NYC-WTC_000197670

NYC 9/11 Public Portal Document

104 East 25th Street

ASSOCIATES TC INC. New York, New York 10010 www.atc- envi ro .com 212.353.8280 Fax 212.353.8306

December 10, 2001

Mr. Bernard P. Orlan Director, Environmental Health and Safety 'i New York City Board of Education 28-11 Queens Plaza North Long 1 sland 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 November 15-16, 21 and 27, 2001, 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 a total of thirty-six (36) samples (12 per session) 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. Six (6) samples were collected on November 15^’ and six were collected on November 16*'’. Twelve samples were collected on November 20* and 27*. Four (4) outdoor samples and thirty-two (32) indoor samples were collected. The samples were sent to PSC Analytical Services, Inc., an American Industrial Hygiene Association accredited laboratory in Reading, PA. Four blank filters were also submitted. Analysis was performed by x-ray diffraction according to OSHA Method 142. A copy of the analytical report is attached.

Silica was found above the limits of detection in only one of the thirty-six samples. This was the sample (#ATC-1115-STY-S4) collected on November IS* in Room 635. This sample contained 0.023 milligrams of silica per cubic meter of air (mg/m’). The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for silica-containmg dust is based on the percent of quartz (SiO2) 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

The amount of quartz in Sample #ATC-1115-STY-S4 was 18%, therefore the PEL for this dust would be; 10m g/m^ 0.50 mg/m^ 18 + 2

The silica concentration in this sample was 0.023 mg/mg\ which is 4.6% of the calculated PEL.

CITY_21MC100_003046948

NYC-WTC_000197670