Abstract
The operation of the Washington, D.C. rapid rail transit system has produced stray current activities on limited portions of Washington Gas Light Company's (WGLCo) underground gas system. The approach taken to mitigate these stray currents has been to identify pickup and discharge areas, increase the pipe-to-earth resistance through selective line insulation points to reduce the network system's susceptibility to stray currents, and add supplemental levels of cathodic protection.
As a result of selective maintenance activities, there has been a significant reduction in stray current at pickup and discharge areas along the pipeline system. The isolated sections of piping within the discharge areas responded very favorably to cathodic protection due to the overall reduction of stray current discharge, and increased resistances to earth. There were also benefits experienced in the current pickup areas. Pipe-to-soil potentials became much more stable with substantial reduction in current flows which could have resulted in discharge from remote parts of the system commonly referred to as endwise current effect.
This method of stray current mitigation can prevent the necessity for mitigation bonds and some of the undesirable side effects that could result from the further spread of stray currents to distant parts of a gas system.
