May 2019 Vol. 74 No. 5


How to Select the Right Trench Protection System

Blake Smith

How a utility contractor chooses to excavate on a job site can make all the difference in the project outcome. When you consider that 30 to 40 percent of all excavations lack the appropriate protective solutions, it should come as no surprise that projects are often over budget and overdue. When you add the very real risk of injury or death, a lack of proper protection makes no sense at all.

Appropriate trench protection solutions and safety training are the difference between a safe, productive worksite and putting your project at risk. The time spent in choosing the right protective system and ensuring that your team is up-to-date on training is an investment in project success.

The Occupational Safety and Health Administration (OSHA) mandates that a protective system be used any time an excavation is at a depth of 5 feet or more. With four types of workable, OSHA-approved protective solutions available—sloping, benching, shoring and shielding—utility companies and contractors will be safest and most productive if they learn how to select the most effective system for a given job site.

A protective system has multiple components, all of which factor into the selection and installation processes. It starts with aligning the system to the soil and job-site conditions. This is followed by thorough inspections throughout the project and mandated safety training. In addition, there is a balance between keeping the project moving and knowing when to call on the expertise of a professional engineer.

Trench protection system considerations

As an organization assesses a project, here are four considerations to help align the right protection system with the job.

Start with soils. Soils are probably one of the most important factors to consider. Properly identifying the soil type will help the competent person select the appropriate protective system. Sloping and benching angles are different for different types of soil, and the depth ratings of shields and shoring change from one soil type to the next.

Dimensions/working area required. Consider the necessary dimensions of the excavation, depth, length and width. For example, a large installation, such as an electrical vault, needs a different protection system than an installation of a long, linear gas pipe or water main.

Then think about the working area available for the employees. Is there sufficient room for them to safely complete the task? Lightweight aluminum boxes and vertical hydraulic shores are both commonly used options, but the working area available within those protective systems is physically very different.

Conditions in the surrounding area. Another important consideration is the conditions in the working area. Factors such as existing utilities, adjacent structures, surface encumbrances, overhead obstructions and groundwater issues must all be considered when selecting the best protective system
for the job.

For instance, the use of a sloping or benching system often requires a mass excavation of dirt, which means an area large enough to house the pile is needed. This can pose a unique challenge in urban environments, where work space is limited. Crews working in these environments may need to come up with a creative alternative.

Machinery available. The machinery that is available on a job site greatly changes the options of protective systems that can be used. For example, the dimensions of an excavation and the soil conditions may warrant a steel trench shield. However, if the only machine on the job is a backhoe (which can’t handle that kind of weight), an alternative method would need to be considered, such as aluminum boxes or hydraulic manhole braces and sheeting.

When to custom-engineer a solution

Excavations near adjacent structures, underground utilities and roadways may come with unique and complex challenges that often require professional input. Although contractors can utilize manufactured systems with tabulated data, there are times where additional guidance and stamped drawings from a professional engineer (PE) are necessary.

Any excavation over 20-feet deep automatically requires the use of a PE. A PE is also necessary when there are heavy surcharges—such as heavy equipment, stockpiled equipment, roads, bridges and buildings—close to the excavation. PEs look at all the conditions for the site and develop a shoring or sloping design that will work for that specific location. Working with an experienced engineering team can speed up the process considerably.

Contractors may be reluctant to turn to a PE because they fear the PE will develop a shoring design that requires more-expensive, non-standard equipment. But many site-specific designed shoring systems use off-the-shelf equipment.

Inspecting trench shoring, shielding

Once a trench protection system has been selected and installed, contractors naturally want to feel confident that the shoring and shielding equipment they’ve installed to protect their workers is doing its job. This is where inspections come in.

OSHA requires every job site to have a competent person who has been trained to inspect trenches and identify existing and predictable hazards or dangerous working conditions in the surrounding area. The competent person is responsible for overseeing all aspects of the excavation, including the inspection of the shoring and shielding equipment.

This requires a daily check, at a minimum. It is also necessary to do an inspection every time there is a change in conditions. This could be a rainstorm, for example, that can directly affect the stability of the soil. It is critical for the competent person to continually monitor job-site conditions and reclassify the soil, if necessary.

Training is essential for safety

Maintaining up-to-date training on safety regulations and equipment solutions is essential to keeping construction workers safe. Too often, workers doing this type of underground work think an accident won’t happen to them. In some cases, workers may not even realize they are facing a hazard due to lack of training.

Unfortunately, accidents happen all-too often. When a worker suffers a life-changing injury or fatality, the cost goes beyond citations, fines and court settlements. In the end, families are left with the burden of moving forward and coping with their loss.

Consider participating in the annual Trench Safety Stand Down, which takes place June 17–21 this year. This is a valuable resource and an excellent opportunity to discuss safety with workers, including the hazards of working in and around trenches and excavations.

Additional support

The challenges of job-site safety and productivity are factors utilities and contractors face every day. It can be a good strategy to tap into third-party experts which offer quality safety training, as well as other types of support outside the classroom.

As an organization looks to deploy the right trench protection system for each job site, consider the advantages of using third-party resources to tackle areas that are outside a company’s usual range of performance or experience. These experts can solve gaps in a variety of skills, such as providing specialty equipment, training, pre-bid analysis on protective systems, on-site consultation and engineering designs.

The fundamental objectives of trench protection systems are to advance worker safety and job-site productivity. A well-made, OSHA-compliant and all-inclusive trench protection system tackles both objectives on two levels: equipment and personnel. With these needs addressed, utilities and contractors not only maintain safety on the job site, but also produce quality work without risk to budgets or deadlines.


United Rentals, (800) 213-5373,

Editor’s Note

This article discusses common industry processes and is not intended to be a substitute for site-specific professional/expert advice, instruction and supervision. It is recommended to consult with shoring and excavation experts to ensure full compliance of Federal OSHA 29 CFR, Part 1926, Subpart P-Excavations and Trenches.

Blake Smith is a sales and marketing director at United Rentals and a former region product development manager for trench safety.

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