Eleventh Street East Tracy Overhead, City of Tracy, CA

The project replaced the existing 11th Street East Tracy Overhead, which crosses Union Pacific Railroad (UPRR) tracks and North MacArthur Drive in the City of Tracy, California. The new overhead is a single-span structure in combination with retaining walls and embankment fill at the approaches. A temporary on-site detour was constructed to allow the demolition and the construction of the new overhead in one stage. The permanent embankments are supported by two-tiered Mechanically Stabilized Embankment (MSE) walls up to about 40 feet.

PARIKH is the geotechnical engineer-of-record and provided recommendations for the overhead structure (supported on eight-foot diameter CIDH piles), the detour structure (supported on four-foot diameter CIDH piles), the two-tier MSE walls, and pavement sections.

Challenges

• The abutments were designed with pile columns instead of a tall abutment wall to minimize the lateral earth pressure, which is a more cost-effective alternative compared to the conventional tall abutments.
• Due to the presence of liquefiable soils, the lateral spreading potential was considered high and was the major design challenge. PARIKH performed analyses per Caltrans lateral spreading guideline to estimate the potential deformation and the additional force due to lateral spreading for the design of the structure and foundations.