Lost time and money aren’t the only considerations when an excavation accidentally hits an underground utility line; the safety of all of your workers is at stake, too. A ruptured natural gas line can cause a fire or explosion. The voltage from a severed electric line can be deadly.
The problem with locating these lines stems from the fact that electric, telephone, gas, and water lines might be buried almost anywhere under a construction site. Separate utility companies own them and install them at different times. According to the Construction Safety Council, a non-for-profit organization dedicated to the advancement of safety and health interests in the field of construction, there are several other factors that further complicate locating underground utilities:
- Utility lines are made of a variety of materials: Steel, cast iron and ductile iron pipes, clay, polyethylene, polyvinyl chloride, and fiberglass reinforced plastic.
- Cable might be made of copper or fiber optics.
- Conduits have different shapes, compositions, densities, and diameters, and their depths might be as little as 0 to 0.5 meter or in excess of 50 meters.
- Some lines (usually local telephone, electric and gas lines) might be stacked vertically in a common trench. Multiple lines might be grouped in a single conduit or duct bank. Multiple utilities might be grouped in common utility tunnels often called utilidors.
- T-Connections and looped service lines are usually overlooked if they are placed near utility boxes.
To help you keep your workers safe, the Council has established the following guidelines:
- Locate all underground installations by notifying the one-call system in your state, and follow all local policies and procedures for locating utility lines. You can find your state’s call center here: http://www.rmis.com/lib/safety/digsafecontacts.php.
- Become familiar with locating technologies and all their uses and limitations.
- Mark the proposed site that is to be excavated, and then have utilities mark the location of all underground installations.
- Pothole along the trench path to visually expose all utilities.
- Establish a zone around the excavation and allow only essential equipment near the edge. The size and area of the zone is based on soil type and anticipated surcharge loads. Be sure your employees observe this limited access throughout the course of the excavation.
- Dig carefully by hand if you suspect a utility was overlooked after the locations of buried utilities have been determined. Many cables are buried side by side.
- Allow only a qualified person to operate any equipment with the potential to make contact with an underground installation.
- Protect, support, or remove underground utilities as necessary to safeguard employees.
- Document the time of the call to the state system and keep proof at the job site.