NYC-WTC_000202081

NYC 9/11 Public Portal Document

(SftTC 104 East 25th St New York, New York 1Q010 www.atc-enviro.com 212.353.8280 Fax 212.353.8306 ASSOCIATES INC.

February 19, 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 P. S. 89M ATC Project No. 15-19125-0297

Dear Mr. Orlan:

ATC Associates, Inc. (ATC) is pleased to provide this letter report of air sampling for silica- containing dust conducted on January 31, 2002 at the referenced school. The New York City Board of Education (BOE) requested this sampling at the recommendation of Environ Corp., the consultant to the parents association.

ATC collected ten (10) samples 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. All samples were collected indoors. The samples were sent to PSC Analytical Services, Inc., an American Industrial Hygiene Association accredited laboratory in Reading, PA. One blank filter was also submitted. Silica 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 two samples. These were Sample #S1-ATC- 0131-89M collected in the 1“ floor hallway-north and Sample #S6-ATC-013I-89M collected in Room 326-north. The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for silica-containing 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-i-2

The floor hallway sample contained 0.0137 milligrams of silica per cubic meter of air (mg/mQ. The amount of quartz in this sample was 28%, therefore the PEL for this dust would be:

lOmg/m^ 0.333 mg/m^ 28+2

The silica concentration in this sample was 4.1% of the calculated PEL.

CITY_21MC100_005390064

NYC-WTC_000202081