Trench Wall Collapse Leads to Worker’s Suffocation & Death
On March 20, 1998, a 45-year-old, male pipe layer (the victim) died when a trench wall gave way and the sand/dirt fully engulfed and suffocated him. The TX FACE program officer was made aware of the incident through a newspaper clipping on March 26, 1998. On April 8, 1998, the TX FACE program officer visited the employer. The safety director was interviewed. No other employees were available. No photographs or measurements could be taken because the trench had been covered prior to the investigation. EMS, fire department and autopsy reports were obtained.
The employer is a civil contractor specializing in water drainage and sanitation sewer work. The company employs 250 workers, 125 of whom are of the same occupation as the victim. The company has been in business for 43 years. At the time of the incident, there were five employees at the site.
The safety program has a designated safety director. There is a written safety program which addresses some aspects of excavation and trenching safety. Safe work procedures, specific to the various tasks employees must perform, are included in the safety program.
The company’s training program includes a basic safety orientation. Safety meetings /refresher training are conducted on a weekly basis. Task-specific training is also conducted. Training is generally provided on the job.
The victim had been working for the company for one and a half years. According to a company official, the victim had more then 20 years of experience with the task being performed. In addition, the victim was also identified as a “competent person.” A competent person meets specific criteria described in OSHA standard 1910.650.
Trench Box Death Investigation
The employer was in the process of replacing an existing sewer line. Two excavations were made, one at each end of the sewer line. In this case, one trench was excavated approximately 20 feet long, 18 feet deep and six feet across. An eight by ten-foot long trench box coupled with eight feet wide, 16 feet long, quarter inch steel plates were used to provide protection for the victim. The steel plates were placed vertically along the trench walls and the trench box was placed inside the steel plates. This method provided shoring protection for 16 feet in both length and height.
A four-foot section of the trench was not shored for several reasons. This area was not considered a work area and no workers were expected to be in this area. There was also an existing water line and a gas line that projected out approximately two feet from the opposite end wall. The lines ran perpendicular to the trench. In addition just below the water and gas lines was wood shoring from a previous excavation that had taken place years before.
The method used to replace the sewer line eliminated the need to excavate the entire length of the line. A hydraulic rod pusher with a pipe burster attached was used in this process. The pipe burster attachment pushed/crushed the existing pipe into the soil. A new line was then attached and pulled back through. Once the new line was in place, the pipe burster was detached and the hydraulic rod pusher machine was lifted out of the hole. A backhoe was used to lift the machine out of the trench. The backhoe was positioned over a manhole at the end of the trench where there was no shoring. After the machine was lifted from the trench, the back hoe was left idling in its current position.
For an unknown reason the victim left the protection of the trench box and entered the area that lacked shoring. On previous jobs and also the day before this incident, the victim had been admonished by his supervisor for stepping outside the protection of the trench box. While the victim was in the improperly shored area a side wall caved in and engulfed him in sand/dirt. The victim was covered over his head for seven to eight minutes according to a fire department report. Moments before the initial cave-in, the competent person left the immediate area and walked down to the other trench opening which was approximately 350 feet away.
Immediately after the cave-in fellow workers jumped into the trench and began to uncover the victim. Fire department personnel were dispatched and arrived two minutes later. Upon their arrival they observed the victim’s head and neck were uncovered. Rescuers entered the trench and started to provide oxygen to the victim and shore the trench up with boards. Approximately 40 minutes into the rescue, the end wall without shoring gave way and covered the victim. The cave-in also covered the legs of the rescuers up to their knees resulting in an injury to one rescuer.
Fire department personnel then determined the trench was unsafe to enter. A determination was made that this was no longer a rescue operation but instead a body recovery operation. The employer was then ordered to obtain steel planks to use to shore the trench. This task was completed at 10:30 p.m. The victim was then removed and transported to a trauma center.
Cause of Death
The autopsy report indicated the cause of death to be from asphyxia due to upper airway obstruction and external compression of the chest.
Recommendation #1: Employers should require a competent person to remain at the trench as long as a worker is in a trench.
Recommendation #2: Employers should develop a system of successively heavier penalties for violation of safe work practices.
Recommendation #3: Employers should perform a job safety analysis (JSA) to determine what hazards employees may encounter while performing their work.
Recommendation #4: Employers should develop an emergency action plan for employees and emergency responders that describes the rescue and medical duties to follow and insures that all employees and rescue personnel are knowledgeable of those procedures.