In New York, contractors often underestimate how much of Lower Manhattan and parts of Brooklyn sit on artificial fill and loose alluvial deposits. The subsurface conditions along the Hudson and East River waterfronts can hide layers of saturated sand that are susceptible to liquefaction during a moderate earthquake. A standard boring log alone will not flag this risk. Our team applies site-specific liquefaction analysis following the New York City Building Code, which references ASCE 7 for seismic ground motion parameters. We correlate field data from CPT testing with cyclic stress demands to quantify the factor of safety against liquefaction. For deep foundation design in areas like Long Island City or the Financial District, we also integrate findings from seismic microzonation studies to refine the acceleration values used in the analysis.
Loose saturated sand can lose all bearing capacity in seconds. A factor of safety below 1.2 demands a mitigation design.
