As a grading and excavation contractor, you’ve seen it a million times. A contractor stands on a job site, hands on his hips, and shakes his head in disbelief as water shoots from an open trench. All while the operator in the excavator’s cab and other crewmembers look on apologetically.
What’s worst than witnessing this scene? It’s being that contractor who has hit the utility line.
Even the mention of accidentally hitting a utility line creates a pit in a contractor’s stomach. Not only do such mishaps result in unnecessary downtime, but they can also disrupt utility service, making your customer angry, along with the affected local utility company. All of these costly consequences equate to loss of revenue.
Over the years, grading and excavation contractors have placed a greater importance on investing in underground utility detection systems, or locators, because they have proved to be just that—an investment. By accurately pinpointing where utilities lie, they prevent contractors from hitting the lines or cables, thus saving hundreds of thousands of dollars in downtime and fees.
Locating in the Early Days
The need to locate utility lines surfaced shortly after the first bucket teeth of an excavator ever pierced the ground.
“When they started excavation, they would cause damage and even endanger lives by hitting electrical, gas, and other utility lines,” says John Bieberdorf, senior product manager of Ditch Witch.
It prompted utility companies to spend time researching ways in which they could detect and find utility lines.
Industry leaders say the first utility detection system hit the market sometime between the mid-1960s and early 1970s. “There were some individual utility companies who had invented their own systems, so it’s kind of hard to give credit to who was the first,” Bieberdorf says.
It may not come as much of a surprise that in the early days locator systems weren’t user friendly. They were heavy, crude, and not very easy to hold, Bieberdorf says.
Operators used some of the first utility detection systems in much the same way as many are used today. When using the systems, operators were in search of a strong signal that would sound when a utility line was detected. As they walked around the job site with the equipment, they would listen for the signal, but Bieberdorf says it was often hard to hear with some of these early systems. Also, the systems were not waterproof, so they could only be used in the best weather conditions. “It was kind of a fair-weather type of approach,” he says. “Some of that had to do with taking it from a lab instrument out into the field. It’d be like taking your desktop computer outside.”
Picture this: One of the first locator system prototypes was designed to be stationed on a 20-foot-long wooden frame with trenchers on either side. The system took two to three people to carry. “Some of the first ones were not necessarily a one-person job,” he says.
Fast-forwarding to today, a lot has changed.
Over the years, contractors have demanded that the systems be more accurate. “Contractors are always saying, ‘I need to know exactly where things are,’” Bieberdorf says. Many of the advancements on utility detection systems have been geared toward trying to obtain a more accurate pinpoint or location of utility lines. Also, modern electronics have made the systems lighter an easier to carry. “With modern techniques of plastics and things, it’s made the systems more durable, weather-proof, ergonomic, and they’ve become easier to use,” he says.
Today’s Choices in Locating
The first systems used only an audible tone to signal operators that a utility line was present. Today, operators get visual indication as well. And some of the more modern advancements take into account not-so-perfect environments where interference can pose problems.
The three main technologies used to locate utilities include magnetics, electromagnetics, and ground-penetrating radar. “All of these work well in certain instances, and there are certain instances where they don’t work well,” Bieberdorf says. “Each has its own niche where it works well. In the future, a locating system that combines the best features of all of them would be the best option because it could give you the better feel of where the lines are.”
There are several different types of locators on the market. Single-frequency split-box locators involve the placement of a transmitter on the ground, inducing a signal to be picked up by the cable or pipe. The signal is then radiated back to the receiver. Multifrequency utility detection systems enable operators to designate a frequency that they’re sending into the ground to the type of line or pipe they’re attempting to locate. With these systems, contractors will typically have an easier time locating the utility line if they use a lower frequency.
Antennas on utility locator systems play a critical role because they can help in filtering interference. While a receiver with one antenna might perform well on a single-frequency system in an open, rural area, multiple receiving antennas might be required for congested urban areas.
Today, many utility locators can be used to perform both types of locating methods—conductive (direct connection) or inductive. When locating utility lines conductively, an operator will connect cable leads to the cable or pipe to be located and will then generate an alternating current down it.
There’s also the inductive method, which requires the operator to set the transmitter on the ground while a signal is radiated through the ground and onto the cable.
“Unlike in conductive locating, where most of the focus is on the receiver, inductive locating requires expert use of the transmitter,” says David Dodd, sales and marketing director of Pipehorn Utility Tool Co. Dodd says higher frequency transmitters, ranging up to 480 kilohertz, are best suited for inducing a signal. In addition, he says, operators much consider the target conductors, adjacent conductors, and site conditions.
Usually, contractors don’t have the ability to hook up to fiber-optic lines. So if a fiber-optic line is buried deep or has an extremely small pressure wire on it, they’ll have a hard time getting a signal from their locator onto that fiber optic line to confirm its location.
“Because the contractor is so limited in how he can do a connect, inductive locating is one of his best methods of trying to find out what’s in the ground so he can expose those utilities and do an inductive sweep,” says Matt Manning, product specialist for McLaughlin Boring Systems. “So they can actually use this method as a last-minute check to see if anybody’s missed anything.”
“In this industry … many people are educated in the fact that direct connection is the best way to locate, and they steer far away from inductive locating. Then that kind of transpires over into the regular market. Everybody thinks direct connect is the best way; but, for a contractor, he has a lot more options out there,” Manning says. “It’s typically a much faster locating method than direct connection.”
Proper Operating Techniques
As with any piece of equipment, being able to properly operate a utility detection system is critical. Not having a good understanding of how the system works could be compared to searching for utilities while blindfolded. That’s because improper operation translates to unreliable and ineffective results.
When performing conductive locating, contractors set up their locator transmitter to create a signal loop. To do this, they’ll hook the positive end to the utility. The negative end will then be hooked to a ground stake, which must be perpendicular or at a 90-degree angle to the utility.
If a contractor can’t get a good signal, then he should try pouring water on his ground stake. “It’s a pretty simple thing to do, and it will drastically improve your signal,” says Mike Moore, vice president of McLaughlin Boring Systems.
“The other thing we encourage people to do is, even though you’re hooked up to a utility, when you start to locate, make sure you follow it to a logical conclusion,” he says. “For example, you’ve hooked up at a house to a telephone line, make sure you’ve followed that to the telephone box so that you know you’re on the right line. And then turn around and walk it back to make sure you get the same path in both directions.”
Often, contractors go out on a job site, and the locating signal bleeds off onto another utility. Because this can happen, Moore says it’s important that they follow the signal to a logical conclusion or ending point.
The frequency in which contractors operate utility detection systems is one of the major obstacles they must overcome. Every time they pick up the system out in the field, they almost have to retrain themselves completely on how to use it, Moore says. Construction companies tend to switch the equipment between workers, so a different crewmember is operating the locator each time it’s needed. “It’s best if you pick someone to be that locator guy, and make him your expert,” he says.
There are other things that can cause contractors problems with utility locating. There are two types of interference created in this world—one is active interference and the other is passive interference. Active interference includes such things as invisible dog fences, microwave transmissions, and radio and TV stations—all of these things are creating noise, and cables will pick up on that noise and carry it. Passive interferences, such as chain-link fences, can also cause problems.
“You’re locating next to a chain-link fence and the system starts to pick up on that, too. Suddenly, it’s very difficult to determine whether you’re locating the utility or you’re getting pulled over by the fence,” Moore says. “In those situations, knowing that your locating system not only has a peak mode but also a null mode will allow you to avoid some of that problem. You have to understand your locating system and how to use it.” In addition to chain-link fences, rebar underneath highways will block a signal or send out a signal, making it difficult to find the exact position of the utility.
Interference can also contribute to locators giving inaccurate depths. Most instruments currently on the market feature a current measurement index, which measures the current you are placing on the cable. This helps operators determine if they’re locating the right utilities.
Unfortunately, Manning says, many contractors out in the field don’t even realize their utility detection equipment has this feature. “A lot of these guys have just been handed this piece of equipment and have been told, ‘Here, go find cables,’ and they don’t have the extent of training that someone who locates on a daily basis has,” he says.
In addition, contractors should follow the 1-foot method, Manning says. To apply this, contractors should take a depth measurement at ground level (or with the receiver sitting on the ground), and then they should lift it approximately 1 foot to see if the reading reflects a 1-foot difference in depth.
“If there’s distortion, you definitely will not see that change,” he explains. “If it’s a good signal, you’ll get approximately a 12-inch difference. It gives the contractor an idea as to whether the depth reading on his instrument is somewhat correct or completely wrong.”
Contractors frequently have a hard time identifying which utility they’re getting a signal from, Manning says. One of the reasons contractors run into this problem is because they typically don’t have access to all of the facilities, meaning they can’t open telephone patches, transformers or test stations on a natural-gas line. “They’re really limited in the access of sending a signal,” Manning says. “They can’t always connect the proper way.”
Not only do they not have access to other facilities, but they also are not usually equipped with the adequate information. When a contractor is hired to do work for a utility company, he receives a blueprint of that company’s utility lines, but it doesn’t include where other underground utilities might lie.
In most states, all contractors must call their local One Call notification system prior to digging. The nationwide system is a free service that locates existing infrastructure in rights of way and other public property. While the service can be extremely beneficial, it’s not as helpful to contractors who perform most of their work on private property. Also, some contractors find that the One Call markings are not always as accurate as they need them to be.
“The only thing they have to go by are the marks that somebody has put on the ground,” Manning says. “The reason most contractors buy a locator is because those marks on the ground have a window in which the utility can be within. That window, depending on the state, can be anywhere from 18 inches to 3 feet on either side of the line.”
Training Is Key
Training is important, and the more a person uses the locator, the better skilled that person becomes. “It’s a tool where we can go out and teach them how to use that locator, and they’ll be good with it,” Moore says. “But they have to pick it up again the next day and the next day and get a pattern going so they really understand it. Once they understand it, then they can use it once a week here and once a week there, and they’ll be fine because they understand the locator and how it operates in different situations.” Training is so critical because success is dependent on getting time on the equipment.
Moore says that his company spends time training customers one-on-one and customers also call asking to be walked through a particular locating issue. Contractors tend to be hands-on people, which is why training should preferably occur in the field. “We have found that we can do some classroom training and give them a basic idea of what a locator is, but it always clicks once you get to the field, because they can see how it works in their applications,” he says.
Manufacturers provide an operator’s manual that covers complete operation of the unit. In addition to training CDs and DVDs, most locating units have an informational decal that walks the operator through the proper steps.
Again, the main purpose of underground utility detection systems is to give contractors a position or depth estimate of where the utility line is located. Then, using nondestructive means, contractors dig down and expose the utility where it will be crossed.
“If a person goes out there and just whips through the job as quick as he can, he can be off a little bit—right and left. If he doesn’t follow operating techniques of hooking up, he can get on the wrong service or the wrong line. Suddenly, the utility he should have found, he didn’t, and he ends up hitting the utility,” Moore says. “So it’s important that the person follows the basic A-B-C steps. As long as they do that, things will work out.”
What’s to Come?
While underground utility detection systems have progressed significantly since entering the market more than 40 years ago, they’re not quite perfect yet. And like almost any piece of construction equipment, they may never be. But manufacturers say several advancements are on the horizon that will change the way locator systems are used.
It may sound like something out of a comic book, but incorporating technology similar to x-ray vision may be next big thing to come to the instruments.
“We could simply put on x-ray glasses and see through the ground and see three-dimensionally where the lines are located. That’s where I think we’re headed in the future,” says Bieberdorf. “It’d be something that’s easy to understand, because you wouldn’t have to interrupt things that are hard to understand, such as radar maps.”
Whatever improvements are made to underground utility detection systems, the equipment will continue to be a necessary tool in the construction industry. Because damage prevention and safety are so important, manufacturers say they’ll never stop promoting utility locating.“Always, always look for pipes and cables; pinpoint, dig down, and expose them before you dig,” Bieberdorf says.