. . . and old portion being dismantled. This is the work required by damage to the bridge during the earthquake in 1989. To read more about the damage, and the new work, go here and scroll down.
en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
The tall light colored part is new; the dark framework is the old bridge, the sections now being fully taken down.
View seen from Treasure Island/Yerba Buena Island, the land that divides the east and west sections of the 5-mile bridge.
baybridgeinfo.org/projects/sas 