Document fragment from DEP Box 53 regarding West Street

NYC 9/11 Public Portal Document

Eli ■ Hilimann Environmental Group, LLC

■ SECTION 3— SAMPLING PARAMETERS AND METHODOLOGY

■ 3.1 General. Hillmann's air and dust sampling had been conducted in response to the client's concerns over possible exposure to asbestos fibers by contractors and employees conducting cleanup and restoration work at the Hotel. As a result, air and dust samples were collected in a number of locations throughout the Hotel.

• The inspection and sampling was performed by trained industrial hygienists, using Environmental ■ Protection Agency (EPA) and National Institute for Occupational Safety and Health (NIOSH) sampling techniques. Sampling was conducted either by a Certified Industrial Hygienist, a New York City DEP ■ Certified Asbestos Investigator or a New York State Certified Asbestos Inspector. Samples were analyzed at an ELAP and NVLAP accredited laboratory.

3.2 Sampling and Analysis Parameters and Methodology. The following sampling parameters and analysis methodologies were used to determine airborne asbestos concentrations and asbestos content in dust/ debris samples. Hillmann selected the sampling parameters based on federal, state and local regulations, consultations with the client, the laboratories performing the analysis and our in-house experts. ■

I. Airborne Asbestos fiber concentrations were determined by drawing air through a 25 mm PCM or TEM cassette, for a minimum volume of 580 Liters. Samples were then analyzed by either Phase Contrast Microscopy (PCM) or Transmission Electron Microscopy (TEM). The analysis was conducted ■ by an appropriately accredited laboratory, in accordance with NIOSH Methods 582 and 7402. Hilmann technicians collecting samples were all New York State certified project monitors or air sampling technicians.

I A) Phase Contrast Microscopy — The air samples analyzed by PCM report the average number of fibers per cubic centimeter of air sampled. The fiber concentration established by New York City as acceptable for the re-occupancy of an area is 0.01 fibers per cubic centimeter (f/cc). Fibers are defined by NIOSH as any particle greater than 5 um in length with at least a 5:1 length to width aspect ratio. NIOSH believes that this is a reliable method for quantifying airborne levels of asbestos fibers. However, this method is not exclusively a measurement of U asbestos concentration. A number of other materials meet the criteria of a fiber and are also counted by this method without differentiation. To confidently characterize fibers as asbestos U structures, TEM, a more stringent analytical method is required.

B) Transmission Electron Microscopy — The air samples analyzed by TEM report the number of asbestos structures per cubic centimeter of air and square millimeter of filter media. This analysis is capable of determining both the concentration of asbestos structures and the type i of asbestos mineral identified in the sample. This is the most accurate method of analysis commonly available. The OSHA and New York City regulations have set the acceptable level of asbestos at any number less than 70 structures per millimeter of filter media.

U If an air sample analyzed by PCM was found to exceed the acceptable re-occupancy level, the same sample was subsequently analyzed by TEM to positively classify the fibers as asbestos. Using this combination of methods, Hillmann was able to determine whether acceptable air quality with respect to asbestos was being attained

Marriott World Financial Center/Project Number YI-3508 Page 3

NYC-WTC 000131158