EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

3.0 SAMPLING APPROACH/RATIONALE 3.1 Selection of Sampling Area Location The geographical area (Figure 1) for the Background Study (78th Street and North) was selected based on preliminary modeling of meteorological data on September 11,2001 and shortly thereafter. The modeling was performed by EPA’s Office of Research and Development (Huber, 2003). This geographical area is an area well north of the portion of Manhattan that may have been affected by the deposition of particulate matter from the collapse of the WTC. The distance of buildings sampled in the Study with respect to the WTC site ranges from 8 to 19 kilometers (5 to 12 miles).

The modeling produced isopleth plots which present the dilution of the particulate emissions from the WTC site. These plots indicate that the plume was dispersed and diluted, with the concentration of particulate matter ranging from 1,000 to 10,000 times less than at the WTC site as one moves away from the WTC site in a northeast direction. These isopleths are based on how much the plume was dispersed and diluted by weather conditions and are not based on the amount of emissions from the WTC site.

3.2 Selection of Building Types and Obtaining Access EPA and other members of the Indoor Air Working Group selected the building types designated for this Study. This Study attempted to focus on sampling sites that are similar to the downtown residential housing stock. This stock included: post-1920 non-doorman mid-rise apartments, high-rise condominiums, high-rise co-operatives, and tum-of-the-century tenements. Downtown residential lofts could not be represented in the Study, since lofts located uptown are designated for commercial use only.

In order to solicit volunteer participants from the targeted building types, a list of buildings matching the housing stock described above was provided to EPA and the NYCDOHMH by the New York City Department of Housing Preservation and Development (NYCHPD).

Initially, the task of obtaining access to buildings that would be included in the Study was the responsibility of NYCDOHMH. During the month of June, 2002 EPA assumed the responsibility for obtaining building access. EPA staff exhausted the list provided by the NYCHPD, Due to the lack of willing participants on this list, the difficulty with obtaining access, and time constraints under the Inter-Agency Agreements (lAA), EPA initiated cold calling and essentially door to door solicitation in order to solicit volunteers and gain access to buildings for participation in the Study. Therefore, not all of the buildings sampled as part of the Study were obtained from the list provided. Any building willing to participate in the Study was considered for sampling until fourteen buildings were obtained. This is a deviation from the initial sampling plan regarding representation of the diverse housing stock mentioned above. The

WORLD TRADE CENTER BACKGROUND STUDY 9

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