For excavation activities, a construction employer will be required to determine the location of all underground installations (sewer, telephone, fuel, electric, water lines, or other underground installations, according to 29 CFR 1926.651. These construction employers generally call a state “diggers hotline” that sends a person to the site to use instruments to detect underground installations. Then the installations are marked according to state requirements. Many states have adopted the Uniform Color Code published by the Utility Location and Coordination Council of the American Public Works Association.
Also, see the answer to the question, “Does OSHA require pipes to be labeled?”