Safety in the Trenches
The right attitude and the right equipment keep workers alive.
If you have no idea what it is like to be crushed and trapped by earth in a trench, you should meet somebody who has suffered that trauma…and can talk about it. I know such a man. He has great difficulty talking, walks slowly and painfully with two canes, and doesn’t work at the job at which he used to be a well-paid expert. Just once, just for that one occasion, they didn’t bother to shore the trench they were working. Apart from crushing Dan, the soil ruined a backhoe. “It was only a small trench, less than a day’s work, and we wondered why we should bother to shore the sides and protect those of us who had to work in the trench,” explains Dan. “Now we know why.” He smiles ruefully about it now, struggling along the sidewalk to watch his grandson play baseball.
The earth caving in is not the only danger when we are trenching, even if it is the one most likely to cause a serious injury or death. Trenches are holes. Things and people can fall in if they are not properly secured. If we have room at the site, we could slope the top of the trench so that a cave-in is unlikely (but don’t park anything valuable on the slope!) but shoring and shielding are the choices of professionals for protection of those in the trench. If your work is next to houses, for basements or foundations perhaps, some of the trench regulations do not apply to that specific job but many contractors are always careful when they have to dig below the surface level. From a retired earthmover I learned this gem of advice: “Keep your workers out of the excavations as much as you can, and put your soil loads as far back from the hole as possible.” A general rule would be that you should shore the trench if it is 4 or 5 feet deep. That’s most trenches. Such trenches or pits can be for any number of jobs that fall under the title of public works or infrastructure installation and repair.
Protection at Bigger Excavations
Sometimes the trench required is more than 5 feet deep. Tri-City Groundbreakers, in Midland, MI, won the bid for a project that required an excavation deeper than their usual work. The contractor was to place a lift station (24 feet by 26 feet) some 40 feet deep for Bay City’s Township Pump Station No. 1. “We’d never gone that deep before, but we decided to go ahead and bid on it,” notes Tri-City President John Schmidt. Such an installation would pose challenges from soil conditions, site encumbrances, and shoring the excavation for an extended period. “It was a postage stamp lot,” comments John Briggs, the contractor’s project manager for that project. “There were railroad tracks on one side, and the dig was within a few feet of a residential street. And there were other underground utilities running all around it.” The biggest challenge, however, was probably finding shoring that would work efficiently for such a large and deep excavation. “We researched the cost of sheet piling and compared that with a couple of manufacturers’ slide rail systems,” explains Schmidt. “We decided to go with a slide rail system from Efficiency Production.” The Universal Slide Rail from Efficiency comprises steel panels (like those of trench shield sidewalls) and vertical steep posts. There are several configurations possible. Apart from the popular, obstruction-free ClearSpan configuration the Universal Slide Rail can be turned into small, four-sided pits, or in a multi-bay configuration for the installation of large tanks and structures. That latter style can be used for lengths of pipe over 40 feet.
“When we got the quote on the system from Efficiency, there was quite a sticker shock,” admits Schmidt. “But, after factoring in the cost of sheeting, hiring a sheet piling crew, and the length of time it would take to install sheeting, slide rail started to be a most economical and competitive alternative.” Slide rail is installed as the trench (or pit) is being excavated. A standard size excavator can handle the component pieces; that means that most earthmoving contractors can install the system themselves. For the project in Michigan, Tri-City used a Komatsu PC 600 and Cat 330 to install the system. In the pit itself, the contractor used a Komatsu PC 128 to dig under the posts and panels, and any spots the bigger machines could not reach.
Installation of the Efficiency slide rail system involves sliding the panels into integrated rails on the posts as the pit is dug. The process is usually known as a “dig and push” shoring system and the equipment and workers can be safely in the hole throughout the entire installation (or removal) process. “We’d never used slide rail before so this was a learning curve for us,” observes Schmidt. “The initial installation took longer than we’d anticipated but, once we started going, it went really easily.” That’s typical for first time users, according to Greg Ross, Efficiency’s director of slide rail systems and an experienced slide rail installer. “The first day, they are usually intrigued on how and if it’s going to work,” says Ross. “On the second day, there’s a usually a bit of consternation, as they may have to overcome unexpected ground conditions and they are trying to put the system in one piece at a time. By the third day, they’ve got the hang of it and really start to realize that this is a great system.”
For this lift station project, after cutting the site down about 5 to 7 feet, Tri-City installed a 38-by-50-by-32-foot deep ClearSpan configured slide rail system. The ClearDesign design is unique in that it shores a large excavation without the need for cross braces; the system stays open by using waler i-beams on the outside of the system at the top and inside the system to prevent deflection. The inside waler brackets have rollers on the back that allow it to move up and down easily as the system is installed or removed. “We learned a lot of things on that project,” comments Schmidt. “Not the least was that the slide rail system is awesome for excavation safety. It worked so well, we’ve used it on two other projects since that one.”
The solutions that give us safety in all our trenching operations are not necessarily this or that equipment. We have to start at the beginning, or even before the beginning. One of the most experienced companies in trenching and shoring and safety on the job is Baker Corp. The company offers many trench shoring products, including modular aluminum shields, slide rail systems, steel trench shields, steel sheeting, and aluminum hydraulic shoring. Baker also offers competent person training and trench rescue training classes. We asked Dana Buchholzer, an acknowledged expert in this field, if there were ways to prevent accidents and ways to keep our workers and equipment safe. “A lack of training must be a prime cause for the accidents,” asserts Buchholzer. “There are still too many workers who have had little or no training, some who don’t even know that hazards exist. Some of this attitude is caused by the complacency of owners and supervisors, a complacency that can be based on their experience or their inexperience. We must teach our employees the importance of providing and using protection. We should tell them the rates of deaths and injuries, noting that the known numbers are almost certainly less than the real number.”
|Photo: Efficiency Production
The safe place to be is not in the hole while the big pipe is being placed, even though the hole is well shored.
Main Image: Hydro and vacuum excavation is ideal around buried utilities in crowded urban areas.
|Photos: Efficiency Production
|The sides of this hole for a new lift station had to be safe and secure before work could be started.
OSHA regulations are not simply the government wanting to interfere! OSHA regulations are based on our unpleasant history of trench accidents and the reasons for them. Since OSHA introduced stricter regulations (do you and your employees know them?) there has been a marked improvement in trench safety nationwide. The high fines put on those who do not follow the wise regulations have probably helped to make those regulations more observed, but we’d like to think that contractors are more genuinely concerned, too. “It helps to know why there have been cave-ins,” says Buchholzer. “It helps to know details of locations, to see the kinds of soil that were involved, to understand the volume and weight of soil that has caused cave-ins. Do your employees know how much soil weighs?” A cave-in can be compared to somebody dropping a car on you as you work in the trench or pit.
There are many options for protective systems, including sloping the ground above the trench, shoring, and shielding. For most contractors the affordability of available equipment is a necessary concern, but the cost should be weighed against the costs of not having protection. Loss of life is an obvious cost, but fines and insurability are major considerations. If you have a history of cave-ins and accidents, you will almost certainly see negative results in your future bidding; you may even be disqualified from bidding on some contracts. “The availability of protective equipment is important,” Buchholzer reminds us. “It would be wisest to consult a full line supplier of protective products, because a supplier with only a limited line of products could recommend some that he has available but which are not what you really need. The supplier should be familiar with different protective products and their particular best uses.” One bad habit to avoid is that of having the right equipment available on site, but not using it, or using it only now and then during the excavation. “Having possession of the right equipment does not satisfy the need. Almost complying with regulations and instructions does not keep everybody safe and does not make a contractor innocent of any charges for illegal operations.”
One aspect of trench accidents that Mr. Buchholzer mentioned (and one that is rarely discussed anywhere by anyone else) is: What happens after an accident? Something that is surely worth knowing is how to contact the local emergency services. How fast will those services react? Unfortunately, no reaction is fast enough for the cave-in that causes instant death to the victim, and that is how too many cave-ins finish. If there is no death, but serious injury, it becomes important to know how to dig the person out with a minimum of further harm. It is unlikely that most emergency services have had any or adequate training in excavation of trapped workers so cooperation between contractor and emergency personnel is essential. The two different types of expertise (contractor’s and emergency technician’s) can work well together and may save a life that would have been lost through ignorance or carelessness. All of this emphasizes yet again the importance of training your personnel before any trench accidents occur. Apart from knowing the dangers of trenches, workers should know the limitations of all equipment used, and perhaps you should ascertain that your suppliers provide good training, too.
Vacuum and hydro excavation seem to address the safety of equipment more than that of people. Workers do not always stand in the trenches for underground pipes and cables. Some trenches are only inches wide and the machines that dig them can lay the cable, too. One of the companies involved in that kind of trenching (and almost everything to do with underground construction) is Ditch Witch. The company makes an impressive range of equipment for trenchless excavation; it also offers equipment for vacuum excavation. This technique of excavation, where excavators and backhoes may be too big and too likely to cut the wire, pipe, and cable buried under today’s streets and neighborhoods, has been most popular for projects like exposing buried utility lines, valve box cleanout, debris cleaning at residential sites, and similar small sites. The Ditch Witch FX20 would do those tasks easily and it can fit in the back of a pickup. It takes danger out of some excavation, and protects hidden utility lines underground with its gentle but powerful excavation.
“Given the broad range of applications that a Ditch Witch vacuum excavator can accomplish, there is really no such thing as a standard machine,” suggests Jeri Lamerton of Ditch Witch. Each of several available models and sizes can be configured to the needs of the user. Do you need it trailer or skid mounted? No mounting required? Do you require the reverse flow option? If your work is in the northern states you could probably benefit from a tank heater for cold weather work. I’ve mentioned the FZ20, but there are also the most productive (and quiet) systems, the FX60 and FX30. The owner can select the tank size, horsepower, and other options for smooth operation.
It’s the possible liability for damaging underground infrastructure that has prompted municipalities, contractors, and energy companies to invest in hydroexcavation with its non-destructive approach to such potentially dangerous equipment like gas lines, fiber optic lines, and all the other utilities that are everywhere in today’s communities. H2X is another leading company in hydroexcavation, with a fleet of its own trucks to handle projects for customers. “We’ve seen a new acceptance of the technology recently and a willingness to make the commitment to a nondestructive way of working on underground utilities,” comments Mike Clark, chief executive officer of H2X. “We are all going to be safer as a result of this.” Nobody expects hydroexcavation to compete with an efficient backhoe or trencher when the work is cross-country over a long distance. But if you don’t know where the underground infrastructure is sitting in residential and commercial areas, be safe. As Clark points out, avoiding one line strike can pay for hydrovac services several times over.
Vacmasters (a division of Barone, Inc.) offers air-vacuum excavation systems. These use high-pressure air together with a powerful vacuum to break up the soil and then remove it. Safety is the key to the success of this method. It can dig a trench or pothole quickly and easily, with no risk of damage to buried infrastructure. Once workers have exposed the utility, they will mark its precise location. When the repair or other adjustment is complete, the removed spoils are placed back in the hole as backfill. There’s no manual digging with an air-vacuum excavation system; the spoils can stay dry, easy to put back; and there is no cost for disposal of spoils. Vacmasters has systems that vary in size from the small, trailer-mounted System 1000 to the larger, more powerful, truck-mounted System 4000 and System 6000. “We install and service more than 10 million feet of energy distribution systems annually,” says Todd Davisson of NPL Construction Co. “We have to know what’s down there and we can’t damage any utilities while we’re trying to find out. Potholing with a Vacmasters system is more economical than water because we can dig a hole faster, with no mud hauling or disposal, no returning with backfill, and no road base or underground utility damage resulting in costly claims. Air is non-conductive, so we think it’s definitely safer for our operators.”
Reasons for Buying Protection
After an accident, the reasons for having worker (and equipment) protection in trenches are obvious. It’s rather like wondering if your house is strong enough to resist bombs. Once a bomb has hit you, you know the unfortunate answer, and too late. So why do contractors delay getting protective equipment? “A primary reason contractors give for not using a protective system like trench boxes or hydraulic shoring is not that they are careless or ignorant of the dangers, but rather that they are just trying to save money,” commented James McRay of Efficiency Production to me a couple of years ago. “What they may not realize is that trench shields and shoring were developed originally as a production tool, not a safety device.” Forty years ago Efficiency Production began commercial manufacturing of trench shields. That was some 10 years before OSHA said we had to have protective systems. It became obvious to users that removing as little soil as possible was a cost-effective way of excavating.
Most manufacturers offer a wide range of shoring equipment and each one will claim particular benefits from its range of products. You need to do research from all manufacturers or from your local, expert distributorship. Kundel Industries lists some advantages for its shoring equipment and it could be a good idea to check the states features against competitors that you are considering. Why is one configuration or material of construction superior? Kundel says its equipment has a continuous solid weld, 16-inch support centers for the pouter skin (others may have 32-inch centers), thick steel where needed, internal pounding members, true C soil rating for tabulated data, a clean, continuous knife edge, stacking lugs as standard components, and cold-formed steel design metal. These are good strengths. How do they compare with other brands?
Kundel Industries offers the Basic all-steel trench box in many sizes, and you can check weights, ratings for different soils, and sizes of available spreaders from an excellent chart published by the manufacturer. The Basic 3 model comprises a series of shields for small excavators or rubber-tired backhoes; the B3 has been especially popular with municipalities, plumbers, and maintenance crews because it’s good for spot repairs and minor mainline work. The Basic 5, for small excavators, is designed to work well in 12-foot sewer line installations. This model would be good for a contractor with a machine in the 6-to-19-metric-ton class. Kundel’s Titan slide box design has been popular with those installing pipe. The Titan telescopic box is a kind of cross between a drag box system and a slide rail system. You assemble the system from standard components of a drag box, socket rails, and rolling spreaders. It is a fast-production shoring system. You can tell from these descriptions that there is much to learn about the vocabulary of shoring systems. The study is worthwhile because you’ll end up with the right system for your project.
“But how good are those little trench shields?” I was asked by a young contractor who thought everything had to be made of thick, cumbersome metal that could be moved only with the assistance of an excavator. The name GME came to mind in my answer. GME has an impressive array of lightweight shielding equipment, and it’s particularly practical for those thousands of small trenches that are dug every day across our continent—small but big enough to have a worker down in them. Lightweight shields are easy to install, and they can be used for bracing during projects like public works repair jobs. You can carry them by hand, and it’s hydraulic pressure that gives the shields their strength. GME hydraulic shields have aluminum sidewalls with heavy-duty hydraulic struts. The strut has a hydraulic cylinder and return spring. On the subject of smaller trenches, please check your local regulations for the depths where you need to have shoring and shielding. Regulations change (based on experience nationwide) and where 5 feet used to be the depth where you had to use protection, many places have already reduced that to 4 feet.
There are several variables in trenches. The most important may be the soil itself. How much does that type of soil move? If you don’t know, find out, because all soil looks the same to most people…but it isn’t. Anybody who grew up in an agricultural environment knows that, and so does anybody who has done much gardening. Some soil hates to be disturbed and wants to fill any hole you make in it; that’s the dangerous soil for trenches. Are there utilities already going through the soil? Are there loads on the soil that will change the lateral earth pressure? Heavy excavation equipment can do that. Is there likely to be water in the trench? (As a child, did you ever dig a hole on the beach and then see how it filled from the water hidden below? Once I had this fantastic castle of sand and, suddenly, half of it gave way. Water has come in and taken my foundations.)
The good aspect of trenching and shoring problems is that the correct help is readily available. Allow me to mention some names that spring to mind when I think of safety in trenches; this list is not complete, I’m sure, but they are the companies that came to my mind. Speed Shore Co., Efficiency Production, GME, the ICON Group, Kundel Industries, United Rentals, Trench Shoring Co., American Shoring, and Trench Shoring Systems. The protective systems available have proved their strength and value many thousands of times over the years; they have saved lives and property. We don’t know how many lives have been saved, how many life-wrecking injuries avoided, by the use of shoring and shielding systems. We don’t know how much equipment has been saved, how many business-breaking fines, penalties, and contracts saved because of the simple use of a protective system for a simple trench. Keep it simple. Dig the trench. Protect the people who must work in it.
Author's Bio: Paul Hull is a frequent contributor to Forester Media publications.