Presented by Jeffrey M. Hammer, Project Engineer / Tunnel Engineer, Traylor Brothers, Inc. Receiving the approval to design, plan and/or construct an underground structure requires tunnel engineers to work through numerous challenges and consider many options in order to reach a successful completion of a project. Engineers specializing in this field must understand, and even count on, the fact that the ground conditions they encounter may be very different than initially planned. In some cases, this difference is a footnote on the project; in other cases, this difference sets the tone for the rest of the project—for better or for worse. The solutions to overcoming these issues require a multidisciplinary approach and the commitment to working together as a team to address challenges. This presentation will focus on the author’s personal experience on some of the nation’s largest, most challenging and highest-profile underground, design-build projects and the lessons learned along the way.