| The Lone Tree landslide area has been an actively eroding debris flow since the late 1970's, and suffered localized failure as a result of the Loma Prieta earthquake on October 17, 1989. The slide closed a section of California State Highway One.;This study is a review of California coastal policies applied to this road repair, and a geotechnical investigation of the subsequent fill.;In 1991 the California Coastal Commission approved repair of this portion of State Highway One in Marin County. The Commission required mitigation of 5.61 acres in Bolinas Lagoon, and monitoring of the fill's potential impacts.;The geotechnical monitoring investigation found the average volume of sediment eroding from the fill per month during 1991-1994 was 4,145 cubic yards, with estimates of the fill's life to be between 15 and 31 years, and erosion rates an order of magnitude greater than natural conditions. |
