After you contact 811, utility owners send locators to mark the approximate location of their underground lines with paint, flags or stakes. The colors follow the American Public Works Association (APWA) uniform color code, used across the country.
The color code
| Color | Meaning |
|---|---|
| Red | Electric power lines, cables, conduit and lighting cables |
| Orange | Telecommunication, alarm or signal lines, cables or conduit |
| Yellow | Gas, oil, steam, petroleum or gaseous materials |
| Green | Sewers and drain lines |
| Blue | Potable water |
| Purple | Reclaimed water, irrigation and slurry lines |
| Pink | Temporary survey markings |
| White | Proposed excavation limits or route |
Reading the marks
- Lines and arrows show the direction of the facility.
- Letters identify the owner or type, often an abbreviation of the company name.
- Numbers may show the size of the line or number of conduits.
- Offset marks may be used when the line can't be painted directly over (for example "2' →" meaning the line is 2 feet in that direction).
- "NO" or "clear" markings, or a positive response, may indicate the owner has no facilities in the area.
Marks show an approximate location. State laws define a tolerance zone, commonly 18 to 24 inches on either side of the outside edges of the line, where only hand digging or vacuum excavation is allowed. See potholing and vacuum excavation.
Before you dig
- White-line your excavation area where your state requires or recommends it.
- Contact 811 within your state's notice period, often two to three working days.
- Wait for all owners to respond and check for every color you'd expect on the site.
- Arrange private locates for lines 811 doesn't mark, such as private sewer laterals, irrigation and site lighting.
While you dig
- Protect the marks and keep a record (photos) in case they fade or are damaged.
- Refresh the ticket before it expires, or if marks are destroyed.
- Expose lines by hand or vacuum inside the tolerance zone and support exposed lines.
- Stop and report any damage, even a scrape, to the owner. Call 911 for gas leaks or electrical contact.
OSHA's excavation standard, 1926.651(b), also requires employers to determine utility locations before digging and to find the exact location by safe means as excavation approaches. Learn the full process in utilities and 811.
Sources and official references
Last reviewed: October 25, 2026 · Free general education based on OSHA 29 CFR 1926 Subpart P. It does not replace the site-specific training and competent person your employer must provide, and it does not issue a certificate. Nothing you enter on this page is saved or sent.