Electrical Utility Exposure

Duct bank, conduit and direct-buried are three different problems

Grouping them under electric hides the part that matters. A concrete-encased duct bank is physically tough and the encasement protects what is inside, so the risk is less about the cable and more about chipping concrete, cracking a duct at a joint, or undermining the bank so it loses support along its length. Conduit without encasement, whether PVC or fiberglass, is easy to crack with a tooth and easy to uncover with water. Direct-buried primary is the one that keeps people awake. There is no duct and no concrete between the soil and the insulation, so the only thing standing between an excavation and a fault is the method and the hand running it. That is the case where non-destructive excavation stops being the convenient option and becomes the only defensible one, and it is more common on older residential feeds and campus distribution than the drawings usually suggest.

Locating electric is harder than locating a pipe

Marks near electric come with more caveats than most. Concrete encasement can attenuate a signal so a heavy duct bank reads faintly, or the locator ends up tracing a ground conductor or a neighboring metallic line and marking that instead. Multiple circuits stacked in one trench come back as a single stripe of paint, which is exactly the condition where an assumption gets somebody hurt. Past the meter, the one-call ticket does not apply at all, and on a commercial property that means parking lot lighting circuits, sign feeds, gate operators, generator and transfer switch feeders, and building to building distribution are all unmarked by default. Around here FPL owns the utility side of that boundary and everything on the customer side is somebody’s private installation with private records, which on a property that has been renovated twice is a polite way of saying no records at all.

Energized, wet, and the hole in between

An energized cable in a hole that is filling with groundwater is a situation to engineer rather than improvise. The table sits high across South Florida and moves with the tide near the coast, so an excavation over a duct bank takes water on its own schedule. The vac truck lifts water and spoil together while excavating, and a pump with a sump keeps the hole workable while the electrical crew is in it. Where something in the excavation genuinely has to stay dry, a splice, a termination, an open pull point, air excavation is worth discussing before the day since it leaves the spoil and the work dry, though it is slower and it does not argue with limestone. That trade-off gets settled in the yard. What does not get improvised is standoff: the wand keeps its distance from exposed cable, keeps moving, and uses a tip that spreads energy rather than concentrating it into one spot on a jacket.

What the electrical crew needs the hole to be

An exposure that another trade works in is a workspace, and electrical work has particular demands. Pulling a section of cable, cutting in a splice, setting a repair sleeve or landing a new conduit into an existing bank all need room around the facility, room under it, and length rather than depth. Splice cases in particular want far more open cable than people plan for, and a hole sized to the fault is a hole somebody widens by hand at the worst moment. Depth means shoring, since anything a person enters gets sloped, benched or shored for the soil it is actually in, and loose fill over the rock through Miami-Dade sloughs once water moves through it. Ladders, plating, barricade and a cover overnight are ordinary. Tell us the task, the tool and the duration and the excavation gets built for that instead of being adjusted around it.

Backfill matters more on electric than on almost anything else

How an electrical excavation gets closed is part of the work rather than cleanup. Duct banks and direct-buried cable are frequently specified to be bedded in sand or flowable fill, and slurry from a water-cut hole is neither. It leaves in the tank under our haulers and dumping permits to a permitted facility with a record of the trip, and the backfill going back in is imported material selected for the specification. Warning tape sits at its specified height above the facility and goes back where it belongs, because the next crew will be relying on it. Compaction happens in lifts, since settlement over a duct bank in a parking lot is the defect a property manager sees every day for years. Where the utility owner or the project specification names its own bedding and restoration detail, send us the wording and the hole gets closed to it.

Worth knowing

If anything in the excavation has to stay dry, a splice, a termination or an open pull point, say so before we roll. It decides whether we cut with water or with air, and that is a much easier decision to make in the yard than at the edge of an open hole with your crew waiting.