Heavy Lifting News
Case Studies on Innovative Problem Solving
Retrieving WWII Miter Gates from St. Marys River
09/16/2024
By John Kuka
Director of Business Development
Engineered Rigging
In the 1940s, the Soo Canals, which contain five locks, were a critical bypass for heavy shipping in the St. Lawrence Seaway which spans the United States and Canada. During WWII, ships carried iron ore from the mines near Lake Superior to the steel mills along the lower Great Lakes. The original locks were built in 1914 and 1919, and the Army deposited replacement gates for the locks down river, close at hand in the event the locks were damaged. The gates sat on the bottom of the St. Marys River in Michigan for over 80 years. The original locks are currently being removed or rebuilt, so the replacement gates are no longer needed. To restore the river bottom to its natural state, the Army Corps of Engineers needed to identify the best heavy lifting solution to lift and remove the mud-covered replacement gates.
There were a few specific project considerations:
- The Army did not have a large enough crane barge for the job.
- The lifting solution would need to be powerful enough to lift the 350,000-pound miter gates.
- River traffic would remain uninterrupted during the project.
Alta Equipment Group, a material handling and construction equipment company, collaborated with Engineered Rigging to identify an integrated strand jack system as the optimal lifting solution for the Army Corps project. With a lifting capacity of 77 tons each, the strand jack’s small footprint and low height of just 6’ 4” allowed the system to be housed on a single barge.
Drawing upon its extensive rental fleet, Engineered Rigging delivered four Strand Jack Systems, the Enerpac Smart Cylinder Control (SCC) and a laptop to the project site. Each system included one Enerpac HSL7006 Strand Jack, a strand guide, recoiler and SLPP7E hydraulic power unit mounted in a single frame (see Figure 1). In addition, Engineered Rigging conducted onsite training on the strand jack equipment and SCC System which allowed a single operator from the Army to simultaneously control the four systems, monitor the load on each jack and view the lift from a remote location which optimized safety. The SCC can control up to 60 strand jacks simultaneously, providing synchronous lifting and lowering operations and precise load control. The SCC also features user-defined alarms to trouble-shoot concerns during lifting and lowering operations.
To conduct the lift, the Army assembled a customized jack-up barge which was positioned over the gates (see photo below). The strand jacks were located on the deck, which was comprised of 12 modular pontoons with 80-foot jacking spuds. The four-strand jack cables were lowered down to the gates through moonpools on the jack-up barge.
Divers used a dredge pump and clamshell bucket to remove 80-years-worth of muck, clay and silt that had settled on the gates. Once cleared, they cut four access holes into each gate. The holes were large enough to secure the rigging which was attached to the strand jack load anchors. With a combined lifting capacity of 616,000 pounds, the strand jacks were more than able to break the suction from the underlying mud and lift each gate.
Once each gate was raised out of the river, the Army positioned a barge underneath it. The strand jacks then lowered the gate onto the barge to be transported to a nearby boat basin for recycling.
“The mission went better than expected with no major surprises thanks to the continuous input from our experienced employees and support from SPO’s excellent equipment manufacturers and rental supply base,” said St. Marys River Section Engineering Technician Theodore Clark, as reported in an Army news article.
As a US Army veteran and a history buff, this project was special for me. Whether it’s helping the Army Corps of Engineers retrieve some long-lost lock gates or another unique challenge, it’s a good day when our customers use our equipment to find success. If you need assistance identifying a heavy lifting solution, please contact me or any of our experts listed below.
