Flood Protection System for Infrastructures: Methodology and Instrumentation TestingÂ-Paper

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The paper describes the design and construction of a flood protection system for New York City Transit’s Hammels Wye substation in Far Rockaway, Queens. Damaged by flooding during Superstorm Sandy, the facility was protected by a roughly 1,200-foot perimeter barrier designed to safeguard critical transit infrastructure from future storms.<br /><br />The site’s proximity to Jamaica Bay, active tracks, existing buildings and buried infrastructure limited access and complicated subsurface investigation. Borings found loose fill over sand and gravel, soft organic silt and clay, and deeper silty sand with occasional soft layers. Groundwater was shallow, making seepage control an important design consideration.<br /><br />The system combined concrete retaining walls supported on micropiles with steel sheet-pile walls. Jet-grout columns were used beneath some sheet-pile walls to reduce seepage. Existing walls were extended to the design flood elevation, and flood gates provided access to the protected area. Micropiles also supported gates and new facilities, including a compressor-room building.<br /><br />Because vibratory sheet-pile installation could affect nearby tracks and structures, the contractor used a variable-moment hydraulic hammer. An instrumentation program monitored 38 prisms on tracks, walls and buildings using automated total stations, alongside vibration monitors. Measurements showed less than 0.2 inch of lateral movement and 0.1 inch of vertical movement; peak particle velocities remained below 0.1 inch per second, well within applicable guidelines.<br /><br />The project demonstrates how geotechnical investigation, tailored foundation and seepage-control measures, and real-time monitoring can manage construction risks while improving the resilience of critical infrastructure.

Keywords

flood protection

New York City Transit

Hammels Wye substation

Superstorm Sandy

perimeter barrier

micropiles

sheet-pile walls

jet grouting

seepage control

vibration monitoring