Hazen and Sawyer independent review of Jones Ferry Rd main break: manufacturing defect in pipe is root cause
On November 5, 2018, a water main break occurred on Jones Ferry Rd in Carrboro which affected water storage levels and water pressure in the system. Customers in OWASA's service area were asked to conserve water over a 24-hour period to protect water supply, and boil water before consuming it for a 31-hour period to ensure public health. Immediately following the event, OWASA commissioned an engineering consulting firm, Hazen and Sawyer, to conduct an independent review of what caused the break and why it took 7.5 hours to stop the leak (as normally it takes about 1 hour to locate and stop a leak).
According to Hazen and Sawyer, the root cause of the main break was a manufacturing defect in the pipe. The area where the pipe cracked was significantly thinner than other areas of the pipe. This defect, compounded with the age and material of the pipe plus the fact that it was originally installed over another pipe over 70 years ago, resulted in localized cracking.
Given the complexity of the underground pipe network adjacent to the Water Treatment Plant, it would have required 8 valves (at minimum) to be closed to stop water from coming out of the break. However, the large volume of water flowing from the break limited access to these valves. In order to stop the water flow, OWASA crews had to move further away from the break to close more valves, some of which were found to be inoperable. The Hazen and Sawyer report notes that the increased complexity of turning 31 valves overall resulted in 7.5 hours passing before OWASA slowed the leak to a point where the necessary repairs could be made.
OWASA is evaluating the Hazen and Sawyer report and will act on recommendations to improve system resiliency. We have already started the process. For example:
- We are working with a consultant to improve our water pipe assessment and replacement prioritization model.
- We are establishing a dedicated valve maintenance crew. OWASA has over 12,000 valves in the distribution system; their operation is necessary to efficiently and effectively prevent breaks in water pipes from draining the distribution system.
- We have made improvements to our pressure monitoring indicators. Better pressure monitoring and integrated alarms provide valuable information regarding water quality.
- We are developing plans to improve our piping infrastructure at the Water Treatment Plant.
We continue to meet with community partners to understand their unique needs and collaborate on solutions. Together, we are committed to increasing the resiliency of our water and wastewater system. We are deeply sorry for the impact this event caused. We take very seriously our responsibility to deliver high quality and reliable water and wastewater services to the community.
What follows below are links to the executive summary of the Hazen and Sawyer report, as well as the full report (note that certain sections in the report have been redacted to protect sensitive location information regarding critical assets). A link to questions and answers about the report and actions OWASA is taking is also provided below.
View the 3-page executive summary from the Hazen and Sawyer Main Break Root Cause Analysis and After-Action-Review (December 19, 2018).
View the full Hazen and Sawyer report (December 19, 2018).
View questions and answers about the report and actions OWASA is taking (December 20, 2018).
Community update: November 12, 2018
Following the event, customers wanted to know more about what happened. OWASA compiled a list of frequently asked questions and shared information as it became available in the days following. View the frequently asked questions document that OWASA shared on November 12.
Timeline of events
Updates during the event
During the event, customers, community partners, and reporters asked OWASA to provide timely information on what was happening when. View the chronology of updates provided throughout the event, on www.owasa.org and on Twitter @OWASA1, here.
Update to the Chamber of Commerce
On November 11, 2018, the Chapel Hill-Carrboro Chamber of Commerce invited OWASA to meet with Chamber members. During this meeting, OWASA listened to how the Jones Ferry Rd water main break impacted community members, and shared information on what happened during the event. View the OWASA presentation to the Chamber of Commerce here.