Design Challenges of a NYC Waterfront Development

The footprint and topography of New York City has changed dramatically over the last three centuries. The shorelines, particularly of the Manhattan Island, have expanded well beyond their original locations into the adjacent rivers and bays. As the city continues to expand, marginal filled-in land with difficult subsurface conditions is being developed. This paper discusses some of the design challenges and associated engineering analyses performed for a large waterfront development project that includes seventeen high-rise residential towers and a large multi-level riverfront park. An emphasis is placed on the numerical evaluations that were performed during design. The project area is a former railroad yard with hydraulic fill placed over compressible river bottom deposits. The presence of loose fills and compressible deposits presented numerous design challenges. The development required raising existing grades by placing over 10 meters (32 feet) of new fill to extend the existing street grid onto the site and to create the new park space. Measures had to be taken to limit the settlement induced by the new fill and to reduce the impact of the development on adjacent structures, including an elevated highway along one side and active passenger railroad tracks at grade along the other side of the project site. Those measures included construction of pile-supported relieving platforms, improvement of compressible soils by pre-loading with surcharge fill, and use of lightweight fill. Extensive engineering evaluations, including both analytical and numerical analyses have been performed to provide efficient designs.