The Federal Energy Regulatory Commission on May 31 released a final environmental impact statement, which is a key step in the licensing process for the 19.8-MW Sweetheart Lake Hydroelectric Project in Alaska.
In May 2014, Juneau Hydropower Inc. filed an application for an original license for the project, which would be located on Lower Sweetheart Lake and Sweetheart Creek, within the City and Borough of Juneau, Alaska. The project would occupy 2,058.24 acres of federal lands within Tongass National Forest, administered by the U.S. Forest Service. The project also would occupy 131.18 acres of tideland and submerged lands of the state of Alaska.
The project would generate an average of about 116,000 megawatt-hours (MWh) of energy annually.
The proposed project would include these new facilities:
- a 280-foot-wide, 111-foot-high roller-compacted concrete dam to be constructed at the existing natural outlet of Lower Sweetheart Lake, with a 125-foot-wide ungated overflow spillway at a crest elevation of 636 feet;
- a 525-foot-long, 10-foot-high, 10-foot-wide arched reservoir outlet tunnel at the right dam abutment;
- a 45-foot-long, 25-foot-wide, 16-foot-high rectangular concrete intake structure, with six 7-foot-diameter, 10-foot-high cylindrical fish screens adjacent to the right dam abutment;
- a 9,612-foot-long, 15-foot-wide, 15-foot-high horseshoe-shaped, unlined underground power tunnel;
- an 896-foot-long, 9-foot-diameter saddle-supported steel penstock installed within the lower portion of the power tunnel;
- three 160-foot-long (mean length), 7- to 9-foot-diameter buried steel penstocks connecting the lower portion of the power tunnel to the powerhouse;
- a 160-foot-long, 60-foot-wide, 30-foot-high concrete and steel powerhouse;
- three 7.1-MW Francis turbines with 6.6-MW generators with a total installed capacity of 19.8 MW;
- a 541-foot-long, 30- to 90-foot-wide rock tailrace with a fish exclusion structure, discharging to Sweetheart Creek;
- an 8.69-mile-long, 138-kV transmission line traversing Gilbert Bay, the Snettisham Peninsula, and Port Snettisham, consisting of: two buried segments, totaling 4,800 feet in length; two submarine segments, totaling 25,700 feet in length; and one 15,400-foot-long overhead segment;
- a 22,000-square-foot fenced switchyard adjacent to the powerhouse; a 60-foot by 60-foot switchyard at the end of the transmission line on the north shore of Port Snettisham;
- a 4,800-foot-long, 12.47-kV service transmission line and communication cable extending from the powerhouse to the dock and caretaker’s facility, providing operational electricity and communications; and
- a 10,000-foot-long, 12.47-kV service transmission line and communication cable extending from the powerhouse to the dam site, providing operational electricity and communications.