Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

General Procedures for Cleaning WTC-Related Contaminants from Ventilation Systems at 110 Liberty Street, New York, New York

1.0 SCOPE

The procedures contained in this document provide guidance for cleaning WTC-related dust in two commercial ventilation systems and in a combustion air make-up riser for the residential units within the building located at 110 Liberty Street, New York, New York, and for post-cleaning verification sampling. This document includes performance requirements and post-cleaning verification sampling for cleaning WTC-related dust and debris from ventilation systems consisting of fans, housings, ducts, air control devices, grilles and other components.

2.0 PURPOSE

The purpose of this document is to provide minimum requirements for cleaning ventilation system components that were impacted by airborne dust from the WTC collapse, and to provide procedures for post-cleaning verification sampling following clean-up.

WTC-related dust is generally considered to have common, consistent, and readily observable characteristics visually and tactilely differentiating it from common dust. WTC-related dust generally contains extremely fine particles similar in consistency to talcum powder, is light-colored, contains pulverized concrete and/or gypsum wallboard, and may contain asbestos fibers. Unless otherwise indicated by sampling and analytical testing, the following components shall be assumed to be present in WTC-related dust:

• Man-made Vitreous Fibers • Crystalline Silica • Lead • Asbestos

For this project, all specified ventilation system components shall be assumed to contain WTC-related dust and shall be cleaned accordingly.

Where sampling and analysis indicate that dust and debris in ventilation systems contain only crystalline silica, man-made vitreous fibers, lead, or <1% asbestos contamination, this procedure specifies that duct systems shall be cleaned only while maintained under negative pressure using HEPA-filtered vacuum collection equipment specific to the duct cleaning industiy. All cleaning of air handling equipment shall be performed within containment structures that are maintained under negative pressure using HEPA- filtered air filtration devices.

Where sampling and analysis indicate that dust and debris within a ventilation system contains 1% or greater asbestos as determined by standard sampling and analytical techniques, the ventilation system cleaning procedure shall be designed by a New York-licensed Project Designer. The cleaning will be performed in accordance with local, state and federal regulations as specified in the Project Design.

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