La Loma Road Bridge Seismic Retrofit and Reconstruction

This challenging $11.5 million contract called for the seismic retrofit and reconstruction of the La Loma Road Bridge elements, which was initially constructed in 1914. The structure runs over the Arroyo Seco Channel. The retrofitting strategy provided the bridge the capacity necessary to satisfy the “no collapse” condition without relying on the support of Pier 4, which lies in the zone of potential rupture of the Eagle Rock fault.

During the 18-month outage, OHLA USA replaced the 390-foot-long x 40-foot-wide bridge deck, rehabilitated the arches and spandrel columns, and strengthened the end piers. In addition, the existing slab girder deck was replaced with a new post-tensioned concrete box superstructure that is capable of clear spanning from Pier 3 to Pier 5.

Essential features of the contract included new foundations at the abutments featuring cantilevered retaining walls at the approach to Abutment 1 ranging in height from eight feet to 26 feet, in addition to the construction of wing walls supported on the Abutment 5 foundation. Retrofitting using micropiles was required to increase uplift and compression capacity.

The project received a Design Restoration Award from the California Preservation Foundation.