By: F. X. Ashland
Landsliding in the Creekside Drive area of Mountain Green, Utah, in 2005 and 2006 damaged three houses, a road, and buried utilities, and threatened a buried sewer line, another house, and several other residential lots. The landslides resulted from the total and partial reactivation of preexisting slides in slopes underlain by Tertiary Norwood Tuff. Monitoring by the Utah Geological Survey showed that two of the three largest slides remained active between June and December 2005. Renewed or accelerated movement of the landslides in 2006 was accompanied by the formation of new slides, one of which affected two residential lots and threatened a house.
Damaging landslides occurred despite both subdivisionwide and lot-specific, predevelopment, geologic and geotechnical studies by consultants hired by the developer. The earliest study recommended avoidance of the landslide hazard at many of the proposed lots, and adherence to this recommendation would have reduced the losses in 2005 and 2006. None of the studies indicated the potential for reactivation of the large, pre-existing, deep-seated landslides in the area, which resulted in the largest and most damaging of the slides, the Creekside Drive landslide, in 2005. Damaging landsliding occurred less than four years after construction of a house on the head of the Creekside Drive landslide and the completion of lot-specific geotechnical studies.
The potential for continued landslide movement is high in the absence of expensive landslide stabilization. Thus, additional losses are likely as landslide movement and ground deformation continue. This landslide case history illustrates the marginal stability of pre-existing landslides in the area (western Morgan County) and the need for stabilization of the slides prior to development.
Pages: 25 p.
Location: Morgan County
Media Type: Paper Publication