Stray Currents and Soil Corrosivity: Dual Drivers of Premature Water Main Failures

Abstract This paper presents two case studies of water main failures involving ductile iron and riveted steel pipes, where external corrosion was driven by a combination of aggressive soil environments and stray current interference. In the first case, a ductile iron pipe exhibited through-wall graphitic corrosion after 30 years of service. Soil testing revealed highly corrosive conditions based on the ANSI/AWWA(1) C105 10-point system, while pipe-to-soil potential measurements indicated the presence of stray currents. Elemental analysis of the surrounding backfill confirmed the presence of carbon cinders, which can create galvanic cells and accelerate external corrosion. The second case involved a large-diameter riveted steel pipe with a perforation observed at the 6 o’clock position after ≈100 years of service. Field measurements showed electrochemical potential differences consistent with stray current pickup and discharge zones. Soil analysis confirmed moderate to severe corrosivity, with high corrosion rates and elevated concentrations of chlorides and sulfates. Both failures were attributed to the synergistic effects of corrosive soil constituents and stray current activity. Key recommendations for the new/replacement pipe include the use of protective backfill, sacrificial anodes, concrete encasement, and continuous monitoring of pipe-to-soil potentials. These studies emphasize the importance of a comprehensive corrosion risk assessment and mitigation strategy to extend the remaining useful life of aging water infrastructure.