Both Ground Penetrating Radar (GPR) surveys and Hydro-Geochemical Water Testing (HGWT) have been performed at the Cumberland Gap Tunnel to determine why the reinforced concrete pavement has settled in various areas throughout both tunnels. To date, approximately 7,300 total square feet of pavement surface has voids beneath it that range from 0.05 to 40 inches in depth. Both GPR and HGWT results indicate that approximately 0.75 to 1.5 cubic yards of limestone sub-base material leaves the tunnel in solution form on a monthly basis. Furthermore, HGWT results indicate that the ground water beneath the tunnels is calcium deficient. Thus allowing the water to dissolve the limestone sub-base. Approximately 500,000 to 1 million gallons of water flows through the tunnel’s ground water collection system on a daily basis.

Attempts to fix/shore-up the settled pavement areas were performed in 2002, 2007, and 2008. In 2002, UreTek foam was placed beneath approximately 2000 square feet of settled pavement for shoring purposes. In 2007, approximately 150 lineal feet of both pavement and backfill were removed and replaced with inert granite backfill material and a new reinforced concrete pavement. In 2008, approximately 51 cubic yards of cement grout material was placed beneath approximately 7,400 total square feet of settled pavement for shoring purposes.

There are several strategies outlined in this report to address both short-term and long-term remediation. However, there are certain strategies that may prevail over others. It is proposed that grout material should be placed beneath the pavement structure, at an estimated cost of $50,000 to $100,000/year, as a short term assurance measure. It is proposed that approximately 2,800 lineal feet of pavement and backfill material be removed in both tunnels and replaced with an inert granite backfill and a new 10 inch reinforced concrete pavement be installed for a long-term remediation (estimated costs $10,000,000).

Report Date


Report Number


Digital Object Identifier



The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky or the Kentucky Transportation Cabinet. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and trade names are for identification purposes and are not to be considered an endorsement.