Aging of Distribution and Other Lifeline Systems Due to Corrosion

Statistics derived from public works maintenance records for buried steel and cast iron pipelines indicate that aging may be seen in increasing rates of repairs. Maintenance increases with age due to cumulative traffic loads, ground settlement and, among the most important causes, corrosion. The tendency for repair rates gradually to increase and the opposing effects of corrosion control and planned replacement are punctuated by the rapid rise in leakage and required maintenance in the aftermath of an earthquake. These data were uncovered as a byproduct of studying five western US earthquakes in which performance of steel pipelines under seismic conditions and under normal operating conditions appear to be correlated. Evidence also points to temporary and, sometimes, to permanent increase in the rate of leakage and failure in the aftermath of an earthquake. The underlying cause of this correlation is thinning of pipe walls due to corrosion, which is facilitated by stray current and conductive soil.