Upstream Approach Walls at the Soo Locks Complex

The challenge

Situated along the U.S.–Canada border connecting Lake Superior and Lake Huron, the Soo Locks Complex serves as a cornerstone of North American transportation. Annually, over 4,500 ships transit the locks, moving roughly 80 million tons of cargo, including advanced high-strength steel essential to the nation’s automotive and appliance manufacturing sectors. However, because just one lock was capable of accommodating modern-day freighters, the historic, 19th-century infrastructure posed a significant vulnerability to Great Lakes commerce.

Phase 2 of the U.S. Army Corps of Engineers’ plan to add a second lock capable of handling the largest 1,000 foot lake freighters required the rehabilitation of the upstream approach walls by installing more than a mile of new structures in a newly deepened channel reaching 30 feet in depth. The approach walls included a combination of sheet pile cells, z pile walls, and soldier piles with concrete lagging, all topped with reinforced concrete cap slabs, integrated mooring bits, lighting, and fendering.

Construction called for more than 60,000 cubic yards of concrete, produced in an on site batch plant operated by the joint venture team, and 30,000 cubic yards of underwater tremie concrete placed under strict mass concrete thermal control parameters. The site’s location on an island made it inaccessible by vehicle, requiring all materials and labor to be ferried across the active federal navigation channel or delivered directly by lake freighter. The work had to be completed in extreme weather conditions, with limited laydown space, and without disrupting continuous vessel traffic.