Design of a Large-Diameter HDPE Wastewater Force Main via Horizontal Directional Drilling under the Colorado River

The Boggy Creek Lift Station, located within the city of Austin, TX, was designed and built to achieve a minimum firm pumping capacity of 25 MGD. The Lift Station currently routes this wastewater flow under the Colorado River via two siphons before discharging at the Lockheed Drop Shaft approximately 1.8 mi away. For over 10 years, Austin Water (AW) has been investigating the feasibility of replacing the existing undersized siphons in order to handle the firm pumping capacity from the upgraded Lift Station. The AECOM Team was tasked with evaluating the lift station operation and developing the design of a single, large-diameter wastewater force main to connect the Boggy Creek Lift Station to the Lockheed Drop Shaft. This paper will primarily focus on two aspects of the design process: the decision to implement HDPE, where historically DIP would be the pipe material of choice, and the process that the design team followed to determine how and why Horizontal Directional Drilling was chosen to be the river crossing method of choice.