Coast Guard Island Bridge

• Client:  Moffatt & Nichol
• Location:  Alameda, California
• Project Manager:  Lori A. Simpson
• Principal-in-Charge:  Richard D. Rodgers
• Designer:  Moffatt & Nichol

Treadwell & Rollo performed a geotechnical investigation and developed site-specific seismic response spectra for the 260-meter-long Dennison Street Bridge replacement, a precast, bulb T-girder structure with spans of approximately 36 to 40 meters. 

Challenging conditions included the presence of weak compressible clay in the channel as well as poor fill at the abutments.  Because of these poor soil conditions, the bridge is supported on driven, octagonal, precast, prestressed concrete piles gaining support in the stiffer and denser soil below the fill and Bay Mud. 

To address abutment settlement concerns, we evaluated fill options, including surcharging.  In addition, our engineers provided construction observation during pile installation.  Finally, as the existing bridge contained hazardous materials, Treadwell & Rollo also performed a hazardous materials investigation, making recommendations concerning handling and disposal of creosote-treated wood, lead-based paint, non-friable asbestos and contaminated soil.