Gas pipeline erosion failures: January 1993 floods, Gila River Basin, Arizona
Brian J. Doeing, David T. Williams, Jeffrey B. Bradley, 1997. "Gas pipeline erosion failures: January 1993 floods, Gila River Basin, Arizona", Storm-Induced Geologic Hazards, Robert A. Larson, James E. Slosson
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Flooding occurred throughout Arizona in January 1993 as a result of record pre-cipitation, early snow melt, and saturated soil conditions. The high flows in the Gila River and its tributaries caused failure, damage, or exposure of many natural gas pipelines crossing rivers, streams, and washes. This chapter presents a case study of erosion analysis for six El Paso Natural Gas Company (EPNG) pipelines that failed or were exposed in Arizona during January 1993. The failures were critical because these were major transmission pipelines that supplied natural gas to residential and industrial users in whole communities and groups of communities. The scour evalua-tions conducted were significant because they provided a scientific and engineering basis for emergency pipeline replacement or repair.
Detailed scour and sediment transport studies were conducted to compute the design scour depth for pipeline replacement. The studies incorporated a hydrological analysis for the 100-yr design flood, surveys of channel geometry for hydraulic com-putations, and geotechnical analyses of sediment samples for grain-size distribution in the streambed. The scour part of the studies considered not only vertical scour but also lateral scour due to bank erosion, channel meander migration, and channel braiding. The scour studies were used in the design, construction, and permitting process to expedite replacement of the pipelines. For many of these pipelines, it was the first time that the engineering methods of river hydraulics and sediment transport and the science of river morphology were used in the pipeline crossing design.