Recent PRCI Guidelines for Pipelines Exposed to Landslide and Ground Subsidence Hazards

This paper summarizes key considerations in guidelines published in early 2009 that were developed through a Pipeline Research Council International, Inc. (PRCI) supported by PRCI, the Pipeline Hazardous Materials and Safety Administration of the Department of Transportation, and the California Energy Commission. Past practices for pipelines, as well as almost all other construction projects, have focused on avoidance of areas that have a reasonable probability of experiencing geohazards (defined as large ground displacements that may arise from slope failure, slope creep, earthquake triggered slope movement, and subsidence). This approach has been generally successful when there are limited restrictions on selecting a pipeline alignment. Avoiding potential geohazards is becoming increasingly difficult because of the inability to obtain landowner agreements, the lack of space in common utility corridors, environmental restrictions, incompatibility with existing land use, and/or public opposition. In route corridors where geohazards cannot be avoided, the potential risks associated with these hazards must be managed. Pipeline integrity management strategies to mitigate geohazards consist of: (1) design measures that improve the pipeline resistance to the geohazard, (2) measures that limit or control the severity of the geohazard, and (3) operational programs to monitor ground displacement or pipeline response and identify conditions that may warrant further engineering investigations or mitigation activities. Identifying the most appropriate mitigation strategy needs to be based upon specific hazard scenarios and operating circumstances. The PRCI guidelines provide recommendations for the assessment of new and existing natural gas and liquid hydrocarbon pipelines subjected to potential ground displacements resulting from landslides and ground subsidence. One of the most significant benefits of the guidelines is the systematic approach developed for managing pipeline risks from landslide and ground subsidence hazards. It is hoped that this approach, presented in detailed flow charts, will lead to improvements in current practices by providing a common framework for pipeline operators, the local, state, and federal agencies that have regulatory oversight, and the general public to engage in discussions regarding potential risks from pipelines in areas of unstable ground and the most effective and practical means to reduce those risks to an acceptable level.