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In 2017, there were 305,799 incidents of damage to utility lines in the U.S., an average of 837 per day. The sobering statistic is from the Damage Information Reporting Tool (DIRT), a database compiled by the Common Ground Alliance (CGA). By allowing damage prevention stakeholders to anonymously submit information about damages and near-misses, the data presents an industry-wide picture of opportunities to improve safety.
The report shows most incidents with damage (52 percent) are the result of ”Insufficient Excavation Practices.”Falling into this classification are “marks faded or not maintained, failure to maintain clearance, failure to use hand tools where required, excavator dug prior to verifying marks by test hole (pothole), excavator failed to protect/shore support facilities, and Improper backfilling practices. About a quarter (24 percent) of damage incidents are due to “notification not made” and 17 percent are due to “locating practices not sufficient.”
“Incidents and damage can be reduced with better training programs, both on the locating side and excavating side,” says Mike Parilac, founder of Planet Underground TV and American Locator magazine. Parilac believes the industry is moving from a focus on liability avoidance to damage prevention.“It used to be that an excavating contractor would complain about the locator,” says Parilac. “Now they do what they can because they understand the cost of downtime – even if it’s not their fault.”
Safety is a key factor when selecting contractors and in many ways that is driving industry change. “Contractors are now rated on safety,“ said Brian Showley, director of sales for Vermeer MV Solutions, which manufacturers the Vac-Tron and McLaughlin equipment lines. “The days of the cowboys are over.”
The Challenge of Locating Utilities
There are several reasons why locating utilities continues to be challenging. “For me, the main issue centers around an ever-changing underground infrastructure,” says Joe Weiland, principal of SubSurface Instruments. “Not only are new pipes being added daily, rarely do they remove unused or abandoned utilities.” Weiland also believes the use of non-conductive plastic pipes continues to be an issue for most locating entities. If a tracer wire or detectable tape was not installed with the pipe, it can be difficult to locate.
Parilac says utility maps are incorrect 10-15 percent of the time. In addition, the maps don’t locate the depth of the lines. Also, while anyone digging is required to call 811 before digging, private utility lines are not located through the service. “Half or more of all buried are not going to be located with 811,” says Parilac.
In addition to maps, visual observation, locating instruments and vacuum excavators are all tools for locating utilities. Visual observation training helps participants learn to identify above ground clues to locate utilities. “You have to have to understand how utility systems work,” says Parilac.
Types of Locators
The most common locators are electromagnetic and limited to locating metal pipes or pipes with a metal tracer wire. A transmitter emits a frequency that induces onto nearby pipes and cables. The receiver detects these radio frequencies, and the operator is able to accurately locate and trace pipes and cables.
Ground penetrating radar (GPR) locators can find non metallic utilities based on identifying changes in density. Short pulses of high frequency radio signal travel into the ground at a velocity that is related to the electrical properties of the subsurface materials. When the radio signals interface with two materials having different dielectric properties (utility and surrounding soils or surrounding concrete), a portion of the energy is reflected back to the transmitting antenna on the surface.
One drawback is that the depth at which you can find pipe varies depending on the type of soil. “Its usefulness depends on the type of soil,” says Parilac. Showley says GPR location devices require more training to operate.
In addition to magnetic and pipe and cable locators, SubSurface Instruments offers an All Materials Locator (AML) that uses a combination of ultra high radio frequency in conjunction with a microprocessor that contains hundreds of algorithms for different materials. Information is processed within a micro-second and alerts the AML operator of a change in density, indicating the pipe’s edge.
“What makes the AML unit different than typical methods of ground penetrating radar is that the AML uses a continuous, unmodulated ultra high radio frequency that does not need to make contact with the ground,” says Weiland. The amount of training required (two days minimum) is a downside for users.
Vacuum excavation is yet another method of locating pipes that has gained traction in the field over the years for the last step in visually verifying the line. Its key advantage is that doesn’t damage utilities in the process of locating them. “It’s safer than hand tools,” says Showley. “It is the preferred method.”
Wet or dry soils can be removed from a 12” hole, sucking down four or five feet or until the line is visually located. High pressure water assists with vacuuming more difficult soils. The only limitation is it can’t excavate solid rock. It will remove soil faster than other digging methods, and in all cases it will be safer.
According to Showley, in many cases contractors can pay for the machine with savings generated from finding the lines themselves vs. calling a vacuum excavating locating service. Trailer units and rental make vacuum excavation an affordable option.
With an estimated cost to stakeholders of at least $1.5 billion annually, you can understand why preventing utility line damage is a high priority for the industry. The DIRT data allows stakeholders to compare their company data with comparable firms so they identify areas for improvement.