About our Sessions

The I-35 Capital Expressway Project aims to enhance the infrastructure and traffic flow of one of the most critical thoroughfares in Austin, Texas. The project necessitated innovative drainage solutions due to the lowering of the main travel lanes, which disrupted the natural flow of large watersheds draining across the roadway. To address this challenge, a deep drainage tunnel was designed to efficiently collect stormwater runoff directed towards I-35. The tunnel is 80-200’ deep, 22’ in diameter, runs for six miles along I-35 and Cesar Chavez Boulevard, and discharges at a pump station near the Colorado River. The CapEx Pump Station (PS) Facility is designed to pump and discharge stored stormwater from the tunnel into the Colorado River, featuring six mechanically cleaned trash rakes, four concrete volute pumps, a discharge box structure with slide and flap gates, and an outfall structure at the Colorado River. Eight vortex drop shafts were employed over the length of the tunnel to convey stormwater runoff from near-surface to the deep tunnel. This presentation discusses the payoff of using computational fluid dynamics (CFD) modeling and physical modeling of various aspects of the design to ensure optimal hydraulic conditions and operational efficiency of the drop shafts and PS facility. In total, there were six CFD and physical models used to validate various aspects of the design. The presentation will cover the reasoning for each of the studies, how the studies or models were conducted, and what information was gained through the studies.