ABSTRACT With a thick and highly variable mixture of glacial and nonglacial soils overlying bedrock, punctuated by seismically active fault zones, Seattle is a challenging arena for geologists, engineering geologists, and geotechnical engineers. Because of this geologically complex stratigraphy, Seattle has a higher density of geoprofessionals and subsurface explorations than other cities of equal size. Even so, the subsurface always delivers surprises when construction begins. By visiting three major civil works, SR 520 floating bridge, Alaskan Way Viaduct/SR 99 tunnel, and the Beacon Hill Transit tunnel, you will discover the interaction between Seattle geology and the engineering that made these projects successful.

Abstract Engineering geology is inter alia concerned with the application of geology to the civil engineering industry to ensure safe and economic design and construction. It is a discipline that advances through practice, and case studies of both successes and failures are critical to its development. In this concluding chapter, 19 case studies have been compiled, mainly by those who were directly involved in the projects, to illustrate the nature and complexity of the ground conditions that can be encountered when working in relict glacial and periglacial terrain. The chapter finishes with a section on how the Working Party volume as a whole can be used to guide and improve best practice.