As the gas encounters groundwater, the pressurized gas and water are pushed to surface.  The mud spring fluidized the sediment and carved an approximately 75-foot wide and 25-foot deep channel which filled with a mud slurry discharge.  Moving in a relatively straight line at a rate of about 10 feet per month, the mud spring remained a discrete, point-like structure.  To our knowledge, the behavior of this mobile mud spring is unprecedented. 

The UPRR retained Shannon and Wilson in May 2018 to evaluate the mobile mud spring (about 80 feet from the tracks) and develop options to mitigate the threat.  Our geotechnical services included geophysical surveys, subsurface explorations, relief wells, and construction of a sheet pile wall.  Our efforts focused on maintaining railroad operations while attempting to understand and affect the mud spring movement.  We contained the mobile mud spring behind a sheet pile wall for about four months.  During this time, UPRR constructed a shoofly track on the far side of their right of way from the mud spring and commissioned relief wells in an attempt to depressurize the gas feeding the mud spring.  However, in October 2018, the mobile mud spring passed below the sheet piles and emerged in the main line tracks.  

In less than 12 hours, UPRR diverted train traffic to the new shoofly track and constructed a second shoofly track behind the mud spring’s path.  During the summer of 2019, UPRR placed rip rap behind the mud spring as the mud spring continued on its southwest journey through the UPRR right of way.  The UPRR plans on restoring the main line tracks over the rip rap backfill once the mud spring is beyond the right of way.

The unique mobile mud spring has been featured in the Los Angeles Times, National Geographic, and ASCE Civil Engineering magazine.  The mechanisms driving the mobile mud spring are currently being studied by NASA, the Jet Propulsion Laboratory, and several universities.