
Stevenson Dam Hydroelectric Plant

The Stevenson Dam Hydroelectric Plant is a hydroelectric power plant located on the Housatonic River at the boundary between the towns of Monroe and Oxford, Connecticut. The plant was built in 1917 by the Connecticut Light and Power Company and is currently owned by FirstLight Power. It was listed on the National Register of Historic Places in 2000. The site includes three contributing structures: the Stevenson Dam, the Stevenson Dam Bridge, and the Stevenson Powerhouse. The impounding of the Housatonic River by the Stevenson Dam created Lake Zoar, a lake with 27 miles of shoreline. The plant was covered in a Historic American Engineering Record (HAER) study, record CT-183.
The Stevenson Dam Bridge, a reinforced concrete bridge that is integrated with the dam, carries Route 34 across the river.
The Stevenson Powerhouse is a 160 by 80 ft building rising 131 ft in height. Its exterior includes "massive" pilasters. The hydroelectric plant began producing electricity in 1919 with 3 turbine/generator units, for a total of 19 MW. A fourth unit of 12 MW was added in 1936 and, with improvements over the years, the plant now produces a total of 28.9 MW of power.
The Stevenson plant was developed by the Rocky River Power Company, founded in 1905 by J. Henry Roraback to produce hydroelectric power on a tributary of the Housatonic, with operating rights expanding to the entire Housatonic watershed in 1909. Roraback's company was a predecessor to the Connecticut Light and Power Company, now part of Eversource. The dam was the first high dam on the river, and the highway bridge it carries is unique among period dams in the eastern United States. The project was probably designed by Charles T. Main Associates of Boston, Massachusetts, and was built by W. A. Blakeslee, a local contractor.