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← Document results/DEP Box 11/WTC DC TO RC LETTERS CALLEHAN WHITMAN ETC. WARD DOCTOROFF KENNY
Document / 18 pages

DEP memo on 114 Liberty Street clearance data validity, Aug

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A letter defending the validity of DEP and contractor data used to clear residential units at 114 Liberty Street for re-occupancy.

NYC-WTC_000151361–000151378

Folder label: “WTC DC TO RC LETTERS CALLEHAN WHITMAN ETC. WARD DOCTOROFF KENNY

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NYC 9/11 Public Portal Document z .

COPC document, which was adopted as a secondary clearance value for this project, is 1 gg/m’. Although the value chosen for this project was 1 the analytical detection limit available for analyzing crystalline silica in indoor air samples is higher than this value, therefore a result that is below the detection limit is considered to be protective of public health. Four out of eleven samples (36%) were above the detection limit of 11 ranging from 17.2 to 22.1 gg/m\ These values are also above the secondary clearance value.

Although these values are above the clearance value, they are similar to concentrations detected in a background study conducted by USEPA. In the USEPA background study, there was a frequency of detection of 25%, with a range of 4 to 259 Further, the values from the background study without the maximum value of259 gg/m’, provide a range of 4 to 28 gg/m’. This indicates that the range of values observed in 114 Liberty Street are similar to those observed in the background study.’’Based on this, it has been determined that the crystalline silica results are similar to background values and therefore additional cleaning is not nccessaiy.

NYC-WTC_000151371

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NYC-WTC_000151371Source: NYC Law Department, mirrored locally

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