Joint venture to co-develop Sweetheart Lake scheme in Alaska

Japan’s Electric Power Develop­ment Co, operating under the name J-Power, has signed a joint development agreement with Juneau Hydro­power Incorporated (JHI) for the Sweetheart Lake hydro project near Juneau, the capital of the US state of Alaska.

Under the agreement, which was signed on 17 August, the two companies will cooperate on the development of the project, including the construction of the 19.8 MW plant and associated transmission lines, as well as a district heating system in Juneau. The project is 53 km south of Juneau on the east shore of Gilbert Bay. Sweetheart Lake drains into Gilbert Bay via Sweet­heart Creek. Construction of the project, which has been under development since 2009, is scheduled to begin next year, according to JHI. Construction could take around two to three construction seasons, depending on weather conditions. It will include 65 km of high-voltage transmission line that will connect the plant across Juneau via the state-owned Snetti­sham transmission line, which is the main power source for Juneau. It will also connect to the Kensington Mine, which will include submarine components through Berners Bay, about 65 km north of Juneau. The facility, which is designed to generate average output of 116 GWh/year, is expected to increase the supply of electricity in Juneau by about 20-25 per cent, while replacing diesel generated energy used by the nearby Ken­sington Mine, according to Duff Mitchell, Managing Director of Juneau Hydropower. The Federal Energy Regulatory Commission (FERC) issued a final licence and environmental impact statement in September 2017, and, in November 2017, the project de­veloper was issued a Special Use Permit (SUP) by the US Forest Service, marking the last governmental milestone required to begin construction. Since receiving its FERC licence, JHI has completed a successful drilling programme that has verified a solid foundation at the site, and has made preparations to begin full scale construction. According to the SUP, the project will feature a 34 m-high, 85 m-long concrete dam at the existing natural outlet of the Lower Sweetheart Lake, with a 38 m-long ungated overflow spillway, and a powerhouse to be equipped with three 7.1 MW turbines. The project will also involve the construction a 160 m-long reservoir outlet tunnel, a 13.7 m-long intake structure with six cylindrical fish screens adjacent to the right dam abutment, a 2.9 km-long underground power tunnel, three 48.8 m-long steel penstocks connecting the power tunnel to the powerhouse as well as a 165 m-long tailrace with a fish exclusion structure. The dam is to be built above a series of waterfalls that block natural salmon passage into the lake. JHI was established in 2009 by local businessmen Keith Comstock and Duff Mitchell, who saw the benefits of using local hydropower resources to meet increasing electricity demand and allow the city to switch from diesel heating and pow­er supply to a more sustainable source of energy that was responsive to local needs and community values. JHI said that the project development had been fully funded by local Juneau investors, without the need to resort to federal and state grants. The project is being financed through the Department of Energy with equity provided by both J-Power and JHI. Mitchell said that funding was substantial enough to take the project to and through construction.