DEP letter regarding dust survey, 101 Maiden Lane, April 2002

NYC 9/11 Public Portal Document 04/09/2002 15:11 FAX Q005 0003 04✓09/2002 0852 FAX 2129444618 AMBIENT GROUP

ambient group, inc.

Bulk Samcle Collection and Asbestos Analysis Procedurq~; with a Representative bulk samples were collected by penetrating the total depth of the material sample container providing a core of all materials present. Representative sampling is based upon the material's physical character and distribution throughout the survey Fuea. The sample is first determined lathe laboratory to be either friable or nor-friable, organically-bound (NOB), and either homogenous or heterogeneous. Sample analyses of both friable and NOB materials are performed in accordance with procedures described in the New York State Department of Health l;nvironmeutal Laboratory Approval Program (NYSDOH ELAP) Certification Manual as "Polarized-Light Microscope Methods for Identifying and Quantitating Asbestos in Bulk Samples," Item No. 198.), dated 03/01/97. If the analysis of a friable material reveals the presence of asbestos, t]w asbestos is quantified by type and the asbestos concentration is expressed as a percentage of the total matrix. The total amount of asbestos in the sample is also reported. If the analysis of a. friable material indicates the presence of asbestos but at a concentration less than 1% of the total matruc, the result is reported as a trace for each type of asbestos found. If the analysis of a f fable mat:rial does not indicate the presence of asbestos, the result is reported as no asbestos detected ("NAD)"). All NOB materials are gravimetrically reduced by ashing and -acid digest ion prior to analysis. If the weight of the residue after ashing and acid digestion is less than 1% of the starting weight, then the results are reported as non-asbestos containing (i.e., less than 1% asbestos by weight). If the analysis of an NOB residue which weighs 1% or more of the starting weight reveals the presence of asbestos, the asbestos is quantified by type and the asbestos concentration is expressed as a percentage of the total matrix. The total amount of asbestos in the sample is also reported. If the analysis of a NOB material does not reveal the presence of asbestos, the results are reported as inconclusive by polarized light microscopy (neither negative nor positi. a for asbestos). Polarized- light microscopy is not consistently reliable in detecting asbestos in f oor coverings and similar NOB materials. Before this material can be considered or treated as non-asbestos containing, confirmation must be made by quantitative transmission electron microscopy (TEM). Sample analysis of NOB materials by transmission electron microscopy is performed in accordance with procedures described in the NYSDOH ELAP Certification Manual as "Transmission Electron Microscope Method for Identifying and Quantitating Asbestos in Non- riable Organically Bound Bulk Samples," Item No. 198.4, dated 03/01/97. If the TEM analysis of a NOB material reveals the presence of asbestos• the asbestos is quantified by type and the asbestos concentration is expressed as a percentage of the total matrix. The total amount of asbestos in the sample is also reported. If the analysis of a t~fOB material indicates the presence of asbestos but at a concentration less than 1% of the total matrix, the result is reported as a trace for each type of asbestos found. If the analysis of a NOB material does not indicate the presence of asbestos, the result is reported conclusively as no asbestos &I acted ("NAD").

NOTE: AMBIENT LABS, INC. ELAP #10865

NYC-WTC 000100055