The Central Montana Rail site contains a steel railroad trestle (early 1900’s) approximately 1300 feet long and 160 feet high. Both approach abutments were constructed on existing landslides. Local geology is characterized as 8 to 15 feet of terrace gravels overlying Cretaceous Colorado shale. Groundwater seepage occurring through the gravels and softening the shale is the primary contributor to the instability of the slopes. Since 1994, TD&H Engineering conducted annual monitoring, inspections, and movement analyses, as well as performed periodic cleaning and flushing of the internal slope and horizontal drainage systems (see photo below). We provided topographic surveying, measured groundwater levels, and installed new slope inclinometers and groundwater wells. In addition, TD&H Engineering developed slide mitigation contingency plans.