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EPA interim final report on WTC background study, April 2003

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Interim final report from EPA Region 2 detailing a background study of environmental conditions at the World Trade Center site.

NYC-WTC_000145869–000146029

Folder label: “INTERIM FINAL April 2003

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NYC 9/11 Public Portal Document

Revised May 14,2003 6»3.3 Gypsum Bulk Dust - There were nine bulk dust samples collected from residential areas. These samples were analyzed for gypsum. -There were no bulk samples collected from common areas. Only one of the samples detected gypsum above the detection limit. The 95% UCL for gypsum in bulk dust is 2.33%, and this value can be used as an estimate of the backgroimd concentration.

Air - There were forty-six air samples collected with thirty-two collected from residential areas and fourteen collected from common areas. The samples were analyzed for gypsum. Gypsum was not detected in any sample. However, since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated using the entire combined data set from the residential and common areas. The 95% UCL for the combined data set is 9.3 pg/m\ which can be used as an estimate of the background concentration of gypsum in air.

Wipe - There were 114 wipe samples collected with eighty collected from residential areas and thirty-four collected from common areas. The samples were collected from hard surfaces including counters, floors, and walls. The samples were analyzed for gypsum. Gypsum was not detected in any sample. However, since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated using the entire combined data set for all surfaces from the residential and common areas. The 95% UCL for the combined data set is 49.9 pg/ft^, which can be used as an estimate of the background concentration of gypsum on hard surfaces.

6.3.4 Portlandite Bulk Dust - There were nine bulk dust samples collected from residential areas. These samples were analyzed for portlandite. There were no bulk samples collected from common areas. None of the samples detected portlandite above the detection limit. However, since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated. The 95% UCL for portlandite in bulk dust is 4.69% and this value can be used as an estimate of the backgroimd concentration.

Air - There were forty-six air samples collected with thirty-two collected from residential areas and fourteen collected from common areas. The samples were analyzed for portlandite. Portlandite was not detected in any sample. However, since the detection limit for the samples varied slightly, a theoretical background concentration can be calculated using the entire combined data set from the • residential and common areas. The 95% UCL for the combined data set is 9.3 pg/m’, which can be used as an estimate of the background concentration of portlandite in air.

Wipe - There were 114 wipe samples collected with eighty collected from residential areas and thirty-four collected from common areas. The samples were collected from hard surfaces including counters, floors, and walls. The samples

WORLD TRADE CENTER BACKGROUND STUDY 30

NYC-WTC_000145905

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