Impact of Drought-related Subsidence on Gas Infrastructure in California

This project developed an approach for characterizing the risk posed by drought-related subsidence to gas infrastructure in California. Project innovations include estimating vertical and horizontal ground displacements from remote sensing data, providing guidance on the characteristics of areas in particular need of such monitoring, and developing a displacement gradient threshold to identify areas where risk to gas infrastructure merits site-specific analysis, and if necessary, remedial actions.

Geospatial analysis of historic cropping patterns revealed that the presence of high waterdemand crops correlates with occurrence of subsidence, and the magnitude of subsidence correlates with the fraction of irrigation met with groundwater, well density, and well depth. Some sustainability plans for adjacent groundwater basins articulate substantially different limits to future subsidence, suggesting differential subsidence could develop at their boundary as a regulatory outcome.

Coupled ground deformation and pipeline modeling based on extrapolation of recent subsidence suggested thresholds of differential subsidence to trigger site-specific risk analysis and possible remedial action: 1.5 feet per quarter mile for horizontal differential displacement along the pipe and one foot per quarter mile for differential vertical subsidence along the pipe. Proposed vertical and horizontal ground deformation monitoring technology along with differential subsidence limits can more accurately identify areas where gas infrastructure is at risk of damage from land subsidence.