Learn and ExploreUpdate: December, 2020 Pretty Rocks Landslide Comparison (November 2019 vs January 2020)![]() ![]()
Late November, 2019. The area had fallen around 10' from grade since September.
NPS Photo
Early January, 2020. The area had fallen significantly further since late November.
NPS Photo
Pretty Rocks Landslide Comparison (September 2018 vs March 2019)![]() ![]()
The eastern landslide scarp through the road on September 29, 2018. The road was last graded on September 14th and closed to most vehicle traffic on September 19.
NPS Photo
The eastern landslide scarp on March 22, 2019. Survey rod held by park employee is 6.5 feet (2.0 m) tall and is placed near center-line of the road. Note employees had recently shoveled dirty snow in foreground to aid in measuring the scarp.
NPS Photo
BackgroundLandslide impacts have been experienced at Pretty Rocks since at least the 1960s and, until recently, only required maintenance every 2-3 years. During the 1990s, landslides in this section only caused small cracks in the road surface. Between 2016 and 2017, the full width of a 300-foot section of road slumped up to six inches per month, creating a slump that steepened the road gradient and limited sight lines for drivers approaching the sharp turn. Next StepsIn May, 2020, NPS and FHWA partnered to conduct an Expert-Based Risk Assessment (EBRA) that evaluated the geotechnical attributes of the alternatives. Informed by the EBRA, a value analysis was conducted in July 2020 to determine which alternative provided the greatest value.
Informed by these evaluations, the NPS will address maintaining access west of Polychrome Mountain in three stages:
![]() NPS Graphic Long Term Options
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Last updated: December 10, 2020