Environmental assessment section on physical resources, 2001

NYC 9/11 Public Portal Document

magnitude of 5.3 occurred on August 10,1884 at Rockaway Beach, Queens (GSA 1998). This earthquake was the largest recorded in the New York metropolitan area and was felt throughout most of the northeastern United States. There are faults in the WTC area and there is a history of low magnitude earthquakes. Combine these factors with high-density and multi-story structures and there is a moderate risk of earthquake damage to the region.

During earthquake or seismic activity, the liquefaction of soils would be expected to amplify damage in the areas of fill or “weaker” soils, especially landfill areas such as Battery Park City, as indicated by the New York City Consortium for Earthquake Loss Mitigation. Soils in the project area of lower Manhattan are weaker soils that may be subject to liquifaction during earthquake events (NYCEM 2000).

A soil survey of Manhattan has not been performed; however, soils at the WTC would likely be mapped as the Made Land soil map unit. This unit consists of areas of cuts and fills and areas covered almost entirely with streets and buildings in an urban enviromnent. Cuts are of various depths, and the fill material consists of various materials, including materials that are not classified as “soil.” Based on an analysis of available soil boring logs, fill material in the vicinity of the WTC ranges in thickness fi-om 40 to 60 feet (NYCDDC 2001).

Environmental Impacts

Since fill material in the vicinity of the WTC consists of various materials including bricks, rock and timber, there is a potential for planned excavation activities to encounter buried construction and other types of debris. In lieu of subsurface testing, specific management practices to address buried debris that may be uncovered during construction may be required by the applicant or responsible party to avoid or minimize delays in the schedule and to protect human health and the environment.

Construction and demolition activities for any ot the proposed alternatives would not affect soil characteristics, but may cause the top layers to mix. These activities may also temporarily increase soil erosion. Construction activities that affect 5 acres would require preparation of a Notice of Intent (NOI) under the requirements of the National Pollutant Discharge Elimination System (NPDES) General Permit for Construction Activities. The requirements of the NOI include the preparation and implementation of a Stormwater Pollution Prevention Plan (PPP). This PPP must include erosion and sediment controls, including interim and permanent stabilization practices. Recommended methods of erosion control include the use of silt fences, hay bales, check dams, and temporary vegetation 6a aw cover. In addition, the NPDES permit would require that, during construction, the responsible party immediately report to the National Response Center any spills of regulated hazardous substances that are equal to or exceed the Reportable Quantity levels listed in 40 CFR 110,117, and 302. The responsible party would also be required to submit a written description of the spill to the EPA Regional Office, would be responsible for any required cleanup, and would be required to modify the Stormwater PPP to document these steps. The responsible party would be required to comply with all

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