Potholing (Daylighting)

Purpose

Potholing, also called daylighting, positively confirms the type, size, depth and direction of every utility the bore will cross or run close to. Locate marks give an approximate horizontal location and no depth. The pothole gives the real numbers the bore plan depends on. Skipping it is how crews hit gas lines.

When to Do It

• Trigger: marks are verified on a valid ticket (UG-03) and the bore profile is drafted.
• Prerequisites: valid ticket, verified marks, the draft bore profile, and traffic control where needed.
• Previous step: UG-03 One-Call Locates (811) and Ticket Management.
• Next step: UG-05 Bore Planning and Rig Setup.

Roles

• Foreman: decides where to pothole, checks the data and updates the bore profile.
• Vacuum excavation operator: runs the vacuum excavation truck inside the tolerance zone.
• Laborer or hand digger: hand digs where vacuum excavation is not practical.
• Spotter: watches open crossing potholes during the pilot bore (UG-06).

Equipment and Materials

• Vacuum excavation truck, hydro or air, with operator.
• Hand tools; insulated or fiberglass handles where electric lines are expected, per your employer’s safety program. Where the exact location of buried electric lines is unknown, OSHA 29 CFR 1926.416(a)(2) requires insulated protective gloves for anyone using hand tools that may contact them.
• Measuring rod or grade rod for depth photos.
• Camera and GPS receiver.
• Barricades, plates or covers for holes left open.
• Backfill and restoration materials per the permit.

Safety

Procedure

Hold Points

Records to Keep

• Pothole log: pothole id, utility type, depth to top, size, material, offset, direction, stationing or GPS.
• Photos with a measuring rod in view.
• The updated bore profile.
• Damage reports and owner notifications, with photos, for any facility damaged, however minor.

Common Mistakes

• Skipping crossings. One unpotholed crossing is enough to hit a gas main.
• Trusting plan depths. Record drawings are often wrong; grading changes cover.
• Not exposing the whole utility. You need the bottom as well as the top to plan clearance.
• Leaving holes unprotected. An open pothole is a fall hazard for the public and the crew.
• Digging with a backhoe inside the zone. That defeats the purpose of potholing.

Standards and References

• 29 CFR 1926 Subpart P: excavation rules, including protective systems, spoil placement, and finding and protecting exposed utilities (1926.651(b)).
• CGA Best Practices: daylighting and tolerance zone practices.
• State one-call law (811): tolerance zone width and hand-digging rules vary by state.
• MUTCD Part 6: traffic control around the vacuum truck and open holes.
• 29 CFR 1926.600(a)(6), Equipment (Subpart O): minimum clearance from overhead power lines for the vacuum truck boom, and an observer where the operator cannot judge it.
• 29 CFR 1926.416(a)(2), Electrical (Subpart K): insulated protective gloves for anyone using hand tools that may contact buried electric lines whose exact location is unknown.
• 29 CFR 1926 Subpart M: guarding wells, pits, shafts and similar excavations (1926.501(b)(7)).
• 49 CFR Part 196: excavation near gas and hazardous liquid pipelines, including reporting any pipeline damage to the operator and calling 911 on a release.

On the Map

• Pothole: vacuum or hand excavation exposing an existing utility before the bore crosses it.
• Water Main: a typical crossing utility to expose.
• Gas Main: the highest-consequence crossing; strike response is evacuate and call 911 and the utility.
• Sewer Main and Lateral: laterals are often unmarked and a crossbore risk.
• Underground Power: buried electric, marked red; expose it like any crossing, because a strike can energize the tool, truck and ground.
• Existing Communications: other companies’ buried cable, marked orange; expose and protect it at every crossing.
• Tolerance Zone: the band either side of the marked facility, measured from its outside edges, where you dig only with the methods state law allows (typically non-powered hand tools or vacuum excavation).

Related Tools

Not applicable: no FAHMY tool covers potholing.