Article Summary
The APWA color code system uses six standardized colors to identify underground utilities before excavation. Knowing what each color and marking style means helps excavators quickly assess a job site and avoid costly, dangerous strikes.
When utilities are marked in the field, there's a standardized system used across the industry to ensure clarity and consistency. Knowing that system isn't just good practice — it can prevent costly, dangerous mistakes before a shovel ever hits the ground.
Here's how to read utility markings, what each color means, and how to work safely around them.
Each color in the APWA (American Public Works Association) system represents a specific type of utility. The six standard colors are:
These colors help excavators quickly identify what type of facility is present in the area before a shovel hits the ground.
A universal color system means a crew in Indiana reads a mark the same way a crew in Michigan does. That consistency removes guesswork and keeps everyone — locators, excavators, and utility owners — speaking the same visual language.
When every stakeholder interprets markings the same way, the risk of a mistaken assumption drops dramatically. That's the whole point of standardization: fewer surprises underground.
In addition to color, the style of the markings carries important information:
Reading the style is just as important as reading the color. A dashed line or an offset marking is telling you something specific — don't overlook it.
At Northern Lights, our locators apply these markings across 21 states — including Indiana, Illinois, Wisconsin, and Michigan — following CGA (Common Ground Alliance) and APWA standards on every single ticket we complete.
Consistent, accurate marking is the foundation of everything we do. Following these national standards on every job means the crews we serve always know exactly what they're looking at, no matter the state.
It's important to understand that markings are not exact. They communicate the presence and general alignment of underground facilities — not the precise depth.
Treat markings as a reliable guide to what's below and roughly where it runs, not as a guarantee of the exact position. That distinction is what keeps careful excavators out of trouble.
Before digging, always:
Taking a few minutes to read the site correctly is far cheaper than repairing a struck line. When in doubt, slow down and confirm.
Utility marking standards exist to keep every crew safe — but they only work when the people on the ground know how to read them. For excavation in the Northern Lights service area, call 811 to start your ticket, and our team will respond promptly to get your project moving safely.
The APWA color codes are: red for electric power, yellow for gas/oil/steam, orange for communication lines, blue for potable water, green for sewer and drain lines, and purple for reclaimed water. These colors are used across the industry to identify underground utilities.
Yellow is used to mark gas, oil, and steam lines under the APWA color code system.
APWA (American Public Works Association) established the standardized color code system for marking utilities. CGA (Common Ground Alliance) promotes best practices for damage prevention and safe excavation. Northern Lights follows both on every ticket.
Dashed lines, offsets, or labeled markings can indicate changes in direction, multiple lines, or other important details. Solid lines represent the approximate path of a utility.
No. Markings communicate the presence and general alignment of a utility, but not its precise depth. Always use safe digging practices to confirm depth and exact location.
If you need a locate in Indiana, Illinois, Wisconsin, Michigan, or another service area, contact Northern Lights. Their team applies CGA- and APWA-compliant markings and can answer questions about markings on your job site.
