US Army Corps of Engineers
Detroit District

Compensating Works

General

The Compensating Works were constructed between 1913 and 1919 (although the Lake Superior outflow was not completely controlled until 1921 when the south dike was constructed).  The Compensating Works consist of 5 masonry piers and 12 concrete piers bearing on sandstone bedrock.  Mounted to the piers are structural steel towers, which support an operating deck, constructed of steel grating and a structural steel superstructure.  Suspended between the towers and piers are 16 steel sluice gates and their associated counterweights and roller trains.  The gate machinery is positioned on the operating deck. 

Gates 1 through 8, which are located in Canadian waters, are owned, operated, and maintained by the Brookfield Renewable Energy Group, Sault Ste. Marie, Ontario.  They were formerly owned by Great Lakes Power Limited, Sault Ste. Marie, Ontario.  Gates 9 through 16 are on the U.S. side of the International Boundary.  These eight gates are owned by the U.S. Government and are operated and maintained by the Cloverland Electric Cooperative through a contract agreement with the U.S. Army Corps of Engineers. Outflow from Lake Superior into the St. Marys River is governed by the International Lake Superior Board of Control of the International Joint Commission (IJC).

Approach Dike

 

The approach dike, also known as the north dike, connects the south end of the Compensating Works to the Main Powerhouse.  It lies in an east-west orientation and separates the rapids to its north from the headrace of the Main Powerhouse to its south.

Piers and Masonry Structures

 

The Compensating Works consist of 17 piers and concrete aprons bearing on sandstone bedrock.  Piers 1-9 are located north of the international boundary in Canada, while Piers 10-17 are located south of the boundary in the United States. Piers 1-5 are masonry and piers 6-17 are concrete.  Piers 1 and 17 are the north and south abutments, respectively.  There are two sizes of piers with similar shapes and geometry; Piers 9 and 13 are larger, while the rest are of the smaller variety.  Mounted to the piers are structural steel towers, which in turn support an operating deck, constructed of steel grating and structural steel.  Piers 9 through 17 are constructed of non-reinforced concrete.  There is a concrete apron between each pier that extends several feet downstream of the piers.  The upstream nose of each pier is protected from ice damage by a steel angle.  The piers have an overhanging concrete cap.  A series of rock anchors were installed in 1982 on the US piers to increase the stability of the structure.

Gates and Gate Machinery

 

Suspended between the towers and piers are 16 steel sluice gates and their associated counterweights and roller trains.  The water control gates are each 54 feet 6-1/2 inches wide and 13 feet ½ inch in height.  The gates are constructed of riveted steel plates and angle wales.  They bear on vertical tracks, which are mounted to recesses in the piers.  The gate machinery, consisting of shafts, journals, spur gears, pinions, pawls, and winches is positioned on the operating deck. Gates 9 and 10 are electrically operated either from the Main Powerplant or the deck of the Compensating Works.  All other gates are hand operated.