I am very grateful for all the assistance given to me, without which this study would have been very difficult to complete. Dr. Kenneth Cruikshank suggested the research topic and methods for analyzing the problems. His insight on field mapping, landslide mechanisms, and stability analysis have proven to be very helpful. Dr. Scott Burns proved very helpful by suggesting the study area and providing an excellent background on slope stability in this area. Dr. Marvin Beeson helped me with delineating the highly irregular stratigraphy within the Troutdale Formation and the rest of the geologic units within the study area.
Many fellow students here at Portland State University have helped to complete some of the detailed mapping needed for this study. David James and Tom Braibish mapped the Spady Landslide with me in 1996 and did some of the soil analysis and drafting of the detailed map. Stuart Cowburn, Glenn Gettemy, Robert Schlichting, and Sean Wilson mapped the Spady Landslide after the second failure in 1997. Their help proved essential for the completion of this study.
I am indebted to the city of Oregon City, especially Jessica Schriever, who provided the digital data for the creation of the base map used throughout this study. Bob Pinotti spent many hours helping create this base map and setting the stage for the creation of the paper and digital output maps. I am also indebted to Sha Spady for letting me run around her property mapping and taking soil samples for several months. Ron Jennison, at the Oregon Department of Transportation, graciously gave me bore hole logs and aerial photographs taken during the construction of Highway 213.
Last but certainly not least, I wish to thank my family. My wife, Amy, helped me with field work and spent many hours proofreading. She has lent moral support throughout my studies here. My sister, Tonia, also helped me with field work and continues to lend her moral support. My uncle, Gary Quinn, is an excellent mentor who sparked my interest in slope stability studies. I’d also like to thank my brother and sister in law, Greg and Audrey Brown-Spitz, for their final editing. Finally, I’d like to thank my parents, Joe and Kay, who gave me tremendous moral support and financial help, without which this would have been infinitely more difficult, if not impossible.
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