Excavation support practices in the Pacific Northwest

Temporary and permanent excavation support techniques are constantly evolving in the United States. It is clear from observing excavation support practice across the country that there remain considerable regional variations in the contract procurement design, and construction techniques. Many of these differences reflect the logical response to local conditions-both geological and economic-but certain other variations now appear to be due to a relative inertia in research and development at one extreme and, regrettably, a lack of understanding of fundamentals at the other extreme. This paper reviews aspects of the procurement, design, and construction of excavation support systems typically used in the Pacific Northwest. Attention is focused on local geology history of use, and current contract procurement practices. Three case histories are presented to further illustrate the innovative excavation support techniques used in the Pacific Northwest.