Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

Ventilation system components may be evaluated by the Environmental Cleaning Contractor for visible cleanliness via direct visual inspection or with a visual inspection system (i.e., mirrors, boroscope, remote camera). The Environmental Cleaning Contractor may direct the ventilation system/duct cleaning firm to provide additional access openings into the ventilation system, as deemed necessary to thoroughly verify cleanliness.

8.2.1 All porous and non-porous ventilation system surfaces must be visibly clean and capable of passing a visual inspection.

8.2.2 Cleaning of non-porous ventilation system surfaces shall be verified by surface wipe sampling performed by the Environmental Cleaning Contractor using specified methods. Surface wipe sampling for man-made vitreous fibers, crystalline silica, lead and asbestos will be performed. Wipe sample results must meet the following criteria to established that cleaning has been adequate; • Lead - less that 25 micrograms of lead per square foot using the specified method • Asbestos - no asbestos detected using the specified method

8.2.3 Pre-occupancy air testing: After successful completion of 8.2.1 and 8.2.2, and removal all polyethylene sheeting, containments and any remaining visible debris, the ventilation system shall be started up and air sampling for man-made vitreous fibers, crystalline silica, lead and asbestos will be performed performed by the Environmental Cleaning Contractor using specified methods. Airborne concentrations of these contaminants shall be within recommended guidelines for acceptable indoor air quality. Occupants may re­ enter the building only after successful completion of air monitoring.

8.3 Materials and Workmanship:

8.3.1 Work shall be executed by skilled persons who are thoroughly trained, experienced and completely familiar with the specified requirements and the methods needed for proper performance of the project, and shall be in conformance with the best practices of each trade involved.

8.3.2 Work shall present a neat and workmanlike appearance when completed.

8.3.3 Finish of materials and components shall be consistent with industry good practice.

8.4 Cleaning: Work and storage areas shall be maintained and kept clean on a daily basis. The ventilation system/duct cleaning firm shall final clean the immediate work area(s) with a HEPA- filtered vacuum cleaner to be free of any residual visible WTC-related dust. Materials removed and debris resulting from the ventilation system/duct cleaning firm's work shall become the property of the ventilation system/duct cleaning firm and shall be removed for appropriate disposal (see 7.6 of this document).

9.0 WORK SEQUENCE AND SCHEDULING

9.1 As a general procedure, cleaning work should follow the ventilation system airflow, beginning at the system's return air intakes. Cleaning should proceed from those points to the air handling unit (AHU), then out through the air discharge points. This work sequence will reduce the 8

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