Hydroexcavation and Conventional Digging Work Together

From:  Municipal Sewer & Water

Written By:  Doug Day

Working in sales and marketing for the largest fleet of hydroexcavators in Texas, Karl Lassberg doesn’t see conventional excavators as competition. “We’re really working in conjunction with mechanical equipment,” says Lassberg, of T-Rex Services Hydro Excavation and Industrial Vacuum Services.

Founded with one truck in 2001 by former NASCAR driver Bobby Hillin Jr., T-Rex now has a fleet of more than 38 hydroexcavation and vacuum excavation trucks. “At the time, there wasn’t a lot of hydroexcavation going on in the southern Gulf region,” Lassberg says. “He just went out there and hustled, and the popularity of hydroexcavation has grown over the last decade as the awareness of the technology has grown.”

Besides the usual safe exposure of underground utilities, it has also grown more popular for many other uses, especially in confined areas. Lassberg cites a recent job as a good example, a lift station for a restaurant. The excavation was only 4- by 4- by 6-feet but required hand digging because the location was inside a parking garage. “It would have taken several days to dig and carry out 3.6 cubic yards of dirt by hand,” he says. “We ran a remote hose down a stairwell and it took us less than three hours. Our bill was much cheaper than a hand dig.”

He adds that hydroexcavation is also a good alternative to an auger for digging holes. “If you have only a couple of holes to dig with an auger, hydroexcavation can be competitive because the material is sucked straight into the truck and dumped off site,” Lassberg says. “You don’t have to worry about additional equipment to scoop it up and haul it away.”

The advantages are even greater when it comes to utility pole holes, usually 18 inches in diameter and 8-feet deep. Two people with post hole diggers will need about two hours to do a single hole while it’s a 10- or 15-minute job with hydroexcavation.

Lassberg says electro-mechanical work has led to a lot of hydroexcavation work in recent years, such as grounding wire trenches, 6 inches wide and 18 inches deep, that used to be dug by hand. “We can hydroexcavate 300 to 400 feet of that in one day and cover it with a skid-steer instead of putting five guys trying to dig for days at a time.”

One such project was at a lighting conduit project at the Galleria Mall in Houston in September 2010 – 700 feet of trench (2 feet wide and 2 feet deep) underneath a sidewalk bordered by a long line of historic oak trees. “With all those tree roots, you have to dig a little differently and more conscientiously,” Lassberg says. “If you even skin a tree root you can kill the tree, so digging by hand is very tricky business.”

In this case, all the roots crisscrossing through the excavation area made any other sort of excavation impossible. Since tree roots can also be damaged by high-pressure water, the excavators used lower pressure and kept nozzles well way from the roots. The job also had to be done in 48 hours in a high traffic area of the city’s busiest area. T-Rex brought in five trucks. “We started Friday at 9 p.m. and finished 40 percent ahead of schedule,” Lassberg says. “Two years later, the trees are still in great condition.”

Lassberg says there are three main issues to think about when considering hydroexcavation. Is there a source of water on site? Can the spoils be dumped on site? And how close can the truck get to the excavation?

“Most trucks require a water source, whether it’s a frac tank, water truck, hydrant, or a pond,” he says. “Dumping on site usually makes a job much more productive. Dumping off site means driving to a dump site and back, sometimes there are dumping fees. Access within 15 or 20 feet from the dig site allows for the greatest productivity but we can work 300 to 400 feet away from the truck when necessary.”

When he first got involved in the industry, it seemed people assumed he was in competition with other excavators. “They were a little leery of me,” he adds. “The first thing I tell people is that hydroexcavation is a great tool to have in their arsenal — for the right job.”

 

Dangerous Business: Safe Hydroexcavation Requires An Understanding And Respect For All The Potential Risks

From: Cleaner Magazine
Written By: Doug Day

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 on site 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,” Toothe says.

Adding water to the situation makes it more dangerous. He adds, “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,” Toothe says.

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. “Hydroexcavation 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.”

Applying Pressure: Customers must understand the equipment for hydraulic and vacuum excavation before putting it to work.

From: Grading & Excavating Contractor
Written By: Carol Brzozowski

Hydro- and vacuum excavating systems are becoming so much an increasing part of the construction site landscape these days that one manufacturer states it’s been the busiest year for his company to date, with the demand in some cases exceeding supply.

The driving factors: increasingly strict construction site regulations, the growth of oil and gas exploration in North America, and not truly knowing what lies underneath the ground despite line locating technology.

Vacuum excavation is a technology that uses water or air as the medium to loosen the soil surrounding buried utilities, points out Ben Schmitt, product manager for Vactor Manufacturing. A vacuum source will remove the soil into a debris body for offloading at a remote location or back into the excavation site. Since only water or air is being used to disrupt the ground, buried utilities are exposed without disruption or damage, he adds. “By using vacuum excavation as the preferred method of exposing utilities for repair, the user protects the asset from damage along with any other buried utility that may or may not be known to occupy the same general area,” Schmitt says. “Not knowing the exact location of other buried utilities is a leading cause of unintentional utility strikes.”

Schmitt explains that on most dedicated hydroexcavators available today, end users can choose either a fan system or a positive displacement (PD) blower as the vacuum source. Each has distinct advantages. A fan system “moves an incredible amount of air, excavating more rapidly than other systems,” he says. “It’s also easier to operate and maintain, and the unit’s overall weight is usually less. Also, fan units are generally less expensive than the PD versions. “A PD blower moves air over longer distances and generates higher amounts of vacuum, allowing for excavation at greater depths, but at slower speeds than fan units,” he adds. End users often have unique applications that lead to a preference for one type of vacuum system, so Vactor offers both PD and fan machines, says Schmitt. “In either the fan or PD configuration, a simplified airflow path design will maximize pickup and filtration effectiveness,” he says. “Additional features that improve the unit’s overall productivity include extendable or telescopic booms offering a wide range of rotation and mounted on the curb side, large-capacity water tanks and debris bodies, heavy-duty solid construction, heated pump and hose reel cabinets, convenient operator controls, and tool storage.”

Vactor’s typical customers are primarily municipalities, contractors, and utilities, as “non-destructive vacuum excavation is quickly gaining acceptance as a relatively safe, effective alternative to traditional excavation methods,” notes Schmitt. “We see a rapid growth in vacuum excavation,” Schmitt adds. “The method is increasingly becoming the preferred alternative to conventional excavation practices. The cost of strikes to buried utilities is a risk most construction companies, utilities, and cities are no longer willing to accept. As a result, there is a desire to seek alternative means. Vacuum excavation is true damage prevention.”