Warning signs to alert motorists to the dip were placed near mile point 11.5 on the Audubon with a 55 mile per hour advisory speed, April 24, after motorists reported a drop of about a foot along about a 60 ft. section of roadway. Engineers conducted an initial assessment of the area and called in a drilling crew to check the stability of soil beneath the site.
A check of historic mine maps indicated a tunnel about 120 ft. below the roadway near the dip, leading engineers to suspect mine subsidence as the most likely cause. Soil and rock samples pulled from beneath the site indicated an old stream bed about 60 ft. below the surface and turned up a number of natural gas pockets. Geologists indicated water moving through the old stream bed could be contributing to the problem, but a lab analysis did not indicate a specific movement of material in that layer of soil that might account for the surface movement. The geotech drilling team also located the mine tunnel, but it showed no signs of subsidence that might have contributed to the sag at the surface.
With the soil and rock samples providing no clear cause of the dip, engineers plan to run a camera through nearby drainage structures to determine if water leakage could be eroding soil under the road base. They expect that work to be completed in the next 2 to 4 weeks.
Engineers are continuing to check the dip on a regular basis. If they observe any degradation of the road surface they will move to make more immediate repairs. Meanwhile, The Transportation Cabinet is working on plans for a rehabilitation project along the Audubon Parkway from mile point 0.0 to about the 8 mile marker during the 2015 construction season. At this time, engineers plan to include a repair of the dip in the scope of that project.
KYTC District 2 Spokesman Keith Todd noted that the sagging roadway on the Audubon is among a number of sites engineers believe may have issues due to the wet winter weather with numerous rounds of freezing and thawing. He noted that highway crews have had to deal with several sinkholes and landslides across the region, including a land slip that damaged approach spans on a closed bridge near Paducah. Add in the development of a sinkhole below the National Corvette Museum in Bowling Green, and Todd says there are plenty of indications the severe winter weather may have contributed to soil movement at some locations.Timely traffic advisories for the 11 counties of KYTC Highway District 2 are available by going to www.facebook.com/kytcdistrict2. You do not have to be a Facebook member to access this page.
Information provided by Keith Todd
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