Geotechnical Investigation for Oakland Harbor Navigation Improvement (-50-Foot) Project

The existing Oakland Harbor channels and berth areas are too shallow to accommodate the latest generation of deep-draft container ships. The Oakland Harbor Navigation Improvement (–50-Foot) Project will deepen the Oakland Harbor channels and berth areas from Elevation —12.8 meters (—42 feet) Mean Lower Low Water Datum (MLLW) to Elevation —15.2 meters (—50 feet), producing approximately 9.8 million m³ (12.8 million yd³) of dredged soil. The unique aspect of the –50-Foot Project is that it will be one of the first major dredging projects in the United States where the large majority of the dredged materials is earmarked for beneficial reuse. Most of the soil will be used as fill to create wetlands or shallow water habitat at three sites. This type of soil reuse required extensive characterization of both the environmental and geotechnical properties of the dredged materials. This paper focuses on the methods used to investigate the subsurface conditions and characterize the geotechnical properties of the dredged materials, as well as the methods used to estimate the quantities of anticipated dredged materials. The distribution and geotechnical properties of the soils are important for channel slope design, for the allocation of dredged materials to various reuse sites, for determining the dredge sequencing and for providing baseline geotechnical data for bidding purposes. Digital-terrain-modeling was used to develop accurate quantity estimates and facilitate three-dimensional portrayal of the subsurface conditions. Finally, the lessons learned and the key issues associated with the geotechnical investigation are discussed.