An estimated 250,000 gallons of raw sewage spilled from a ruptured pipe in western Johnston County last Sunday morning, and about 125,000 gallons made it into Swift Creek, a tributary of the Neuse River.
The cause of the break is under investigation, said county public utilities director Chandra Coats, but early indications are gases in the the sewer line built up and broke the line along Cornwallis Road in the Cleveland community. Coats said the line was repaired Monday afternoon, though cleanup efforts continued throughout the week.
The busted line wasn’t particularly old, having been installed within the last five years, Coats said.
The public utilities department discovered the break Sunday morning, Coats said, and shut the line off within two hours. Sewage from the line was diverted to a parallel line on Cornwallis Road, and the Town of Clayton began accepting some of the system’s sewage for treatment, Coats said.
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The 250,000 gallons spilled from the line represent about 5 percent of the 5 million to 6 million gallons the county treats each day.
Officials with the state’s Division of Water Resources characterized the spill as significant and are aiding in the investigation and cleanup. Coats said her department is testing the water in Swift Creek up and downstream of the spill to help determine the risk to wildlife and water quality. By Monday afternoon, Johnston County had filled seven tanker trucks with recovered sewage, but Coats said that accounted for only about 22,000 gallons of the total spill.
“We wish (the spill) were a lower volume, but we were able to identify the break rather quickly, and because of redundancy in our system, we were able to continue moving the wastewater to our treatment facility,” Coats said.
Coats said the county would examine the line near the break for any other potential failures.
The impact of the spill on Swift Creek could end up being less than initially projected, as much of the sewage collected in a wetland near the creek rather than running into the creek itself, said Rick Bolich, assistant supervisor of water quality with the state Department of Environmental Quality.
But the impact on the wetland is perhaps an even greater issue, as a community of endangered dwarf wedgemussels was known to live in the area. Bolich said accessing the wetland is another challenge and that a temporary road may need to be cut to get heavier cleanup equipment close to the area.
“The good news is the spill going into the creek will be diluted by the wetland, if you can call that good news,” Bolich said. “It was contained before it hit the main body, but unfortunately, some undoubtedly did make it into Swift Creek.
“Our primary purpose now is determining the potential impact to an endangered species in the area; the dwarf wedgemussel is known to be be in the area. That’s our primary concern.”
A DEQ report on the spill said sections of water in the wetland were black and had a foul odor. More than a dozen small fish were seen floating on the surface of the water. The report speculates that the spill collected in the one- to two-acre wetland and then overflowed, spilling down into Swift Creek.
At the point where the sewage fed into Swift Creek, the water wasn’t black or pungent on Monday, the report said. But 200 feet downstream, some black water was trickling into the creek.
The spill seemed to come from a 3- to 4-inch leak in a 12-inch main pipe made of 3/8-inch-thick steel, the report said.
Bolich said his office is offering any assistance it can in the cleanup and will investigate what caused the break.
“Our goal is to make something like this as rare as possible,” Bolich said. “Something like this, if there’s a pipe failure, that’s going to happen. Our goal is to find out why and figure out what we can do to prevent it from happening again.”
Drew Jackson; 919-603-4943; @jdrewjackson