Inspection Detail

Inspection: 312770282 - Pioneer Concrete Pumping Service, Inc.

Inspection Information - Office: Atlanta West Area Office

Investigation Summary

At approximately 9:00 a.m. on December 19, 2008, Employees were pouring concrete onto a metal decking (walking area) structure for the Atlanta Botanical Garden Canopy Walk construction project. They were working from an elevated structure approximately 400 ft long (compose of several 30 ft sections) and approximately 35 ft from the ground. After pouring approximately 25 to 30 yd of concrete, the structure suddenly collapsed, killing Employee #1 and injuring 19 others, 10 of those employees were hospitalized. Based on the onsite investigation and interviews, noncompliance with the shoring tower design caused the accident. The shoring contractor failed to comply with the design, because three of the steel beams used in shoring towers number 6 and 9 did not meet structural design requirements, and the helical anchor was inadequately embedded in the soil and not braced for shoring towers of 20 ft or greater in height requirement. Additionally, the shoring contractor did not provide the required diagonal cable bracings between the anchors. Anchors with shallow depths would make them highly susceptible to differential settlement and lateral movements. This created the collapse hazard. The shoring contractor had received instructions to provide lateral bracings. Seven anchors under tower number 7 and 8 had embedment depths that varied from 43 in. to 17 in., but none were braced.

Keywords: ANCHOR, SHORING, TOWER, COLLAPSE, WALK PLATFORM