Draft memo forwarding thread, April 2002

NYC 9/11 Public Portal Document

V. Residence Selection/Sampling Rationale The selection of residential sampling locations will be decided upon by New York City Department of Health (NYCDOH). The general NYCDOH approach is described as follows: A total of approximately 60 residential units will be sampled (a unit is an individual apartment in a multi-apartment building). A series of three concentric circles is being drawn around the WTC location. These circles will be divided by direction or zone from the WTC (north, south and west, and east). From five to seven of the multi-residential buildings will be selected for testing from within each zone. Testing locations will mainly focus on occupied residences. However, approximately five unoccupied units nearest the WTC will be targeted for testing. In addition, approximately five units will be selected outside of the concentric circles, that were not impacted by the WTC collapse, to serve as background sample locations. Sampling personnel will document the rationale for selecting buildings and residential units for sampling. They will also document sample locations, conditions during sampling, and possible interfering factors (e.g., traffic, construction). In addition, unit occupants and building owner/operators will be requested to provide information that will better assist in evaluating the results. Appendix A of this plan contains the information needed/requested. VL Sampiing/Analvsis Approach 1.Indoor Air and surface dust sampling will focus on both a common entryway area into the building (e.g., lobbies, front entryways) and on a selected number of apartments/units in the building. Attempts will be made to select apartments/units where dust is visible as well as units where dust is not visible. Selecting entryways and common areas should be representative of worst case conditions for contaminant/material track-in from outdoors. Selecting two apartments/imits in the same building-with and without visible dust—should provide information on the ranges of contaminants found in indoor living spaces. If the building is unoccupied and no central HVAC system is present, aggressive (leaf blower, high-power fan) indoor air sampling should be conducted. If the building is occupied, air sampling should be conducted with the building/unit heating, ventilation, and air conditioning (HVAC) system’s fan in continuous operation. After sampling is completed, filters for the HVAC system, if applicable, should be inspected. If dust is present, recommend filter replacement. Indoor air sampling for asbestos will be conducted and analyzed using NIOSH methods 7400 and 7402. Respirable crystalline silica will be sampled and analyzed using NIOSH method 7500. Air sampling for inhalable and thoracic size particles will be conducted using EPA method IP- lOA. The respirable silica sample will be used to analyze the respirable fraction of the dust. The relative amounts (percent weight) of each fraction present will be determined. Each fraction will be analyzed for silica, gypsum, mica, and calcite using X-ray diffraction (XRD) analysis. Fibrous glass will be analyzed using scarming electron microscopy (SEM).

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