been addressed, and the surface motion effects of a large event are likely to be far more severe than seen in the Loma Prieta event. Freeways and overcrossings Many modifications have been made to freeway structures to reduce life hazards during seismic events. Significant adverse conditions remain which can cause disruption with possible long-term effects upon critical traffic infrastructure despite these modifications. Warren Freeway portion of Highway 13 In its northern extent, the Hayward Fault lies directly beneath the portion of Highway 13 (the Warren Freeway) that is south of its intersection with Highway 24 and north of its terminal connection with Interstate 580 (the MacArthur Freeway). In this rift valley there are a number of elevated street crossings in the Montclair District that cross the fault. Highway 24 State Highway 24, connecting Oakland to Orinda, Lafayette, and Walnut Creek through the Caldecott Tunnel, is composed of extensive earth fill at the location where the fault is crossed. An earthquake may cause minor landsliding on some slopes of the freeway, and the plastic movement of the fill would likely disrupt the pavement if the movement here of the surface displacement is substantial, possibly presenting a hazard to motorists and shutting down the highway for a while. More extensive disruption and greater hazard could be caused by the failure of elevated structures, both those over which the highway passes and overcrossings of the freeway, of which there are two nearby. As elsewhere in the area, such structures have undergone extensive retrofitting for safety. Highways 80 and 880 and the Port of Oakland A severe earthquake is more likely to disable the offshore causeway portions of Interstate Highway 80 (the Eastshore Freeway), since it is built on fill placed in the 1930s atop mudflats whose upper layers were deposited in the 19th century as a result of extensive hydraulic gold mining in the distant Sierra Nevada mountain foothills. This soft mud is expected to amplify earthquake shaking, and the mud supporting the heavy fill may liquefy, and so possibly cause major disruption of the highway due to failure by sinking of the highway and by differential movement of large sections. (More modern construction for these conditions employs linked and "floating" – in mud – lightweight concrete and plastic foam box structures to support a road.) Similar conditions underlie the eastern approach roads to the Bay Bridge. Better, but still locally poor soils