[Docket No. PHMSA-2015-0105]
PHMSA has released five Advisory Bulletins on the subject of potential for damage to pipeline facilities caused by flooding, river scour, and river channel migration, with the earliest issued July 29, 1993, (ADB-93-03), and the most recent on July 27, 2011, (ADB-11-04; 76 FR 44985). Each of these bulletins followed an event that involved severe flooding that affected pipelines in the areas of rising waters.
River bottom scour and channel migration may occur due to seasonal flooding, increased stream velocities, and man-made and natural river bank restrictions. River scour and channel migration may damage a pipeline as a result of additional stresses imposed on the pipe by undermining underlying support soils, exposing the pipeline to lateral water forces and impact from waterborne debris. Lateral water forces may cause excessive bending loads that lead to pipeline failures, and possible impact forces from debris in the river or harmonic vibrations from water rapidly passing over pipelines can also increase the potential for pipeline failures.
Additionally, the safety of valves, regulators, relief sets, pressure sensors, and other facilities normally above ground or above water can be jeopardized when covered by water. Not only can these facilities become inoperable when submerged, but they are also at a greater risk of damage by outside forces, floating debris, river currents, and craft operating on the water. Boaters involved in rescue operations, emergency support functions, sightseeing, and other activities are generally not aware of the seriousness of an incident that could result from their craft damaging a pipeline facility that is unseen beneath the surface of the water. Depending on the size of the craft and the pipeline facility struck, significant pipeline damage may result.
Although accidents at river crossings account for less than one percent of the total number of pipeline accidents, the consequences of a release in water can be much more severe because of the threats to drinking water supplies and the environment. Unlike hazardous liquid releases on land where it can be easier to respond to and contain spills, swift-moving river currents will carry hazardous liquids further downstream, potentially impacting much larger geographical areas and more communities. Product releases in rivers can create difficult, costly, and lengthy spill response and remediation scenarios and activities for operators, communities, and local, state, and Federal responders.
The latest advisory bulletin lists 14 steps that pipeline operators may need to take to address these issues. For a copy of the entire bulletin, contact Jessica Foley.