Environmental assessment report, 100 Church Street, April 2002

NYC 9/11 Public Portal Document

The AHERA regulations were promulgated to protect school children from exposure to asbestos. This regulation defines inspection and management requirements as well as clearance re­ occupancy testing requirements. The re-occupancy testing requirements are designed to facilitate re-occupancy of a classroom following an asbestos abatement action. The AHERA regulations apply to all public school buildings from K though 12* grade. In accordance with AHERA, an abatement action can be considered complete and the classroom reoccupied by school children when the results of final clearance air samples collected within the work area are less than 70 str/mm^. In fact the AHERA regulations allow for a statistical analysis of the clearance data relative to 70 str/mm*, which allows some samples to be greater than 70 str/mm^. The clearance criteria for this project required that all results be less than 70 str/mm^, which in fact is stricter than the AHERA regulations for school children.

Sampling Methodology The air samples are collected by drawing air through a mixed cellulose ester filter (MCE), 25 millimeters (mm) in diameter, with a pore size of 0.45 micrometers. The air is pulled by a 120- volt AC powered, constant flow vacuum pump operated at nominal flow rate of 10 liters per minute (1pm). The pumps are calibrated prior to sampling, using a secondary calibration standard (rotometer). The secondary calibration standards are calibrated periodically (at least once every six months) using a primary standard. The flow rate of each pump is rechecked following each sampling period.

To analyze a sample, circular sections of the filter are cut and placed on a clean glass slide. The slide(s) is then placed in a petri dish containing acetone to fuse and clear the filters. The filter is then plasma etched and transferred to a rotating stage inside a bell jar of a vacuum evaporator. A 1- by 5-mm graphite rod is than evaporated on the filter and the filter is transferred to a clean petri dish. A wicking substrate covered with filter or lens paper is then placed in another petri dish. Carbon-coated TEM grids are then placed on the filter or lens paper and acetone is placed in the petri dish until the wicking substrate is saturated. A portion of the carbon-coated filter is removed from the glass slide and placed carbon-coated side down on a labeled grid in the acetone saturated petri dish.

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