The San Francisco-Oakland Bay Bridge (SFOBB) is a component of Interstate-80 that is one of the principal corridors linking the San Francisco Peninsula and the East Bay (Figure 1-1). The East Span Seismic Safety Project (East Span Project) will provide a seismically upgraded replacement bridge to the north of the existing bridge alignment between Yerba Buena Island (YBI), in the City and County of San Francisco, and the City of Oakland, in Alameda County. The construction of the new East Span will entail driving 259 large-diameter piles in San Francisco Bay to support the Skyway and Self-Anchored Suspension (SAS) components of the new side-by-side eastbound and westbound bridge structures. Pursuant to the Marine Mammal Protection Act (MMPA), the California Department of Transportation (Caltrans) requested and received an Incidental Harassment Authorization (IHA) from National Marine Fisheries Service (NMFS) to incidentally take, by harassment, small numbers of California sea lions (Zalophus californianus), Pacific harbor seals (Phoca vitulina richardsi), and possibly gray whales (Eschrichtius robustus) in San Francisco Bay. This marine mammal monitoring plan has been prepared and submitted in compliance with NMFS’s requirements for an IHA. This plan discusses construction activities for the East Span Project, potential impacts to marine mammals, and methods for monitoring and reporting the activity of marine mammals near the construction areas.