Great Lakes Lock Infrastructure

Lock infrastructure on the Great Lakes and St. Lawrence Seaway forms an elaborate lift system allowing Great Lakes ships to move across a vast expanse of territory in which water levels fall more than 182 m (600 feet) from Lake Superior to the Atlantic Ocean. During that journey, a vessel will pass through 16 separate locks.

The Great Lakes - St. Lawrence Seaway Locks

The Soo Locks

Located on the St. Marys River at Sault Ste. Marie, Michigan, the Soo Locks enable ships to transit between Lake Superior and Lake Huron, an elevation change of 7 m (21 feet). There are four side-by-side lock chambers at the Soo. The Poe Lock is the largest at 366 m (1,200 feet) long x 34 m (110 feet) wide x 10 m (32 feet) deep. The MacArthur Lock measures 224 m (800 feet) long x 24 m (80 feet) wide x 9 m (29.5 feet) deep. The Davis Lock and the Sabin Lock measure 411 m (1350 feet) long x 24 m (80 feet) wide x 7 m (23.1 feet) deep. The vast majority of Great Lakes transportation and commerce utilizes the Poe and MacArthur locks. The Davis Lock is infrequently used and the Sabin Lock has been retired. The Soo Locks complex is owned and operated by the U.S. Army Corps of Engineers.

St. Lawrence Seaway - Welland Canal Section

Linking Lake Erie to Lake Ontario, the Welland Canal cuts 42 km (27 miles) across Canada's Niagara Peninsula from Port Colborne, Ontario to Port Weller, Ontario. A series of eight locks lift or lower vessels 99.5 m (326 feet) and enable maritime commerce to bypass Niagara Falls. Each of the eight locks on the Welland Canal measure 233.5 m (766 feet) long x 24 m (80 feet) wide x 9.14 m (30 feet) deep. The Welland Canal is owned by the Government of Canada and managed by the St. Lawrence Seaway Management Corporation.

St. Lawrence Seaway - Montreal/Lake Ontario Section

Located on the St. Lawrence River between Iroquois, Ontario and Montreal, Quebec, a series of seven locks lift or lower vessels 74 m (243 feet) and enable maritime commerce to navigate between Lake Ontario and the lower St. Lawrence - effectively connecting the Great Lakes to the Atlantic Ocean. Of the seven locks, the Iroquois, Upper Beauharnois, Lower Beauharnois, Cote Ste. Catherine and St. Lambert locks are on the Canadian side of the waterway. These St. Lawrence Seaway locks are owned by the Government of Canada and managed by the St. Lawrence Seaway Management Corporation. The Eisenhower and Snell locks are located on the American side. They are owned by the U.S. Department of Transportation and managed by the Saint Lawrence Seaway Development Corporation. Each of the seven locks measure 233.5 m (766 feet) long x 24 m (80 feet) wide x 9.14 m (30 feet) deep.

How a Lock Works

A vessel traveling downstream would find the lock chamber already filled with water. The entrance gate is opened and the vessel moves in. The entrance gate is then closed. A valve is opened and the lock chamber is drained, lowering the vessel. Once the vessel reaches the desired level, the exit gate is then opened and the vessel moves out of the chamber.

This process is reversed for a vessel traveling upstream. The vessel would enter the lock empty. The entrance gate would be closed. Water would be pumped into the lock chamber to raise the vessel. Once the vessel reaches the desired elevation, the exit gate is opened and the vessel moves out.

The entire process takes about 45 minutes.

Within a lock there are a number of components – structural, mechanical and electrical – that must work together seamlessly to provide safe passage for a ship:

Approach and guide walls: The purpose of these structures is to help align the vessels as they approach the lock and guide the vessel into the lock chamber. These walls also provide a place for the vessels to tie-off while awaiting entry to a lock chamber.

Lock chambers: These are comprised of huge concrete walls with either concrete or rock floors. Culverts or narrow tunnels run through the walls and/or floors through which water flows during emptying or filling of the chamber, and within which are located the emptying and filling valves used to regulate water flow.

Lock gates: These massive structures are made of steel and open to allow vessels to enter or exit the lock chamber. The end of the gates are mitered (angled) and use the difference in water levels to provide the force necessary to achieve a nearly water-tight seal.

Valves: Numerous valves are employed for the control of water in a lock. Culvert valves are opened and closed during each locking cycle to fill and drain the lock chamber. They are actually large steel gates located within the concrete culverts, which are an integral part of the lock chamber.

Other mechanical and electrical machinery: Additional components of the lock infrastructure include control systems and motors that are required to operate the machinery of the lock gates, valves and lift bridges.