A technology first used to scan for land mines will soon be coming to San Antonio’s front yards.
The San Antonio Water System signed a $4.5 million contract with White River Technologies to start using an advanced metal detection technology at the public utility’s June 2 board meeting.
The metal detectors — a sensor on top of a hand-pushed cart like a cross between a Martian rover and a lawn mower — aren’t being used to find unexploded ordnance. They’re part of SAWS strategy to identify lead pipes near San Antonio households.
The Environmental Protection Agency (EPA) required utilities to inventory water pipe materials beginning in 2021. Kirstin Eller, a potable water quality supervisor at SAWS, said utilities also have to know the material on customers’ side of the water connection.
Lead pipes can be corroded over time and contaminated drinking water can create negative health effects, including anemia, behavior and hearing problems for children and cardiovascular issues for adults.
Texas builders stopped using lead in pipes in 1989, Eller said, and SAWS has a team sifting through historical records and examining data to determine which older pipes might be at risk of leading to water contamination.
Normally, the only way to test pipes would be to dig up a section of pipe to see what it was made out of.
The problem? “A lot of customers do not want us to dig on their property,” Eller said.
Because water lines go under private property, SAWS cannot force an inspection on customers. Using a low-impact sensor, though, is typically well-received.
SAWS began to communicate with federal officials about alternatives.
“SAWS took a stance from the very beginning to see what emerging technology might work for San Antonio,” Eller said. “[The EPA] came to SAWS and said, ‘Would you guys be willing to check this out?’”
SAWS agreed to do a pilot program and study for the new technology.
Eller said the pilot is popular with residents. SAWS is working with the EPA to develop a peer-reviewed article on how advanced metal detection can be used by utilities.
The sensor is wheeled over the ground, Eller said, where it sends a signal that will bounce back from buried objects. It was originally developed for the Department of Defense, she added, because it can create a 3-D map of underground space with the locations of metal objects.
Eller said the sensor has worked well for SAWS with a few minor modifications to its code. The sensor can distinguish between metals like iron or steel and metals like copper or lead that don’t contain iron.
If a pipe isn’t metal, Eller said, SAWS knows it’s plastic.
Data is gathered in the field and sent to an analyst who determines pipe material and location.
It’s not perfect, Eller added. Sometimes, yards will contain old construction materials or pieces of metal that get in the way. In those cases, SAWS has to dig its “potholes.”
The utility hasn’t identified any lead pipes so far, Eller said. But SAWS has removed around 80 galvanized steel pipes. Galvanized steel pipes can attract lead dissolved in water and then later release it.
If SAWS can’t confirm that lead-contaminated water has never touched those pipes, they can be removed, too.
“We have not found any lead. We are excited about that,” Eller said. “We are definitely still going to work to comply with the rules.”
Eller said pipe replacement is funded by customers, though SAWS is trying to put together a program to assist with the work. Customers interested in signing up for the advanced metal detection program can submit an interest form online.
SAWS is hiring its field teams right now, she added, and plans to start outreach neighborhood by neighborhood, focusing on homes that were built before 1989.
“We’ll be operational as soon as possible,” Eller said. “We’re the first utility to be able to offer this in the country.”
