SAWS W-6 Upper Segment: Construction for the Ages

The San Antonio Metropolitan area has experienced sustained growth for decades, putting increased pressure on existing wastewater infrastructure. In June 2013, the San Antonio Water System (SAWS) approved a settlement agreement with the USEPA in conjunction with a consent decree that requires significant improvements to the SAWS wastewater system over a 10-year period to reduce sanitary sewer overflows (SSOs). This work includes the targeted replacement and rehabilitation of an aging infrastructure system that consists of over 5,200 mi of sewer pipe. One of the critical projects that evolved from the consent decree was the W-6 Upper Segment Tunnel project to reduce sanitary sewer overflows on an existing sewer main running through Lackland Airforce Base. The replacement project consisted of a new tunnel nearly 29,190 LF of primarily 104″ FRP gravity sanitary sewer pipe. The project also includes nine shafts and multiple trenchless crossings to make near surface connections to the new works. This unique paper will focus on the related, yet contrasting, perspectives and key challenges faced by the overall project team: owner, design engineer, contractor, and construction manager. As the largest capital improvement project undertaken by the utility, this project was bid at the start of the COVID-19 pandemic and endured the severe Texas winter snowstorm of 2021 and an estimated 50-year flash flood event the following summer. Even with those challenges, the tunnel excavation was completed nearly six months ahead of schedule and under budget. This project utilized fiberglass reinforced pipe (FRP) and polymer concrete shaft structures to combat the severe, harsh environment associated with wastewater systems. This project was designed and constructed to last 100 years or more. Substantial completion was completed toward the end of the first quarter of 2023. This project is expected to serve the greater San Antonio community for generations to come.