|Harry Butler, P.E., shows Pete Richter of A.W. Oakes how to test soil type during a recent competent-person for trenching and excavation class. Understanding soil characteristics is one key to safe and effective trenching operations.|
Excavating and trenching are part of nearly every kind of construction project you can think of.
Whether you’re laying sewer and water pipe, burying electrical service, digging footings for commercial buildings, putting in a box culvert for a road, or building a deep tunnel hundreds of feet deep in the earth, the vast majority of projects require some excavation.
Because trenches are prevalent on so many types of job sites, and because improperly constructed trenches can quickly become deathtraps for workers caught in them, it is vital for everyone involved in trenching to know how to properly construct one and how to assess conditions that might threaten worker safety.
Required By OSHA
Trench safety is so important that OSHA requires every job that has an excavation of any type to have on site at least one person certified as competent in trenching and excavating.
And not only does that competent person have to be on site, he or she has to have the authority to stop work if he or she deems that a trench or excavation doesn’t meet OSHA’s fairly complex requirements.
OSHA’s seriousness about trenching can be seen in the fines it levies for even small infractions.
For example, OSHA requires the top width of a V-shaped trench to be a specified amount wider than the bottom. That amount varies with the soil type, depth of trench, and other factors. For every condition, there is a specific minimum top-width to bottom-width ratio.
In some cases, OSHA has fined a contractor $40,000 for having the top width just three feet narrower than it should be. That’s an expensive 36 inches.
Preventing Accidents Is Even More Important
|Group discussion keeps attendees actively involved and helps students learn from each others’ experiences.|
Even more important than avoiding fines, however, is being sure a trench or excavation is safe for the workers who work in and around it.
Many factors can affect an excavation’s stability and safety, and most of them can change rapidly.
Water from rain, a pipe leak or flooding can destabilize once-solid soil. Vibrations or compaction from nearby roadway traffic can cause excavation walls to give way. Occasionally, deadly gasses like hydrogen sulfide, carbon monoxide, and propane can collect and concentrate in a trench, with lethal results.
Because a trained competent-person for excavation or trenching can spot, assess and properly address these kinds of hazards, he or she plays a key role in preventing deadly cave-ins, suffocations and explosions that can shut a job down, or even worse, kill workers.
A certified competent-person for excavation or trenching helps make sure all his or her co-workers get to leave the site safe and sound each night.
Training Readily Available And Economical
The good news is that training and certifying someone as an OSHA-qualified competent person doesn’t have to cost a lot and can be done in a one-day seminar taught by a qualified teacher.
Cost varies by sponsoring agency, but generally ranges from $75 to $150 per person.
One organization offering the training is the Wisconsin Underground Contractors Association (WUCA), headquartered in Milwaukee, whose membership is heavily involved with trenching and excavating.
The course, offered by WUCA about every two months on a Saturday, is taught by Harry G. Butler, P.E. In addition to being a registered professional engineer, Butler worked as a tradesman for 10 years, holds a master’s degree in engineering, is a licensed master plumber and a certified soil tester.
Bringing a wealth of practical knowledge from his engineering and safety consultant business, Butler uses every-day examples to illustrate principles, laws and consequences.
Comprehensive, One-Day, Eight-Hour Course Covers Key Topics
Competent-person training can be completed in as little as one day. Butler’s thorough, eight-hour course digs into trenching from top to bottom.
It covers: OSHA’s trenching regulations; identifying and counteracting hazards related to trenching and excavations; soil testing, types, and the requirements for working in each; understanding various protective systems; and safe work practices.
Says Butler, "Nationally, about 100 construction workers are killed by cave-ins and another 400 are killed in confined-space accidents. In addition, thousands are injured. Trenching looks simple, but it can be dangerous if not done correctly."
Competent person training is not just for workers who go into the hole. It is valuable for everyone in a company that deals in excavation. Butler says his classes frequently contain a mix of not only laborers, but also equipment operators, foreman, superintendents, project managers, engineers, municipal department heads, vice-presidents, and presidents of companies.
"Knowing the ins and outs of trenching," says Butler, "is important for people in a company to design the work, manage the processes, and set the company’s rules and policies. That knowledge helps their crews work more effectively and safely."
"Having students from a broad range of backgrounds and positions helps make a class more lively and interesting. Each brings a different viewpoint, which helps everyone consider things from many angles," said Butler.
Plumbers who complete the class and pass the test at the end of the day can earn eight hours of continuing-education credits to apply toward their licensing requirements.
Practical, Down-To-Earth Information
One of the topics covered is recognizing hazards. This section educates students to be aware of potential dangers like cave-ins, buried utilities, traffic, and atmospheric hazards such as deadly carbon monoxide and hydrogen sulfide gas, which cannot be detected by the sense of smell at high concentrations.
Equally important, it tells them how to protect against them.
The section about OSHA rules not only tells what the rules are; it also explains what they mean and how they apply to specific situations.
What, for example, are the maximum degrees of slope allowed for trenches in stable dry soil? Wet soil? Solid clay?
What are permissible dimensions for stepped walls in various types of soil?
When do you need a shoring system, and what specifications must it meet?
Another topic is soil testing. Butler brings into the classroom samples of different soils and the equipment to test them. Students see and feel granular and cohesive soils, test them for moisture, and learn how to classify them as "A" (most stable), "B" (middle of the road), or "C" (unstable).
They also learn how soil types – and mixes of them – affect trench-wall slope and the type of shoring system to use for each.
They also learn the full range of trench-wall construction and shoring systems available, from sloping and benching, to shields, engineered systems, hydraulic shores, and timber shores.
Students who score 80 percent or higher on the end-of-day written examination are recognized as being competent for trenching and excavation.
Says Butler, "Students who successfully complete an OSHA-approved competent-person class should be able to help their companies trench and excavate effectively while maintaining a strong focus on safety and meeting OSHA’s legal requirements. That’s a win all the way around."