The accident report fits a familiar pattern: Workers are installing a water or sewer line. They dig a ditch 7 to 9 feet deep and a worker climbs in, even though the trench hasn’t been properly shored, benched, or supported with steel walls.

Sometimes, someone on site notices a crack forming in the soil above the trench just before the wall cleaves off and buries the worker under 3 to 5 cubic yards of dirt, each weighing more than a ton. Attempts at digging the victim out often result in a second wall breaking loose and the rescue effort quickly turns to a recovery mission.

For the past two years, in places like Blue Springs, Mo., Grand Rapids, Mich., and Jacksonville, Fla., deaths from trench cave-ins have hit an all-time high on single-family construction sites. According to the Bureau of Labor Statistics, 2016’s 23 excavation and trench-related fatalities were double the average of the previous five years. Although 2017 saw only 17 deaths, when combined with injuries reported to OSHA involving trenches it was the most dangerous year for trench safety in recent history.

The accidents plague residential projects, often occurring when sewer lines are updated or new water pipes are laid. According to OSHA, nearly one quarter of all trench accidents from 2013 to 2017 happened at single family jobsites. During the same period single family jobsites saw more trenching accidents than at pipeline dig sites and road construction. When multifamily jobsites are added to the mix, residential construction sites accounted for 30% of all trench-related deaths and serious injuries.

In most cases, deep trench work is done by plumbers or excavators working for plumbing contractors to dig the troughs needed for water or sanitary lines. The National Utility Contractors Association (NUCA), a Fairfax, Va.-based trade group, has been offering trench excavation safety training for 28 years. The group’s vice president of safety says the roots of the problem have to do with the country’s growing shortage of skilled labor. “In 2008 the industry went downhill and the numbers of fatalities went way down, because there was less work,” George Kennedy says.

But now that the construction industry has bounced back and skilled labor is in short supply, builders are hiring more unskilled workers to replace those who left during the Recession. “Now 10 years later, you’ve got a bunch of young guys coming to work with no experience, especially with trenching and excavation,” he says.

The NAHB has also taken note of the issue. Robert Matuga, assistant vice president of safety and health agrees that the fatalities are a symptom of an over-stretched labor force. “There’s a labor shortage right now, there’s high turnover in the industry which means that we have folks coming in that may or may not have been trained,” he says.

Legal Questions
Even though trench digging is usually handled by plumbers or excavators working for plumbers, builders can be liable in the event of an accident. In order to avoid trench-related problems and keep crews out of harm’s way, NUCA suggests looking at an excavator’s OSHA history online, along with checking references. Requirements about adhering to proper excavation techniques should be included in any contract binding the builder and the excavator. Since the builder can be held accountable by OSHA via third party liability, the builder should oversee and inspect the work.

Responsible parties face stiff penalties and fines. For instance, in January, the owner of a residential construction firm near Seattle was charged with felony manslaughter after one of his workers was killed in the collapse of an unshored 7-foot-deep trench. In addition to the criminal charge the company was fined $51,500. Other fine amounts levied by OSHA for recent cave-ins across the country range as high as $294,000.

Prevention 101
OSHA rules about trench excavation are quite specific, starting with any ditch that is more than 5 feet deep that is not cut into stable rock must be protected from cave-ins. The job site must be supervised and inspected by a “competent person” who is qualified to recognize hazards and has the authority to take quick action to eliminate the hazard including if necessary, stopping the work. That same competent person is also charged with testing the soil via a visual and hands-on inspection.

OSHA has four classifications for soil including stable rock, and types A, B, and C based on the stability. The classes can be effected by depth of the trench and existing climate conditions--including rain. For any trench deeper than 5 feet or any trench that shows signs of collapse, OSHA requires sloping, benching, shoring, or shielding:

Sloping refers to angling the walls of the trench away from the center. For type A soil in trenches less than 20 feet deep, OSHA wants to see a slope angle of 53 degrees or 9 inches out per 1 foot of trench depth. For type B, OSHA requires 1 foot sloped out for every one foot depth, an angle of 45 degrees. Type C requires an angle of 34 degrees or 18 inches out for one foot of trench depth.

Benching is similar to sloping and involves widening the slope of the trench and adding ‘benched’ intervals in the wall for added support.

Shoring systems are made up of braces, sheeting, and shores that provide reinforced, temporary walls to prevent cave-ins. Most are made from timber or aluminum with hydraulic braces, which is the most common type used. Soil type, length, width, and depth of the trench determines the specific design of the shoring system.

Shielding uses trench boxes also known as trench shields comprised of two large, solid plates held by four cross members. The specific conditions of the trench also determines the kind of box that can be employed.

According to NUCA the best way to get in and out of a trench is via a secured ladder that extends 36 inches above the point of access. Besides NUCA and OSHA, the U.S. Department of Labor also offers training in safe excavation techniques. Information is available in the forms of audio, printed material, web pages and videos. On October 1, OSHA officially kicked off its National Emphasis Program targeting trenching and excavation.

OSHA tries to make it easy to comply with trench excavation regulations and offers free on-site consultations that are separate from the enforcement division and will not result in penalties or citations. “Education is the key,” says Kennedy. “People take it for granted because they do a lot of trenching with nothing going wrong and all of a sudden it caves in and it’s tragic.”

This article was originally published on Builder.