Location: Sault Ste. Marie
Contractor: Bacco Construction Co.
Supplier: Northern Sand and Gravel
General Contractor / Design Engineer: Greenland Enterprises
Owner: U.S. Army Corps of Engineers - Detroit District
Oftentimes, a concrete contractor’s best work is covered up, rarely to be seen again! Such is the case with this project at the Soo Locks – the third tunnel that Bacco Construction has constructed on the Locks since 2010. The Boiler Replacement project, built to allow the locks to operate in cold weather, consisted of constructing a 55-foot-long concrete tunnel approximately 21 feet deep. The 8-foot by 8-foot tunnel was cast in place using a slide rail system as the shoring system.
All materials and equipment for the project had to be barged to the work site, as crews were working between the Poe and Davis Locks. It was very challenging to schedule barge trips around the freighter traffic. All barging operations were coordinated with the Lockmaster to try and obtain longer timeframes to achieve productivity.
Northern Sand and Gravel supplied all the concrete for this project and added a set retarder to the mix to extend its workability time. This allowed construction crews up to 3 hours from the time it was batched to get it out of the trucks. Even given this extended window, concrete placement was a challenge at times. Due to core mission requirements, priority was given to freighters moving through the Locks, meaning that the work barge would occasionally have to be moved out of the way, even in the middle of a concrete pour!
The bottom of the tunnel floor was installed 21 feet below finished grade and the entire trench and tunnel were wrapped in a bentonite waterproof membrane before and after all concrete placements. Now, the only pieces of construction visible from the top are two vent pipes and the top of the utility trench.