‘Build It Back’ Resiliency

by Omer Kalafatoglu

Sited in Rockaway, Queens, only 500 feet from the ocean, the Dayton Towers Condominium Complex incurred flooding from three sources in the wake of 2012’s Hurricane Sandy: the ocean, the bay, and rising groundwater.

Constructed between 1967 and 1968, the complex of seven multi-family housing buildings is subdivided into East and West campuses. In the West complex, the flooding water level reached up to 6 feet above grade, causing extensive damage. To prevent this from happening in the future, Dayton Towers called upon HLZAE to implement a Resiliency Program that includes a combination of dry floodproofing and wet floodproofing methodologies.

A dry floodproofed structure is made watertight below the Design Flood Elevation (DFE) to prevent floodwaters from entering. This is accomplished by sealing the walls with waterproof coatings, impermeable membranes, or a supplemental layer of masonry or concrete. Wet floodproofing applies permanent or contingent measures to a structure or its contents to prevent or provide resistance to damage from flooding while allowing floodwaters to enter the structure, thereby greatly reducing the effects of hydrostatic pressure.  By reducing the loads imposed on the building during a flood, the likelihood of structural damage may be greatly reduced.

Through the Resiliency Program, electrical equipment damaged during the hurricane will be renewed and installed above the DFE. Booster pumps will also be elevated above the DFE, as will the fire pumps in the mechanical rooms. The boiler room walls of each building in the complex will be reinforced to withstand the lateral hydrostatic forces. Finally, a backwater valve will be installed to the sewage line of each building to stop any floodwater backing up to interior spaces. In the event of an emergency, all of the openings at the first-floor perimeter will be sealed by flood panels. These dry floodproofing methods will reduce the water that needs to be discharged by the wet floodproofing measures.

Boiler rooms and steam room pits are the only places that will stay below the DFE. A high-capacity industrial open-trench line will collect and divert any residual flood water to newly installed high-capacity duplex sump pumps to be installed in the boiler rooms, the electrical room, the steamroom pits, and each of the vacuum rooms. These 20-feet head at 250 gpm-rated high-capacity sump pumps are designed to discharge 6 feet per hour of rainfall. A 750kW standby generator will power all the emergency loads of each building at the East Complex, as will a 500kW standby generator at the West Complex.

Once completed, the Resiliency Program will ensure that the Dayton Towers Condominium Complex is able to withstand the triple force of water in any future flooding situation.

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