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Tolerance Zones


(© 2001 VISTA Training, Inc.)
  • The tolerance zone protects buried utilities.
    The tolerance zone is the width of an underground utility plus a specified tolerance distance on both sides of that utility. Do not use power-digging equipment within this zone. The zone provides a margin of error in case the locator marks are slightly off. It also provides a buffer zone to prevent damage resulting from nearby excavation.
  • The tolerance zone also protects you.
    If you do not respect the tolerance zone, you risk contacting buried utilities. You also risk damaging them indirectly by removing supporting soil, which could cause the utility to bend or break. You could be injured or killed, and your company could be liable for any damages that occur.
To avoid damaging buried utilities, do not power dig within the tolerance zone. Hand dig or use vacuum technology instead.