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Water main break complicated by system’s age and complexity, OWASA says

Employees of the Orange Water and Sewer Authority work at the intersection of W. Main Street and Greensboro St. in Carrboro, N.C. on Monday, Nov. 5, 2018. A major water main break occurred outside of OWASA’s Jones Ferry Road water treatment plant early Monday morning.
Employees of the Orange Water and Sewer Authority work at the intersection of W. Main Street and Greensboro St. in Carrboro, N.C. on Monday, Nov. 5, 2018. A major water main break occurred outside of OWASA’s Jones Ferry Road water treatment plant early Monday morning. jwall@newobserver.com

It’s not clear why a critical Orange Water and Sewer Authority pipe broke Monday on Jones Ferry Road, but the utility’s board learned Thursday how difficult it was to stop the 9.4 million-gallon leak.

It could take about a month for an independent review of the cause and the response to the emergency, said Mary Darr, OWASA director of engineering and planning.

They are “very sorry” for the broken pipe and how it affected the community, Executive Director Ed Kerwin said during a meeting Thursday of the OWASA Board of Directors.

“While it is not possible to predict all water main breaks, we are doing and we’ll do more in the future to minimize the impact and risk of such failures,” Kerwin said.

“Our team is certainly committed to earn back the trust and confidence of this community in the services we provide,” he said. “We know how essential they are, and we know we have a lot of work to do to earn that trust and confidence back.”

Broken and corroded

Security camera footage showed the 16-inch pipe broke around 6 a.m. Monday in front of OWASA’s building, spewing water down the hill and filling Jones Ferry Road. Employees noticed it when they arrived for work about 15 minutes later, officials said.

The break left more than 80,000 customers in the Chapel Hill-Carrboro area with limited water and a boil-water advisory for over 24 hours. It also forced UNC and UNC Health Care to cancel classes, divert emergency calls and postpone elective surgeries. The Chapel Hill-Carrboro City Schools sent students home for two days.

After eight hours, crews stopped the leak and found a big hole at one end of the 77-year-old cast-iron pipe, said Todd Taylor, OWASA general manager of operations. . A long crack ran down the side, and a camera inspection revealed “quite a bit of corrosion” around an older tap in the pipe, he said.

The pipe had an expected lifespan of 80 to 100 years, Darr said.

The utility, which normally keeps 6.4 million gallons in storage, lost that and more over the next 18 hours, because the broken pipe drained four water towers, Taylor said. The draining water pushed back through the plant on it way through the broken pipe.

Customers asked to cut their water use by roughly 25 percent, Taylor said, and Chatham, Hillsborough and Durham piped in another 3.6 million gallons of water. The treatment plant’s underground “clearwell” tank also helped keep water flowing, he said.

“During this whole event, we were pumping a tremendous amount of water out into the system just to keep up with the demand of customers and the leak that was going on at the time,” Taylor said.

OWASA framed.jpg
A water main going to the Orange Water And Sewer Authority’s storage tanks broke on Monday, Nov. 5, 2018, and the agency asked customers in Carrboro, Chaperl Hill and the University of North Carolina to cut use back to drinking and hygiene uses until crews could find and fix the break. Orange Water and Sewer Authority

More problems uncovered

But the search for the leak was stymied by the rush of water over the hill, which obscured the shutoff valves. Crews went further down the line to turn off other valves, but that did not stop the leak, Taylor said.

The next step was rerouting the water away from valves near the break.

“Plan B was also ineffective,” Taylor said. “What we found out was some of them were inoperable, some of them were broken, some we couldn’t locate very well, and this plan also did not work as far as isolating the break.”

They moved farther from the plant, finally shutting off the water around 2 p.m. Monday. A private contractor was hired to coordinate the repair while OWASA searched for the leak to save time.

The Moffat Pipe crew dug a hole 12 feet to 14 feet deep and removed a storm drain to reach the pipe, which laid adjacent to two other large pipes. Only about 99 percent of the main leak was isolated, Taylor noted.

The leak and stress from the repair caused other pipes to break in Carrboro, he said, but the storage tanks reached 6.9 million gallons by midnight Monday. Crews were still cleaning up the mess Thursday evening on Jones Ferry Road.

The boil water advisory was lifted at 4 p.m. Tuesday, after all 43 water samples taken from across the system tested clear, Taylor said. They took 25 more samples Tuesday morning as a backup, he said.

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Crews worked through the day Wednesday to complete the repair and replace soggy soil with fresh, Darr said.

Among other concerns, OWASA board members wanted to know more about the faulty valves. Taylor said the valves should be tested once every five years — 400 valves every three months. He did not know the last time the Jones Ferry Road valves were tested.

Replacing priority lines

The break “definitely is going to influence” how OWASA prioritizes its water mains, Darr said. A new model for finding high-risk and high-consequence pipes is already underway, she said. They also will examine how to isolate problems in bigger pipes more quickly.

OWASA’s complicated, aging network of pipes and valves has been installed over the last 70-plus years as the community and the needs have grown, Darr said. About 20 percent of OWASA’s 380 miles of pipes are at least 40 years old; the average age is 31, Kerwin said last year.

Darr said quite a few large water lines need replacing, and high-priority projects are being added to the long-term construction budget.

OWASA spends roughly half of its $40 million budget on equipment and buildings. This year’s budget funds about 60 projects, including $5.5 million for water main upgrades — part of a five-year, $24 million plan to replace 16 miles of pipe.

OWASA’s revenues come largely from water and sewer fees.

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Monday’s break was the second time in less than two years that a broken pipe disrupted the utility’s water service. Darr noted there may be some similarities between Monday’s break and the one in February 2017.

That water main break shut off service to residential and business customers for more than 24 hours. An independent report blamed human and system errors for that incident, which started with a fluoride overfeed at the Jones Ferry Road water plant.

In that case, the 44-year-old pipe was lying 3 feet underground and less than a foot above a sanitary sewer pipe. External force and fluctuating water pressure was blamed for bending the pipe, causing it to break.

Grubb: 919-829-8926; @TammyGrubb
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