Stay Outside the 24-Inch Zone
Mechanical equipment must stay outside the marked tolerance zone. Inside it, use hand tools, hydro excavation, or vacuum excavation to expose the utility before powered work continues.
Guides
How Close to Marked Underground Utilities Can You Safely Dig ?
Before excavation begins anywhere in the Salt River Valley, Phoenix Excavation Co. follows Arizona's 24-inch tolerance-zone rule around marked underground utilities. Powered equipment must remain outside that zone until a line has been safely exposed, and every project requires an 811 locate because no digging depth is automatically safe.
Quick Summary
- Request an Arizona 811 locate at least two full working days before every dig, regardless of planned depth.
- Within 24 inches on either side of a marked utility centerline, keep powered equipment out and expose the line with hand tools or non-destructive excavation.
- Typical Phoenix-area depths vary widely: electric and communications lines often run 18-24 inches, gas 24-36 inches, and water or sewer from about 12 inches to 4 feet.
- Homeowners must request locates for tilling, tree planting, fence posts, sprinkler trenches, and other small yard projects too.
Three Rules for Safe Digging
Never Assume the Depth
Locate paint and flags show a utility's horizontal path, not how deep it is. Shallow fiber can sit only 6-12 inches below grade, while caliche and older installation practices can shift other lines from expected depths.
Call 811 Before Work Starts
Arizona 811 coordinates public utility marks at no cost. Submit the request at least two full working days before excavation, then wait for all required marks before tilling, grading, trenching, or digging.
Safe Digging in Context
Marked 24-Inch Tolerance Zone on a Phoenix Lot
Paint or flags marking the utility path, the full buffer on both sides, and excavation equipment positioned beyond the restricted area.
Typical Utility Depths Beneath Desert Soil
Compare shallow 6-12-inch fiber with 18-24-inch electric and communications lines, 24-36-inch gas lines, and water or sewer lines that may range from 12 inches to 4 feet.
Hydro Excavation Exposing a Marked Line
Pressurized water loosening soil while a vacuum removes slurry, revealing the utility without direct blade contact.
Safe-Digging Snapshot
First Required Step
Mark the planned dig area with white paint, contact Arizona 811, and allow at least two full working days for utility owners to respond.
Depth Is Not Protection
There is no automatically safe depth. Edging, tilling, and shallow post holes can still reach fiber, irrigation, or electric lines.
When Equipment Must Stop
Excavators, skid steers, trenchers, and augers stay outside the 24-inch tolerance zone until the marked line's exact path and depth are visually confirmed.
What a Strike Can Cost
A utility strike can bring $56,000 or more in repairs, fines, and delays. During foundation work, repairs and inspections can hold up a build for weeks.
Utility Clearance Planning Matrix
| Site Condition | Equipment Rule | Next Action |
|---|---|---|
| No locate marks | Do not dig at any depth. | Request an Arizona 811 locate and wait at least two full working days. |
| Outside the marked tolerance zone | Mechanical digging still requires care because marks do not show depth. | Protect the marks and verify the planned excavation path. |
| Within 24 inches of a mark | Keep excavators, trenchers, and augers out of the zone. | Hand dig or use hydro and vacuum excavation to expose the line. |
| Utility visually exposed | Mechanical work may resume around the confirmed line with continuous observation. | Use a spotter and protect the exposed utility. |
| Work enters a public right-of-way | A utility locate does not replace the required excavation permit. | Confirm the City of Phoenix permit before disturbing a sidewalk, alley, or street. |
What the 24-Inch Rule Means
Under Arizona's underground-facilities law in Arizona Revised Statutes Title 40, the tolerance zone extends 24 inches on each side of a marked utility centerline. Treat that whole corridor as restricted for mechanical digging; the 18-inch guidance used in many other states does not replace Arizona's wider requirement.
Conditions That Change the Risk
Caliche hardpan, older installations, easements, and tightly grouped services can move utilities away from expected depths; on some Phoenix lots, several lines run within a few feet of one another. Most municipal water mains and service laterals sit 24-48 inches deep, while commercial higher-voltage lines may be 30 inches or more below grade with concrete encasement, but neither range is a substitute for locating and exposing the actual line.
Common Follow-Up Questions
Can you till without calling 811? No; tilling counts as excavation, and shallow lines can sit within reach of the blades. What do the locate colors mean? Red marks electric, yellow gas or petroleum, blue water, green sewer, orange communications, and pink temporary survey markings, but none of those colors shows depth. What extra rules apply to trenches? OSHA's 29 CFR 1926 Subpart P requires protective systems for trenches deeper than 5 feet, and spoil piles should remain at least 2 feet back from the edge.
Plan a Safer Dig
Need Help Confirming Utility Clearance?
For utility trenching, grading, foundation excavation, pool work, concrete removal, or drainage projects, share the work area and current locate status. A local excavation team can help determine where hand exposure, hydro excavation, vacuum excavation, or additional private locating is appropriate before equipment moves.