I first noticed the white panel truck on the streets of Middlebury with this puzzling name emblazoned on the side: “Vermont Underground Locators Inc.” In smaller type, it elaborated: “Finders of Lost Utilities in Vermont, New Hampshire, New York and Beyond.” But that explanation did nothing to answer my immediate questions: WTF is a lost utility. And why would anyone need to find one?

So I asked the driver of the truck.

“There’s a lot of ways utilities get lost,” said Kirsten Corcoran, who identified herself as a professional locator. “Generally, it’s poor recordkeeping. Or there may have been great records, but they’ve been lost in fires or floods. The most common thing is that people retire — the water guy who worked there since he was 15 laid everything in the ground himself, knew where everything was, and everyone just assumed he’d always be there.”

Turns out, the ground beneath our feet is crisscrossed with buried streams of the essential ingredients of civilization — water, gas, oil, sewage, steam heat, electricity, telephone signals, and cables for TV and internet. For safety and by law, nobody in Vermont may excavate without first calling in Dig Safe, a service of the Vermont Electric Cooperative, which will come and mark the lines to avoid. But Dig Safe’s purview is limited to lines belonging to member utilities, and much more can be going on below. Independent companies such as Vermont Underground Locators have sprung up to fill the gap.

Not everyone bothers to check before digging into the earth. According to Corcoran, landscapers and fence installers are often lax. But it pays to double-check, because the stakes are high. Whack your backhoe blade into a sewer line, and you get a stinky mess along with a stiff repair bill. A pierced gas line can trigger an enormous explosion. Slice into a hidden high-tension power cable, and you’re literally toast.

In 1984, Vermont Gas worker Dick Mulvaney jackhammered his way into live wires and received an instant, near-fatal 15,000-volt electrocution. His survival was considered a miracle, and rehabilitation and recovery took a couple of years. When Mulvaney returned to work for Vermont Gas, he became a locator. In 1992, he started his own company, Vermont Underground Locators — which, as its truck announces, now serves a tri-state area and beyond.

Locators don’t have X-ray vision, but their trained eyes and intuitions come close. Tools range from low-tech fiberglass probes and electromagnetic wave detectors to Corcoran’s favorite tool, a rolling cart fitted with ground-penetrating radar (GPR), tuned antennas and an imaging screen. Its powerful radar signals penetrate the earth and then bounce back a sort of topographical image of what lies beneath. The depth the GPR can “see” depends on the soil conditions, but 15 feet is typical — or up to 30 feet for conductive lines such as TV or power cables. By contrast, radar might penetrate as little as four feet in Addison County’s dense clay, particularly after last spring’s endless rain, according to Corcoran.

Exact details about where cables are buried are important, but the information tends to be released on a need-to-know basis. Corcoran called this security through obscurity. “First, people are stealing copper. Then there’s terrorism, domestic or foreign,” she said. “Some cables, if taken out, would knock out all of Vermont and New Hampshire. It’s best if the general public doesn’t know exactly where they are.”

Utility lines aren’t Corcoran’s only quarry. Recently she volunteered to map unmarked paupers’ graves in a Barre cemetery so that a planned bike path could be routed respectfully. “When we see a body, we’re not seeing the bones. Sometimes there’s a casket, but paupers’ graves don’t even have that,” she said. “What I’m looking for is a void, the air pocket left by the body when it decomposes, leaving a calcified shell.

“Every time I learn to look for something new,” Corcoran continued, “it’s something I can take back to the utility work. We look for voids under parking lots and cement slabs. If an area has been backfilled with large rocks, or hasn’t been compacted well, that’s something you need to know before you build above a sinkhole.”

What’s the strangest thing she’s ever found? Corcoran laughed, remembering a September day on a property in Bolton. As she guided her radar cart across a pasture in search of a lost leach field, a puzzling image on the screen stopped her. It seemed to show an enormous trench framing a peculiarly shaped air pocket. Her client saw her looking completely confused, and sang out, “Oh! You’ve found Magic!” Magic, it turned out, was a horse that had died just before the owners were leaving for vacation. “The easiest place to bury him was where our old swimming pool was backfilled with sand,” the client explained.

Corcoran, who originally trained as a pilot and aviation tech, described her work as trying to assemble a 3-D jigsaw puzzle, except someone has taken away the box top with the picture.

Among locators, a common occupational hazard is that they can’t stop imagining all that hidden infrastructure underground.

“It drives me nuts when I’m on vacation in some stunningly beautiful place,” said Corcoran. “I’ll be riding with a friend, talking, and she’ll say, ‘Hey, quit looking at the poles!’”