The Federal Energy Regulatory Commission on June 28 released for comment an environmental assessment on Wisconsin Electric Power’s plan to upgrade and uprate its Twins Falls hydroelectric facility.
In October 2012, Wisconsin Electric filed an application for a non-capacity license amendment to decommission an existing powerhouse, construct a new powerhouse and spillway, and make improvements to the dam at the Twin Falls Hydroelectric Project, FERC Project No. 11831 (Twin Falls Project). The project is located on the Menominee River near Iron Mountain in Dickinson and Iron counties, Mich., and near the community of Florence in Florence County, Wisc.
Wisconsin Electric proposes to install a closure dam at the site of the existing powerhouse forebay, remove the existing powerhouse on the Michigan side of the river, construct a new powerhouse on the Wisconsin side of the river that would increase the installed capacity from 6.1 MW to about 9 MW, and construct an additional spillway with a capacity of about 17,800 cubic feet per second.
The existing powerhouse was constructed in two phases. The original powerhouse and units 1–3 were constructed in 1912. In 1915, a powerhouse addition was completed when units 4 and 5 were constructed. The original equipment continues to generate electricity at the site. A 2010 safety report identified conditions at the existing forebay, intake structure, and penstocks of the powerhouse that are in need of repair. Furthermore, the rock face on the right side of the forebay is susceptible to freeze-thaw damage and unraveling. The rock face on the downstream side of the intake structure near the unit 4 penstock also needs repair, and the powerhouse penstocks have reached the end of their service life.
The Public Service Commission of Wisconsin issued a May 13 final decision approving an application by Wisconsin Electric for this project. In November 2012, the Wisconsin commission received an application from Wisconsin Electric seeking authority to construct a new hydroelectric facility at the site of its existing Twin Falls facility, at a total estimated cost of $72.3m.
The proposed project is expected to generate about 43,600 MWh per year. The new powerhouse would consist of two 4.5-MW identical Kaplan vertical-type turbines.