Preliminary scope of work document for cleaning 114 Liberty Street,

NYC 9/11 Public Portal Document

December 17,2002 114 LIBERTY STREET REMOVAL OF DUST, DEBRIS. AND CONTAMINATED MATERIALS

9. The Contractor shall isolate the Work Area for the duration of the work by completely and individually sealing off all openings, windows, skylights, etc. with two (2) layers of polyethylene sheeting.

10. The clean side of these barriers shall be monitored by Ambient Group, Inc. If at anytime airborne concentrations for any of the target metals exceed their respective exposure limits and/or airborne fiber concentrations are equal to or exceed 0.01 fibers/cc, the Contractor shall halt all operations and shall be required to completely clean all areas as directed by the Owner.

11. The contractor shall completely cover the floor of the Work Area with two (2) layers of reinforced polyethylene sheeting.

12. All polyethylene sheeting shall be securely attached to walls, floors, etc. with quality "duct tape", glue, and/or mechanical support.

13. The Contractor shall install a sufRcient number of negative air filtration units in the Work Area, as well as window mounted HEPA filtered manifold systems for make-up air, to provide both a minimum of four (4) air changes per hour and 0.02” wc negative pressure.

14. The removal operations will not begin until the Work Area has been inspected and approved by Ambient Group, Inc. A minimum differential pressure between the Work Area and adjacent occupied spaces shall be negative 0.02 inches water gauge. The contractor shall install a manometer by the personal decontamination chamber in order to verify and monitor the pressure differential.

END OF SECTION 07

34 © AMBIENT GROUP. INC. - 2002

TEMPORARY ENCLOSURES AND WORK AREA PREPARATION

NYC-WTC_000155562