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The Sault Ste. Marie Canal, constructed in 1887-1895 through St. Mary’s Island on the north side of the rapids of the St. Mary’s River to furnish communication between Lakes Huron and Superior overcomes a difference in water levels which is about 19 feet. It is the most westerly canal on the Inland Seaway route. This Canal is a cut through red sandstone rock, 7,294 feet (about 1.4 miles) long from end to end of upper and lower piers, and its general width is 150 feet at the water surface, 141 feet 8 inches at the bottom. The approaches above and below the canal are channels dredged through boulder shoals and marked by suitable buoys and range lights. The Canadian canal, 1 ½ miles long, 150 feet wide, and 23 feet deep, with lock 900 feet long and 60 feet wide, originally having 22 feet of water on the miter sills (16.8 feet at present low-water datum), was built on the north side of the river in the years 1888 to 1895. The Welland Canal The locks at the Welland Canal have the same controlling dimensions as those in the new Seaway. Locks 1-7 of the Welland Canal are lift locks. Lock 8 is essentially a guard lock. Locks 4, 5, and 6 are twinned and in flight. The Welland Canal is 27 miles long, overcomes a difference in level of 326 feet between Lake Erie and Lake Ontario. All locks in the Welland Canal are similar in size to those of the St. Lawrence Seaway.
The controlling channel dimensions for the Seaway, Lake Erie to Montreal are:
Lock 1 is at Port Weller; 2 is between there and Homer; 3 is south of Homer. These three are all single locks of identical construction. At Thorold, the sharp rise in contour required, for simplicity of construction and convenience of navigation, three double or twin locks, 4, 5, 6, connected end to end. The operations of these six locks in one group are electrically controlled, with an elaborate interlocking system, so that the locking of boats is done with utmost safety at all times. The Twin Flight Locks have a total aggregate lift of 139 ½ feet. They are similar to the Gatun Locks on the Panama Canal, which, though of somewhat larger dimensions, have only an aggregate lift of 85 feet. Just south of the Twin Flight Locks, at Hoover St., Thorold, is a single lock 7, giving the final lift up to the summit level, that of Lake Erie. At Welland the Welland River crosses under the canal through a concrete inverted siphon culvert, consisting of six tubes 22 feet in diameter. Control lock 8 is at Port Colborne, the longest lock in the world, its length being 1380 feet.
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