Published March 2008

Yet Another Reminder

By Scottie Dayton (page 16)

The death of a 52-year-old worker in a trench collapse underscores the importance of protective measures.

Fatalities from trench collapses continue to occur despite Occupational Safety and Health Admin-istration (OSHA) standards that specify sloping and benching, shoring, and trench boxes or shielding to reduce excavation hazards.

Such an incident took place last December in the Town of Somers, Wis.

Juan Oviedo, 52, was 25 feet down laying sewer pipe when the mud caved in below his trench box. Oviedo was submerged up to his neck. Two area rescue teams using vacuum trucks worked for two hours to free him to about the chest before the earth collapsed again, burying him.

Recovery attempts were hampered by groundwater and mud that continued to fill the hole. Steel plates up to 20 feet long were brought in to shore the trench as crews battled for 12 hours in below-freezing temperatures before recovering Oviedo’s body.

All too common

Based on data from the U.S. Bureau of Labor Statistics, an average of 54 workers die in cave-ins annually — half of them while working on sewer or water systems. A person buried alive can survive for only a limited time due to the pressure exerted by dirt, rocks, and debris.

According to Canada’s National Occupational Safety and Health Director Dr. J. Donald Millar, these deaths can be “almost without exception, anticipated and avoided using existing safety precautions. They are not accidents.”

More than half the time, earth, rocks, and debris inflict fatal injuries. A single cubic yard of earth weighs 3,000 to 4,000 pounds, depending on soil type and moisture content. Only a few feet of soil can prevent lungs from expanding and cause suffocation in as little as three minutes. Heavier soils can crush the body in seconds.

Once the earth moves, there is a 98 percent chance of a second collapse. This shows the importance of soil analysis to determine appropriate sloping, benching, and shoring. If an excavation is less than five feet deep, OSHA does not require a protective system unless the competent person sees signs of a potential cave-in.

For trenches five to 20 feet deep, shoring and sheeting, shielding, sloping and benching are acceptable protective measures. Project planners and the competent person onsite must determine which systems will work best. If an excavation is greater than 20 feet deep, a registered professional engineer must design the protective system.

“Regardless of the depth of the trench, OSHA requires a competent person to inspect conditions at the site daily, and as frequently as necessary during the work to assess hazards,” says Keith Lamberson of Safety Corporation of America in Atlanta, Ga.

Barriers to safety

A study by the Center to Protect Workers’ Rights published in March 2006 lists a casual attitude toward safety by employers and workers as a main barrier to ensuring safe trench work. “Many workers believe a cave-in will not happen to them or that they can outrun it,” said a safety specialist.

The second major barrier to trench safety, according to the report, is a lack of appropriate safety training for competent persons and workers. Also problematic are contractors who are inexperienced in and ignorant about trenching hazards.

“Contractors may lack information about the specific protection needed, where to get it, or that it may be rented,” says author Barbara A. Plog, University of California at Berkeley. “The problem is particu-larly acute among contracting companies that employ fewer than 10 workers.”

The study also cited as barriers insufficient OSHA enforcement and the cost of implementing safety measures. “Many contractors believe that the cost of trench protective equipment, as well as its transportation, installation, and storage, are excessive and affect company profits,” says Plog.

Keys to prevention

The consensus among safety experts is that consistently implementing the requirements of the OSHA excavation standard (Subpart P, Excavations, of 29 CFR Part 1926.650, .651, and .652) would prevent most trenching-related deaths and serious injuries. In particular, they emphasized the need for a properly trained competent person at every trenching worksite to assess the hazards and ensure the appropriate use of trench protective systems.