Environmental assessment report, 100 Church Street, April 2002

NYC 9/11 Public Portal Document

Sampling Methodology Sampling and analysis for Dioxins on surfaces was conducted utilizing sterile wipes impregnated with hexane. A known surface area (100cm x 100cm) was wiped and the wipe sample submitted to the lab and analyzed.

4.5 Results of Air Sampling and Analysis

Air sampling was conducted for a comprehensive list of substances as indicated above. All air samples collected by TRC were collected with the HVAC operating. The following discussion summarizes the findings of the air sampling program.

4.5.1 Asbestos Air Sampling and Results

Air Sampling Results

Sixty (60) air samples (excluding blanks) were collected in an aggressive manner and analyzed by TEM for asbestos. Results of asbestos air samples are presented in Table 10 of Appendix A. None of the samples were found to be greater than 70 structures per square millimeter (s/mm^), which is the AHERA clearance criterion established for re-occupancy following asbestos abatement in schools. In fact, all samples were less than the detection limit of the analytical method, that is no asbestos fibers were formd in any of the air samples.

Aggressive Asbestos Air Sampling Methodology Asbestos air samples were collected using “aggressive” techniques to simulate a worst-case scenario and re-suspend into the air any settled dust that could be the source of asbestos fibers. Aggressive sampling techniques involve agitating air within the space using an electric leaf blower. The exhaust from the leaf blower is directed against vertical and horizontal surfaces on which dust may have settled. Particular attention is given to hard to clean areas such as comers of the room and behind desks. Additionally, the exhaust was directed into the air to assist air movement and circulation. During the clearance air sampling period, the building’s HVAC system in the areas was in operation.

Asbestos Standard

20

CITY_21 MC100_014586928

NYC-WTC_000176269