Safe hydroexcavation requires an understanding and respect for all the potential risks.
Gary Toothe has seen enough injuries and deaths in his years to realize that hydroexcavation involves much more than a water hose and vacuum. “There’s a huge void in training,” says the training manager for Federal Signal’s Environmental Products Group, who also spent decades in private business dealing with such equipment.
The most common mistake, he says, is sending an operator out alone. If something goes wrong, yelling for help is the only option. “There’s not much else you can do.”
Trenching and excavation violations are another common safety mistake, according to Toothe. “If you’re going more than 4 feet down, you’re covered by the OSHA standards,” he says. “You have to worry about benching or sloping, and you need shoring or a shield system if someone is getting into the hole.”
OSHA requires that a competent person be onsite during such excavation, someone who knows how to classify soils and knows the requirements. “If there were a competent person on site, a lot of situations wouldn’t develop because people would know better.”
Adding water to the situation makes it more dangerous. “If you add too much water, you’re destabilizing that which you’re trying to create. You’re supposed to keep everything 2 feet back, but if you’re not benching or sloping, that 2 feet can easily give way.”
That’s why you should never stand within 2 feet of the hole. If you have to be that close, Toothe says you should use proper fall protection, such as tying off to the truck.
The risks of vacuum and high pressure water injuries are recognized by most people, though they may not understand the level of risk. A typical hydroexcavator operates at around 3,000 psi. “That is certainly enough to damage the human body,” he says.
An operator must also understand how much pressure the underground utilities can take. “Part of the training I do is about determining what you’re trying to locate, what else may be in the area and setting your pump pressure so you can’t possibly damage any utilities you’re trying to locate.”
Fiber optic cable can handle 1,500 psi even with direct contact. But at less than 3 inches, 2,000 psi can damage the cable. “That’s a lot of money if you take it out,” he warns. HDPE gas pipe can suffer damage at 2,000 psi. Even coated steel gas pipe can be damaged at the typical 3,000 psi.
The vacuum presents risks as well. Toothe investigated an accident in which a man’s arm was caught in the hose up to the shoulder. “He was working by himself,” he recalls. “When they finally got him out, the vacuum had sucked all the muscles and ligaments from his upper arm into his lower arm below the elbow. Above the elbow was just bone and skin.”
While some people may consider safety a trade-off with efficiency, Toothe disagrees. “Hydroxcavation should be used primarily to loosen the material so the vacuum can pull the dirt out of the hole,” he stresses. “It is not meant to dissolve soil. That’s both inefficient and unsafe.”
In fact, he adds, safety devices can make you more efficient. “I can move more water at 1,500 psi than I can at 2,000. By selecting the right tip, the right pump and nozzle configuration, I can actually be more productive at the same time I’m being safe.”
While some companies provide training with a truck purchase, the responsibility lies with the employer. “There are certain things you can do and certain things you ought not do,” says Toothe. “Rather than learn them the hard way, let’s talk about it so you can come out of the blocks safely and efficiently.”