Minnesota Power has announced that its Thomson hydroelectric station is expected to begin generating power early this summer following extensive repair work at the historic project.
The 120MW Thomson project – the largest hydroelectric facility in the US state of Minnesota – sustained major damage following severe flooding almost two years. About 10 inches of rain fell in the St. Louis watershed during a 24-hour period beginning June 19, 2012, swamping the six Thomson turbines, overtopping Thomson Reservoir and breaching a portion of an earthen dike at the forebay.
Working in consultation with the Federal Energy Regulatory Commission (FERC), Minnesota Power and its contractors have undertaken a 22-month repair project, planning and rebuilding the forebay, cleaning, repairing and refurbishing the powerhouse and its six turbines.
The utility’s hydro engineers anticipate that one of project’s turbines will begin generating energy again early this summer, with all six expected to be operating by year’s end.
The reconstruction and improvements at Thomson, estimated to cost about $90M, include refurbishment of the substation and replacement of much of the electrical infrastructure, cleanup of the turbines, which were underwater for several weeks, pipeline refurbishment and the replacement and repair of valves.
Beyond the Thomson flood recovery work, Minnesota Power also has invested in upgrading and reconstructing other hydro facilities on the system.
A new, more efficient turbine was installed at the Fond du Lac facility downstream from Thomson, and a penstock was replaced at that facility, built in 1923. This turbine work, which was underway when the 2012 flood occurred, was financed in part with a Department of Energy stimulus grant of $800,000.
Additionally, Minnesota Power’s Prairie River hydro station, destroyed by fire in 2008, was rebuilt and put back into operation in the spring of 2013. In the fall of 2013, the company celebrated the centennial of its Sylvan Hydro station in the western area of Minnesota Power’s service territory. In 2005 the company replaced the penstocks at its Winton hydro facility, and extensive work was also done to rebuild the Birch Lake Dam, Minnesota Power’s last wooden structure. There were also improvements made to recreational facilities, at Island Lake and elsewhere across the hydro system.
Image: Thomson hydroelectric station. Courtesy of Minnesota Power
