Workers In Trenches:
Beware Of Cave-In

Seven workers lost their lives while working in trenches over the past three years in Iowa. Most were buried in narrow trenches when the walls caved in. Five men were working on sewer lines 8-10 feet deep. Wet soil is unstable, unpredictable, and extremely heavy. If trench walls collapse, there is no time to react. It is impossible to escape quickly from a deep, narrow trench. The pressure of the ground is easily capable of crushing or suffocating the buried worker. Rescue is very difficult and takes precious time which increases the risk of serious or fatal injury.

When a worker is standing at a depth of 8-10 feet, he may feel safe enough, however, when crouched down working on a pipe, there is 6-8 feet of dirt above him.

Excavator operators are often tempted to dig a narrow trench, creating a spoil pile adjacent to the trench opening, making it easy to fill-in later. This may seem efficient, yet it is a dangerous practice, for unsloped walls may collapse and the pressure of the soil adjacent to the trench increases the risk. If excavation is through concrete, the hazard to workers is greatly increased.

OSHA standards require removing adequate soil on both sides, and placing the soil away from the opening. Another option is to use an approved trench box or shoring system designed to prevent cave-ins. For some contractors, or at certain job sites, sloping of trench walls may be more practical. Additional shoring may be required if an excavation is adjacent to back-filled soil, or if soil vibration is present, from highways, railroads, or other construction.

Employers should periodically review OSHA guidelines for trench work with employees doing construction or sewer work. Supervisors, foremen, and all excavator operators should be instructed to develop safe working habits when digging trenches. This includes using a shoring system or sloping the walls of the trench to prevent soil from falling and burying workers. This is required for all excavations of five or more feet deep. If an excavation will be over 24 feet deep, it must be reviewed by a qualified engineer prior to construction. This is to ensure that soil types and layers are identified, and appropriate OSHA standards are used.

(1, 2.) 19-year-old male, and 21-year-old male, were working in a trench to connect an apartment building to a sewer line. They used a backhoe to dig a 10 ft. deep trench, entering through a concrete parking lot. Dirt and broken concrete were placed too close to the trench and the walls caved in, completely burying the two men. One man was struck by a large piece of sharp concrete, then both were buried under dirt and mud which slid into the trench.

(3.) 62-year-old farmer was working in a 12-foot trench which was dug 6-foot wide, replacing a spill tube for a farm pond. Soil was wet but did not appear dangerous to the excavator operator, who was digging at the opposite end of the trench, 25 feet away from the victim. Suddenly a large section of the trench wall caved in, burying the farmer. His hired hand and the excavator operator also had been working in the trench, but luckily were not there when the wall collapsed, otherwise there would have been three deaths.

(4.) 49-year-old construction worker / plumber was operating a backhoe installing sewer pipe for a new house. He was working in the bottom of an 8-foot trench when the sides caved in and buried him. He died from asphyxiation and multiple rib fractures.

(5.) 39-year-old owner of a plumbing and electric company was installing an earth energy heating system at a lakefront home. The man was working in a 15 ft. trench when one side, under the dirt pile, collapsed and buried him. The trench was dug 30 ft. from the lake edge and the soil was wet hard clay. He was rescued and partially revived by off-duty firemen skiing nearby, but died the next day in the hospital.

(6.) 22-year-old plumber’s apprentice was installing new sewer plumbing at a new residential construction site. The crew had dug an 8-foot deep trench outside the house and the victim jumped to the bottom of the trench. The walls immediately caved in and buried him. He was rescued within ten minutes, but suffered anoxic brain damage.

(7.) 26-year-old construction worker was helping a co-worker bury sanitary sewer pipes in a 10 ft. trench. They were using a backhoe and a 20 x 8 ft. steel trench box in the trench, trying to remove a concrete casing around a sewer pipe, using the bucket teeth. The victim was using hand signals to direct the operator who could not see the casing. The bucket suddenly slipped sideways off the casing and snapped back towards the victim, pinning him to the side of the trench box. The man received massive internal injuries to the chest and abdomen and died at the scene. The backhoe did not malfunction. The victim had put himself in a dangerous position, in line with the direction of force of the backhoe bucket.