The Missouri Dept. of Transportation tentatively has set September 15 as the target date to restore access between I-470 and I-435 in southern Kansas City, following an existing fill-supported ramp collapse on July 17.
Pyramid Contractors, Olathe, Kan., was awarded the contract to build a 225-ft-long, four-lane replacement structure currently being designed by HNTB, MoDOT’s engineering consultant. Expected to cost about $4.46 million, the precast structure will be built atop two bents with drilled shaft foundations socketed to bedrock.
“It will provide the same access as before, only as an extension of the I-435 bridge instead of a ramp on 40 feet of fill,” says MoDOT spokesman Steve Porter.
Pyramid will have a $40,000-a-day incentive to finish the bridge ahead of schedule and could face a comparable penalty if the deadline is missed. The I-470/I-435 ramp is a key link between south Kansas City and the Kansas suburbs.
Meanwhile, the Federal Highway Administration has joined MoDOT and HNTB in the investigation of the collapse, which resulted in the partial failure of 42-ft-high mechanically stabilized earthen retaining wall and left a 35-ft-wide, 200-ft-long hole in the pavement.
Soil tests conducted at the base of the wall revealed groundwater approximately 10 feet below the surface, a condition that wasn’t present when Clarkson Construction Co., Kansas City, Mo., began work in that area under a six-year improvement project in 2001.