811 (One-Call System)

811 is the national call-before-you-dig number for requesting underground utility marks before excavation in the United States, and state law requires the call. Each state has its own 811 program; calling notifies all member utilities to mark their buried lines on the dig site.

The 811 system was created to reduce damage to underground utilities. Excavators must call 811 (or use the state's online portal) before any digging, providing the dig location, scope, and timing. Member utilities then dispatch locators who mark their buried infrastructure with paint and flags using APWA color codes. Notice periods vary by state: most require about 2 business days (often written as 48 hours), some 72 hours or 3 business days.