Cold water, not freezing ground, was one of two major factors in hundreds of water line breaks across the City of Tulsa during February’s winter storms.
City Asset Manager Joan Gausvik told the Tulsa Metropolitan Utility Authority on Wednesday the other factor was pipe material.
"About 50% of our pipe system is cast iron … there were failures in other materials, but cast iron is probably 80% of the failures in this event," Gausvik said.
Water starts expanding when it gets below 39 degrees Fahrenheit. Gausvik said reservoir water coming from city treatment plants stayed above freezing but below 39 degrees for several days, increasing the pressure inside water mains getting more brittle in the same temperatures.
"You know, as long as we are still operating cast-iron water lines, we will have a risk form a cold-water event. … There are some communities that maybe switched to groundwater or do something to try to warm up their distribution system water, but we do not have any way to remediate a cold-water event," Gausvik said.
The city had 450 water line breaks from Feb. 8 through March 4, and there were even more private line breaks. Many of those went undetected for extended periods because they were at unoccupied businesses.
Nearly 5,600 customers lost water during that timespan, most for more than 24 hours. Between municipal and private line breaks, water demand during the winter storm surpassed summer maximums.
The city also faced conditions that compounded the strain on its water system, including impassable roads to facilities, frozen equipment and a tunnel that brings water from Lake Spavinaw being shut down for scheduled maintenance.
The city is still determining what it spent on emergency water system repairs so it can submit a reimbursement request to the Federal Emergency Management Agency. The latest total estimate is $1.9 million.
