Below but Visible
Underground obstacles may be hidden but today you can see them easily
Underground obstacles may be hidden but today you can see them easily
Every year we imagine it will be unnecessary to warn utilities and contractors about the dangerous (and expensive) consequences of digging without first ascertaining what is in the ground. But every year there are many accidents caused by striking underground obstacles. None of us test for underground hazards by running a loader, dozer blade, iron bar or shovel below the surface… do we? Yet there are still explosions, property damage, utility services curtailed, and life-changing injuries. Most of us are careful most of the time about how we approach hidden, underground obstacles, but it takes only one lapse in carefulness, or one uninspired guess that there’s nothing down there, to cause injury, damage, or death.
The way to find out what’s below the surface of your jobsite is to look. Caution blows away down the alley when a worker sees it’s only a few yards of ground that are affected by the new work and hopes there are no obstacles in those few yards. I’ve used this analogy before. It’s like an x-ray. You usually can’t see where and how a bone is broken, or a cancer beginning, or a lung is in danger of collapse, just by looking at arm, leg or chest, but the x-ray can tell you. Think of today’s locating instruments as x-ray machines. Rejoice that those instruments are much less expensive and much easier to work than your hospital’s x-ray machine.
Among Goldak’s products are the Triad Series. Courtesy of Goldak, Inc.
You get a good start by calling your local One Call (or similarly named) number to find out what hazards are known to be buried where you want to excavate. It’s unfair to call them hazards, because most of them give good service. Yes, your own utility’s lines could be among those “hazards”. The perilous problem is that we often don’t know what is buried, because of poor record-keeping or lost records. In some communities you are advised to call whenever you are going to dig deeper than six inches. That’s shorter than my garden spade! When my neighbor had a new CATV line installed from the alley to his house, the existing utilities were, in fact, just about a spade deep! A mistake could have blown Todd (and me) to Kingdom Come.
The depth of the hidden obstacles is of paramount importance. You should certainly check with your supplier or manufacturer about the efficiency of their devices at specific depths below ground. For some applications, the ability to see what is present at four feet below the surface is fine. The ability to search deeper than that may be essential at some sites. The responsibility for selecting the correct technology and instruments is yours. Virtually all the devices advertised and marketed are good performers at the levels they offer and it is the user’s task to choose which levels are those most suited to his or her daily requirements. Some of the devices we mention in this article may be too much, or too little, for your needs and not, therefore, wise investments. Some frank questions and site information from you should get the right answers from suppliers.
The Innspector 007 claims to be the only handheld locator for all materials, including plastic. Courtesy of SubSurface Instruments
The hidden obstacles to your sub-surface work could be made of several materials. An offering from SubSurface Instruments, called the Innspector 007, claims to be the only handheld locator for all materials, including plastic. Among the targets you can find with the Innspector 007 are all types of cables and pipe, sprinkler systems of any composition, rebar, culverts, wood!, tanks and drums, bones, septic tanks, and fiber optic installations. There are more than that, but you can see this instrument can find almost anything. It’s a self-contained device with no separate transmitter, receiver or cables, wires and clamps to manage. No calibration is necessary. Four “C” type batteries (contained in the handle) power it. The Innspector 007 is very much an on/off, point and shoot device. It weighs about two pounds and travels in a standard 4-inch briefcase with form-fitting foam padding. The laser pointer is built in and depth is determined by triangulation. Among other locators from SubSurface Instruments is the ML-1M, a magnetic locator with an LCD meter that indicates polarity, signal strength, gain (sensitivity), and low battery condition. This model uses two alkaline 9-volt batteries and it’s shipped with a spare pair.
Peaceful Penetration of the Ground
Ground Penetrating Radar (GPR) systems work by sending a tiny pulse of energy into the ground from an antenna. An integrated computer then records the strength and time required for the return of any reflected signals. Subsurface variations like pipes (metallic and non-metallic), wire and voids will cause signals to bounce back. When this occurs, all detected items are revealed on the computer screen in real time as the GPR equipment moves along. The data collected is then analyzed and specific recommendations can be made, relevant to drilling, digging, and other underground procedures. “GPR sounds like something extremely scientific or a tool straight out of a space movie, doesn’t it?” suggested Cheryl Duszak at Geophysical Survey Systems (GSSI). “Although its name rings of technicality and science fiction, it is one of the most versatile, easy-to-use locating methods on the market. GPR was pioneered by GSSI over 35 years ago and began as a tool for scientists. Our time since then has been used to simplify and perfect the equipment so that anyone in utility locating can use it with ease.”
“In many cases, GPR is the only practical, non-destructive method available to locate non-metallic and non-conductive utilities such as cast iron, PVC, or other plastic pipes, concrete and various composite pipelines,” noted Erica Davis for MALA GeoScience, another worldwide leader in the GPR field. “Systems like the Easy Locator and the X3M can accurately locate and determine depths to utilities of many types, including pipes, cables, conduit and duct banks in soils favorable to the GPR method.” MALA says its Easy Locator is affordable and designed for the utility locate professional. Among options are the IXM upgrade, which records data collected in jpeg format for later printing and download, and the EXM+ monitor for readability in direct sunlight. Readability is important. Much locating work could be in bright sunlight and you will require a screen on which you can truly see the results. The MALA RAMAC/X3M has a monitor that provides the resolution you would expect from only the best laptop monitor, with a display that is fully readable in sunlight. The display is what is known as transreflective (TFT).
You really can hold the helpful device in your hand. Courtesy of Ditch Witch.
MALA introduced a Rough Terrain Cart for use with the two models mentioned. The cart offers oversized wheels and a strong frame with quick-release wheels for easy dismantling and transporting. Carts are popular for users of GPR systems, because they allow you to move steadily along the area you wish to investigate (such as sidewalks, lawns and roads) and they carry the weight of the system with little effort to yourself.
Sensors & Software offers the Noggin SmartCart. The large wheels on the little cart make it easy to push. Some users say it is easier than pushing a mower with no grass to cut. The real time display is visible on a digital video logger (DVL), which is mounted at the handle of the cart, clearly visible to the user. There are several models of Noggin available. “GPR is particularly useful for locating and differentiating between metallic and non-metallic pipes and conduits,” comments the company. “Noggin can operate in a wide range of environments, rain or shine, and be stored at outside temperatures.”
At the Jobsite
“Easy-to-operate” is an important feature of locating devices. Ditch Witch (a world leader in underground construction equipment of all types) makes and markets several interesting locating tools. The 300 SR/ST is designed to locate buried telephone, power, CATV, gas, sewer and water lines. It is “easy-to-operate”. The receiver runs on six C-cell alkaline batteries, with a battery life of about 40 hours, and it shuts off after five minutes if no key is pressed. It’s almost a foot long and weighs only 5 lbs. The transmitter, with the same length and weight, uses six D-cell alkaline batteries and that battery life is about 150 hours. This system has found good acceptance by contractors and utilities. Another Ditch Witch locating device that caught our attention is the 150R/T, described as a cable avoidance system and one of the easiest, most affordable ways to decide where to dig, and where not to dig.
“Jobsite awareness is critical,” advised John Bieberdorf, product manager for Ditch Witch underground construction equipment. “You should gain as much knowledge as possible about the facilities before pulling out your pipe and cable locator. Make use of any available facility records that indicate approximate location, number of facilities, and access points for buried facilities within your jobsite area. The facility owner usually has those records.” As those facility records are not completely accurate sometimes, Bieberdorf recommends that the crew should look for poles, dips, enclosures, pedestals, valves, meters, risers and manholes to ascertain if there may be additional facilities or other obstacles not recorded.
Most of today’s devices for locating underground obstacles are not heavy or cumbersome. Courtesy of Schonstedt
The big question for most contractors is whether to purchase their own locating equipment or hire somebody else (a professional locating company or individual) to do it for them. Most contractors told us it would depend on how often the tool was needed (making the choice similar to that in the purchase or rental of any equipment). The professional locator may seem more expensive but he or she will probably do the job more quickly, possibly more accurately, and the contractor won’t have to store equipment not needed for another three or six months. There is no correct answer. The only requirement is to get the locating done as accurately and productively as the job demands.
Goldak has been creating underground locating equipment for almost 75 years. Some of their customers are still successfully using Goldak instruments purchased three decades go. The company says its products are accurate, simple and rugged: just what you need for this kind of work. One reason this company believes it keeps abreast and ahead of locating requirements is that they are not only manufacturers but users, too. Goldak has a full-time contract locating division comprising expert underground locating technicians. This combination lets new products be tested in real conditions and the technicians bring feedback to the engineers about the challenges and solutions for underground locating. Among Goldak’s products are the Triad Series, the 902 Subscanner for locating underground substructures like conduits, pipelines and cables, and the 5600-SI (one of whose abilities is to separate pipes and cables in close proximity to each other).
Like most decisions that concern equipment use and purchase, the key consideration is the frequency or regularity with which the equipment will be needed. If you have irregular requirements for locating underground utilities, you’ll probably hire an outside expert to do that work. It would still be wise to ask that professional what products he uses, to be sure that they are adequate for your project needs. To be practical, productive and profitable, you may not be able to justify purchasing equipment described in this article, but you should certainly be aware of devices and technologies available.