The company constructing a 41-storey condo tower in Coquitlam where a shoring wall collapsed says it followed all the proper protocols when it erected the temporary structure.
Stepan Vdovine, the vice-president of executive operations for Vancouver-based developer Amacon, said the shotcrete wall that cracked and then failed in spectacular fashion last Wednesday, Nov. 29, sending soil and rocks cascading into the excavation site at 500 Foster Ave., did contain a standard eight-gauge wire mesh.
Vdovine was responding to speculation by a University of British Columbia engineering professor that the welded wire mesh that helps reinforce the shotcrete after it's been sprayed in place seemed to be missing in a video of the incident that was recorded by a witness and then widely circulated on social media.
Dr. Perry Adebar, who teaches structural engineering at UBC’s department of civil engineering, told the Tri-City News the apparent lack of the mesh support or poor application of the sprayed shotcrete could have been factors in the collapse.
But Vdovine said all the work at the site was done "with appropriate permits, consistent oversight and monitoring," adding, "the contractors on this project are some of the most experienced trades and engineers in the region who oversee the vast majority of large scale residential projects."
Vdovine said the company continues to investigate what happened, adding nobody was injured because the problem was detected several hours before the collapse, giving time for all the trades working on site to evacuate the excavation and close Foster Avenue to traffic pre-emptively.
Adebar said temporary shoring walls are commonly used to support the dirt walls at excavations until a permanent concrete foundation can be constructed.
He said they’re built in stages and anchored with tiebacks or soil nails, adding those still seemed to be in their original position after the wall at the Foster Avenue site failed.
Since the collapse, the wall has been stabilized with backfill said a statement from the city of Coquitlam on Monday, Dec. 4. Sandbags and plastic sheeting were also put in place to protect the work from heavy rains.
Foster Avenue remains closed between North Road and Whiting Way but the company no longer needs to keep working through the night.
Last Friday, Dec. 1, the city advised Amacon it needed to hire an independent third-party geotechnical engineer on site to supervise the repairs.