Kansas City, Mo. Missouri highway officials say a combination of heavy precipitation and old construction led to the collapse of a section of highway in Kansas City last summer.
A ramp on Interstate 470 in south Kansas City collapsed July 17, leaving a 34-foot-wide, 200-foot-long hole. The highway was closed for 43 days.
The Missouri Department of Transportation said that heavy rain last summer and heavy snow last winter seeped into old fill material from when the highway was built in 1971. That moisture became trapped behind newer, less permeable material used when the highway was rebuilt in 2003.
Forces built to the point where the embankment supporting the highway slid.
Department Engineer Beth Wright said tests on the old fill material turned up nothing suspicious about its stability.