This project provides a new bridge crossing of the Ohio River on Interstate 265 from the east end of Louisville, to southern Indiana, with surface roadway approach sections from each end.  The approach route to the Kentucky side of the bridge involves construction of twin three-lane tunnels below U.S. Route 42 and the historic Drumanard Estate in sedimentary rock consisting of limestone, shale, and dolomite.  The tunnels have mined dimensions of approximately 55 ft in width by 31 ft in height, will be lined with reinforced concrete, and have connected with two cross-passages through the 40-ft wide rock pillar that separates the tunnels.

Tunnel excavation was by drill-and-blast using the Sequential Excavation Method (SEM), with a central and two side headings for the upper arch of the tunnel and followed by excavation of the bench below.  During construction, initial support consisted mainly of rock bolts and shotcrete, with other support elements available as required.  During an earlier phase of the project, Schnabel evaluated the project budget for a previous planned tunnel configuration and developed a new Class 5 budget estimate for the project based on a revised tunnel concept.  This estimate was prepared as a contractor-style, bottom-up estimate using the commercial estimating software HeavyBid.

During the proposal phase of P-3 procurement, Schnabel assisted Walsh-Vinci (WVC) by preparing a geotechnical pre-bid evaluation of the project and by preparing estimated initial support requirements for use in project bidding.  Following WVC’s selection for the project, we prepared a Geotechnical Design Memorandum based on review of all project geotechnical data, performed rock mass classification, performed numerical analysis of the proposed tunnel cross section, and prepared initial support design drawings and specifications for the tunnels and required geotechnical instrumentation for monitoring of groundwater levels and ground deformations.