Our team was part of the Gerald Desmond Bridge replacement design/build team, providing geotechnical design services for the Port of Long Beach’s (POLB’s) “iconic” cable-stayed, six-lane bridge, which will span the Back Channel in the Port of Long Beach. This bridge replacement, designed to ease traffic congestion and improve navigational safety, is budgeted at almost $700 million and being jointly procured by the Port of Long Beach and Caltrans. The bridge will replace the existing Terminal Island steel span bridge, which is at the end of its useful design life and faces critical long-term maintenance issues. Also, the old steel span bridge was not designed to manage currently roadway traffic volumes and, at 154 feet air draft, is a navigation obstruction to larger container ships that are now common at the Port.
Being that the project was under the regulatory of Caltrans, design process followed the standard Caltrans process in which a Preliminary Foundation Report (PFR) is prepared in conjunction with a Type Selection Report (TSR) for the review and approval by Caltrans of the foundation type in the case of bridge structures and earth retention systems (ERS) in the case of retaining walls. We were responsible for the design of the of the retaining structures associated with the west approach embankment; preliminary design of the retaining structures associated with the east approach embankment; design of the foundations and alternations of the existing embankment associated with the Terminal Island Freeway bridge (at the western terminus of the project area); and design of the cast-in-drilled-hole (CIDH) bridge foundations of the low level approach regions of the bridge.
What makes design/build project delivery attractive to owners is reduced cost and schedule. To reduce cost, innovations must be “unleashed” and embraced. Our California licensed Geotechnical Engineers (GEs), with our local experience, helped to build a consensus between the innovations of the international design team and the requirements and expectations Caltrans reviewers. As an example of this, the I-710 approach embankment to the north of the bridge (i.e., east approach) was entirely constructed using lightweight cellular concrete backfill to reduce settlement of underlying old fill and estuary deposits. The retaining walls required for this approach embankment were designed as Mechanically Stabilized Earth (MSE) retaining walls but the lightweight cellular concrete was used as the “backfill” material in conjunction with embankment construction.
Considerable time was spent building a consensus for seismic design to mitigate liquefaction and lateral spreading for these embankments and retaining walls over soft soils, using finite element analysis to evaluate the magnitude of wall displacement and distortion. This required both mastering state-of-the-art earthquake engineering concepts required in California, mixed with a bit of tact and diplomacy; which was delivered.
In addition to geotechnical seismic issues, there were significant geoenvironmental issues for this site. Soils and groundwater at the site were impacted with petroleum hydrocarbons and heavy metals from past local oil production and industrial facilities. Field exploration activities required the preparation of a Health and Safety Plan and a Work Plan were prepared prior to initiating subsurface explorations, which consisted of over 120 borings and 70 Cone Penetrometer Test (CPT) soundings. Soil samples were collected and tested simultaneously for both engineering properties at our Irvine in-house geotechnical laboratory, and for potentially hazardous compounds, including total petroleum hydrocarbons (TPH) carbon chain, volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and Title 22 metals. Soil cuttings and groundwater from borings were stored in 50-gallons drums, tested for hazardous materials, and then properly disposed of offsite. Our cross-trained staff is experienced working in urban environments where geoenvironmental issues need to be addressed simultaneously with geotechnical issues. We provide seamless geotechnical, geoenvironmental and materials testing services, safely and efficiently to reduce cost