Asbestos air monitoring report, 120 Wall Street, Sep 2001

NYC 9/11 Public Portal Document

dvanced Environmental Corp. September 17, 2001

Mr. William Dacunto Managing Director of Operations Silverstein Properties 140 Broadway New York, New York 10005

Re: Asbestos Air Monitoring, 120 Wall Street, New York, NY

Dear Mr. Dacunto:

On September 16, 2001, Advanced Environmental Corp. performed air monitoring within various tenant floors within the above referenced building. Samples were collected within these floors to document the asbestos fiber concentration levels of the ambient air.

A total of eight (8) samples were collected and analyzed using the Transmission Electron Microscopy (TEM) method according to the EPA AHERA protocol. TEM with energy dispersive X-ray analysis is an analytical method that enables a fibers chemical composition to be identified.

At the present time, there are no non-industrial indoor air quality standards, or permissible exposure limits for airborne asbestos. This fiber specific protocol is generally utilized to determine clean air following a "large" abatement project. TEM sample analysis detects filter loads (the number of structures detected per square millimeter of collection media surface) which, if less than or equal to EPA-AHERA release criteria of 70 structures per square millimeter (s/mm2), determine whether or not the area is safe for re-occupancy.

A review of the analytical data shows, no structures were detected on all samples collected within 120 Wall Street, which is well below the EPA-AHERA release criteria of 70 s/mm2.

In conclusion, the TEM sample analysis data show acceptable concentrations of fibrous materials in the am Tent air.

If ou ave any questions or need further clarification on air sampling methodology, please call me.

Sincerel

Robert uorro Principal

1018.003 \\cpgserver1\data\aec\clients\silverstein\120 wa1Pa r sampling 9-16-01.doc

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