One of Kansas City’s biggest traffic nightmares has ended.
After 43 days, highway crews this morning reopened a key ramp in the Three Trails Crossing that connects 60,000 daily commuters from the southeast corner of the Kansas City area to the Kansas suburbs.
The ramp collapsed July 17 when groundwater buildup caused soil underneath a retaining wall to slide, leaving a 34-foot-wide gap in the highway. Engineers are still investigating the collapse but said again Thursday that the retaining wall functioned properly.
“There was not a smoking gun that caused this to happen,” said Beth Wright, district engineer for the Missouri Department of Transportation’s office in Kansas City.
The collapsed ramp took drivers from westbound Interstate 470 and northbound U.S. 71 to westbound Interstate 435.
It was replaced by a 225-foot-long bridge that was completed 19 days early for about $5.2 million — including a $760,000 bonus for beating the deadline.
“We feel very strongly this is a safe and reliable repair,” Wright said.
Engineers have inspected the entire Three Trails Crossing — also known as the Grandview Triangle — looking for soil movement similar to what led to the collapse on I-470, Wright said. None was found.
Wright said testing equipment also was placed in the embankment east of the collapsed area, and no movement was found there either.
“We are very confident that when we open this area back up we will be able to use it for many years to come,” she said.
The section of road that collapsed was part of a six-year, $300 million project to rebuild the web of highways that converge in southeast Kansas City. The highway section that collapsed opened in 2003.
Wright said the retaining wall supporting the road came apart when the ground beneath the wall moved. Engineers said the ground had pushed out into a creek near the wall.
Wright said there was no reason to think, based on the original soil testing, that the area was unstable or couldn’t support what was constructed.
“Nobody could foresee, based on common engineering practice, the slide would have occurred in this place,” she said.
By November or December, designers, contractors, geologists and other engineers will be brought together to analyze the collapse, she said.