Why Did A Nashville Water Main Break Mid-Summer? Maybe Poor Installation

MWS officials say ground water eroded the concrete pipe, eventually weakening the wires that give the concrete its strength. Credit: MWS

It took less than a week to replace a 50-foot section of water main in south Nashville that burst, leaving 15,000 customers with reduced service. Now Metro Water Services officials are starting to explain what may have happened.

In Nashville, water main breaks are usually a wintertime problem, not mid-summer.

At a press conference Monday morning, assistant director Hal Balthrop said the initial forensics suggest there was some water eroding the outside of the 30-inch concrete pipe. Eventually, the weakened line operating at 160 PSI blew out.

Besides the groundwater erosion, Balthrop says there wasn’t the typical layer of gravel around the water main.

“Usually we put a gravel envelope around the pipe to protect it from the environment,” MWS assistant director Hal Balthrop said. “We think this particular segment of pipe may have been put on solid rock and not had that cushion of a gravel envelope around.”

MWS has 3,000 miles of pipes and water mains throughout Davidson County. The section that burst had been in the ground for 40 years. Balthrop said the department no longer uses the same kind of concrete pipe, although MWS has some water mains that are much older.

Another challenge to repairing the line was its remote location.

“We try to put our infrastructure where it is accessible, but we also try to coexist with development,” Balthrop said.

The problem section fell between Interstate 65 and a CSX rail line. Metro Water had to build roads to the site before it could even begin work.

Metro Water is still asking customers in South Nashville to refrain from irrigating their lawns. But the system is expected to be back to normal by tomorrow.