Air and bulk sampling results letter, Sept 2001

NYC 9/11 Public Portal Document

97!2812001 0:i4 6315803195 ENVIROSCIENcECNSLTAN PAGE 03

American Stock Exchange, 28 Sapternber 2001

centimeters) to produce the asbestos air coticentration. The NIOSH 7400 or 7402 methods used by OSHA to evaluate worker exposure results in values of fibers per cubic centimeter. Fibers greater than 5 micrometers in length and greater than 025 micrometers in diameter are counted. Structures counted in AHERA include the fibers in the NIOSH OSHA approach and includes much smaller. structures. So the MYRA, air concentration presented in the attached tables are more protective than the NIOSH OSHA approach

Samples that met the U.S. EPA AHERA clearance criteria of 70 structures/square millimeter are considered acceptable and are considered safe for reoceupancy.

The 9s' floor has three samples (Room, 909. Cubical 49, and Casseleggi room) that exceed the U.S. EPA A1xT-RA, clearance criteria of 70 structures/square millimeter and one that approaches the clearance criteria ( Cubical 52). Cubical 39 has a value of 37.88. These results are less than the OSHA PEL of 0.1 fibers per cubic centimeter.

We believe the asbestos in the air in these areas is due to the catastrophe and we do .not believe that the asbestos was from the 22 Thames nuilding because of the residue from the explosions and collapse was found it significant quantities on this floor and because the other results in 22 Thames and. 86 Trtriryy Place are so low. Other floors such as the 6"' Iloor also had sign iicant quantities of the residue from the explosions and collapse. On September 23, 2001, we recommend that the floors in 22 Thames that had not been tested be tested. This sampling was comp feted on September 24`r 2001.

Outdoors samples were collected on the 4" floor, and tho 8' floor. These samples were all less than detectable litnits. These outdoor samples may be compared with the U.S. EPA collected asbestos air monitoring local=.osss Lower Manhattan that are presented on www. epa goviepahome.•/don nap02. hmr.

Asbestos bulk samples were collected on September 20' and September 24'. Dust samples were collected from exterior window ledges and different sites where material was available inside the building. All samples collected are not considered asbestos contaiT.irg material since they contain less than one percent asbestos. The Asbestos bulk sample results are presented in the attached tables.

The asbestos clean up must be conducted by New York State and U.S. EPA certified asbestos abatement contractors and workers. The general cleaning protocol once gross debris has been removed is to HTPA vacuum, followed by an amended water wash, followed by HEPA vacuuming. Porous surfaces such as carpets, furniture, ceiling tiles (and support office parcitions, and other soft goods must be grids),

evaluated for the feasibility of cleaning. If surfaces can not be cleaned they must be discarded. The electrical equipment must be evaluated and speciali5 cleaned or discarded.

The asbestos cleaning started with the floors most needed by the American Stock Exchange and proceeded to other floors or a priority basis. Asbestos fibers from outside the building and from the 9`" floor of 22 Thames have not appeared to migrate to the other iloo:s because the samples collected on later days show virtually all zero counts for strictures per millimeter squared or structures per centimeter squared.

The lead in air samples were collected from areas considered represeutative of the building. Only

to accelerate

one sample was collected from each the

area lead building

process. screening

The in

sir results are presented in the table be!cw.

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NYC-WTC 000094470