This project, located in Austin, Texas, encompassed work associated with the design and evaluation of a flood control tunnel system and its associated components, including designing a system of storm drain interceptors, inlet and outlet structures, retaining walls, weirs, and vertical shafts. An evaluation of the tunnel alignment and design feasibility, providing alternatives to minimize the costs, was also included. The existing storm drains, which discharged into Waller Creek downstream of 12th Street, were analyzed for methods and costs of conveying their flow into the proposed diversion tunnel to reduce the flows into Waller Creek. As part of maintaining the quality in the tunnel and in Waller Creek during dry weather, a tunnel water recirculation system was required. Floodwater flows into the flood control tunnel via vertical drop shafts or channel side overflow weirs. A large diameter tunnel that connects the inlet structure and the outlet structure, lined with precast concrete liner panels or cast-in-place concrete, allows for easier maintenance access for tunnel de-watering and de-silting operations.