WTC site damage assessment map, Sept 21, 2001

NYC 9/11 Public Portal Document

relocate out of the floodplain or to minimize future damage from flooding. Because WTC impact area is low-lying in the vicinity of the Hudson River, flooding risks are associated with rainfall and storm surge from northeasters and hurricanes. The location map of the 100-year and 500-year floodplains is provided as Figure 3-5.

Regulated floodplain areas have been defined by FEMA and include areas that flood during storms that have a one percent change of occurring in any given year, which is equivalent to a likelihood of occurring once every 100 years (100-year storm event). FEMA also maps the 500-year floodplains, but these are not regulated. Federal regulations require an analysis of impacts and options to avoid 100-year floodplain encroachment. FEMA has the responsibility for mapping and regulating floodplain areas. Federal regulations stipulate that in the case of a “significant encroachment” on the floodplain by a proposed project, a finding of an “only practicable alternative” is required. While a project is permitted to encroach on the 100-year floodplain, this encroachment may not be significant. In addition to federal requirements, NYSDEC Environmental Conservation Law regulations (6 NYCRR Part 502) require state agencies contemplating projects in the floodplain to consider the effect of these actions individually as well as cumulatively with other projects in the vicinity. In all cases, habitable structures must be flood-proofed or raised above the 100-year floodplain.

The WTC site is mapped on the Flood Insurance Rate Map (FIRM) panel number, 54 of 131, Community Panel Number 360497 0054B, effective date November 16, 1983. According to the FERM, the western-most edge of the complex along West Street is located in the 100-year floodplain, specifically special flood hazard area, Zone A5, having a base flood elevation of 10 feet (Figure 3-5).

The FEMA is currently evaluating potential projects in order to comply with Executive Order 11988 Floodplain Management imder the requirements of 44 CFR Part 9. The Executive Order and presence of a floodplain will not prevent restoration or redevelopment of the site. As with other types of facilities where FEMA has determined that there are no alternatives to reconstruction within the floodplain, FEMA intends to provide assistance for the construction, reconstruction, restoration and improvements in and around the World Trade Center disaster site, but may require upgrades to prevent the potential of flooding. Increased costs of restoration and repair projects associated with upgrades required by code are generally eligible for reimbursement..

Projects and facilities that fall within the mapped 100-year floodplain may include:

• Restoration of damaged and destroyed transportation infrastructure, including streets and subway systems • Restoration of damaged and destroyed water control facilities, pipes and distribution systems • Restoration of damaged and destroyed public buildings and related equipment

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