high south concrete abutment section, a 345 foot-long by 45 foot-high uncontrolled spillway section topped with 5 foot-high flashboards, and an 84 footlong by 45 foot-high tip section topped with 6.5 foot-high flashboards. An intake structure with a 36 foot-high headwall with two concrete wing walls contains a steel trashrack, timber platform, and vertical sliding wood gates. Two 3 foot-diameter steel/diversion penstocks and four 9 footdiameter steel/diversion penstocks extend from the dam to the powerhouse. The reinforced concrete and brick powerhouse is 156.5 feet-long, 65 feet-wide, and 55 feet-high. The powerhouse contains four horizontal Francis-type turbines with an installed capacity of 2,223 kW each, and four horizontal shaft General Electric generators rated at 1,800 kW each, as well as a minimum flow unit located in an old unused exciter unit bay, which is a double horizontal Francis-type turbine with an installed capacity of 874 kW connected to a generator rated at 850 kW.

The Project impounds 352 acres at a normal maximum water surface elevation of 275.0 feet United States Geologic Survey (USGS) datum. The impoundment has a gross storage capacity of about 1, 950 acre-feet and a useable storage capacity of 905 acre-feet is available between impoundment elevations ranging from 275 to 272 feet USGS. The surface elevation of the Project impoundment is maintained between elevation 272 and 275 feet USGS.

GMP operates the Project largely as a modified peaking facility as provided in the 1995 License, with seasonal minimum flow releases, low-flow restrictions, and ramping rates.

From May 16 – June 15, GMP provides a minimum flow of 1,000 cfs, or inflow to the reservoir, whichever is less, for the protection of sturgeon spawning and incubation habitat. The Project is operated as run-of-river when flows are less than 1,000 cfs. Peaking operations occur up to the
Project’s hydraulic capacity of 2,275 cfs when flows are greater than or equal to 1,000 cfs using ramping rates.

From June 16 to – September 30, GMP provides a minimum flow of 450 cfs, or inflow to the reservoir, whichever is less, for the protection of salmonid habitat. Peaking flows in this timeframe are limited to 500 cfs, and may only occur when river flows are greater than or equal
to 450 cfs.

The minimum flow from October 1 – March 31 remains 450 cfs, but peaking operations at the Project can occur up to the Project’s hydraulic capacity of 2,275 cfs.

From April 1 – May 15 GMP operates the Project in a run-of-river mode with a minimum flow of 50 cfs whichever is less, into the bypassed reach via the fish passage facility (since installment of the minimum flow unit, GMP releases all flows less than 100 cfs to the bypassed reach via the downstream fish passage facility). Outflow approximates inflow on an instantaneous basis for the protection of walleye spawning and incubation habitat.

When river flow is greater than 275 cfs GMP operates flows through both the bypass (via the downstream fish passage facility) and existing units, when river flows are greater than 100 cfs GMP operates flows through both the bypass and the minimum flow unit, and when flows are below 100 cfs GMP operates flows through the bypass.

LIHI is seeking public comment on this application. Specifically, we are interested in knowing whether you think the Essex 19 project meets the LIHI Low Impact Certification Criteria. The Essex 19 application is subject to review using the Criteria in the LIHI Certification Handbook of 2014.  Please review the program and criteria in LIHI’s 2014 Handbook and then review the Project’s 2016 application materials posted on the project page. 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 “Essex 19 Project Comments” in the subject line, or by mail addressed to the Low Impact Hydropower Institute, PO Box 194, Harrington Park, New Jersey 07640.  Comments must be received at the Institute on or before 5 pm Eastern time on March 12, 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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