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County engineer Richard Macchi told commissioners during Monday’s workshop that he estimates between 60 and 80 percent of county bridges need some type of repair work as a result of last year’s flash floods.
Macchi’s assessment came after recently reviewing reports from state inspectors who conduct biennial inspections.
None of the bridges pose any danger to traffic, Macchi told the Telegram on Tuesday.
Damage was minor in most cases, he said. Two structures were downgraded in their ratings.
One is on Chaparral Road in Harker Heights where it crosses Trimmier Creek. The other is on Reeds Lake Loop where it crosses Knob Creek near Little River-Academy, Macchi said.
The Harker Heights bridge is concrete of pan girder construction, he said. The damage was the result of erosion under the abutment next to a drilled concrete pier.
The state dropped the rating from unlimited use to 21,000 pounds, Macchi said.
It doesn’t pose a hazard to cars or even heavy trucks driving over it, but the bridge does carry a large volume of traffic, he said.
“That’s why we are doing the work so that it doesn’t get worse,” Macchi said. “When we complete the repairs, the rating will go back (up).”
He said riprap rock - large chunks of concrete or limestone - would be placed in the eroded spot and concrete poured over it to bind it.
Work will begin when an adjacent landowner gives written approval for work crews to have access to the damaged area, said Macchi.
“We could do it without the landowner, but it would be a lot more work and harder,” Macchi said.
Macchi said in his experience requests for access are usually honored.
The bridge over Knob Creek is a concrete box culvert design, Macchi said.
“The damage is to the downstream end,” he said. “Water coming out of the box eroded the streambed out in front of the box and in this particular instance it actually undermined an area under the box.”
Macchi said repairs are under way.
“We’ve already put the rocks in,” Macchi said. “But since the water is running right now we are waiting to pour the concrete.”
Macchi said the rest of the county bridges had only minor damage.
“It’s not critical but it’s something you want to do something about,” he said. “I haven’t finished going through all the reports yet. I’m in the process.”