Duke Energy
Understanding the Tolerance Zone
What Is the Tolerance Zone?

The tolerance zone is a safety area that spans the width of a marked underground utility plus a specified distance from each indicated outside edge of the utility. This distance varies from state to state: It is 18 inches in Kentucky and Ohio, and it is 24 inches in Indiana, North Carolina, South Carolina, and Florida.

RED Electric power lines
PINK Temporary survey markings
WHITE Proposed excavation
YELLOW Gas, oil or steam
BLUE Potable water
GREEN Sewer and drain lines
ORANGE Communications lines, cables or conduit
PURPLE Sewer and drain lines
Locator Marks
Dig with Care

If you plan to dig or move earth in any way, notify 811 and then wait the required time before you dig. The 811 service will arrange to have buried utility lines located and marked by their member utilities, so you can dig a safe distance away. (The 811 center will let you know if you must contact non-member utilities to have their facilities privately located.)

Dig with Care

Once buried utility lines have been marked, respect the tolerance zone to help protect these lines from excavation-related damage. Before you power dig in or near this zone, hand dig to expose all marked utility lines and visually verify their precise location. Use reasonable care and these nondestructive digging methods:


Hand dig with a rounded or blunt shovel. Never use a pickaxe or pointed spade, and never stomp on a shovel with both feet. That’s a sure way to damage a utility line.


Start your digging off to the side of the marked utility line. Use a gentle, prying motion to break away soil as you approach the utility laterally.


Never pry against a utility line to remove soil.


Vacuum excavation. This method uses suction and water to quickly and safely remove soil. Be mindful of water pressure; use lower pressure and tips with multiple nozzles.

Proceed with Caution

Proceed with extreme caution around exposed utility lines. Power digging equipment can damage a section of electrical conduit or pipeline in no time. Even hand digging can compromise buried utilities by removing supporting soil. Take all necessary precautions to protect buried utilities from damage.

Would You Like to Know More?

Additional digging and overhead guidelines, case studies, instructional videos and training tools can all be found, at no charge to you, on Duke Energy's e-SMARTworkers website.

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Duke Energy Emergencies

Most state laws require at least two to three full working days' notice; some may be longer. Call 811 or go to call811.com for the best information for your state.

Carolinas: 800-769-3766

Florida: 800-228-8485

Indiana: 800-343-3525

Kentucky/Ohio: 800-634-4300

Duke Energy Progress: 800-419-6356

North Carolina: nc811.org
South Carolina: sc811.com
Florida: sunshine811.com
Indiana: indiana811.org
Kentucky: kentucky811.org
Ohio: ohio811.org
Call 811
For more contractor safety information, visit duke-energy.com.