APWA Color Code

The APWA Uniform Color Code assigns specific colors to each type of underground utility to prevent confusion during excavation. Red marks indicate electric power lines, cables, and conduits. Yellow indicates gas, oil, steam, petroleum, and other hazardous liquid or gaseous materials. Orange marks telecommunications, alarm, signal lines, and fiber optics. Blue indicates potable water. Green indicates sewer and drain lines. Purple indicates reclaimed or non-potable water. Pink indicates temporary survey marks. White indicates the proposed excavation boundary.

This color code system is used universally across the United States and is recognized by ANSI Standard Z535.1. Utility locators, excavation contractors, and anyone working around underground utilities must know these colors and their meanings. Misidentifying a utility type based on its color code can lead to dangerous situations, such as treating a gas line as a water line.

The white markings are particularly important because they define the area where the contractor intends to excavate. Utility owners use the white marks as the boundary for their locate work. If the contractor's excavation area extends beyond the white marks, additional locate requests may be needed. Pre-marking the excavation area in white before calling 811 helps ensure that all utilities in the work zone are properly identified and marked.