Not long ago, beneath a street in downtown St. Augustine, Fla., construction crews discovered the remains of a 19th-century fishing vessel. 

“We were on-site to do an electrical upgrade, and road construction crews were digging to find a water main before the arrival of a subcontractor,” said William Watson, vice president of safety and security for Miller Electric Co., Jacksonville, Fla. 

The site took on the appearance of an archaeological dig, with hand digging aimed at preserving historical information. 

Such a cautious approach is sometimes necessary, Watson said, who conducted a presentation about digging safety and utility tracking technologies at NECA 2024 San Diego with co-presenter Denise M. Elliot, damage prevention specialist at 3M Co.

Like many electrical contractors, Miller Electric uses ground-penetrating radar (GPR) to locate buried utilities. 

“The technology can tell you if a water main or a power feeder is there, but it cannot tell you if the feeder is energized,” Watson said.

Besides GPR, engineering drawings suggest where things are, but often something like a repair to a city sewer system introduces a deviation. 

“We’re always asking, ‘Did we get the latest version of the drawings?’” he said.

Serious consequences

CPWR, the Center for Construction Research and Training, wants the construction industry to know just how serious the consequences can be for hitting some buried utility lines.  

A story posted on CPWR’s website goes like this: “… suddenly the auger hit a small plastic gas line. Escaping gas reached a nearby building and ignited. Four people died and 15 were injured in the resulting explosion. Three buildings were destroyed, and more than a dozen others were severely damaged ...”

Root causes of utility strikes almost always relate to failure to properly identify the locations of utility lines. 

In about 32% of cases, a locator misread the ticket and did not identify the dig zone, according to a recent report by Common Ground Alliance, an organization with 4,000 utility members. 

Another 30% of cases resulted from an excavator not using proper care. And for the rest, no one bothered to call 811 to request location service, a process that can take two to three days.

The first Dig Alert call centers were established in the 1970s, followed by the 811 ”Call Before You Dig” system in 2005. Buried utility damage dropped dramatically for the next 10 years, but it still persists, with billions of dollars and lives lost every year.

RFID's rise to the top

In the late 1980s, radio frequency identification (RFID) technology came to the forefront. More recently, RFID marking systems have become memory-chipped devices that have revolutionized the way utility lines are marked and identified. 

When triggered by an electromagnetic interrogation pulse from a nearby RFID reader device, an active tag transmits digital data, including an inventory number, back to the reader. 

Slightly different in their operation, passive tags are powered by energy from the RFID reader’s interrogating radio waves. Transponders are now contained in color-coded balls unique to each utility—telephone, power, water, wastewater, gas, CATV and reclaimed water. Trace wire also helps in identifying utility lines and must be properly installed. 

3M also has developed early warning tape placed underground, 2–3 feet above utility lines. It has a Kevlar core that discourages excavation.  

For safety’s sake, dig equipment operators must also have proper training and familiarity with digging equipment such as digger derricks and backhoes. 

“Just because someone has a certificate saying they can operate one piece of equipment doesn’t mean he will automatically be able to drive similar equipment made by another manufacturer,” Watson said. “The controls are different on a John Deere versus a Caterpillar.”

Dig safety plans must also be site-­specific and include visual hand-signal communication between equipment operators and spotters. 

“Sometimes the equipment operator decides they don’t need the spotter and starts ignoring them,” Watson said. “That’s not good, because someone can get hurt.”

Another big challenge to digging around utility service lines is water, Watson said. 

Florida’s high-water table and rising tides make it a good place for demonstrating water safety strategies. Rather than requiring electricians to work below the water line, Miller Electric uses cranes to install electrical rooms preassembled in controlled environments. 

Dusan Petkovic/STOCK.ADOBE.COM