Toronto-based company specializes in heavy lifting

Toronto-based firm Mammoet bills itself as “worldwide specialists in heavy lifting and transport.” Hercules and Atlas might be jealous.

The company specializes in moving heavy things, everything from a sunken Russian submarine in the Bering Sea to a 1.5 million-ton crane in Mexico. It built and furnished a 40,000square-foot office building for its U.S. headquarters near Houston in 2011 and then moved it several hundred yards, mostly to prove it could.

The company will be in Pittsburgh next week to move the 70-foot-long, 270-ton bridge spans from a nearby parking lot to assemble the new Shaler Street Bridge above Route 19/51 near the West End Bridge. It’s the first time the process, using a series of hydraulic trailers, will be done in Pennsylvania.

Patrick Heer, a project engineer for Mammoet, said for this project the company will create a self-propelled modular transport using two sets of 12 small hydraulic trailers. Mammoet worked with a German company that invented the hydraulic technology to develop the system.

The trailers have four wheels that each have hydraulic axles, which allow them to go up and down individually as much as 2 feet each direction. If you’re old enough to remember astronauts landing on the moon, picture the moon rover rolling over lunar rocks.

That variation in the wheels allows the trailer system to go over humps and into potholes while keeping the load-bed level. The 24 trailers that will be used at Shaler Street will have 96 wheels and each can hold up to 30 metric tons.

Mr. Heer, who has supervised this type of bridge project a half dozen times, said the “unique” challenge at Shaler Street is that the spans were built at a 14-degree angle. That’s because the bridge connects higher Mount Washington on one side of the highway with lower Woodville Avenue on the other side.

The engineering key to making the entire operation work, Mr. Heer said, is using a mathematical formula to find the center of gravity for the pieces to be moved and creating a triangle of trailers underneath it.

Mr. Heer said his crew will begin assembling the trailer system two or three days before moving the pieces. A technician will use a remote control power pack to control the speed and direction of the trailers, which can move anywhere from walking speed to just over 10 miles an hour.

The plan is to move the higher piece into place first, from the Mount Washington side to the pier in the median, then place the piece from the median to Woodville Avenue. PennDOT has set aside Oct. 31 and Nov. 1 for the placement, but Mr. Heer said it’s possible it would be finished in one day.

“It takes patience,” he said. “You really have to understand the hydraulics.”

Mr. Heer said he still gets excited watching huge pieces move.

“It’s definitely something that’s hard to visualize. It strikes a lot of awe in me even today.”