Contractors Use Variety of Tools to Efficiently Locate Utility Lines Underground
It takes time, skill, up-to-date technology and dedicated contractors to safely and efficiently locate existing infrastructure.
Many unforeseen challenges await contractors who plan to drill underground. Before contractors can use their utility locator and start digging underground, they need to first call Call Before You Dig, a nationwide utility locating service. However, to avoid catastrophic mistakes, it is imperative for contractors to verify lines with their own locator paired with the “soft-digging” method using a vacuum excavator.
Using Call Before You Dig to Locate Utility Lines
Communication before excavating on the jobsite is crucial. So before contractors locate a utility line, they need to contact their regional Call Before You Dig to dispatch a jobsite ticket. One-Call takes down the company name, a contact name and the phone number of the person calling in the ticket. They will take down the address and nearest intersection of where the work is going to be taking place.
“We call them to mark everything,” says Dany Jeansonne with TRJ Telecom Inc., in Anjou, Quebec, Canada. “We make sure it’s the same as the drawing they send us. We never take chances.”
The Call Before You Dig service marks what utilities could be in that area, such as rights of way; however, it does not always locate utilities that continue past those easements onto private property, adds Matt Manning, electronics project manager for McLaughlin Group Inc.
“An example of this would be Call Before You Dig marks the easements up to the property line of an apartment complex. They wouldn’t mark the lines from the parking lot to the buildings, so this is where you need to do your own locating,” he says.
Without proper identification, current or abandoned utilities could be damaged or severed. Many times, abandoned lines are not marked, creating headaches for contractors.
“As communities grow, they need to install larger lines, but they keep the old lines in the ground,” Manning says. “Call Before You Dig comes out to mark the existing facilities, but sometimes they don’t mark the abandoned utilities.”
If utilities are struck, the contractor has to stop working until a utility company — typically a telephone, cable or electrical company — comes out and assesses the damage. Contractors occasionally face other last-minute challenges including redesigning the jobsite after the engineer comes out to assess the site.
“The contractor is shut down for whatever time period until engineering redesigns it,” Manning says. “Sometimes it’s as easy as the engineer saying, ‘Ok, just move it over there,’ (but) sometimes they’ve got to go back and draw it out again.”
At that point, the contractor has to call in another ticket, mark and expose the lines again and start the job over. Manning says with a good working relationship and communication between all parties, that work can get done quickly and efficiently.
Using a Utility Locator
When contractors go to locate utility lines, they will use a utility locator to narrow down marked utilities.
“(When) you are working in a manicured yard, you’ve got restoration of that yard,” Manning says. “That homeowner is going to want their yard put back together as best as possible. So by minimizing your excavation to find that utility, you’re going to minimize your restoration cost.”
An example Manning cites is a contractor who didn’t use a utility locator and dug for an electrical line based on the Call Before You Dig marks, but wasn’t able to visually find the line. When Manning used a McLaughlin utility locator, he told the contractor the utility line was a few feet off the mark and only 4 ft down. “So he had wasted 45 minutes trying to find that utility,” he says. “Being able to use a utility locator on the jobsite speeds up the process of finding the utilities, saving valuable time.”
Jeansonne says that his McLaughlin G2 Verifier hand-held utility locators have saved him from costly mistakes on a daily basis.
“Almost every day we find something by ourselves,” he says. “Every job we go to, we use the hand locator. (Sometimes) you can’t see where you are going with the drill, so we have to think twice before we start drilling.”
Types of Utility Locators
Contractors can choose from a variety of utility locators including audio-only or multiple-frequency locators. Audio only are generally single-frequency units that will only make a tone when it goes over a line. These are one of the least expensive locators on the market and can run from $800 to $1,500 — a minimal investment, Manning says.
Although a single-frequency locator can provide an accurate reading, Manning adds that it doesn’t give you everything you need on the jobsite.
“A contractor should invest in a multiple frequency locator with the ability to directly connect to a utility,” Manning says. “It needs to have the capability to induce, which is where you sit the transmitter on the ground inducing into the earth. And it needs to have passive capability. Passive capability is the ability to pick up signals created by the utility or reradiated signals from utilities.”
Multiple frequency locators can range from $3,000 to $6,500 with most units transmitting an audible tone when over the utility, an LCD with a visual reference and some with an estimated depth, Manning adds.
Excavating Utilities with a Vacuum
The safest practice is a soft-digging method called potholing. This method uses a vacuum excavator to visually identify and confirm the location of buried lines. A vacuum excavator has the capability of hydro or air excavation and is the preferred method rather than using a mechanical machine to minimize the damage to utilities on the jobsite.
“Every state law says when you’re in that tolerance zone, that you’re not supposed to use any mechanical equipment to expose that utility,” Manning says.
According to Manning, mechanical equipment includes excavators, rubber tire backhoes or mini excavators, all of which can damage utility lines. Shovels are technically an approved way of excavating utilities; however, some cause more harm than good when locating utilities.
In some applications, workers cannot see the trench lines so they decide to use other methods to try to find the utility. “Next thing you know, you’ve nicked the gas line, you’ve nicked the telephone line, you’ve nicked the power line and you’ve damaged the utility,” Manning says, emphasizing that workers should use soft-digging techniques with vacuums.
Inflicting the least amount of damage and being proactive on the jobsite are essential and can be accomplished by investing in a utility locator and a vacuum excavator. “If a contractor has done all he can do to spot those utilities, he is going to avoid the things you’ve seen on TV,” Manning says. “Nobody wants to see their company truck on TV (with) water or flames shooting up behind it.”
This article originally appeared in the May 2015 issue of Trenchless Technology. For information, please visit www.trenchlessonline.com