Lessons Learned During the Startup of the Phoenix Valley Light Rail System

Severe pipe-to-soil potential swings, indicating DC stray current interference were observed on the natural gas distribution system in Phoenix Arizona during the startup and initial operation of the Valley Metro Rail (VMR) system.  Cooperative testing involving VMR and SW Gas resulted in a timely identification and resolution of the stray current sources.  The VMR was operating within the design stray current limits shortly after revenue operation.  This paper describes the cooperative testing, the unique problems identified and the effects of the repairs completed.