Shimmick Construction with its joint venture partner, Nationwide Construction, successfully completed the seismic retrofit of the 710/60 Interchange in East Los Angeles. The 710 Freeway and the 60 Freeway are two vital arteries in the Los Angeles Basin. Shimmick and Nationwide performed the strengthening with no disruption to the normal traffic and finished on schedule.

The project required the strengthening of six bridges. The bridges required extensive retrofitting with many bents requiring adding CIDH piles, enlarging footings and setting steel column casings. The bridges expansion joints were also strengthened using post-tensioned high strength bars to keep the joints from separating.

The centerpiece to the project was the retrofitting of the bridges four main column bents. These bents supported three levels of roadway and the foundations are located in-between the lanes of the 710 Freeway on either side. To perform the footing retrofits Shimmick and Nationwide excavated using a soldier pile and lagging system to thirty-five feet below grade while supporting the 710 Freeway on either side. Then a drill rig was lowered into the excavation to drill the CIDH piles. The footings were then enlarged. Off the new footings temporary steel columns were used to lift the top roadway section so the existing bearing pads could be replaced. In addition, heavy steel casings were placed around the columns. Finally, the link beams between the columns that supported the third level of roadway were enlarged using reinforced concrete. Shimmick and Nationwide performed a majority of the work required to complete the project. Managed subcontractors were used to perform the reinforcing steel, painting, welding, post-tensioning, electrical and drilling.