Tolerance Zones
Excavators should observe a "Tolerance Zone" when digging close to a service line. The width of the Tolerance Zone is specified by law. The width of the facility (service line or pipeline, etc.) as marked plus at least 18 inches, or 450mm, measured horizontally from each side of the facility. See illustration.
Any excavation within a Tolerance Zone should be performed with non-powered hand tools or a non-invasive method until the marked facility is exposed.
Paint or flag color indicator
Property owners and excavators should use white markings to define the entire area where excavation will occur. Include a wide safety buffer when marking the area.
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Property Owners/Excavators mark area of Proposed Excavation |
One Call member utilities will use the color codes listed below when marking underground utilities where excavation will take place.
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Electric |
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Temporary Survey Markings |
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Gas, Oil, Steam, Propane |
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Communication, CATV, Fiber |
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Water |
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Reclaimed Water, Irrigation |
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Sewer |