The Importance of Trench Safety
by James McRay
March 1, 2011
Trench safety is not complicated. If it is choice between sloping an excavation for safety or using a trench box for safety, using a trench box requires removing less dirt and reduces restoration cost.
In 1978, OSHA mandated the use of a trench protection system for all excavations deeper than 5 feet. These protection systems can include trench shields, shoring or simply sloping trenches or excavations.
All of a sudden, “trench safety” became an integral part of the construction industry’s vernacular.
But long before OSHA’s 1926 Subpart P Excavation Standards became law, trenches were dug and deep utilities were installed. Did contractors not bother with trench safety before then?
They did, but more on an ad hoc basis. Contractors would typically build their own trench safety device, with trench shields or trench boxes serving as the most popular and easiest safety systems to build. Sheet piling and timber shoring were also commonly used. Even then, most contractors knew that “trench safety” was good for their production and ultimately their bottom line.
Today, some contractors still do build and use their own trench shields or other trench safety equipment. A contractor’s designated Competent Person (CP) can design a shoring system if the excavation or trench is not deeper than 20 feet and remain in compliance with OSHA. However, once an excavation gets deeper than 20 feet, OSHA requires a trench protection system to be designed and engineered by a professional engineer (P.E.).
Options for Safety
One trenching safety option is for a contractor to use a premanufactured shoring system. The advantage? Using shoring or shielding built by a shoring manufacturing company takes the guesswork out of making or designing your own trench safety device or system.
An additional benefit of going with a manufactured system is that shoring companies are required to supplement all their trench shield and shoring equipment with tabulated data. The tabulated data sheet stipulates the engineered restrictions of the device or system depending on the soil conditions—Type-A, B or C—as classified by OSHA’s standards. As long as a contractor abides by the tabulated data and keeps a copy of the data at the worksite while the system is being installed, then the contractor is compliant with OSHA.
Another advantage to using premanufactured shoring? Most shoring companies have a PE on staff that stamps the tabulated data sheet. Some states require a PE stamp on the tab data.
Efficiency Production is one of the companies that commercially engineers and manufactures a modular, reusable trench shield. Today, the company builds a wide arrange of trench safety equipment including lightweight aluminum trench shields, hydraulic shoring and Slide Rail Systems.
Dangers to Avoid
Yet, despite all the availability of trench safety equipment, the assistance and information from shoring companies and the oversight from OSHA, trench cave-in accidents still happen all the time, sometimes fatally.
“It’s not that contractors don’t know about trench safety equipment; it’s just a choice on some contractors part not to use it,” says Mike West, Efficiency’s vice president of engineering. “There have been instances where a contractor has brought a trench box out to a jobsite, left it on the side of the road to scare off the OSHA inspectors, and never put it in the hole.”
But OSHA inspectors really aren’t fooled. And when they come onto a jobsite, the first question they will ask is to see the CP. The second question they will ask is to see the tabulated data for the shoring.
Another potential risk is created by using shoring improperly or outside the engineered limitations listed in the tab data. Sometimes this can be just as dangerous as not using shoring at all.
“Contractors can get a false sense of security thinking that ‘well, my guys are in a trench shield, they are going to be safe,’ but the trench shield is only rated to 8 feet, and they are in a 15 foot deep trench,” West says. “That shield may not protect them, and because they were using it beyond the engineered limitations, it voids the tabulated data.”
West says it also does not do any good to have a trench shield in the hole, but workers stand outside of it, usually in the front or back.
Trench safety is not complicated. And it can really benefit a contractor’s bottom line. To put it simply, the less dirt you remove from an excavation, the less—potentially expensive—backfill is needed to replace the dirt. If it is a choice between sloping an excavation for safety or using a trench box for safety, using a trench box requires removing less dirt.
For contractors that choose to not practice trench safety, the risks—and costs—are high. If a contractor’s employee or other personnel is hurt or killed in a trench accident—and the excavation safety standards were not followed—the contractor may be liable for all costs and compensation to the victim and the victim’s family. If the rules were willfully disregarded, the contractor may be liable criminally.
Don’t forget, shoring companies are ready and willing to help contractors design, implement and supply a good trench safety system, or simply to offer advice and expertise. Many resources are available. There is no excuse to not practice trench safety.
Excavation Safety Checklist
- Is there a contractor appointed Competent Person (CP) on the jobsite? Have all personnel received trench safety training?
- Has the CP conducted a thorough determination of the soil conditions and classified the soil as Type A, B or C per the OSHA standards?
- Have the estimated locations of all underground installation and utilities been determined prior to excavation? If underground utilities will be exposed, is there a plan for the utilities to be protected, supported or removed while the excavation is open?
- Are stairways, ramps or ladders present when needed?
- Are personnel who are exposed to either public or project traffic wearing reflective or high-visibility vests or shirts?
- Have any overhead obstacles been identified? Is there a plan to remove or work around the overhead obstructions?
- Are employees protected from falling rock, soil or equipment by placing these materials a minimum of 2 feet from the edge of the excavation or behind a retaining device?
- Are standard guardrails provided on walkways and bridges that cross over 6 feet or wider excavations?
- Are all excavations that are accessible to the public adequately barricaded or covered when unattended?
- Are employees removed from the excavation if the CP finds evidence of a situation that could result in a possible cave-in, protective system failure, hazardous atmosphere or other hazardous conditions?
- Have all shielding, shoring or other protective systems (for excavations more than 20 feet) been designed by a registered professional engineer and/or accompanied by tabulated data from the manufacturer?
- Are shielding, shoring and other protective systems checked each day to detect movement and possible failure?
James McRay
James McRay is the director of marketing and media at Efficiency Production.
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