Site Investigations
The site investigations were conducted in three phases:

• The Phase 1 program was conducted to collect geotechnical and geophysical baseline data within a corridor encompassing the possible bridge alignments.
  
  
• The Phase 2 program was concentrated at proposed pier locations along the preferred bridge alignment.
  
  
• The Phase 3 program included a detailed study (using marine CPT soundings and a geophysical survey) to evaluate the potential for faulting near Yerba Buena Island, and to develop detailed characterization at the locations of important temporary structures.

The investigations were conducted using sophisticated marine geophysical survey vessels, two marine drill barges, and wheel-drive and tethered CPT system. During field work phases, the team:

• Collected 130 kilometers of 2D geophysical data,
• Collected 3 square kilometers of high resolution 3D geophysical data,
  
• Drilled 44 marine exploratory borings in the Bay, to a depth of up to 500 feet (into Franciscan bedrock)
  
• Conducted 100 wheel-drive CPT soundings in the Bay,
  
• Drilled 30 borings and advanced 14 CPT soundings on land at the bridge approaches
  
• Completed 15 CPT soundings on the tidal flat north of the Oakland Mole using Fugro's all-terrain equipment.
  
• Conducted extensive sampling, rock coring, in situ testing, downhole geophysical logging, and onboard laboratory testing.

Advanced sampling techniques and downhole in situ testing produced high quality data for determining the characteristics of the subsurface soils. As a result, the design pile capacity was increased by nearly a factor of two resulting in significant savings in foundation costs. The information generated by this study represents the most comprehensive set of high quality data for in-bay soils and will result in revisions to many of the state-of-the-practice soil correlations.