Shallow trenches don’t always command the same respect as deeper trenches, yet they account for well over half of all trench-related fatal accidents in the United States.

From 2000 to 2009, 350 workers died in trenching or excavation cave-ins in the United States – an average of 35 fatalities per year, according to figures from the National Institute for Occupational Safety and Health. Most incidents involve excavation work or “water, sewer, pipeline, and communications and power line construction,” according to the NIOSH bulletin, “Preventing Worker Deaths from Trench Cave-ins.” An analysis of OSHA data from 1997 to 2001 showed that 64 percent of fatalities in trenches occurred at depths of less than 10 feet.

The last fact is of particular interest as it pertains to an incident last October in Somers, N.Y. According to media reports, a 29-year-old man who was part of a crew working on a local school’s water system was trapped in a relatively shallow trench for about two hours after it collapsed around him and buried him up to his neck. Different sources reported the depth of the trench at three to seven feet.

For the rescue, local firefighters and emergency responders were assisted by a Westchester County trench-collapse team, along with members of the highway department and local law enforcement. Yet with all these emergency responders flocking to the scene, the biggest help came from a local contractor.

Brian Cook of Fred A. Cook, Jr. Inc., a plumbing firm in nearby Montrose, N.Y., got a call from the local highway department superintendent, who asked if he had one of his Vactor trucks nearby. Luckily, he did, and the truck was on the scene in short order, sucking soil away from the trapped worker. Meanwhile, emergency responders placed sheets of plywood in the trench, which reportedly hadn’t been previously shored, to prevent further collapse.

Emergency personnel were eventually able to remove the man from the trench and transport him to the Westchester Medical Center by helicopter. He survived and suffered only minor injuries, but the situation easily could have ended badly. The incident underscores the critical importance of taking proper safety measures when working in trenches.

The OSHA standard for excavation and trenching describes the precautions needed. There is no reliable warning when a trench fails. The walls can collapse and trap workers in an instant. A single cubic yard of soil can weigh more than 3,000 pounds, more than enough to fatally crush or suffocate workers.

Lack of a protective system was the leading cause of trench-related fatalities in a review of OSHA inspections. OSHA requires that all excavations five feet or deeper use one of these protective systems:

Sloping the ground

Benching the ground

Shoring the trench with supports such as planking or hydraulic jacks

Shielding the trench (using a trench box)

Workers should never enter any trench deeper than five feet unless it has a protective system designed and installed by a Competent Person.

The type of soil, water content of the soil, environmental conditions, proximity to previously backfilled excavations, weight of heavy equipment or tools, and vibrations from trucks and machines all can greatly affect soil stability and the hazards workers face. When the sides of trenches are shored, the type of soil and the width and depth of the trench determine how far apart the supports should be spaced.

The bottom line is that contractors need to know the dangers presented by even shallow trenches and need to be well versed in proper safety precautions. It might be easy to disregard the danger of a 4-foot-deep trench, especially for those who work on underground lines daily, but ignoring the danger is a sure way to put your employees and your business at risk.

The human and financial cost of an accident will far outweigh any time or money saved by skirting important safety measures.

OSHA’s guidelines for trench safety can be found at www.osha.gov. Web-based trench safety training is available at www.cdc.gov/niosh/docs/2006-133D/flash/index.html.