Potholes that Enhance Utility Damage Prevention
|By George KennedyAnyone who drives a local road after a hard winter thinks he knows what a pothole is. If you are a utility contractor, however, you know what a real pothole is. Potholing is the practice of digging a test hole. It is defined in the Common Ground Alliance’s Best Practices as “exposure of a facility [underground utility] by safe excavation practices used to ascertain the precise horizontal and vertical position of underground lines or facilities.” Test holes are more than just a mark on the ground. When a pothole is used to locate a facility, workers can actually see where and how deep it is.Excavators hope the facility is right under the marks placed on the ground by the facility locator sent by the One Call/Dig Safe system or the facility owner/operator. However, the line is not always found beneath the mark. Therefore, state laws prohibit or limit the use of mechanical equipment to excavate within the facility tolerance zone. The tolerance zone is the space in which a line or facility is located, generally 18 to 24 in. on both sides of the facility. Special care must be taken when excavating in the tolerance zone.Utility contractors across the nation will tell you that utilities are often mismarked and you cannot rely on the marks placed on the ground. The only way to know exactly what is below the surface is to see it, and the only way to do that is to dig a pothole. Excavators should hand dig or vacuum excavate potholes to find the actual location of existing underground utilities. Some states require potholing before digging a trench or horizontal drilling and some do not. However, potholing before proceeding with the actual task of installing or replacing a utility is a very good practice — some would call it essential.
Hand digging test holes is accomplished with blunt tip shovels (sometimes referred to as shooters), picks and digging bars which are carefully used to find and uncover utility lines. Although the hand digging method of potholing has been used successfully for a long time, it has its limitations. The cutting edge of these tools can also damage utility lines. It does not take much force to damage a fiber-optic, telephone or electric cable, a cathodic protection on gas lines or to nick and weaken plastic water lines. Care should also be taken when electrical lines are present. In addition, potholes can only be dug about 4 ft deep before they have to be opened up enough to accommodate a worker and digging holes. More than 5 ft deep creates the need for a cave-in protective system (sloping, shoring or shielding).Vacuum Excavation
Vacuum excavation, although not always feasible, is becoming the most popular and efficient method for locating utilities. Trailer- and truck-mounted vacuum excavators use air or water pressure to quickly dig small, precisely controlled potholes to uncover utilities. Both air and water excavation methods have advantages and disadvantages, which should be considered before purchasing a vacuum excavation system.
Some state jurisdictions and local communities frown on or even prohibit potholing when it means cutting through the surface of paved streets. If this is the case, it may be necessary to explain to officials the importance of potholing and what you’re trying to prevent.
After the work is complete, the potholes must be filled and compacted to ensure that patches do not sink with time. The pothole should be clean and dry before backfilling and the pavement or surface must be replaced in accordance with local standards and specifications. Make sure you know the local restrictions and requirements before potholing.Mismarks
Even with potholing, utilities will not always be found where the locator placed the marks. When this happens, mismarks and unmarked utilities should be reported to the facility owner and/or the One-Call/Dig Safe center. NUCA encourages contractors to also file a DIRT (Damage Information Reporting Tool) report with the Common Ground Alliance at www.cga-dirt.com. Reporting mismarks helps the utility owner update its maps and identify locators who may need additional training. It also helps the industry address the issue of contractors being blamed for damages that are caused by mismarks and unmarked utilities.Safety Procedures
Safety is always a consideration. Contractors must ensure that vacuum crews know and follow the necessary safety precautions. In many situations, crews will be working outside the barricaded work zone where they could be exposed to traffic. They should be instructed on how to set up a temporary work zone and provided with the cones, barricades and/or signs needed to safely redirect traffic around the potholing operation. All workers should be provided with high visibility vests or clothing to be worn at all times. In addition, safety glasses — and sometimes hearing protection — must be used. Hand digging requires non-conductive or insulated tools. Companies need to provide dielectric boots and gloves and require their employees to wear them to reduce the possibility of being shocked if an electric line is damaged.Ten-Step Procedure for Damage Prevention
Start your jobs off right by following this simple 10-step procedure to prevent damage to underground utilities:
White-line or mark the area to be located. Meet the locator at the jobsite, if necessary.
Call the One-Call/Dig Safe center to request a mark-out and wait the required time before proceeding.
Verify that all utilities have been marked and notify the One-Call/Dig Safe center if all utilities are not marked.
Report mismarked facilities, inaccurate marks and unmarked utilities to the One-Call/Dig Safe center.
Respect the tolerance zone.
Support and protect exposed utilities from damage.
Report damages immediately to the facility operator and investigate the cause of any damages.
Backfill carefully and fill in potholes properly in accordance with standards and specifications.Conclusion
Utility hits are dangerous and costly. They can only be prevented when companies commit to damage prevention. Contractors have a responsibility to their companies, employees and the general public to do all they can to prevent damage to underground utilities. That prevention comes from knowing exactly where utilities are located, and the best way to accomplish that is to both call before you dig and pothole before digging. Make a difference: Establish a damage prevention procedure, include potholing and dig responsibly.
George Kennedy is NUCA Vice President of Safety.