Utility Locate

When a contractor calls 811 before digging, the one-call center notifies all member utility owners who have facilities in the area. Each utility owner is then responsible for sending a locator to mark the approximate position of their buried lines using paint and flags in the designated APWA color code: red for electric, yellow for gas, blue for water, orange for communications, green for sewer, purple for reclaimed water, and white for the proposed excavation area.

Utility locates provide the approximate horizontal position of underground lines, typically accurate to within 18 to 24 inches depending on the state's tolerance zone regulations. However, locate marks do not provide depth information, and they may not account for changes in utility routing that have occurred since the original installation. This is why potholing with a hydrovac is necessary to verify exact position and depth.

Locators use electronic locating equipment (pipe and cable locators) to trace the electromagnetic signal on metallic utilities such as metal pipes, power cables, and communication cables. Non-metallic utilities like plastic gas lines and PVC water mains are located using tracer wire that was installed above the utility. When tracer wire is damaged or absent, locating non-metallic utilities becomes difficult and may require ground-penetrating radar or other advanced methods.