Utility Location

Utility location is the process of identifying and labeling public utility mains which are underground. These mains may include lines for telephones, electricity distribution, natural gas, cable television, fiber optics, traffic lights, street lights, storm drains, water mains, and wastewater pipes. In some locations, major oil and gas pipelines, national defense communication lines, mass transit, rail and road tunnels also compete for space underground.

Because of the many different types of materials that go into manufacturing each of these different types of underground lines, different detection and location methods must be used. For metal pipes and cables, this is often done with electromagnetic equipment consisting of a transmitter and a receiver. For other types of pipe, such as plastic or concrete, other types of radiolocation or modern ground-penetrating radar must be used.

Location by these means is necessary because maps often lack the pinpoint precision needed to ensure proper clearance. In older cities, it is especially a problem since maps may be very inaccurate, or may be missing entirely.

"Call before you dig", "Digger's Hotline", "One-call", "Miss Utility", or Underground Service Alert are services that allow construction workers to contact utility companies, who will then denote where underground utilities are located via color-coding those locations. As required by law and assigned by the U.S. Federal Communications Commission (FCC), the 8-1-1 telephone number will soon be used for this purpose across the United States.

Failure to call such a number ahead of time may result in a fine or even a criminal charge against the person or company, particularly if such negligence causes a major utility outage or serious accident, or an evacuation due to a gas leak. Hitting a water main may also trigger a boil-water advisory and local flooding.

A few utilities are permanently marked with short posts or bollards, mainly for lines carrying petroleum products.