Cathodic Protection of a Long-Distance, Multi-Material Water Pipeline

The vista ridge water supply project includes a 142-mi pipeline that will deliver up to 50,000 acre-feet of water per year from the Carrizo and Simsboro aquifers to the San Antonio Water System (SAWS). The pipeline design included an impressed current cathodic protection (ICCP) system for the 54- and 60-in. diameter concrete, bar-wrapped, steel-cylinder pipe and polyurethane-coated, welded-steel piping. The pipeline was designed to be electrically isolated at the high service pump station, two intermediate pump stations, and the connection point to the SAWS water transmission system. The long alignment presented a number of challenges to designing an effective cathodic protection (CP) system, including determining the current demand over varying soil conditions and pipe materials, mitigating potential current drains associated with the three river crossings and 115 roadway crossings, avoiding conflicts associated with locating CP equipment outside of floodplains and within available easements, and providing flexibility in the design of a system that included over 50 rectifiers and over 700 test stations. This paper will discuss the methods used to overcome these challenges and lessons learned in providing an effective CP system design on a large pipeline.