A utilities worker in grave danger in an unprotected 15-foot-deep trench, on a rainy day.

Choose proper trench support for job-site safety and OSHA compliance—and for an often-overlooked productivity payoff that saves you money.

By Carol Wasson

When discussing proper trench support—safety and OSHA compliance are at the forefront. After all, no one wants to see an employee or co-worker injured or killed in a cave-in. No one wants to be smacked with fines, penalties, or insurance claims. No one wants a job site to become a disaster area. Yet even today, experts estimate that up to 70% of all trenching sites do not meet OSHA regulations. Why? It’s human nature at play.

Many think cave-ins can’t happen to them—not for the few minutes or hours that the crew is in an unsupported or unsloped excavation. It’s simply a matter of knowing good dirt from bad dirt, some say.

Many tempt fate year after year, believing that in their 10 or 20 years in the business, they’ve never put anyone in harm’s way. Think of this: Just because you don’t crash every time you drive your car, is that a reason not to wear a seat belt? It only takes once, you know. Until that time it’s thought that bad things don’t happen. So apathy takes over.

Unfortunately, a number of folks feel that it’s easier, faster, and cheaper to cut corners. But truth be known, say experts, poor excavation practices cost more too—adding 8% or more to trenching costs. This added expense often stems from utility line damage when excavations fail and increased construction, insurance, and liability costs. Certainly the big payoff and profit potential lies in being compliant. There’s an often-overlooked productivity factor delivered by proper trench support methods—one that reduces your costs by helping your crew work more efficiently and cost-effectively.

Just the Hard Facts
Bottom line, productivity is higher when workers know they are safe. Unprotected laborers work slowly as they constantly look over their shoulders at unstable excavation walls, and for good reason: In the US, more than 400 workers die every year and 6,400 are seriously injured while trenching. A 2004 Centers for Disease Control (CDC) report on trenching fatalities concludes that deaths from trench cave-ins are still a serious problem despite the fact that compliance with OSHA standards (OSHA 29 CFR, Part 1926, Subpart P, effective March 1990) would prevent these deaths. CDC data show the following:

• Of the fatalities, 256 (47%) occurred among employees of companies with fewer than 10 workers, and 381 (70%) occurred in companies with fewer than 50 workers.
• The industries most frequently reporting fatalities were those involved in excavation work, followed by water, sewer, pipeline, and communications and power-line construction.
• A total of 507 (94%) workers killed were employed in private industry, and 31 (5%) of those killed were local government workers.
• Although excavation and trenching fatalities occurred in various occupations, the largest proportion of deaths occurred among construction laborers. Cave-ins accounted for 76% of fatalities.

“Most cave-ins result from a superficial inspection of a site that indicated no apparent chance of a trench collapse,” says David Dow, president of Memphis, TN–based TrenchSafety and Supply Inc., a company that trains excavation workers in trench safety and also sells and rents shoring and shielding equipment. “In fact, the vast majority of cave-ins actually occur in clay-based soils [where wall failures are not anticipated], as opposed to sandy conditions where failures normally would be indicated. Also, most cave-ins happen in trenches between 5 and 15 feet deep, where managers and workers falsely believe they can quickly escape if a trench wall collapses,” says Dow, adding that with the exception of working in stable rock (which is rare), every trench is going to collapse. “It’s just a question of timing. Some will collapse immediately while others will take longer. The good news is that when done properly, trench work can be safe,” he says.

As to 5- to 20-foot-deep trenches, OSHA requires one of three alternatives in providing a safe working environment for trench workers: sloping and benching, shoring and sheeting, or shielding. Sloping and benching requires the cutting back of trench walls to an angle that will ensure no collapse into the work area. Shoring and sheeting devices pre-load the trench walls and provide a positive restraint to soil movement, thus preventing cave-in hazards. Shielding devices are not designed to prevent trench wall collapse, but rather “shield” workers should a cave-in occur.

Sloping Versus Shoring and Shielding
Sloping generally proves to be the most expensive alternative when compared to shoring and shielding. The savings associated with the vertical cut used in shoring and shielding as opposed to the open area and angle cut involved in sloping are dramatic. “To properly slope a trench often requires the acquisition of expensive right of way, along with the additional costs of excess excavation, refilling, and compaction. With the vertical cut involved in shoring and shielding, few if any of these factors are involved,” says Dow, who conducted a study of the cost differentiation between sloping, and shoring and shielding. He outlines the following example based upon numerous similar situations that contractors and crews find themselves in most often:

Suppose your company is bidding on a 400-linear-foot sewer line that will cut across the parking lot of an existing shopping center. The sewer line must be 12 feet deep. It will not be necessary to remove or cut across any curbs, gutters, or sidewalks. In addition, you will not have to remove any light poles, trees, or shrubbery. We are assuming that you will need three feet of width at the bottom of the trench to lay the sewer pipe.

Your choices for trench protection are sloping or using a trench shield. Because you will be working in OSHA Type-B soil, if you slope to the required angle, you will excavate 2,133 cubic yards of material that would not have to be excavated should you choose using a trench shield. What are your costs to excavate, backfill, and restore the surface (as required in sloping) versus using the trench shield? As you’ll see, the total cost for this rather simple job is $55,228 higher when using sloping instead of a trench shield. And that figure doesn’t even take into consideration the most important factor: your worker’s safety.

Pre-Engineered Shoring and Shielding Saves Time and Money
Modern trench shoring and shielding systems ensure that at no point in your operation—from the initial excavation to backfilling and compaction—will workers be exposed to the dangers of an unsupported trench. Systems are generally pre-engineered, eliminating the costs of custom-fabricated systems. Modular shoring and shielding systems make installation fast and easy, without cutting, welding, nailing, or other time-consuming methods. Most systems are installed and removed from above the ground. Also, the range of systems available is large, enabling you to have a shield or shore of just about any trench specification delivered directly to your job site.

“As far as shoring and shielding systems, we have so many more choices than we did even 10 years ago,” says Steve Schulz, national sales manager for Speed Shore Inc., a manufacturer of trench safety systems. Schulz believes that the industry’s biggest challenges are the lack of OSHA compliance and the lack of competent person training. “You can buy or rent equipment for every trenching application. Lack of availability used to be the contractor’s excuse. That’s just not the case anymore. If contractors ignore proper trench support, they’ll often cite financial issues—that it costs money for the equipment, or that it costs to slope, shore, or shield. Our products have to do with safety as well as productivity. We should not lose one person in a trench ever, because there are ways to avoid it. I don’t call these deaths or injuries accidents, but rather incidences, as they are completely preventable,” he says.

“I think much of the industry sees OSHA compliance as costing them money rather than realizing that the shift to compliance saves them money,” says Keith Lamberson, president of Trench Shoring Services, which manufacturers and rents trench-protective equipment and systems. “With shoring and shielding systems, you can narrow that trench. With sloping, you have more open area to restore. Less surface disruption means less dirt to move and more pipe that you can lay per day. Also, you can rent a trench box for $35 to $70 per day. Consider the money you save with a trench box by not having to slope a trench wall. You can’t excavate or backfill a sloped wall for $35 to $70 a day,” says Lamberson.

“Safety is a primary issue, but economic matters are also very important to the contractor. After all, the contractor doesn’t get paid for the excavation, but rather for how many linear feet of pipe they lay,” says Ken Forsberg, president of Efficiency Production, a Michigan-based manufacturer of shielding and shoring products. “So it follows that contractors would want to use shoring and shielding products to minimize the amount of excavation required per linear foot of pipe. At typical costs for material removal and backfill, contractors could save up to $13 per cubic yard of material per linear foot that does not have to be excavated,” he says.

“Sometimes contractors don’t connect the dots. Your costs at the end of the year are related to whether you did the job safely and efficiently. Officially, people will always maintain that safety is the controlling factor, but it’s often really a budget thing,” says Brian Crandall, president of Icon Equipment Distribution, a full-service shoring company that provides a wide range of equipment. Crandall agrees that many contractors only think in terms of feet per day. “They don’t calculate the time that it takes a crew to clean up behind them for three weeks, while the contractor who shored properly may be in and out of the job within a week,” says Crandall who is a member of the Trench Shoring and Shielding Association (TSSA), a product-specific group within the Association of Equipment Manufacturers (AEM). Crandall, along with other TSSA members, educates contractors by sharing the reasons why proper shoring and shielding ultimately saves money. They cite the following issues, among others, on the AEM/TSSA Web site, www.aem.org:

• Helps avoid costly repairs. The cost of repairing existing utility lines or infrastructure damages due to improper trench support can be significant. Loss of adjacent streets, curbs and sidewalks are a common cost. Also, improper trench support can undermine nearby structural foundations, leading to expensive property damage claims.
• Reduces soil removal and replacement costs. When not using shoring and shielding, a large volume of soil has to be removed, replaced, and compacted. Disposal of soil and debris has become an expensive part of any project. Eliminating unnecessary excavation puts disposal dollars in your pocket.
• Minimizes Workers’ Compensation claims. Premiums are based on your three-year experience modifiers. Accidents or fatalities can easily add more than 100% to your company’s insurance costs when compared to your competitors’ costs.
• Prevents heavy fines, legal expenses, and possible jail terms. OSHA fines start at $7,000 and escalate rapidly from there. In addition, defense costs for these fines can be astronomical. Repeated citations, coupled with a history of poor response to citations, could bring about a willful charge ($25,000 minimum fine). The cost of one death or serious violation could pay for all the rentals and purchases of shoring and shielding equipment you may ever use.

Photo: TrenchSafety and Supply Inc.

Lightweight aluminium trench shields work well in many applications.

Photo: TrenchSafety and Supply Inc.

Slide-rail systems are a great alternative to sheet piling.

The TSSA recommends that you survey your company to determine current trench safety practices. Then take effective action to correct any identified problems. Importantly, list all your employees who have received competent person training and those who have not. Note that a competent person class can be conducted and completed in less than a six-hour period. The TSSA also suggests the adoption of the following plan into your yearly strategies:

• Review each project before the excavation to determine what trench shoring or shielding equipment is most appropriate for the job.
• Work with a trench shoring distributor who can supply full service, including rentals, sales, training, engineering, and repairs.
• Staff all excavation projects with competent persons who are designated as having the authority to stop work when unsafe conditions exist. Have them make regular inspections of your protective systems and soil conditions.
• Teach personnel to understand that the depth of the cut referred to on tabulated data is from the top of the ground to the bottom of the excavation. Sloping does not count and cannot be deducted from the overall excavation depth.
• Supply all excavation crews with proper shoring and shielding equipment onsite at the time of excavation.
• Locate all utilities prior to digging and support them when necessary.
• Work with a registered professional engineer who specializes in excavation work in your area.
• Shore trenches as work progresses. Assemble, install, remove, and disassemble shoring and shielding equipment as recommended by the manufacturer. Their tabulated data should be onsite.

Proper Trench Support—Not the Place to Pinch Pennies
Just one OSHA investigation among many is that of a plumbing operation employee who died from injuries sustained in a trench cave-in. Workers had dug a 40-foot-long, 9-foot-deep trench, approximately 7 feet wide, that the victim entered to take measurements in preparation for the installation of two 2,500-gallon tanks. Another worker assisting him at ground level noticed that asphalt around the trench opening was beginning to crack. He called to his co-worker who tried to run to safety, but was hit by the collapsing trench wall. The company received one willful citation with a proposed penalty of $49,000 for failing to protect employees working in an excavation by using a trench box, or by properly sloping the trench walls to prevent cave-ins.

Employers receive a willful citation when they have shown an intentional disregard, or plain indifference to OSHA requirements. This employer was aware of excavation safety requirements, but chose not to use protective devices due to perceived time and cost concerns. That decision ended in tragedy. The message is clear: Don’t pinch pennies when it comes to proper trench support.

Construction-industry writer Carol Wasson owns JCL Marketing & Communications Inc.

GEC - March/April 2005

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