Investigation of Sanitary Landfill Slope Performance During Strong Ground Motion from the Loma Prieta Earthquake of October 17, 1989

This paper evaluates the performance of landfill slopes (refuse fill slopes) during strong ground motion from the October 17, 1989 Loma Prieta Earthquake (M7.1) that affected the Santa Cruz Mountains - San Francisco Bay region. The earthquake\u27s occurrence in a highly populated area that contains the waste disposal sites for this large population offered a unique opportunity to review the performance of slopes on the landfills. Current state and federal regulations require the analysis of stability of landfills under seismic loading. To date, these evaluations have relied on gross simplified assumptions. This paper examines whether these assumptions are reasonably correct. There are approximately 35 active landfills in the seven counties surrounding the epicentral area. The landfills are underlain by a variety of geologic materials ranging from Bay Mud (soft sediments) to hard rock. Fill slopes at the landfills range from a few feet to 250 feet high with inclinations as steep as 2:1 (horizontal to vertical). Contact with operators and regulatory agencies indicate that there was very little damage to landfill slopes during the earthquake. The probable ground accelerations at the landfills during the earthquake are estimated based on comparison with accelerations recorded at nearby CSMIP stations or USGS strong motion stations and the site geologic conditions