What to expect when an underground wire fails

Underground runs are the quietest part of an electrical installation. They feed a detached garage, a lamp post, a workshop at the end of the yard, or the lighting across a commercial parking lot, and they do it without being looked at for decades. Then one day the thing on the far end stops working.

What happens next is where underground work differs from everything else an electrician does, because the expensive part is not the electrical repair. It is the ground above it.

Why the first visit should not involve a shovel

Knowing roughly where a cable failed and knowing precisely where it failed are separated by a great deal of trenching. Roughly means opening a long stretch and following the run until the damage appears. Precisely means one neat excavation.

On a residential yard that difference is a weekend of disruption against an afternoon. On a commercial lot, where the surface above the run is asphalt somebody paid to have laid, it is most of the cost of the job. So the sequence that keeps an underground repair small is always the same: confirm the fault is in the buried section, trace the route, locate the fault, then dig once.

How underground runs actually fail

• Something was driven through it. Fence posts, tree stakes, sign footings and later landscaping account for a lot of underground faults, sometimes years after the event.
• Water found a joint. A splice or a fitting that was never fully sealed will take a long time to fail and then fail permanently.
• Ground movement. Frost heave and settlement work on a cable over many Michigan winters, particularly where it changes depth or direction.
• Roots. Growth around a run does not usually cut it on its own, but it moves and abrades it.
• It simply reached the end of its life, which for an older direct buried cable is a real and unremarkable outcome.

What you can usefully check first

Before assuming the buried section is at fault, it is worth ruling out the two ends, because they are accessible and the middle is not. Check whether the breaker feeding the run has tripped, and whether anything at the far end has failed on its own. A garage with no power because its own subpanel has tripped looks identical from the house to a garage with a failed feed.

Beyond that, the useful thing you can provide is history. When was the yard last dug up? Was a fence, a deck, a patio or a post put in at some point? Has anything changed at the far end recently? That information genuinely narrows the search area, and it costs nothing.

Repair or replace the run

If a run has one clear point of damage, from something driven through it for instance, repairing that point is usually reasonable. If a cable is failing because of age or because water has been getting into it for years, a repair tends to be the first of several, and replacing the run is the cheaper answer measured over any sensible period.

Which of those you are looking at is normally obvious once the fault is exposed, and it is a conversation worth having then rather than in advance.

Record where it runs, while the trench is still open

The single cheapest thing anybody can do during an underground repair costs nothing and takes two minutes. Before the trench is backfilled, photograph it with something permanent in shot: a corner of the building, a post, a driveway edge. Measure off two fixed points and write the numbers down.

Every underground fault we are called to is harder than it needs to be because nobody knows where the cable goes. A photograph taken while it was last exposed turns the next visit, whether that is in two years or twenty, from a search into a repair. Marker tape laid above a new run does the same job for whoever digs there next, including you.

On commercial sites, plan the surface as well as the cable

Where a run crosses a parking area or a service road, the reinstatement matters as much as the electrical work. Knowing before you start which sections are under asphalt, which are under landscaping and which are under something that has to stay open for trade is what allows the job to be staged around your hours rather than across them.

Getting it looked at

Brandon Electric handles underground wire repair and underground wiring for residential, commercial and industrial customers across Oakland and Macomb County, and estimates are free. If something at the end of a buried run has stopped working, describe what it feeds and what has been done to the ground above it, and that is usually enough to plan the first visit properly.