The process for removing seven concrete pillars holding up the now unused Port Mann Bridge—the new bridge is up and running parallel to the old bridge near Coquitlam, B.C., outside of Vancouver—requires extra care to contain the ruble and keep fish as safe as possible.

While two of the pillars were removed prior to this season, the bulk of the concrete removal will now occur in the early morning hours of late fall and early winter, when tides are highest, fish are fewest and traffic is lightest.

But before crews can demolish the pillars, they have to scare the fish. In order to follow guidelines set by the Dept. of Fisheries and Oceans, the work is timed to when the fish run is most sparse.

To make sure that fish and any other wildlife don’t get injured during the process, crews run vibrators in the water to deter fish and wildlife from entering the area. Then, right before the first blast to break up the pillars, small charges around the work site serve as one final warning to fish and wildlife to vacate the space.

Bubble curtains—a wall of bubbles to help protect fish—also help contain the pressure from the original blast, which are layered in order to provide the smallest possible shockwave.

When it comes time to remove the in-water pillar and concrete, though, steel and rubber mats help contain the blasted concrete.

After the detonation to break up the pillars, excavation of the riverbed via machinery removes all the concrete from the Fraser River.

The process for removing the old Port Mann Bridge remains under the purview of TI Corp., the crown corporation that also oversaw the construction of the new Port Mann Bridge and other Highway 1 corridor upgrades. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.