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Geological and Hydrological Foundations of Lower Manhattan and Surroundings

The area encompassing the World Trade Center site, the Hudson River shoreline, Downtown Manhattan, and extending to the approaches of the Verrazzano-Narrows Bridge rests upon a complex interplay of glacial deposits, bedrock outcrops, and dynamic estuarine currents. Manhattan’s bedrock consists primarily of Manhattan Schist, with pockets of Fordham Gneiss and Inwood Marble near the surface in certain upland zones; these formations provide the foundational support for skyscrapers and critical infrastructure. Along the Hudson River’s edge, glacial till and alluvial sediments overlay bedrock at varying depths. Tidal fluctuations—driven by the Atlantic Ocean’s semidiurnal cycle—create strong currents in the Narrows and wide tidal ranges that shape sediment transport. Understanding these subsurface conditions informs the design of deep foundations for structures like the World Trade Center, and also dictates shoreline engineering measures to manage erosion, storm surge, and sea-level rise impacts in Downtown Manhattan and beyond.