Michigan UP Excavation Challenges

November 2010, Vol. 65 No. 11
The biggest challenge wasn't Sault Ste. Marie’s historic buildings or Indian Burial Park, but the price of backfill.

Sault Ste. Marie, MI, like so many other communities, is in the midst of storm-sewer separation upgrades. For many cities, that can mean miles of new pipe or upgraded utilities. Sault Ste. Marie has a unique challenge in that its historic downtown area is essentially an island, with the famous Soo Locks closely adjacent to the excavation area.

Taking on a part of this very unique and difficult project is Bacco Construction Company, headquarter in Iron Mountain, MI, in the center of Michigan’s Upper Peninsula. The $9.5 million CSO Control C-1 C-2 Div A project entails installing 2,000 linear feet of new sanitary sewer pipe as deep as 28 feet, with an average depth of 22-24 feet.

Ironically, it was not Sault Ste. Marie’s adjacent historic buildings and Indian Burial Park that were the biggest excavation challenges for Bacco. Certainly, maintaining the surrounding buildings and structures was important. First and foremost was the safety of the workers due to the depth of the excavation. The other major factor came down to cost and economics.

“Sault Ste. Marie requires Class 3 sand as backfill which is very expensive, especially in the Eastern Upper Peninsula,” said Chris Wentland, Bacco’s project superintendent. “It was very important that we excavate out as little dirt as possible, but also move as quickly as possible.”

Given this consideration, it left Bacco with very few excavation and shoring options. Bacco contacted Efficiency Production Inc., a leading manufacturer of trench shielding and shoring equipment, for consultation and solutions.

Slide rail meets safety requirements
“We knew that Efficiency had a slide rail (shoring) system that seemed like it would work great, but we had never used slide rail or even seen it used,” continued Wentland. “Efficiency sent us out to Salt Lake City, Utah, to see the system in use.”

Explained Mike West, Efficiency Production’s vice president of engineering: “There are a couple of contractors in Salt Lake City using hundreds of feet of slide rail to install the big aqueduct system there,” he said. “One contractor has been using our system for several years, so it was a great example for Bacco to see how slide rail would work on their project.”