The Los Alamos National Laboratory (LANL) has finished refurbishing its high-level radioactive liquid waste treatment facility waste tanks and collection system, which receives waste from the facility’s plutonium processing facility.
During the refurbishment works last year, two workers were injured when a 1,500lb (700kg) staircase slipped free from its rigging and fell approximately 55ft (17m).
The refurbishment work was being carried out after a fire at Los Alamos, in 2000. A programme had been put in place to reduce hazards from waste in case of future fires. The treatment facility had been close to the fire, and so the decision was taken to refurbish it, both to make it more secure, and to provide extra capacity for radioactive liquid waste.
LANL brought in a steel erector to complete the structure for a new radioactive liquid waste storage facility. The two workers who were injured were employed by a subcontractor.
The original staircase at the site was installed to provide access between the tank room floor and a structural mezzanine platform located 20ft above. The top of the tank room wall is 28.5ft above the floor. The stair treads were fabricated aluminium sections, 44in wide. This width would cause the staircase to interfere with tank overflow pipes when they were installed, so project engineers redesigned the staircase with 36in treads.
LANL’s analysis
The lab has completed an internal investigation into the accident, and produced a report. It says that the hitch used did not secure the load. The falling load injured the workers because they had remained underneath the staircase as it was hoisted in the air. The investigation team also concluded that the subcontractor’s iron workers believed they had to work under suspended loads and accepted this as a normal and necessary part of erecting steel. The investigation team found that neither the employees of the steel erector nor the subcontractor understood or accepted LANL’s expectations for implementing a so-called cone of safety around the load fall zone when hoisting and rigging operations were in progress. The investigation team concluded that LANL did not take sufficient corrective action, beyond correcting a specific instance, to modify the behaviour of the subcontractor’s iron workers.
The investigation team concluded that unnecessary personnel were in the cone of safety during other lifts on site, including critical lifts of the fibreglass tanks used to hold waste. Previous instances of not implementing the cone of safety were direct precursors to this accident, it said.
Initially, the steel contractor had been contracted by an outside lead contractor. However, in the course of the project an in-house project team had replaced the lead contractor. The report identified problems with how the different companies and teams involved had managed the workers. The investigation team noted that it believed this was the first time laboratory staff had managed a construction project of this size. The investigative team found that problems with the way the steel contractor had been employed by the lead contractor, and then to a Los Alamos project team, had meant that there was not a clear ‘flow down’ of responsibilities.
There were several instances where opportunities to reinforce the safety culture of the subcontractor were not adequately addressed. Data from the site safety inspections indicated that 10 of 23 inspection findings were directly related to the subcontractor. Five of the findings were directly related to hoisting and rigging; two instances of under slung loads being lifted with a fork lift, one of using a damaged sling, and two instances where the hook latch spring was not functional.
The investigation found that LANL did not recognise and adequately respond to unsafe conditions at the site. The team also found that LANL should have been aware of a past poor safety record at the subcontractor, including an incident in 2003 that led to an OSHA citation. Finally, the team found that problems with the way the tank room refurbishment had been designed meant that the staircase needed to be changed. A better design would have avoided replacing it.
1. The staircase is rigged 1. The staircase is rigged 2. A close-up view of the foreman and the load 2. A close-up view of the foreman and the load 3. The load takes off 3. The load takes off 4. The load rises 4. The load rises 5. The load slips 5. The load slips 6. The load falls 6. The load falls
