The Public Service Commission of Wisconsin issued a May 13 final decision approving an application by Wisconsin Electric Power Co. (WEPCO) to re-construct and uprate its Twin Falls hydroelectric facility.
In November 2012, the commission received an application from WEPCO seeking authority to construct a new hydroelectric facility at the site of its existing Twin Falls Hydroelectric Facility, located on the Menominee River, four miles northwest of Iron Mountain, Mich., at a total estimated cost of $72.3m.
The Twin Falls Hydroelectric Facility, including the dam and powerhouse, was constructed and placed in service in 1912 by a WEPCO predecessor company, Peninsular Power Co., initially with three generating units. Two more units were added during the winter of 1915-1916.
The Twin Falls dam and the main spillway straddle the river, which also forms the state line separating Wisconsin and Michigan. The existing powerhouse is located on the Michigan side of the river in the town of Breitung, Dickinson County, Mich. The right gravity wall and auxiliary spillway are located in the town of Florence, Florence County, Wisc. The maximum total output from the existing five turbines and generators is about 6.1 MW. The dam creates the 960-acre impoundment known locally as Badwater Lake, at a normal maximum pool level elevation of 1,112.7 feet above mean sea level. The river mean flow at the dam is approximately 1,705 cubic feet per second (cfs).
Most of the powerhouse equipment, including the turbines, governing systems, excitation systems, switchgears, and circuit breakers, were installed between 1912 and 1915, and are in relatively poor physical condition due to age and deterioration. A safety inspection report of 2010 identified conditions at the existing forebay, intake structure, and penstocks that require repairs. In June 2011, the Federal Energy Regulatory Commission requested that WEPCO provide a definitive plan and schedule to address these issues.
After evaluating alternatives, WEPCO decided that the most cost-effective approach to address these issues is to construct a new powerhouse and remove, rather than repair, the existing powerhouse. A need for additional spillway capacity was also a factor in WEPCO’s decision to relocate the powerhouse to the Wisconsin side of the Menominee River, as this improvement would be more efficiently undertaken in conjunction with the construction of the new powerhouse, the Wisconsin commission noted.
The proposed project is expected to generate approximately 43,600 MWh per year. WEPCO proposes to:
- construct a new power house on the Wisconsin side of the Menominee River in Florence County, increasing the installed capacity from 6.1 MW to approximately 9 MW;
- add spillway capacity of about 17,800 cfs; and
- remove the existing powerhouse in Michigan. The new powerhouse would consist of two 4.5-MW identical Kaplan vertical-type turbines.