Inspection Detail

Inspection: 109339341 - Circle "A" Construction

Inspection Information - Office: San Francisco Ro

Investigation Summary

At 8:20 a.m. on October 29, 1998, Employee #1, of Circle "A" Construction, an excavation subcontractor for Dillingham Construction--Pacific Basin, was spreading sand in an excavation under some recently erected precast concrete members at the Micronesia Mall expansion project in Dededo, Guam. This $40 million construction project consisting primarily of a new movie theater, two parking garages, and two shopping areas being added to the existing mall. The multiple level structural construction was made of cast-in-place concrete and precast concrete. The precast concrete members above Employee #1 were three double Ts-39 ft, 48 ft, and 57 ft long, respectively-and a 34 ft long ledger beam, for a total weight of approximately 50 tons. They had been delivered by truck to the construction site and erected by Dillingham workers using a crane operated by a diffreent employer. The precast was used to form the second level structure, in a transition area between the existing mall and the new north garage. First, the ledger beam was placed on corbels, which are reinforced concrete projections from the cast-in-place concrete. Next the shortest double-T was set on the ledger beam that had just been set in place, followed by the middle length double-T, and finally the longest double-T. A portion of one of the double-Ts was supposed to rest on a cast-in-place corbel, but it was missing. Temporary supports, consisting of shoring posts and an angle iron that was bolted into a concrete column, were erected to support the double-Ts. The design drawings showed steel plates embedded into the cast-in-place concrete and precast concrete. The temporary connections were completed by welding steel plates between the steel plates of the cast-in-place concrete plates and the previously erected precast members. No temporary connections were done on the precast members erected the day before the accident. Sometime before 8:00 a.m., Dillingham's project superintendent told his workers to weld the temporary connections for the precast installed the day before, and then instructed the Circle A workers to backfill along the footings in the same area. At 8:20 a.m., Employee #1 and a coworker were spreading sand over electrical conduits in the trench while another coworker was using a backhoe to bring in more sand. A fourth Circle A worker was using an excavator to backfill along a cast-in-place footing. A welder's helper for Dillingham was on the precast double-Ts that had been erected the previous day (the ones with no temporary connections) and a Dillingham welder was on double-Ts and a beam that had been erected and temporarily connected. Shortly after 8:20 a.m., the three double-Ts and the ledger beam collapsed. Employee #1, who was spreading sand in the excavation below, became trapped in the debris and was killed. The coworker in the trench with him escaped either by ducking into the excavation or running to avoid the falling concrete. The rollover canopy on the backhoe protected the operator from injury, although the canopy itself was severely damaged and the backhoe's front tires were flat. The excavator operator was in the cab of the machine, which was not under the collapsing precast concrete. He was not injured, although the ledger beam slid down the excavator's boom to the ground. The Dillingham welder managed to grasp onto his helper, who was falling with the precast as it collapsed, and pulled him up onto the secured precast. The welder strained his back, and his helper scraped his fingers, but neither required medical attention. The coworkers immediately called for medical assistance and used the excavator to remove the concrete off of Employee #1. The primary cause of the accident was the failure to weld the temporary connections immediately after each precast member was erected on the day prior to the accident. The Precast/Prestressed Concrete Institute's Precast Erection Manual required the erection contractor to make temporary connections or

Keywords: CONCRETE FORM WORK, EXCAVATION, COLLAPSE, UNSECURED, WORK RULES, STRUCK AGAINST, CONSTRUCTION, CRUSHED, STRUCK BY, FALLING OBJECT