Cathodic Protection Best Practices Employed with the 150 Mile TRWD/DWU IPL Pipeline

Tarrant Regional Water District (TRWD) and Dallas Water Utilities (DWU) are currently working together to meet growing population demands for water with a new raw water delivery system called the IPL (Integrated Pipeline). The IPL is being constructed of primarily 108” polyurethane coated steel pipe with welded joints for a total distance of 150 miles. The design for the cathodic protection (CP) systems consists of a galvanic system using sacrificial magnesium anodes, with an impressed current system to protect the yard piping at the 450 MG Midlothian Balancing Reservoir. In areas of pipeline interconnect where CP systems and pipe types differ, isolation is required. In these areas, TRWD primarily employs monolithic isolation joints (MIJ) and, to a lesser extent, the more traditional and problematic isolation flange kits. Other CP best practices from the IPL include alternating current (AC) stray current mitigation (a significant safety issue with coated steel pipe), coordination with adjacent third party (oil and gas) CP systems, identification and mitigation of CP system drains such as electric motor valve actuators, and use of buried “smart” reference cells/coupons to obtain more accurate polarized potential readings. During the design phase of the IPL project, the OPT (owner’s project team) was established. The OPT works closely with the CP design engineer, construction management team, and contractor to assist in the inspection, testing, and commissioning of the CP system. Commissioning best practices, including pre- and post- polarization of the CP system and desired polarization ranges for corrosion protection will be discussed.