Final Report Volume 1, WTC Unoccupied Building Monitoring, 125 Cedar

NYC 9/11 Public Portal Document

Final Report 125 Cedar Street, NYC, NY

• Asbestos Asbestos clearance air samples were analyzed via Transmission Electron Microscopy (TEM) utilizing the USEPA's PCMe method of structure counting. PCMe

TEM ambient air samples were analyzed by ATC's New York City laboratory under strict AHERA protocol. TEM with Energy Dispersive X-ray analysis (EDX) involves subjecting the prepared filter media to a stream of electrons. The returning diffraction pattern is a signature for the elemental composition of the material. This allows for precise asbestos quantification.

Silica A suspension of the sample particulate in tetrahydrofuran (THF) is created by dissolving the sample filter in THE and then sonicating. The sample particulate is then deposited onto a silver membrane filter and analyzed by X-ray diffraction giving a series of diffraction peaks (lines) occurring at different angles relative to the sample and X-ray source. These specific peaks are indicative of elemental silica and can be quantified.

Quality Assurance 40 Analysis was performed by personnel who have completed the NIOSH 582 Sampling and Evaluating Airborne Asbestos Dust course or an equivalent course.

Personnel also participate in the NIOSH/AIHA (American Industrial Hygiene Association) Proficiency Analytical Testing (PAT) Program to ensure consistency in methodology. All laboratory technicians involved in air sample analysis have received applicable EPA training.

Air Sample Results

Final air clearance samples reported concentrations of airborne fibers less than the concentrations required by the USEPA for this project.

The clearance air sampling criteria for each of the following analytes were achieved in accordance with project specifications.

• Asbestos in air, 0.0009 f/cc PCMe • Fibrous glass in air, <0.01 f/cc • Crystalline silica in air, 0.5 µg/m3 • Mercury, between 1 and 2 mg/m2

ATC Project No. 15.22906.0002 Page 6

NYC-WTC 000129383