#Impact of Land Subsidence on Oil and Gas Infrastructure Discussed at Workshop*

California�s lingering drought is having an impact on the state in ways expected and perhaps not so expected. With the lack of surface water supplies, more water has been pumped from underground sources causing land in parts of the state to rapidly subside. In some areas, subsidence may begin to pose a threat to oil and natural gas infrastructure. PG&E recently said about 50 miles of its natural gas pipelines could be affected by sinking land.

This map shows areas of subsidence in California. Areas colored in purple and magenta have seen the greatest amount of subsidence. Natural gases pipelines are in black.

The California Energy Commission held a public workshop with researchers and representatives from utility companies Nov. 10 to examine ways to coordinate research and develop corrective measures to deal with the subsidence issue.

Speakers explained the science behind land subsidence during the workshop. For example, some soils can rebound as water is replenished, while other soil types remain permanently compressed. They also discussed the complicated process for identifying and quantifying areas of accelerated subsidence � primarily through satellites and aircraft equipped with a variety of sophisticated radar technologies � to create time histories, maps and imaging with centimeter-level accuracy.

According to the California Department of Water Resources, groundwater levels are reaching record lows � up to 100 feet lower than previous records. NASA�s Jet Propulsion Laboratory and the U.S. Geological Survey are monitoring subsidence rates in the state.

Officials predict that climate change will only increase the state�s reliance on groundwater, meaning land subsidence and its impacts will continue to be an issue requiring the attention of the Energy Commission and others as they work to reduce potential threats from above to the ground below.