JOHNSTOWN, Colo. - The catastrophic floods of 2013 affected 411 state bridges.
The Colorado Department of Transportation has repaired the most heavily damaged ones, and is now concentrating on those with less damage.
On Wednesday, CDOT engineers began inspecting all 411 bridges to see how they’re holding up. The first one they inspected was the southbound I-25 bridge over the Little Thompson River.
“It’s obvious that the channel has changed", said CDOT Engineer Scott Huson.
A fellow engineer, Tom Moss, experienced that first hand when he waded into the river adjacent to the bridge pier wall and plunged down a few feet farther than he anticipated.
“That’s why we need these measurements,” Huson said, “to go back and assess whether there are any changes to the foundation of the bridges.”
The engineers measured the distance from the bridge deck to the surface of the water and from the water’s surface to the stream bed. They’re trying to determine how much sediment and rock was eroded by the flood.
“We wanted to come back during this time of year, when the water is a little lower, and figure out how much erosion has occurred,” said CDOT Bridge Engineer Joshua Laipply. “Then, how much do we need to design for rip rap and rock to protect these foundations.”
Huson told 7NEWS that the bridges are designed for a “certain” channel elevation. He said, “We lost channel elevation during the September floods.”
Enough sediment has eroded under one of the pier walls on the northbound bridge that you can almost see to the other side.
When asked if that compromised the safety of the bridge, Laipply said, “No.”
He said there are “H” beams beneath the pier wall that go down to bedrock.
“That’s one of the reasons why these bridges are “low risk,” he said.
Huson added that they don’t want the “H” beams to be exposed. That’s why they want to bring in new rock, sediment and rip rap to fortify the foundation.
When asked when they’ll bring in the rock, Laipply replied, “When the water is at its lowest level, in fall or winter.”