The Niles Boulevard Bridge, which spans the Union Pacific Railroad and BART tracks at the Fremont/Union City border, was in need of a seismic retrofit after the Loma Prieta earthquake. After considering the cost and restrictions of retrofitting the existing structure, it was determined that a replacement bridge was the best option. The new cast-in-place, prestressed concrete box girder bridge was built adjacent to the existing bridge while allowing all tracks to remain in operation during construction.
Malcolm’s scope on the new bridge was to install three drilled piers 9 feet in diameter and 100 feet in depth. The proximity of the piles to the existing tracks and the loose ground conditions required the use of full depth temporary casing installed using the oscillator method.
This project required a very detailed work plan with drawings that documented every position and movement of the equipment hour by hour when the trains were not running and minute by minute when trains were running. Additionally, any work or equipment that could potentially foul the existing track had to be at least 25 feet away from the rails when trains were active. With this in mind, Malcolm performed the majority of its work during weekend nights when the trains were not in operation.
Even with all of the unique challenges presented by this project, Malcolm delivered a quality, integrity-tested product on time and on budget.