To improve pedestrian and bike traffic MnDOT decided to add a tunnel under the new I-35W bridge over the Mississippi River. Working under a sub-consultant agreement TKDA coordinated the design efforts and developed the layout drawings for this project.
The main section of the 262-foot tunnel utilizes 63 precast concrete units. TKDA reviewed and approved shop drawings for the 252-foot precast section of the tunnel. For the remaining 10 feet of the tunnel, TKDA designed and detailed a cast-in place end section to accommodate the skewed alignment of an interfacing retaining wall. The adjacent precast section was cast with reinforcement bar extensions and rebar couplers and placed on a dropwall to allow for excavating and constructing the cast-in-place end section after installation of the precast units. With the help of TKDA’s team, the construction was completed in less than 4 months from the time the design-build contractor received the order from MnDOT.