Utility Mark Tolerance Zones

Excavator strikes underground line.

How close can I dig to the utility marks on the ground with mechanical equipment?

The marks on the ground only represent the approximate location of the buried facility.

Utility owners provide a tolerance distance on their locate reports as a safety precaution, for various reasons, to ensure that their buried infrastructure is not damaged. The tolerance distance is a defined horizontal space from the outside wall or edge of the buried facility.

Excavators are required to hand or soft dig within the hand expose zone, which is the horizontal space equal to the width of the buried facility plus the tolerance distance on both sides of the mark.

1 Meter Hand Expose Zone

The typical tolerance distance for most public utility owned infrastructure is 1 meter; however, it can be up to 3 meters or greater in some cases. The size of the buried facility is sometimes unknown and not indicated on the locate report. If there is any uncertainty, we suggest that you increase the tolerance distance from 1.5 to 2 m as a safety precaution to account for the unknown width of the buried facility.

Private locators seldom work from drawings and generally do not know the size of the buried facility that they are locating. We suggest using a 1.5 to 2 m tolerance distance for private buried facilities to add a buffer of safety to account for its unknown width.

2m Hand Expose Zone

Always check if the site you are working on has a site-specific tolerance distance policy for excavating near buried infrastructure. Some company policies require even greater tolerance distances when excavating around their buried facilities.

Anyone breaking ground should always assume that the buried facility could be anywhere within the hand expose zone on either side of the locate marks.