GEOHAZARD MAPPING AND EVALUATION FOR A NATURAL GAS PIPELINE PROJECT

Geohazard mapping and evaluation was conducted for a planned 1150 mile long natural gas pipeline in Western Asia and Eastern Europe. Covering a variety of terrain from flat agricultural land to mountainous peaks, and changes in elevation from sea level to nearly 3000 m, a variety of geohazards are encountered. From active faults to landslides to karst terrain, these pose a risk to the pipeline during construction and operation either from pipeline rupture, or damage to above ground installations. The pipeline is to be constructed in a highly seismic country, and as a result the majority of the primary geohazards are due to fault-related activity (active faulting, seismically triggered landslides, and potentially liquefiable soil). Non-seismic geohazards include river crossings, severely dissected terrain, karst geology, and high groundwater table.

For preliminary engineering, eight teams of geologists traversed the alignment by vehicle and foot to verify prior desktop geohazard studies and to record previously unidentified geohazards within a 500 m right-of-way. The use of ruggedized tablet PCs to perform the data collection greatly reduced the time in the field, improved the accuracy and precision of the field mapping, and reduced post-fieldwork post-processing. Customized ESRI ArcPad data entry forms were developed and pre-populated with key terminology to enable data standardization given that the geologists performing the field work were from three continents and four different countries.

Published engineering classifications were used for recording landslides, karst geology, and river crossings. For active faults, potentially liquefiable soil, severely dissected terrain, and high groundwater table, project-specific classifications were applied using standard geological terminology. The dataset collected from the mapping was subsequently used as input to a qualitative hazard assessment with particular emphasis placed on landslides, severely dissected terrain, and karst, as these were determined to be of greatest concern at the preliminary engineering level. The purpose of this assessment was to evaluate the level of risk from each geohazard to the pipeline and reduce this risk either through rerouting or planned engineered solutions.