Damage Prevention

Construction professionals understand the importance of not damaging buried utilities while performing any type of new construction and maintenance work.

Even so, accidental strikes of underground utility lines continue to interrupt essential services, cause millions of dollars in damage, result in serious injuries and, in some cases, loss of life. And as utility easements become more crowded, preventing damage to underground facilities has become increasingly challenging.

"Protecting our buried utilities is of critical importance," says Mike Dvorak, electronics sales manager for The Charles Machine Works, Inc. "Utility damage prevention is a responsibility that involves many diverse public and private organizations, making communication and cooperation essential to reduce the number of underground utility strikes."

Locating Is The First Step

The first step in preventing damage to buried facilities is to accurately locate and mark all utilities in a work area before construction. This process is initiated by calling the local one-call center, providing the exact location of the work site and requesting locates be made. The call must be placed at least 48 hours before work is scheduled to begin.

The one-call center then contacts appropriate utility providers, who then locate and accurately mark positions of their buried lines. Some utilities use their own personnel; others employ contract locating specialists.

The basic tool used by locating personnel is the electronic locator, such as the 950R/T receiver/transmitter system from Ditch Witch® Electronics. The 950R/T consists of a lightweight, handheld receiver and compact transmitter unit. It is designed to help make locating buried cable and pipe easier and provide more accurate results.

"The 950R receiver," explains Dvorak, "uses different frequencies and modes to find locations of different types of utilities by detecting magnetic fields created by electrical current passing through the lines."

In some situations, the receiving unit is all that is necessary to locate electrical and television cable signals. To find telephone cable and metallic pipe, the 950T transmitter is connected to cable or pipe and a current is sent through the line, creating a signal that is detected by the receiver.

For PVC pipe with tracer wire, the wire is energized by the transmitter to provide a signal that the receiver can read. The receiver processes information and displays an estimate of depth and other data on an easy-to-read screen.

Dvorak says that some utilities also mark positions of buried facilities with 3M electronic markers that are buried with pipe or cable. Markers are passive, resonant circuits with no internal power source to run down, and their polyethylene shells are impervious to minerals, chemicals, and temperature extremes. They are located using a Ditch Witch 950R receiver equipped with an Electronic Marker Locator (EML) attachment that transmits a signal to the buried marker, which then resonates it back to the EML. Markers, line and cable locators, and EML attachments are available at Ditch Witch dealerships.

"Ground-penetrating radar technology also has been adapted for utility locating purposes," says Dvorak. "One of our newer Ditch Witch Electronics products is the 2150GR ground penetrating radar (GPR). It can be used to detect and locate both metallic and non-metallic pipes and cables, but the method is dependant on soil conditions and antenna selection. GPR products are not effective in all types of soils, but can be helpful in locating some previously unknown facilities."

Potholing

"Potholing"—physically uncovering a buried utility to confirm its location—is the surest method of determining a utility's exact position. Because of accelerated efforts to prevent damage to buried utilities, potholing is becoming a standard practice on a growing number of utility jobsites. Government agencies are adopting regulations that require potholing, and project owners and contractors are establishing their own policies specifying potholing before excavation or directional drilling begins.

The procedure isn't new, but until recently most potholes were dug with backhoes, and even skilled operators always ran the risk of hitting and damaging the pipe or cable they were attempting to locate.

"Soft" excavation has changed all that.

Portable vacuum excavators use high-pressure water or air to quickly dig small, precisely controlled potholes to uncover buried utilities, eliminating the risk of damage inherent with a backhoe, excavator, or other mechanical tool.

"The Ditch Witch FX60 is the perfect machine for fast, efficient potholing," says Dvorak. "Soil is displaced by a high-pressure stream of water, precisely directed by a handheld wand. Water for excavation is carried in the unit's 200-gallon supply tank."

Depending on soil conditions, a 12-inch-square, 5-foot-deep pothole can be completed in less than 30 minutes.

"Vacuum excavators," says Dvorak, "are capable of digging much deeper, but utility potholes seldom need to be more than six feet deep. The vacuum function of the dual-purpose machine picks up soil displaced during excavation to use later as fill or to be removed from the jobsite. Soft excavation causes less surface damage and reduces disruption of traffic and other surface activities. The small excavation is easier, faster, and less expensive to repair."

For many utilities and contractors, potholing is standard procedure on horizontal directional drilling projects when the path of a planned pilot bore either crosses or is in close proximity to buried lines.

"A vacuum excavator's usefulness isn't limited to HDD operations," adds Dvorak. "It is the ideal tool any time a small, carefully controlled excavation is necessary. Vacuum excavators also are used to clean up drilling fluids that escape from bore holes during drilling, backreaming, and product installation, and can be used as a powerful, portable vacuum for just about any type of cleanup need."

Focus On Best Practices

Common Ground Alliance (CGA) efforts focus on implementing best-practice procedures identified in the Common Ground Best Practices Study, recognized as the most effective guidelines for preventing damage to underground facilities. One of CGA's primary roles is coordinating information and communications among the various organizations involved in building, maintaining, and operating the utility infrastructure.

"CGA encourages the shared responsibility of utility damage prevention," says Dvorak. "They help achieve this by refining and disseminating best-practice recommendations, developing public awareness through educational programs, supporting appropriate research, and serving as an information clearinghouse."

A "Dig Safely" public awareness campaign, which includes a damage-prevention brochure and video, and the "Call 811" initiative are in progress to make construction personnel and the general public aware of the importance of notifying one-call centers before construction begins. More information on CGA programs is available on the CGA website: www.commongroundalliance.com.

The Charles Machine Works, Inc., Perry, Oklahoma, is the world's leading manufacturer of underground construction equipment. Its products include Ditch Witch trenchers, vibratory plows, horizontal directional drilling systems, Ditch Witch Electronic tracking and utility locaters, mini excavators, mini skid steers, excavator-tool carriers and the Zahn® family of power utility equipment.

For more information about DitchWitch products, call 800-654-6481 or visit www.ditchwitch.com