NY Landslide Halts Highway Construction

Because of the deep nature of the landslide deposit, and the differences between the relevant soil units and the commonly know local units, the NYSDOT seems justified in claiming that there was no way to forsee the problems (see their Scoby Hill Landslide Report to the FHWA). The initial landslide movement was triggered by earthwork placement which continued for several more months until the full scope of the slide was determined at which point unloading of the new fill was undertaken. The size of the slide is quite large approximately 1,000-m by 400-m.

Investigations undertaken after the slide started included inclinometers, piezometers, additional borings, ground surveying, and a horizontal drain test program. Based on these investigations, NYSDOT’s evaluated several options including a full stabilization, partial stabilization and a "balanced" approach. The approach selected is the balanced approach which is more reasonable from a cost and technical perspective but will not eliminate the need for maintenance and repairs of landslide related damage. It includes drainage measures to attempt to lower the groundwater table, and use of crushed stone subgrade along with geotextiles to help make the pavement more tolerant of ground movement. It appears that the FHWA peer review agrees with the recommendations from the report.