When it comes to creating a safe working environment in trenches, there is no one-size-fits-all solution. Which is perhaps the leading reason why close to 75 percent of the trench safety systems in use today are rented, says Steve Schulz, national sales manager, Speed Shore.
“Contractors have taken to renting these systems because it’s become cost prohibitive to own all the different types of systems you need for all the different types of soils and jobs you encounter,” Schulz says.
“Today, most contractors want to be compliant,” says Terry Rawn, vice president of rental dealer Accurate Laser Systems in Zionsville, Indiana. “That wasn’t true five years ago. They now know the risks outweigh any cost savings.”
Project particulars
Perhaps you’ve done your particular type of job a thousand times and can tell the person at the rental counter exactly what you need. But maybe this job is different, with some peculiarities that have you seeking advice. Whatever the case, when you rent a trench safety system, you should be prepared to tell your rental dealer exactly what your job entails (see “Checklist” sidebar on page XX).
One basic piece of information concerns the length of pipe you’re laying. “Trench protective equipment needs to be 2 to 4 feet longer than each joint of pipe you’re installing,” says Paul McDonnell, district manager trench safety, United Rentals. “This ensures that your crew is protected throughout the installation.”
You also need to relay how close you’ll be to an existing building, street or utility line that runs parallel to the project, all of which need to be protected during the job. “There are some types of shoring equipment that can be installed using a dig-and-push technique,” McDonnell says. “This means the shoring equipment is always ahead of the material being excavated so as to never expose an adjacent structure to undermining.”
Rental dealers should also be asking about what utilities may cross your trench. “There’s a lot of shoring and shielding equipment geared to handle crossing utilities,” says Matt Vogel, sales coordinator, Griswold Machine and Engineering. “For instance, we have a waler system specifically designed to work in areas where there are multiple crossings. It gives you the ability to space your sheeting accordingly and work around those utilities. A solid wall trench box wouldn’t work in that situation.”
Project depth is especially significant. If you own a trench shield that is rated at 16 feet in Type C soil and you have a project where you need to go 20 feet in Type C, you’ll have to rent a stronger trench shield, McDonnell says.
And tell your rental dealer if you want your trench safety system assembled or unassembled, says Randy Goyen, rental store manager for Altorfer in East Peoria, Illinois. “Usually if we deliver it, they’ll want it assembled,” he says.
How much can you lift?
A key piece of information to give the rental counter is the lifting capacity of the machine you will use to place the trench safety system. “It makes a big difference if you’re renting a big steel trench box but you only have a backhoe to lift it,” says Vogel. “It doesn’t work.”
Part of this is making sure that those doing the renting for your firm know what’s happening on the job. Robert Kundel Sr., president of Kundel Industries, got curious when hearing one job foreman declare his dislike for trench boxes and asked why. “He told me, ‘on the last job I was on, the front office sent out a trench box that took two machines to lift.’ That man was required to get productivity,” Kundel says, “but he wasn’t supported with the proper equipment.”
Schulz says renters should always be asked their safety equipment preferences. “If they have a 50-metric-ton excavator,” he says, “they’re probably going to want a big shield.”
Just who is competent?
The person responsible for seeing that a trench safety system is installed and used properly on a project is the contractor’s designated competent person.
The role of a job’s competent person is clearly laid out by OSHA: “A competent person is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary or dangerous to employees and who has the authorization to take prompt corrective measures to eliminate or control these hazards or conditions.”
But too many times, says Kundel, the training they receive doesn’t go far enough. “Competent person training usually offers no instruction on how to use a trench safety system,” he says. “They learn a lot about sloping, but they need to know more about shoring and shielding. They need to know if they’ve got a 20-foot-long pipe and they have a 20-foot-long box, they’re leaving the ends exposed.”
“We can’t recommend any type of system until we know the soil type,” Schulz says, “and that determination has to be made by the jobsite’s competent person. If you ask someone what type of soil he has and he says ‘gray,’ you know you’re in trouble.”
While a number of manufacturers and rental dealers offer both competent person training and instruction in the use of their trench safety systems, the contractor is responsible for the safe and effective installation and use of these systems on the jobsite. Don’t be afraid to ask if you need help, especially when using a system that’s unfamiliar to you.
“Our competent person training is just a break-even business for us,” says Schulz. “There are so many different types of competent person training courses out there, but we don’t think trench safety can be properly taught in less than eight hours.”
Don’t forget the paperwork
How do you know if the trench safety system you’ve rented is strong enough for your job? That information and more is found on the manufacturer’s tabulated data and certification sheet, referred to in the industry as “tabulated data.”
Whether you rent or own your trench safety system, you must have a copy of the tabulated data within easy reach. You’ll be asked for it if your friendly neighborhood OSHA inspector comes calling.
“It’s the contractor’s responsibility to ask for this tabulated data when he or she rents,” Schulz says. “If you don’t have the information contained on it, it can lead to misuse of the trench safety system.
“We build more than 8,000 combinations of trench shields,” continues Schulz, “and there are dozens of different options on the same size shield. Two shields may look the same, but one may be stronger than the other. The only way to determine this is by the tabulated data.”
What information is on this sheet? It includes the unit’s serial number, height, length, thickness, weight, plus the maximum lateral earth pressure the unit will bear. It will also tell you how deep you can use the unit in each soil type and its vertical and horizontal spacing.
“It surprises me that more people don’t request the tabulated data when they rent,” says Rawn. “We’ve got one for every box we rent. It’s our Bible on each box.”
Planning is the name of the game
Kundel says he sees it all the time: Someone has been injured or killed in a trench, and yet there was an unused or incorrect type of trench safety system on the job.
“Planning is critical,” says Kundel. “That’s why we’ve been focusing on how to get the trench safety product married to the project, and why we’ve started our trench engineered design division.”
Started last year, the new Kundel division will consult with contractors on a trench project, giving them a soil analysis that includes the weight of the soil and a blue print on which trench safety system is to be used where.
“Working from the soil analysis, we determine the pressure requirements,” Kundel says. “Then we can more easily pick a trench safety system that the contractor’s equipment can lift. Depending on how severe the problems are, we’ll do an equipment layout that tells them where to put the trench safety apparatus and what kind to use. We’ll have them laid out with serial numbers so no mistakes can be made by using the wrong box in the wrong place.”
For example, on one job Kundel engineered, the company found out one of the boxes the contractor was planning to use didn’t meet the depth rating required. “You discover these things with planning,” Kundel asserts.
While the soil analysis costs around $200, the rest of the services are included in the cost of the rental. “We now have two professional engineers in the division and we do job visits,” Kundel says. “It’s beginning to shape up well because there’s a pent-up demand for it.”
A production tool
Many times contractors view trench safety systems as a cost item rather than a production tool.
OSHA regulations on trench excavation, however, make using trench safety systems a no brainer. “For example,” McDonnell says, “let’s say you’re installing 8-foot-long pipe in a trench 20 feet long and 16 feet deep using a 24-inch bucket in Type B soil.
“The maximum allowable slope that OSHA allows in Type B soil is 45 degrees,” he says. “For this application you would have to dig a trench that’s 34 feet wide at the top, and your excavator would move more than 240 cubic yards of material. If you stacked two 8-foot-tall trench shields instead, you would have to dig less than 80 cubic yards of material.”
Longer pipe, new systems, lighter materials
What’s ahead in trench safety?
The stretch is on: contractors are asking pipe manufacturers to make longer lengths of pipe. “It’s not unusual today to see 30-foot or even 45-foot joints, something you didn’t see much of 10 years ago,” Schulz says. And where the pipe goes, the trench safety system must follow. “As a result,” he says, “we’re building more shields than we ever have that are more than 30 feet long.”
For example, a Kansas City contractor called Speed Shore after he got a job to put in 185,000 feet of 10-inch- diameter pipe. “He had the option to use 36-foot joints instead of 30-foot joints,” Schulz says. With 36-foot joints, the number of joints on the job totaled 5,138. If he had gone with 30-foot joints, the number of joints on the job would have jumped to 6,166. Since every joint represents a chance for a leak and slows down production, “it’s easy to see why they’re doing this,” he says.
Jobs also seem to be going deeper, Rawn says. “My contractors tell me that they’re having to go into less desirable ground these days, and it’s more expensive because they have to go deeper to have the gravity flow work, or they have to build a lift station. To do that, they have to use bigger machines and larger trench safety systems.”
Accurate Laser rents 8-inch wall boxes that are rated to a 25-foot depth. “A couple of years ago, hardly anyone was using them,” Rawn says. “Now we have three of them, and they’re out on rent continuously.”
Although they’ve been used in Europe since the end of World War II, slide rail systems have recently gained momentum in the United States, with a number of manufacturers both selling and renting them. With this system, steel panels slide into tracked rails as the earth is excavated.
“It’s sparked a lot of interest with the larger contractors who’ve used sheet piling in the past,” says Vogel. “More people are becoming educated about it, and they see how much quicker they can get their jobs done, especially when compared to sheet piling.”
Another system making its way to the States is large excavation bracing, which offers 60-foot-by-60-foot spans for open excavations. As for what’s the next new thing, Schulz urges contractors to sleuth around. “Rental companies will guide you to the systems they have in their yard,” he says, “but that may not be the best system for your job. Get on the Internet and investigate what’s out there and then ask the rental companies about it.”
Whatever happens in the future, project owners should take a hard look at including line items for safety in project bids, Kundel says. “Our customers aren’t the small guys, but they need to be,” he says. “They need to get paid for safety.”
