CHARLOTTE, N.C. -- Engineers with Charlotte’s Storm Water Services say they might never know exactly what caused a storm drainage pipe to break Monday morning, causing a sinkhole that closed a portion of Providence Road for much of the day.
But they say drainage problems are one result of building a large city atop 34 named creeks and about 3,000 miles of waterways. Adding unusually heavy rain over a one-week period means trouble.
And, the engineers said, all utilities eventually age, and local government is forced to try to stay ahead of the aging process.
“Almost anything could have caused that pipe to break,” Jennifer Frost, a public information officer with Charlotte Storm Water Services, said Wednesday. “Obviously, water under the surface moved soil, and the asphalt caved in.”
Monday’s break occurred in a pipe designed to drain storm water. That made it different from other recent Charlotte cases where a broken pipe – carrying water or sewage – caused a sinkhole.
What made it similar was that it involved a pipe in an older part of Charlotte. In recent years, Park Road, Queens Road and Runnymede Lane, among others, have been closed when pipes ruptured and the road gave way.
Frost says the city’s capital budget provides money for pipes to be replaced.
“Typically, these projects can take five to seven years and involve millions of dollars,” she said. “That differs from what we call the maintenance cases, which involve one to three homeowners and take a few weeks to a few months to finish.”
City budgets show that many pipe replacement projects in recent years were in Dilworth and Myers Park, two of Charlotte’s older areas. Now the work is moving out to areas like Cotswold and Lincoln Heights.
“Everything has a life span,” Frost said. “We’re in a constant state of maintenance.”
But part of the problem with broken pipes and sinkholes might be due to geology and meteorology, officials add.
Frost said there are nearly three dozen named creeks in the city, and her department oversees thousands of miles of creek beds. Roads and even entire neighborhoods have been built over some of those waterways.
Builders today must deal with flood plain issues before they put cement on anything. Decades ago, that wasn’t the case. The result is water sometimes surging under developed land, sometimes in a different direction than the water, sewer and storm drainage pipes.
“When we have an immense amount of rain, it causes the earth to shift under the ground,” said Sharon Foote, information and education coordinator for Charlotte-Mecklenburg Storm Water Services, the county-wide version of Frost’s agency. “Dirt moving under the ground can cause what we call sinkholes.”
Automated rain gauges around Mecklenburg County showed that some areas received more than two months’ worth of rain in a one-week period from June 2-9. Foote said some locations near Ballantyne in southeast Charlotte and near Mallard Creek in the north part of the city got 6 to 8 inches.
Frost said Charlotte’s sinkholes are not the same as those in places like Florida, where entire houses can be sucked in. She said those happen in places with limestone. Charlotte’s soil is much more stable clay.
“Our problem is due to soil shifting under the ground,” Frost said. “There are a lot of things happening under the ground.”
Frost said sometimes big problems can be prevented if people report small leaks from pipes or the ground.
“If you see water coming from a storm drain or from the ground on a dry day, call 311,” she said. “That can save a lot of trouble.”