Snowbasin Access Road Underdrain System
Snowbasin Ski Area, situated about 10 miles east of Ogden, Utah and host of the alpine downhill for the 2002 Winter Olympics, required a new 3-mile primary access road. The new alignment traverses two active landslides that are several miles in length and 1,000 to 4,000 feet in width. The new road also crosses several streams, wetlands and other landslide terrain that was active during prior geologic time. Landslide Technology was retained at the request of Utah Department of Transportation to assist with an independent geotechnical evaluation of the proposed alignments. The firm's expertise helped to resolve extremely challenging slope stability issues, and as a result, the firm was retained to provide design recommendations for the entire 3-mile alignment.
Evaluation included borings and test pits in Rocky Mountain winter conditions with inclinometers, piezometers and automatic dataloggers. Geotechnical analyses, laboratory testing and design were fast-tracked. Recommendations for design and construction were developed for excavation methods and material sorting, cut slopes, embankment construction, roadway construction over active slide areas, embankment underdrain systems (see photo), and rockfill buttresses. Comparative analyses were performed to minimize earthwork and structural options. Drainage designs were unusual in that wetland areas were protected with clay liners to separate surface water flow from the subsurface drainage necessary for increased stability. During construction, stabilization options for the large active slides were developed and installed at considerable cost savings.