Staying Safe in the Trenches
How to ensure your employees don’t become statistics.
- By Tim Robson
- Oct 01, 2019
To be buried alive, crushed, is an unimaginable fate; as little as two cubic yards of dirt collapsing into a six-foot-deep trench has the same force as a pickup truck moving 45 miles per hour. But trench collapse is all too common, and death and serious injury befall hundreds of workers across the United States every year.
Unfortunately, the problem is getting worse: 2016 saw as many trench deaths as years 2014 and 2015 combined. Why? A booming economy is driving more construction, and there is also a serious lack of awareness of the risks of trenching among companies and workers (and sometimes corner-cutting to save time and money). All of these factors combine to put lives at significant risk.
The private construction industry accounted for 80 percent of all fatalities that occurred during the most recent timeframe for which data is available (2011 through 2016). Within the construction industry, 38 percent of those fatalities were at industrial locations, 30 percent were at residential locations, and 20 percent were at street/highway sites.
OSHA has recently responded to the rise in deaths by launching a National Emphasis Program on Trench and Excavation in October 2018. The purpose of this program is to increase awareness of safe practices and to step-up enforcement.
Construction companies need to take the safety regulations around trench work seriously if they want to ensure their job sites are not liabilities and that their workers don’t become statistics. This article will address the legal requirements involving trench work as well as answer some of the most frequently asked questions about trench safety.
Trenching vs. Excavation: OSHA Requirements and More
According to OSHA, excavation and trenching are among the most hazardous construction operations. Cave-ins pose the greatest risk and are much more likely than other excavation-related accidents to result in worker fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. The regulation that covers requirements for excavation and trenching operations is OSHA 29 CFR 1926.650-652.
People often question the differences between an excavation and a trench. OSHA defines an excavation as “any man-made cut, cavity, trench, or depression in the earth’s surface formed by earth removal.” This can include excavations for anything from cellars to highways. A trench is a specific type of excavation that, by definition, is deeper than it is wide, and no wider than 15 feet at the bottom of the excavation.
Trenches are vastly more dangerous than excavations due to their propensity to collapse. As a result, and in a perfect world, OSHA would prefer all digs to be excavations and not trenches. But, of course, this is not possible. So much construction, especially in densely populated areas, must be done near roadways or existing structures. Thus, trenches are often narrow, deep, and potentially very dangerous.
In the world of trenching, there are two overarching keys to maintaining a safe job site: your competent person and your preplan.
Competent Person: Your MVP
OSHA requires that a competent person evaluate the safety of every trench or excavation every day, every time a person is to enter, or if conditions at a job site change. OSHA defines a competent person as “one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has the authorization to take prompt corrective measures to eliminate them.”
It is the competent person’s job to evaluate all of the components that can impact the safety of a trench. These include soil type, weather, nearby utility lines, adjacent structures (roads, railways, etc. and their potential to cause vibrations that result in trench instability), and more. Becoming a trench competent person requires hours of training including time in a trench evaluating circumstances, learning how to classify soil types, and working with the safety equipment, as well as time spent in-classroom training.
Many often ask, does a competent person need to stand by the trench at all times? Absent any mitigating factors such as water accumulation, by law, the competent person does not need to be present at the trench at all times. However, he or she is ultimately responsible for making ongoing inspections to ensure compliance throughout the process. Furthermore, and to be quite frank, this is the wrong question to ask. The question I much prefer is, “At what point during the process do I get my competent person involved?”
The answer is: as early as possible.
Far too often the competent person is brought in after the trench has already been dug. Doing this hobbles your competent person’s ability to advise on technique and trench shape for optimal safety, provide direction as to which safety equipment should be used, and to properly assess the safety of the situation. Bringing your competent person into the fold before the trench has been dug enables that person to create a comprehensive preplan to guide excavations, ensure the safety of workers, and protect your company from potential liability.
Preplans: Your Key to Safety
A big part of being safe is being prepared. Knowing as much as possible about the job or work site and the materials or equipment needed is a best practice, and building a preplan is an essential part of your competent person’s job. There are many things that OSHA recommends that companies should consider when building a preplan, including:
Traffic. OSHA requires that workers at sites near roadways, or other trafficked areas, wear hi-visibility vests. Also, the site must have a system, such as barriers, in place to prevent vehicles from rolling into the excavation/trench. Sometimes this also means road closure or traffic patterns changes. In addition, vibrations from nearby roads will make a trench more unstable and susceptible to collapse; a competent person will take this into account when assessing the safety of a trench.
Proximity and physical conditions of nearby structures. The presence of nearby structures or underground utility lines almost always means that the soil has been previously disturbed, and previously disturbed soil cannot be classified as “Type A soil” (the safest kind for trenching); it is inherently more unstable than undisturbed soil. Further, the proximity of structures such as buildings, the depth of their foundations, and whether the trench may experience surcharge load from those foundations all factor into the competent person’s safety calculations. Finally, if a trench is deeper than 20 feet, or if the dig will impact another structure, OSHA mandates evaluation by a registered professional engineer.
Soil. During preplanning, the competent person will evaluate the surrounding soil type (classified as Stable Rock A, B or C). The soil will impact the type of trench that can be dug, the safety equipment that must be used to shore the trench, and more.
Surface and groundwater. Anyone who has dug a hole at the beach understands that the presence of water makes a trench inherently unstable and more likely to collapse. Workers cannot legally enter a trench that has accumulated water unless there is a system in place to mitigate and the system is actively abating that hazard. Furthermore, a competent person must monitor the drainage of that water.
Weather and location of the water table. How likely a trench will accumulate water depends on many factors including the depth, water table (and in some areas, the tide), proximity to a storm drain or sewer system, weather and more. A competent person will consider factors such as these when creating a trench preplan.
Overhead and underground utilities. Again, the presence of utilities almost always indicates soil has been disturbed. In addition, if digging above a water or sewer line, your risk of rupturing the line can be high, which poses a very dangerous scenario: a 4,000-gallon per minute water line may rapidly fill your trench and possibly kill or entrap whoever is inside.
Construction materials/equipment/tools. OSHA requires that any materials, equipment, or machinery used near or over a trench project must be prevented from accidentally or inadvertently falling into the trench. This is done by either barricading, stop logs, or active monitoring.
Nobody should die as a result of someone else’s perceived emergency (whether that “emergency” is a loss of water supply to a building or the clock ticking on a hard bid job). But unfortunately, this happens time and again.
It doesn’t matter whether you are the owner of a business or a new hire. Everyone on a job needs to take safety to heart and be empowered to speak up if they see a crack in the trench or if something’s not right. The last thing anyone wants is someone saying, “I knew that would happen,” after a death. While regulatory requirements can change, fundamental values do not change. Thus, during our training, the most important lesson we teach is that safety is not a requirement, it is an inherent value. When lives are a stake, anything less is unacceptable.
This article originally appeared in the October 2019 issue of Occupational Health & Safety.