RALEIGH — A crack in a main sewer line for the city of Burlington caused 3.5 million gallons of untreated wastewater to spill this week into the Haw River, which feeds into the drinking water supply for roughly 300,000 people in the Triangle.
Ranking among the largest spills in recent history, the leak from Monday through Wednesday put the equivalent of six Olympic swimming pools of sewage into the river.
Burlington, following state law, didnt make a public notification until the leak ended, potentially exposing recreational users of the river to pathogens, according to an academic expert.
However, the town of Pittsboro the closest downstream user of the Haw has seen no signs of contamination or biological impact from the three-day overflow. The weeks cold weather likely limited bacterial growth and kept recreational users away from the sewage, said Corey Basinger, a regional supervisor for the state Division of Water Resources.
The overflow resulted from a failure of one of the most important pipes in Burlingtons sewer system, compounded by icy weather, according to the state Department of Environment and Natural Resources.
Burlington officials on Monday night noticed a crack several feet long in the force main that pushes sewage uphill to the East Burlington Wastewater Treatment Plant. The plant, one of two for the city, can handle up to 12 million gallons of sewage per day.
The city notified a state-run emergency response unit within an hour. That night, Burlington shut down the failing line, which is 55 years old. Within hours, the city installed a pumping system and pipe to reroute the effluent.
But the citys emergency replacement pumps werent powerful enough to force all the sewage uphill through 600 feet of temporary replacement line, Basinger said.
The equipment that they had on hand was not quite sufficient to stop the overflow not quite large enough, he said.
Wastewater soon backed up and overflowed from large, trap-door style manholes in a wooded area near the plant, eventually seeping down to the Haw River.
Public notice took days
While downstream municipalities and state agencies were notified immediately, Burlington did not send out a media advisory or other public notification until Thursday, Basinger said. State law allows governments to make that announcement up to 48 hours after sewage reaches rivers, creeks and lakes.
Kenneth Reckhow, an academic expert in water quality, said authorities waited too long to notify the public.
If by chance they were in the Haw boating and they put their hands in the water, where this came through, then that might be a concern, said Reckhow, a Duke University professor emeritus of water resources. I think as soon as they notice that (a leak has) occurred, it seems that it should be required to provide that notice. For boaters, kayakers, it would be something they would want to be aware of.
It is not clear when sewage first touched the Haw River. Basinger said state and city officials wanted to have a full accounting of the accident before making public statements. City officials werent immediately available for comment, but Burlington was acting on the advice of the Division of Water Resources, according to the Times-News of Burlington.
We wanted to ensure the city had proper public information, Basinger said. Speaking too early could have caused confusion and required further statements, he added.
Asked about a potential hazard to uninformed boaters near the plant, he pointed out that extremely cold temperatures had largely cleared the Haw of recreation.
We felt we had made notifications to all the pertinent parties state agencies and sister agencies, Basinger said. Those are requirements that are set in statute.
Though the leak was the largest that many involved could remember, it ultimately was a trickle compared to the flow of the Haw, which was close to 200 million gallons per day this week.
Little long-term impact
Burlington crews stopped the leak Wednesday afternoon by installing a huge temporary pump. The city is still working to repair the force main.
Thirty miles downstream, the town of Pittsboro hasnt spotted any dead fish or seen any changes in the measurements of its drinking water, which it draws from the Haw near U.S. 15-501.
If they hadnt told me, I wouldnt have known there was a spill, said Adam Pickett, superintendent of water treatment for Pittsboro. It was a large spill, and I hate it, but hopefully itll blend really well and there wont be any adverse effect.
Reckhow, the Duke expert, agreed that the spill would not be measurably harmful in the long term to water quality in the Haw or in Jordan Lake. The cold weather should repress organic growths, and any bacteria or viruses would die quickly, he said. At most, he said, the wastewater could feed algae in the Haw.
Both the state and the city of Burlington will investigate why the failure happened and how it could have been prevented, Basinger said.
We will review with them any precautionary measures that need to be taken moving forward on any similar-sized lines and aged lines, to make sure we dont have other issues that come to light, he said.
State rules require yearly inspections of lines like the one that failed; records of the most recent inspection werent immediately available.
Basinger praised Burlingtons response to the leak. Equipment failure is unpredictable, and the citys emergency equipment was inadequate only because of the magnitude of the situation, he said.
We were very impressed by their response, he said. To get this pump-around in place during some very adverse weather conditions, in the middle of the night it was the perfect storm, it really was.
Kenney: 919-829-4870; Twitter: @KenneyNC