TWIN FALLS — A video inspection of a ruptured waterline last summer did not reveal any sections where the line appeared in danger of bursting again.
An arsenic blending line in Twin Falls ruptured on July 24, 2018, creating a sinkhole that downed a semi on Washington Street South. The break was caused by the pipe laying on solid rock.
“It was laying on a ridge of rock,” Public Works Director Jon Caton said. “That ridge should have been removed and the pipe should have been bedded appropriately.”
But it had city staff initially worried that the pipe may have been bedded incorrectly along its entire length due the “shoddy workmanship.” However, after camera footage examined almost 1,000 feet of pipe, Caton believes there is no cause for alarm.
“There were no obvious defects in the interior of the pipe that we could visually tell,” he said.
The video also showed no significant changes in elevation that could indicate the pipe was laid on rock, Caton said. City crews took additional footage with just a little bit of water flowing through the line.
The city in 2011 had provided oversight for crews installing the line to make sure the work met requirements. Caton believes no other ruptures are imminent. The city could excavate areas where it knows there is rock, just to be certain, but he recommends against it.
“It’s like searching for a needle in a haystack, at great cost,” Caton said.
Even months afterward, he still had no estimates of the total cost of the repairs; partially because it was hard to track the cost of removing the semi. The public works department is consulting with legal counsel about whether the city could seek reimbursement from contractors due to faulty installation, but the warranty and statute of limitations may have expired, Caton said.
The July 24 incident was the third time the 2011 blending line had ruptured in four years. A 2014 break was believed to have been caused by a sunken manhole putting pressure on the pipe. And a couple years later, another rupture was caused by the failure of a fire hydrant line overlaying it. It was just coincidence that those two failures happened on the same line, Caton said.