Highway 36 Completely Reopens After Sinkhole Caused Lanes To Collapse
WESTMINSTER, Colo. (CBS4) -- The Colorado Department of Transportation fully reopened eastbound Highway 36 ints original three-lane configuration in time for the Friday morning commute.
On July 11, a crack started to develop in the eastbound lanes, between Wadsworth Boulevard and 104th/Church Ranch Boulevard. This developed into a sink hole up to 300 feet long and about 10 feet wide.
CDOT requested a $20.4 Million transfer from the Colorado Transportation Commission's contingency fund to cover costs associated with the permanent rebuild, although the final costs of the project are undisclosed at this point.
CDOT has contracted with investigators to conduct an independent review of the cause of the road failure. They said that if any legal claims are made, it would be in coordination with the Attorney General's office, but as of yet, no determination had been made.
CDOT's Chief Engineer Stephen Harelson said the failure was caused because of the specific type of soil beneath that stretch of highway, which became saturated with moisture and lost its stability.
To fix the problem, crews traded out the soil, with Geofoam blocks.
"It's going to look just like a normal retaining wall, the only difference is that it's going to be this lightweight foam material," said Harleson.
He says these Geofoam blocks are perfectly suited for this repair because they are strong, yet substantially lighter than soil.
"We removed the old embankment that was made out of soil and weighed about 110 pounds per cubic foot, and replaced it with foam block that weighs about three pounds per cubic foot," he said.
"There's over 6,000 blocks of Geofoam in this wall, each block is 8 feet by 4 feet by 3 and 1/2 feet," said Project Manager Kurt Kionka.
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"Geofoam is lightweight, but very strong, and reduces stress and pressure to underlying soil," CDOT stated. "It safely supports large volume highways and improves slope stability."
Kionka said along with the new foam bricks are about 140 caissons, each drilled 15 feet down, this will eventually support a new wall which will help to cover and protect the foam, which like new bridges, are rated to last 75 years.
"Everything you see out here was built to ensure the longevity of this wall," he said.
The geofoam was topped with a load distribution slab, also made of concrete, and a layer of crushed stone, then covered with concrete pavement.
Harleson says they immediately checked out the wall on the other side and that there was no evidence of motion, "That was one of the first things we did the weekend of the failure was look at that wall, we've also looked at the other walls in the corridor, we think this is a one-off failure, we don't think this is a systemic problem."
While the Geofoam costs more, it substantially saved on time.
"This technique costs I think about 15 or 20% more than the soil would, but we would still be building the soil at Christmas, whereas now we are getting this open by Columbus Day," he said.
Although the highway is back in its original configuration, the bike path still needs to be finished and the wall needs to be placed on the caissons. Kionka says they hope to have that all finished by the middle of December.