Slip-Sliding Away

Sept. 1, 2010
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Safety-focused operations never question their commitment to trench protection. Above all, they know that proper trench safety saves lives. They know that working within a safety culture enhances morale and retains and attracts the best employees the industry has to offer. And finally, they know that there is a link between safety and profits, and that is proved in the way they do business day after day.

On the other hand, there are other operations where trench safety is simply slip-sliding away-and for this reason, as many as 400 workers are killed, and another 4,000 injured each year in trenching mishaps.

Today, trench shoring systems, such as slide rail systems and hydraulic bracing and sheeting, or shielding equipment, such as the common trench box, can be purchased or rented anywhere in the nation. Manufacturers and suppliers, such as Efficiency Productions, GME, ICON, Speed Shore, Trench Shoring Services, and United Rentals Trench Safety, back their equipment lines with site-specific engineering and onsite field technicians who offer installation and training support. Yet with all the available resources, there are always those contractors who “roll the dice and expose workers to the potential of a cave-in, either due to a lack of training and awareness, or pure carelessness and negligence, or merely in an effort to save a few dollars,” says one trench safety expert.

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Much to Learn
As chairman of the Trench Shoring & Shielding Association (TSSA), and president of Trench Shoring Services, Keith Lamberson is a veteran in the trench safety industry. He stresses that among contractors there is a wide variation of skill and knowledge levels where trench protection is concerned. Regarding the lower end of the safety knowledge spectrum, he shares a few of the more memorable comments he’s heard over the years:

“We don’t need a trench box. My daddy taught me, and I know good dirt from bad dirt.”

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“I don’t understand why we need to test the air down there. If a guy gets a little light-headed, I just send two fresh men in and they pull him out by the shoulders, and one of them will take his place.”

“We open the lid on a manhole, and if the cockroaches are moving, we know there is good air.”

“I throw a match in the manhole, and if it blows up then the hazard has gone away…and if it goes out, there was no air.”

The prior statements say it all-truth is indeed stranger (or should we say, more dangerous) than fiction.

As for the midpoint of the spectrum, Lamberson says that many contractors are aware of the need for trench protection equipment, but they are not always certain about the requirements and product options. “Certainly, the traditional utility contractor typically knows what is needed and has the proper equipment onsite, but some of the smaller contractors and municipalities may ignore the potential of a cave-in. Since trench walls don’t cave in every time they dig, they just assume the inevitable will never occur,” he says.

Lamberson stresses getting proper training first, followed by consulting with your supplier to match the requirements of the job with the requirements of the equipment. He adds that proper specification requires an examination of soil types, excavation depth, potential loading on the system, and the overall project parameters.

Trench Safety Systems
Over the past several years, the underground construction industry’s focus on trench safety awareness has become more prevalent, and that has driven trends in the rental environment, reports Lance Palmer, region sales and marketing manager for United Rentals’ Trench Safety division. “On the one hand, contractors are looking to comply with OSHA Standard 1926 Subpart P Excavation Safety, and, on the other hand, they need the most cost-effective solution for the job if they are going to win the bid and still make money on the work. It’s never just a case of the rental rate. The rate is part of a much larger productivity equation.”

Palmer says that in the past, when people thought of trench safety systems, the equipment was the first thing that came to mind: trench shields and boxes, aluminum hydraulic shoring, sloping, and benching. “Today, the economic climate has put a lot of pressure on underground contractors to be on top of their game,” says Palmer. “Now, when a contractor needs to rent shoring, the first thing that comes to mind is ‘how expert is this rental company about trench safety? How many options can they offer me?’ It’s about the partnership.”

Palmer says that contractors should pay special attention to a rental supplier’s range of site experience, familiarity with OSHA 1926 Subpart P, and applications knowledge of the systems they represent, as well as provisions for compliance training.

“The partnership is at its most productive when both the contractor and the rental supplier are working projects together from the design stage to completion,” he says. “We call it ‘Production/Protection’—equal parts worker safety, project productivity, and cost effectiveness.”

—Provided by United Rentals

Systems Link Safety and Profitability
“Approximately 96% of all underground projects for water and sewer are designed using “˜open cut’ methods of excavation. While some of these projects are considered routine and not very risky, others are much more risky-with utility crossings, obstructions and other issues that make shoring these kinds of projects a large headache,” says David Crandall, vice president of ICON Equipment Distributors Inc. “Due to project complexity and the added pressure to be competitive, a very attractive option is using a slide rail shoring system versus conventional methods such as sheet piling,” he says.

According to Crandall, ICON’s slide-rail shoring system is made of grade-50 steel, which is a high-strength, low-alloy steel that finds its best application where there is a need for more strength per unit of weight. Importantly, the system is modular by design, which allows the contractor to install the system within almost any excavation where the water table can be controlled and dewatered.

The ICON slide-rail shoring system is installed simultaneously as the trench or pit is excavated. The contractor starts by excavating the trench to a depth of 4 feet, then installing the first rails and lining plates, and squaring up the system. Digging continues on the inside of the system, removing the excavated material as needed. More panels and rails are added incrementally using the “dig and push” method until the required sub-grade is reached.

“Installation of a pre-engineered modular system of panels, rails and braces allows the contractor to easily sheet a small or large pit 30% to 50% faster than conventional methods such as steel-driven sheet piling,” says Crandall.

“Slide-rail systems have really become the most flexible shoring system on the market today, as it is a component system comprising panels, posts, and moveable cross-section members, which is put together somewhat like an Erector Set,” says James McRay, marketing and media manager for Efficiency Production, Inc. “None of the pieces are particularly heavy and can be handled by the small-to-medium-size excavator. So, the contractors can handle the systems themselves without having to subcontract to a sheet piling crew,” he says.

McRay stresses the design of customized systems for contractors. “We have become a problem solver for very difficult excavation conditions by coming up with creative solutions. For instance, contractors call us about projects that are very deep and have limited access. They may be faced with investing in expensive sheet piling systems and want to look at more affordable options-and often we can meet their needs with a customized slide rail system,” he says.

For example, McRay says that Efficiency Production recently engineered a slide-rail configuration for a contractor who had to dig to a depth of 28 feet right next to an existing wall. A three-sided shoring system was designed to use the existing wall as part of the shoring system.

“Slide-rail systems are a popular rental item,” says McRay. “We’ll provide drawings that can be used in the bid. We’ll ship the system as a rental, send our installers out to the job site to aid in installation, and, when the project is completed, they simply ship the components back. It allows underground contractors to expand their business. They are not limited to only installing sewer pipe, for example. They know they can take on more difficult excavations by calling us for a customized shoring system,” he says. GME Products Manager Dennis Parker agrees that with its modularity, a slide-rail system is a very beneficial tool. “Before the last 10 years, slide rail really wasn’t an option in the US but was prevalent overseas,” says Parker. “It’s really suited to the larger excavations, where more pipe clearance is needed, and it allows you to do three and four-sided protection systems for tanks, and other projects where we had once tried to go with bigger shields-and you just can’t keep building bigger trench shields,” he says.

Parker says that the contractor base is not as educated about slide-rail systems as it needs to be. “The systems are very detailed and require manufacturer support in the equation to assist in specification for the given application. Depending upon the depth, site-specific engineering may also be recommended,” he says.

According to GME, its slide-rail system offers an open-track system that is more functional than other slide-rail systems. It allows for panels to be pivoted into place, more like a door, and then clamped into the linear rails before sliding into place. This is different from systems that thread panels into closed rails from overhead. The system’s self-adjusting rollers in a box frame strut ensures that the struts remain level as the excavation from within the trench is made and the slide rail is pushed to grade. GME maintains that this slide-rail system is one-half of the cost when compared with the use of tight-sheeting systems, and that fewer workers are required for its installation. Gary Hicks, regional sales manager for Speed Shore, says that slide-rail systems require precision and skill during installation. “If one is new to the system, it’s good to have dealer or manufacturer field technicians onsite for installation. Contractors should also have at least two pieces of equipment onsite to put slide-rail systems together. It can be two excavators or an excavator and a forklift, or an excavator and a rubber-tire backhoe to get the job started.

After the initial stage of installation, one machine can do the job,” he says.

Hicks also says that excavations must be dewatered prior to installation. “You may have to start dewatering three to five days in advance of construction. Dewatering makes it easier to put the equipment in and take it out-and of course, OSHA says that you can’t work in a trench that contains water,” he says.

Dewatering experts say that well points and vacuum pumps are required. Good dewatering can reduce shoring costs, while bad dewatering can make any shoring solution fail.

Speed Shore says that its slide-rail systems provide superior trench protection in tough ground conditions for utility installations, pump stations, tank installation/removal, bore-pits, point repairs, vault placement, and more. Systems are available in single-, double-, and triple-rail designs, and can be configured for linear, square, or rectangular excavations to depths of 32 feet.

As to basic trench safety equipment guidelines, options are classified as active or passive, depending upon the type of system. Passive systems (such as a trench box) shield the workers from a cave-in but still allow some soil movement. In contrast, active or “positive” systems (such as slide rails) proactively prevent soil from moving, protecting workers as well as adjacent facilities and structures.

More information about active versus passive systems can be found in a white paper available for download from United Rentals Trench Safety on

Hydraulic bracing and sheeting is another trench protection system that links safety with profitability. Lance Palmer, regional sales manager of United Rentals Trench Safety, says that the system delivers significant cost and labor savings by eliminating the need to cut and weld beams.

“Hydraulic bracing and sheeting is a fairly new technology from the UK that we’ve brought to the US, and one that is available through any of our 60 locations,” says Palmer, referring to 80T and 150T hydraulic struts manufactured by Groundforce Shorco. “This is a hydraulic system that opens the struts, saving time in installation. The contractor can expand it, then retract it, leapfrog it, and send it down the line. The hydraulic system saves considerable time and money versus the option of a weld-in place system or a bench slope, which requires a much larger excavation,” he says.

Palmer explains that before this technology, contractors had to weld the beams together for support, so there could be some concern over the quality of the welding. Is it good enough? Is it going to hold? With the hydraulic systems, contractors simply drop it in, expand it, and lock it into place. “It’s certainly a lot easier and faster than having to cut welds out and reweld,” he says.

United Rentals recommends that all contractors and owners narrow trench protection options and perform cost/benefit analysis before construction. To aid in these evaluations, Palmer says, the company has developed its own cost-estimating programs that enhance its ability to recommend the most cost-effective solutions for customers.

“These diagnostic tools make it possible for customers to evaluate systems based on soil type, trench dimensions and other variables at the site and compare the viability of up to for different system designs,” he says.

Palmer goes on to explain that a solution must fit an entire project, and that a large job frequently requires a combination of protective systems. He says that specifications should allow as many types of systems as possible to accommodate a variety of needs and conditions.

Finally, Palmer stresses that education is a top priority at United Rentals Trench Safety. He says that the company trains 20,000 contractors annually in the OSHA Excavation Standard, and is greatly expanding on that number now and into the future by offering standardized monthly training classes at all its trench safety locations in North America.

  • Build Safety Into Business
    Safety should be a culture that is built to last. An Oregon OSHA publication cites eight ways to build safety into your business:
  • Management commitment to safety as strong as any other critical part of the business
  • Accountability for safe work practices for everyone
  • Employee involvement in day-to-day safety goals
  • Hazard identification skills required for entire organization
  • Ongoing hazard control that consistently reduces exposure to potential mishaps
  • Accident and incident investigations that prevent reoccurring problems
  • A commitment to classroom and in-the-field training
  • Evaluation of yearly goals to set the stage for new safety goals
Safety must be practiced by the entire organization until it becomes the very foundation of the company. There is no room for carelessness and corner cutting. Certainly, disasters such as the Gulf oil spill provide a serious wake-up call to the latter. We have learned that the cost of failure is far too great.