Evaluating Geotechnical Resiliency Solutions in New York City-Paper

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The paper examines geotechnical and structural strategies for improving flood resilience at New York City facilities. Superstorm Sandy demonstrated the city’s vulnerability: floodwaters exceeded the 100-year floodplain in many areas, damaging homes, transit systems, and critical electrical equipment. Resilience designs must account for FEMA and ASCE requirements, site-specific flood elevations, waves, currents, wind, floating debris, soil conditions, and projected sea-level rise.<br /><br />Possible approaches include elevating buildings or critical equipment, installing localized flood barriers, and constructing perimeter walls or berms. Where flood barriers may allow groundwater seepage, protection can involve pumping or subsurface cutoffs such as driven sheeting, jet grouting, or permeation grouting. The appropriate method depends on soil conditions, utility conflicts, constructability, maintenance, and cost. Basement protection also requires evaluation of hydrostatic wall pressure, leakage, and buoyancy that could uplift floor slabs. In some cases, controlled flooding may be more practical than preventing all water entry.<br /><br />Examples illustrate how solutions vary by site. Along the Metro-North Hudson Line, equipment was elevated on spread-footing platforms while the tracks were allowed to flood. At LaGuardia Airport, poor, compressible soils required pile-supported frames to raise critical equipment and resist flood and debris loads. At Hammels Wye, a perimeter wall protecting an electrical substation was paired with sheeting and jet-grout seepage barriers. In Far Rockaway, damaged homes were raised and supported on helical piles. At Bay Park Sewage Treatment Plant, existing piles were assessed for their ability to resist flood-related uplift.<br /><br />The authors conclude that complete protection is not always feasible. Designers should compare alternatives through cost-benefit analysis and prioritize measures according to facility needs, geotechnical conditions, and available space and funding.

Keywords

flood resilience

geotechnical design

structural strategies

Superstorm Sandy

New York City

elevated equipment

flood barriers

sea-level rise

pile-supported frames

hydrostatic pressure