The incident occurred Aug. 30, 2018, in the Knolls of Breckinridge, a subdivision in northeast Richardson. The failure of a 72-inch underground pipeline caused a 6-foot geyser to erupt through Crystal Mountain Drive, damaging 13 homes and displacing many residents, including Council Member Ken Hutchenrider.
In the months following the incident, the district commissioned two engineering firms—Halff Associates and Freese & Nichols—to conduct independent forensic analyses of the failed segment, according to Deputy City Manager Don Magner, who presented the findings to City Council on Dec. 2.
Both studies found cracks in the exterior mortar of the pipe are what ultimately led to the rupture. Those cracks could have occurred during construction of the pipe, he said. They also could have happened during construction of the subdivision, a time when underground pipes are exposed to unusually heavy loads, Magner said.
“If there was a crack when [the pipe] went in at construction, additional weight would have the likelihood of opening it up,” he said.
Those cracks allowed moisture to seep into the infrastructure and cause a degradation of wires used to strengthen and protect the pipe, Magner said.
Neither study found any issue in terms of design of the pipeline, which dates back to 1979, Magner said. However, it is possible that the pipe’s wiring had microcracks at the time of manufacturing, increasing the likelihood of fractures if exposed to moisture, he added.
“Degradation that occured on those wires, over time, finally gave through,” he said.
Underground pipelines experience varying levels of pressure on a daily basis, but that is not what caused the failure, the studies found.
“Had it not been for this series of events, the crack in the mortar, the water degrading the wire, the wire having microcracks that made it more susceptible, this rupture would not have occurred simply based on operations,” Magner said.
As a result of the incident, the water district also commissioned Pure Technologies to conduct a comprehensive analysis of the 60- and 72-inch lines that encompass the North Garland Pipeline system, which stretches from Wylie to Richardson and also includes small portions of Plano and Garland.
Within the city of Richardson, there are 14 miles of water lines operated by the water district. The majority of that infrastructure comprises 60- or 72-inch pipelines, Magner said.
Of the 6,000 segments of pipe inspected, Pure Technologies identified five segments as having some level of wire degradation, Magner said. Those segments have been recommended for repair or replacement, and all work should be done by next summer. Only one of those segments was located in Richardson, near the intersection of Renner and Brand roads. The remainder are located in Garland.
The analysis also identified six leak locations, all of which have since been repaired, Magner reported.
Moving forward, the district has agreed to do a similar comprehensive assessment every five years, Magner said. The city will work closely with the district on future inspections and analysis of pipeline, he added.