A Moving Mud Spring Threatening Critical Infrastructure, Imperial County, California

摘要

Due to the tectonic environment, mud pots and mud volcanoes are common at the southern end of the San Andreas Fault near the Salton Sea. These features are generated from carbon dioxide gas at depth. While their level of activity may fluctuate, they are generally stationary. In 2016, a mud pot (referred to as a mound mud spring) began moving southwest. Critical infrastructure, including the Union Pacific Railroad (UPRR) dual tracks, utility and petroleum pipelines, and a state highway had been previously built in the path of the moving mud spring. The mud spring impacted the UPRR tracks in late 2018, which carries freight from the Ports of Los Angeles/Long Beach to the eastern part of the country. To accommodate the mud spring movement, we utilized sheet piles, shoofly tracks, and rip rap to keep the trains operational. Kinder Morgan evaluated the moving mud spring impact on their critical petroleum pipeline that provided fuel to civilian and military facilities in the desert southwest. Their pipeline is located adjacent to the UPRR tracks. After considering a temporary bridge to support the pipeline, Kinder Morgan elected to reroute their pipeline around the mud spring's path. As of September 2019, the mud spring has moved over 100 m (300 feet) and is located on the (now disabled) UPRR main line tracks. Shoofly (detour) tracks have been constructed to allow train traffic to go around the mud spring. The spring's rate of movement is variable, but averages about 3 meters (10 feet) per month. The UPRR is currently waiting for the mud spring to clear the main line tracks before backfilling the erosion area and restoring normal service. Scientific studies to understand the mechanism behind the mud spring movement are continuing.