NYC-WTC_000226997

NYC 9/11 Public Portal Document

104 East 25th St New York, New York 10010 www.atc-enviro.com 212.353.8280 Fax 212.353.8306 ASSOCIATES INC.

February 28, 2002

Mr. Bernard P. Orlan Director, Environmental Health and Safety New York City Board of Education 28.-11 Queens Plaza North Long Island City, NY 11101

Re: Air Sampling for Silica Stuyvesant High School ATC Project No. 15-19125-0246

Dear Mr. Orlan:

ATC Associates, Inc. (ATC) is pleased to provide this letter report of air sampling for silica- containing dust conducted on February 13, 2002 at the referenced school. The New York City Board of Education (BOE) requested this sampling at the recommendation of H. A. Bader, a consultant to the parents’ association.

ATC collected twelve (12) samples on each day for respirable dust using pre-weighed 37mm PVC filters connected to size-selective cyclones to remove the larger (non-respirable) particles prior to deposition on the filters. One (1) outdoor sample and eleven (11) indoor samples were collected per day. The samples, plus blanks, were sent to PSC Analytical Services, Inc., an American Industrial Hygiene Association accredited laboratory in Reading, PA. Analysis was performed by x-ray diffraction according to OSHA Method 142. Copies of the analytical reports' are attached.

Silica was found above the limits of detection in one sample. Sample SI, collected in the 1” floor lobby, contained 0.0135 milligrams of silica per cubic meter of air (mg/m’). The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) fof silica- A, containing dust is based on the percent of quartz (S1O2) found in the dust, the higher the percentage of quartz, the lower the PEL. The formula for calculating the PEL is found in 29 CFR 1910.1000, Table Z-3. The formula is:

lOmg/m^ %SiO2 + 2

Sample SI, collected in the 1“ floor lobby contained 0.0135 mg/m^ of silica. The amount of quartz in this sample was <22%, therefore the PEL for this dust would be:

lOmg/m^ 0.417 mg/m^ 22 + 2

The silica concentration in this sample was 3.2% of the calculated PEL.

CITY_21MC1OO_OO2897O29

NYC-WTC_000226997