Digging Deep in San Antonio: The Planning and Design of 2 Miles of 54-Inch Pipe 80 Feet Deep

The San Antonio Water System (SAWS) entered into a contract with Vista Ridge LLC to provide 50,000 acre-feet per year of Carrizo/Simsboro Aquifer groundwater to meet the growth needs and to diversify the water supply of San Antonio. As part of the Central Water Integration Pipeline (CWIP) Project, modifications to the SAWS system are required to convey finished water from the new treatment plant at the Agua Vista Station to the existing SAWS system. The CWIP project includes a treatment plant, pipelines, pump stations, concrete tanks, pressure reducing stations, and rehabilitation of SAWS existing tanks. Finished water will either be pumped out of the Agua Vista Station through the new Stone Oak Pump Station or flow by gravity to the downstream facilities. This paper focuses on the planning and design of one of the new water transmission pipeline segments: the segment 5-1 pipeline contract. This portion of the project consists of 10,300 linear feet of 54-in. welded steel pipeline. Several challenging design aspects had to be undertaken in order to meet the aggressive project schedule including selecting a pipeline alignment, providing trenchless construction for over 75% of the alignment, and determining the steel pipe design criteria.