Basic Trench Safety for Excavation Contractors
A re-examination of safety practices that should be routine but are often left out
Trenching and excavation are some of the most hazardous construction jobs in the industry. According to Occupational and Safety Health Administration (OSHA), trench collapses are rarely survivable, primarily due to the weight of soil. One cubic yard of soil can weigh up to 3,000 pounds—roughly equal to the weight of a small automobile. There is little chance of survival in a trench when its walls collapse.
In 2016, injuries and fatalities rose significantly from previous years. “Trench deaths have more than doubled nationwide since last year—an alarming and unacceptable trend that must be halted,” Dr. David Michaels, assistant secretary of labor for OSHA, told the media in Ohio after a 33-year-old worker was crushed to death when the trench walls around him collapsed as he was digging soil out of a 12-foot trench in Washington Township. “There is no excuse. These fatalities are completely preventable by complying with OSHA standards that every construction contractor should know.”
Despite the alarm expressed by OSHA, Mike Ross, shoring specialist for Efficiency Production Inc., says there are always spikes and valleys in statistics, and he doesn’t believe the numbers indicate a trend. “Look at the causes; they all share one component: somebody should have known better.”
In fact, he says that injuries and accidents are not frequent. “There is not a large number compared with falls; it doesn’t happen often.”
Ross cites statistics that indicate the probability of a cave-in is low, but the probability of death in the event of a cave-in is high. “The #1 cause of fatalities is a cave-in.”
OSHA agrees that cave-ins pose the greatest risk and are much more likely than other excavation-related accidents to result in fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. Trench collapses can cause dozens of fatalities and hundreds of injuries each year.
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Very seldom is an accident surprising, Ross declares. “They always know something could happen.”
He says accidents happen for one of two reasons: nothing was done because the contractor was not aware of the dangers, or the contractor was “optimistic or cheap—they knew of a problem, but thought safety methods were too time-consuming.”
An investigation led by OSHA into the cave-in in Ohio determined that KRW Plumbing LLC did not provide trench protection for its employees. The employee was part of a crew installing a sewer line at a residential home under construction.
KRW failed to protect workers from excavated material failing or rolling into a trench or failing from inside the trench walls. Nor did the company train workers to recognize trench hazards. The company was cited for two willful and two serious safety violations. Penalties totaled more than $250,000.
Unfortunately, Ross concludes, bad habits lead to accidents. “If you get away with something once, it becomes routine procedure.”
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Earlier the same day, a portion of the trench had collapsed, but that time, the same worker was able to escape. He had also been involved in a trench collapse a month earlier at another construction site where trench cave-in protection was not provided.
Routine procedure should include OSHA’s general trenching and excavation rules:
- Keep heavy equipment away from trench edges.
- Keep surcharge loads at least 2 feet from trench edges.
- Know where underground utilities are located.
- Test for low oxygen, hazardous fumes, and toxic gases.
- Inspect trenches at the start of each shift.
- Inspect trenches following a rainstorm.
- Do not work under raised loads.
Furthermore, OSHA standards require protective systems for trenches 5 feet deep or deeper. Soil and other materials must be kept at least 2 feet from the edge of the trench. Trenches 20 feet deep or deeper require that the system be designed by a registered professional engineer.
There are several different types of methods and protective systems, the most familiar being slope, shore, and shield. OSHA defines sloping as “cutting back the trench wall at an angle inclined away from the excavation.” Shoring requires installing aluminum hydraulic or other types of supports to prevent soil movement and cave-ins. Shielding protects workers by using trench boxes or other types of supports to prevent cave-ins. Soil and other materials must also be kept at least 2 feet from the edge of trench to prevent the spoils from falling back into the open trench.
Designing a protective system must consider factors such as soil classification, depth of cut, water content of the soil, changes due to weather or climate, surcharge loads (spoil or other materials used in the trench), and the presence of other operations in the vicinity.
The increased scope, complexity, and depth of excavations most likely contributes to the number of accidents, according to Steve Barnhardt, vice president of Corporate Development for National Trench Safety, LLC. “There are now cities in the United States that are consistently digging trenches and excavations at depths of 30 feet or greater as the need for increased infrastructure has grown in large cities,” he observes.
A 30-foot excavation is a significant depth and—when combined with adjacent structures, existing utilities, railroads, and other site conditions—creates a “very complicated environment,” adds Barnhardt.
OSHA requires a professional engineer’s review for equipment that is used in depths in excess of 20 feet. Due to the complexity of some excavations, contractors seek engineered systems on excavations of depths shallower than 20 feet. If the contractor is unsure of how to protect workers, Barnhardt suggests they have an engineered plan developed for the site, whether in-house or through a third party, to ensure appropriate excavation support for the crew.
“Site-specific engineered work has increased dramatically over the last couple of decades as contractors have sought solutions past a standard trench box to address the myriad compliance issues that can exist,” he says.
Trench boxes, shoring, and other methods that prevent unexpected shifts in the soil that lead to wall collapse are part of the safety procedures companies need to institute. According to Ken Montgomery, OSHA’s area director in Cincinnati—where the KRW Plumbing LLC worker was killed due to lack of cave-in protection and proper training—”This man’s life could have been saved by following OSHA’s safety standards that require cave-in protection in a trench more than five feet deep.”
He advises excavating companies to re-examine their safety procedures to ensure they are taking all available precautions. Under the Occupational Safety and Health Act of 1970, employers are responsible for providing safe and healthful workplaces for their employees.
The Right Tools for the Job
“OSHA has special concern for trenches that are 20 feet deep,” notes Ross, “but few people are killed in deep trenches because you can’t make money in a deep hole without something to keep the dirt out. Most are killed in shallow trenches. Shallow trenches lull people into a sense of security. They think they won’t be in there very long. But dirt weighs the same, and it doesn’t take much: three-and-a-half feet is enough to put someone in danger.”
He points out that because OSHA standards require protections from cave-in at depths of 5 feet, many contractors try not to dig deeper than 5 feet. That’s why he blames most accidents on attitude, education, and “how they learned their trade.”
For example, he says many contractors have a box shield onsite, but only use it if OSHA shows up. “It pre-dates OSHA and is designed as a production tool to increase the amount of work they can get done in a day. It’s driven by production; it’s a tool that makes you go faster, but isn’t used because it’s considered a safety tool.”
For most injuries and fatalities, there is likely a trench safety solution already on the market that could have prevented or mitigated the incident, Barnhardt states. The issue resides in selecting the right equipment for the job, installing the equipment properly, utilizing it correctly, and removing the equipment safely.
“Knowledge and education are very important. It’s important that the crew following safety guidelines and manufacturer’s operations manuals when utilizing equipment as well to help avoid injury and or death,” he says.
Technology can also be important to help contractors work more safely, efficiently, and cost-effectively. “We’ve brought several products to market over the last few years that have addressed some of the ancillary issues,” continues Barnhardt.
One is their patented NTS Work Zone Safety System, which features a dedicated trench safety-specific fall protection system to prevent workers and the general public from falling into an open trench or excavation.
United Rentals has never hesitated to invest the financial resources and manpower to collaborate with manufacturers and pilot new equipment, points out Joe Wise, customer training manager. “Our Trench Safety division has been fortunate to have 100% support from the company when it comes to exploring safety innovations.”
Their heavy-duty hydraulic bracing is an example of a product that improves job-site productivity and replaces conventional shoring methods. It’s a modular shoring system that accelerates production by eliminating welding, hot works permits, and the cutting of steel beam walers and struts.
United Rentals also offers shields with higher vertical clearances that allow for safe installation on utility repairs in all soil and site conditions. “We have an internal engineering department dedicated to designing the optimal solutions, often combining multiple systems and technologies for protective systems, as well as dewatering plans,” notes Wise.
With few exceptions, however, Ross says the equipment remains “basically unchanged” for 40 years. “The trench box has not changed much and shoring techniques are ancient.”
So why the increase in accidents? Lack of education.
“The issue … is not just a safety issue, but is also a knowledge and education issue,” explains Barnhardt. “We believe the key is to ensure that all of a contractor’s employees are aware of and trained in the inherent dangers of excavation work.”
While many companies provide extensive training programs and have great safety cultures that seldom have significant accidents, he says there are others that chose not to use the necessary protective system as designated by OSHA, and, as a result, someone was critically injured or killed.
Barnhardt compares it to seatbelt adoption in the United States. “A couple decades ago there was a significant push [to increase] seatbelt adoption, as there was a strong correlation between lives saved when a seatbelt was used. Where we’re at with trench safety is no different today. Trench safety equipment saves lives, and it must be used in every excavation or trench subject to the OSHA standard–or a suitable alternative, such as sloping or benching as allowed by OSHA.”
Education will increase compliance, he believes, adding that one of the biggest things companies can do to address safety is to educate the workforce. He thinks that when everyone from a superintendent to a laborer better understands the risk, they will also realize the value a protective system offers, even if it may be seen as cumbersome at times.
“It’s there to protect all workers and to save lives,” adds Barnhardt.
While Wise admits that there’s “definitely room for improvement in industry safety and education programs,” he thinks the safety record may reflect the divergent teaching methods. “Not all safety training takes the same approach–some are merely a lecture with minimal classroom engagement.”
Wise considers it more effective when contractors solicit feedback from their employees and evaluate their training process. “Training methodologies have evolved in recent years, with research showing that a blended method leads to better retention.”
Choosing training experts who align course content with real-life applications is generally more successful than a strictly classroom approach. In addition, bilingual instruction is also important in many markets to ensure that all workers understand the safety instructions. Wise says that United Rentals incorporates all these techniques, as well as a robust train-the-trainer program that gives larger contractors an effective way to manage training internally.
That’s important because ultimately, training is the employer’s responsibility. Efficiency Production offers an eight-hour training course. Ross says that in 2015 Michigan alone taught 1,100 students. Their national three-day trench safety program has an average of 5,000–6,000 students per year.
Ross points out that OSHA does not define or certify training, although it recently partnered with the National Institute for Occupational Safety and Health (NIOSH), other labor and trade organizations, insurers, and underground utility contractors to develop education and training options on safe excavation and trenching practices.
Resources they intend to make available include a computer-based safety and health training module, a NIOSH Alert in English and Spanish that provides recommendations for engineering controls, training, and safe work practices, and a clearinghouse of resources describing excavation hazards and how to prevent them.
Current resources available to contractors working in underground applications provide subject matter experts in proper safety training, site-specific analysis, and the selection of a proper protective system. Barnhardt lists the benefits gained from these partnerships as improved job-site productivity, profitability, and safe working conditions.
Education is key, as is execution of a safety program. According to Barnhardt, most contractors are addressing the OSHA mandate through employee training with a Competent Person Excavation Safety course. He considers it important for all contractors to know that dedicated safety organizations are available to assist in managing these training requirements. Contractors who utilize United Academy, for example, will find more than 220 unique course titles, in addition to OSHSA-compliant excavation instruction.
“Contractors with safety officers on staff are able to manage employee training records more easily than smaller contractors who may have limited bandwidth to maintain a solid safety program,” explains Barnhardt.
The Competent Person
Training is a start, Ross says, but a key role is played by the OSHA-required competent person. OSHA requires a competent person onsite during excavation operations.
A competent person is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to employees and who is authorized to take prompt corrective measures to eliminate or control these hazards and conditions.
OSHA standards require that prior to worker entry, a competent person inspect trenches daily and as conditions change to ensure elimination of excavation hazards. The designated competent person has a lot of responsibilities—more than some contractors realize, Barnhardt speculates. He believes that there’s a need for increased emphasis on the duties of the competent person as defined by OSHA.
The competent person must make periodic inspections of the excavation, the safety equipment, and the crew to make sure there are no potential risks. The competent person should also make sure that the crew is properly trained and familiar with any equipment being used on a job site. Absent proper training and comprehension of the equipment and how to safely use it, the competent person should not allow work to continue.
“The competent person needs to be able to recognize hazards and proactively plan remedies to address risks,” continues Barnhardt. “They must have the knowledge to conduct proper soil analyses and the experience to determine the best protective system.”
However, Ross believes that the role of the competent person is not well understood–and that the competent person often is not given proper authority.
These days OSHA doesn’t require companies to have a written plan or design to dig a trench. It does, however, require the employer to designate a competent person. Ross says most work from a checklist of potential risks provided by the employer, even if the risks don’t apply to that site.
“It’s a list of minimum and maximum standards. There are so many variables of hazards that the competent person can change the method. The site determines what is safe: slope, trench box, or shore.”
Some choose a method somewhere in between, Ross says, adding that straight digging walls are dangerous and that they need to slope or use a box. “It comes back to training and the relationship of understanding between the company and a competent person. Do they really understand their duties?” he ponders, simultaneously acknowledging the pressure on the competent person to meet deadlines and save costs. “The competent person has two masters: safety and production. It should be set up so the competent person doesn’t have to sacrifice performance for safety; he should have leeway to make decisions and choices.”
Although the employer retains sole discretion over appointing a competent person, that person should have the authority and responsibility for safety on the job. But, Ross cautions, although the competent person is designated, the company is still ultimately responsible for the job site. OSHA requires the employer to provide a work area free from danger.
Rules and Regulations
OSHA subpart b, 1926.651 (Safety and Health Regulations for Construction, Sloping, and Benching) details excavation and trenching standards: configurations, minimum, and maximum allowable slopes for soil types and layered soils, and more. “It addresses everything,” says Ross, although he concedes that the standard doesn’t define the authority.
The Center for Disease Control states that OSHA’s standards for excavation are comprehensive and effective; key elements of the regulations can reduce the risk for trench collapse, and associated injuries and deaths.
However, revised in 1989, it has failed to halt fatalities. Ross blames human error, claiming that “administered properly, it’s a good standard.” The problem lies with people who “don’t know it or don’t follow it. The breakdown is people. Guys in construction are resistant to direction, but underground is different from construction; it has different hours, different conditions, and different terms. They’re not familiar with underground standards and regulations.”
Reducing injuries and fatalities relies on education and communication of the danger to the people involved in excavation work. Barnhardt says a lot of people in the industry are trying to address the problem.
“NUCA and NAXSA are two trade associations that deal directly with excavation and have done a lot to promote these issues. NUCA held a safety stand-down earlier in the year with the goal of promoting increased awareness,” he says.
And, it’s working. Barnhardt credits “some really great contractors with strong safety programs,” adding that there is an ongoing need to ensure the industry aspires towards compliance and that the programs reach all employees so everyone understands the danger of working in a trench or excavation. “One lost life is one too many when dealing with preventable accidents.”
There is a way to be safe, Ross maintains: proper execution of the standards. Should the industry police it? Should OSHA require a checklist? Ultimately, he concludes, it rests with the competent person. “Choose the right person, define his duties and authority, and train him.”