The Soo Locks linking Lake Superior to the lower Great Lakes, particularly the Poe Lock, represent the single most critical navigation structure in the Great Lakes maritime transportation system (MTS). Some 80 million tons of cargo - primarily downbound iron ore for steel manufacturing, coal for electric power generation, and export grain - transit the Soo Locks annually. An economic impact study conducted by Martin Associates estimated that maritime commerce moving through the Soo Locks in 2017 supported 123,172 jobs in the U.S. and Canada, and generated $22.6 billion (C$29.3 billion) in economic activity. Currently there are two locks at the Soo available to cargo carriers, the 800-foot long, 80-foot wide MacArthur Lock built in 1943, and the 1,200-foot long, 110-foot wide, Poe Lock, enlarged to its current size in 1968. As Great Lakes commercial vessels have grown larger, reliance on the Poe has increased: it now handles over 90 percent of the cargo transiting the Soo. Given the criticality of the Soo Locks to the North American industrial supply chain, the 2016 Regional Maritime Strategy prioritized modernization of the locks through two major investments: 1) Acceleration of an asset renewal program for both the MacArthur and Poe Locks; and 2) Construction of a second large, Poe-class lock on the site of two long-retired locks.

The Soo Locks Asset Renewal Plan was developed by the U.S. Army Corps of Engineers in 2007 to pre-emptively identify and prioritize physical needs of the two working locks, the MacArthur and Poe, that could potentially result in catastrophic  failure. While the Army Corps has an ongoing Operation and Maintenance budget for routine upkeep of the Soo Locks, the Asset Renewal Plan was created as an additional long-term program to keep the locks operating reliably through 2035. Its cost is projected at $186 million, of which $115 million has been spent to date. While efforts to build system redundancy with a second Poe-class lock continue, the Asset Renewal Plan assumes that it will take at least seven to 10 years in a best-case scenario to complete that project, during which the existing locks need to remain fully functional.

In November, 2018 the Army Corps of Engineers announced that it had budgeted $32 million toward design and construction of a new Poe-class lock at the Soo, with the State of Michigan concurrently committing an additional $52 million to the project. This marked a major milestone in the 32-year effort to build a new, large lock at the Soo. The Water Resources Development Act (WRDA) of 1986 authorized construction of a replacement lock at the Soo, but did not appropriate funding. In subsequent years, debate over the benefit-to-cost ratio (BCR) of the project prompted extended re-evaluation by the Army Corps of Engineers to justify the cost of a new lock, currently projected to cost $922.4 million. In its most recent calculations, the Corps expects the new Soo lock to provide annual benefits of $77.4 million with a BCR of 2.32, well over the minimum required BCR of 1.0. Research has also shown that there are no viable transportation alternatives to re-route cargo handled by the Poe Lock in the event of a long-term closure, further validating the federal interest in a back-up lock. According to a 2015 U.S. Department of Homeland Security study, “An unanticipated closure of the Poe Lock would likely result in widespread bankruptcies and dislocations throughout the economy. Over 10 million people in the United States and two to five million more in Canada and Mexico would lose their jobs and the North American economies would enter a severe recession.” Looking ahead, to keep the project on track for a 2030 completion schedule, the Army Corps estimates that it will have to allocate $70 million to $145 million annually for the next three fiscal years, and some $550 million for the brunt of the construction work between 2023 and 2030, all of which will depend on ongoing Congressional commitment to the project.