Maintenance of the ballast layer directly below the ties is an essential part of a healthy track structure, as ballast degrades over time and becomes increasingly fouled reducing its ability to drain, provide adequate load bearing support, and withstand vertical, lateral, and longitudinal forces. Southern Pacific used specially trained crews who operated undercutter equipment to restore ballast that had become fouled.
The excavated material could either be fully discarded or screened and returned to the track, with only the finer parts of the ballast not being recycled.
Southern Pacific tie gang working with a scarifier inserter on the San Antonio Division. This mechanical device dramatically sped-up the removal of existing ties and insertion of new ties in their place.
A Southern Pacific track construction crew is standing in the clear, waiting to resume work to replace the existing crossing diamond and to install other trackage which is a part of the project.