Don’t Cut Corners on Trench Safety

Trench accidents can happen when proper safety precautions aren’t taken, regardless of the crew’s experience.

Don’t Cut Corners on Trench Safety

If working in a trench deeper than 4 feet, OSHA guidelines say a shoring box or shoring device must be used with a way out, such as ladders.

Interested in Safety?

Get Safety articles, news and videos right in your inbox! Sign up now.

Safety + Get Alerts

In April 2021, a Long Island contracting company was ordered to cease all excavating operations and pay $136,000 in penalties, the result of a trench collapse accident that killed two workmen in late 2020.

The resulting agreement also commits the company to do the following:

-Develop an excavation safety checklist to identify hazards and protective measures for work in excavations and ensure that a competent person on site will consult and complete the checklist whenever employees enter excavations.

-Engage a qualified professional safety and health consultant to conduct at least one on-site assessment of excavation safety while employees are performing work in an excavation.

-Provide companywide training on ladder safety and hardhat use to employees.

Safety precautions shouldn’t only be driven by punishment or trying to avoid OSHA violations. Protecting your employees and yourself should always be a top priority. Don’t make extra effort for only a few weeks after being reminded about a tragic accident like this. Systemic, lasting change is the only way to prevent these trench collapses from happening. Don’t wait until after an accident to put safety procedures and training schedules in place.

If you’ve done this sort of work for many years, you may hear these stories about people dying in trenches and think, “That’s someone else. I’ve been doing this a long time. I can tell when it’s dangerous.” But unfortunately, these accidents can happen to anyone and the training is not something anyone — no matter how experienced — should ignore.

The General Requirements Section of OSHA’s Subpart P provides a number of common-sense steps to help ensure worker safety. As with any OSHA Standard or other safety procedure, it is important to always remember that these are the minimum requirements to ensure safe job sites.

SURFACE ENCUMBRANCES 

To ensure stability and integrity, surface encumbrances need to be removed or supported while an excavation is open. Examples include rocks, trees, telephone and utility poles, fire hydrants, etc. 

UNDERGROUND INSTALLATIONS

Examples include gas, electrical, water, sewer lines, etc. They must meet the following conditions:

-Installations are located and marked before beginning work. Property owners and/or utility companies should be notified at least 24 hours prior to digging, unless a longer time is required by local law. Some states require 72 hours advance notice. Most other states require 48 hours’ notice.

-Installations are protected, supported or removed while the trench is open.

Most states have so-called 811 one-call laws. Simply dial 811 to contact the one-call center in your state.

ACCESS AND EGRESS

These are fancy words for entering and exiting a trench. The requirements include the following:

-In trenches that are 4 feet or more in depth, provide a means of access and egress (exit).

-Spacing between ladders, stairs or ramps should not be more than 50 feet.

-No worker should have to travel more than 25 feet laterally to reach a means of egress.

-Ladders must be secured and extend 36 inches above the landing.

In addition, it is important to use wood or fiberglass ladders where there is a possibility of electric shock. Many utility companies and contractors always use wood or fiberglass ladders to ensure there is never a problem.

A “competent person” must design all structural ramps used solely by employees. Further, a competent person qualified in structural design must design all structural ramps used for equipment. Usually this person will be a registered professional engineer.

Finally, the components used in structural ramps must be connected, be of uniform thickness, be constructed so that cleats and other connectors do not create a tripping hazard, and if ramps are used instead of steps, they must be provided with cleats or other surface treatments to prevent slipping.

EMERGENCY RESCUE EQUIPMENT

Such equipment must be available when a hazardous atmosphere exists or could reasonably be expected to exist. Employees entering confined spaces must be properly trained. Harnesses and lifelines are required whenever employees enter bell-bottom pier holes and other deep confined spaces. Lifelines must be attended at all times.

WATER ACCUMULATION

Water must be controlled to prevent cave-ins. Methods for controlling water vary with each situation. Employees are not permitted to work in trenches where accumulation exists unless the following conditions are met:

-Special support systems or shields are used to protect employees from cave-ins.

-Water removal equipment is used and monitored by the competent person to prevent water accumulation.

-Safety harnesses and lifelines are used to protect employees.

Surface water must be diverted or controlled. The competent person must inspect the trench after each rainstorm. 

STABILITY OF ADJACENT STRUCTURES

The objective is to protect employees from cave-ins. A support system, such as shoring, bracing or underpinning, must be used to support structures that may be unstable due to excavation operations.

Excavating below the base or footing of a foundation or wall is not permitted unless they have these characteristics:

-A support system is provided to ensure the stability of the structure.

-The excavation is in stable rock (this is very rare).

-The operation is approved by a registered professional engineer.

Support systems must be provided for sidewalks, pavements and other structures that may be affected by excavation operations.

Understanding the difference between shoring columns and trench boxes is crucial. Shoring is designed to pressurize the trench wall and take away its ability to lean or cave in. Trench boxes are designed to be strong enough to take on the collapsing soil. While a trench box is designed to simply hold back any soil that does collapse, shoring is meant to prevent a collapse in the first place.

Shoring functions via a principle called an “arch effect.” Basically, at the point where the shoring contacts the soil, it compresses outward in an arching pattern. So from point of contact, there is a dome of protection in the arch wall, the size of which depends on soil type.

This means you must know the maximum allowable separation between each column of shoring, which is to say how far apart horizontally two shoring bars may be placed. Manufacturers must provide those distances for each soil type.

The manufacturer specifications, or “tabulated data,” also tells users when plywood is required with shoring. While it’s generally not needed due to the arch effect, sometimes it will be required to prevent minor collapses from the arch wall surface soil.

Due to the relatively complex nature of shoring devices, it can be tempting to use only trench boxes, but you could be asking for trouble. Even though they’re strong enough to take the collapse, they can be less convenient and less versatile depending on the situational factors of a given trench. If laterals or other utilities are a factor in digging the trench, it could limit the space for a bulky metal box.

Another factor is that different types of boxes have varying weight limits. Depth is the main factor here — weaker aluminum boxes, while often easier to maneuver, cannot be used past a certain depth because it cannot hold the weight of all the soil that could potentially cave in. Even the sturdiest steel construction boxes have limits, though they are in most cases deeper than any realistic trench.

Boxes are also required to be stacked up to the top of the trench, so multiple boxes may be needed, which is a lot to haul or maneuver to and around a job site.

PROTECTION OF EMPLOYEES FROM LOOSE ROCK OR SOIL 

Employees must be protected from being struck by soil or rocks that are falling or rolling from the edge and face of a trench. Spoils and equipment must be set back at least 2 feet from the edge of a trench.

FALL PROTECTION

It is required that walkways and bridges be provided over trenches that are least 6 feet above lower levels and are greater than 30 inches wide. Bridges and walkways must be equipped with standard guardrails and toe boards. Additional fall protection may also be required.

INSPECTIONS

A competent person must make all inspections.

The fact of the matter is that preventing trench collapses is not always a simple endeavor. OSHA regulations attempt to simplify it as much as possible, but if it were a piece of cake, workers wouldn’t be dying.

Stocking collapse prevention devices and following trench safety procedures to the letter may be a hassle, but supervisors at all levels don’t have the luxury of cutting corners — or fieldworkers will be those who pay, possibly with their lives.

EDITOR’S NOTE:

Kim Peterson and Jared Raney contributed to this story. 



Discussion

Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.