San Patricio Water Transmission Pipeline—Multiple Pipe Solutions

In order to keep up with demand, San Patricio Municipal Water District (SPMWD) evaluated options ranging from increasing treatment capacity to purchasing additional treated water directly from the City of Corpus Christi. After discussions with industrial customers regarding required water quality and quantity, it was decided the way forward was to supplement its existing treated water capacity with additional purchase water from the City of Corpus Christi. This would require a new 48 in. water transmission pipeline extended approximately 23 mi from Corpus Christi to Gregory, TX. As the consulting engineer, J. Schwarz & Associates was asked to design this pipeline with four different pipe materials in mind: bar-wrapped (C303) concrete pressure pipe, ductile iron pipe, PVC, and spirally welded steel pipe. This posed to be a challenge as the variations in the pipe materials properties and joint systems require that the design address the different aspects of each material from acceptable joining methods and corrosion protection system. The paper will review this project in detail from cradle to grave covering aspects from the initial design parameters and construction documents through the bidding process and construction completion. Included in this presentation will also be lessons learned through the design and construction process.