114 LIBERTY 2 OF 2

NYC 9/11 Public Portal Document

3. Sample collection methodologies shall be in accordance with Title 15, Chapter 1 of the Rules of the City of New York (RCNY) and AHERA regarding documentation and sample locations and the requirements set forth herein regarding the rates of flow, and required volumes to achieve the necessary analytical sensitivity.

4. Sampling equipment shall be placed at representative locations and away from obstruction. Sampling cassette must be placed on a tripod and not taped to existing surfaces. All air sampling equipment shall be pre- and post- calibrated to insure accurate air sampling volumes. 5. The Air Sampling Technician shall perform clearance air sampling after the areas are free of dust accumulations as determined by the Project Monitor. All surfaces must be completely dry prior to the start of sampling. Clearance air sampling shall be performed at each apartment, commercial space, and the basement. Five samples shall be collected in each apartment, commercial space, and basement and two samples shall be collected at the first floor lobby. The elevator shaft shall be cleared separately. Clearance air monitoring shall be performed after the completion of all clean up activities at the work site. Clearance air sampling shall be aggressive and performed in accordance with Title 15, Chapter 1 of the RCNY Section 1-43 (a)-(d).

6. Clearance air samples shall be collected in accordance with the procedures specified in the NIOSH 7400 Method. The flow rate for collection of air samples shall be at least 10 liters per minute and no more than 15 liters per minute. Air sampling cassettes must be monitored to ensure the filters do not develop dark spots that would indicate clogging. The minimum sampling volume is 3600 liters. If clogging develops, the cassette must be changed.

7. All clearance air samples and completed chain of custody forms must be transported to the laboratory immediately after sampling is completed.

Clearance Criteria

1. The following clearance levels have been established by the USEPA for clean up activities resulting from the collapse of the WTC.

Table 2: Clearance Criteria Parameter Clearance Level Note Asbestos in air Oj fi'cc PCMe Primary clearance level Lead in settled dust <25 pg/tf Primary clearance level Dioxin in settled dust <4ng/m^ ~ Primary clearance level Fibrous glass in air <0.01 free Secondary clearance level Crystalline silica in air Ipg/m^ Secondary clearance level PAHs in settled dust <0.3 mg/n7 Primary clearance level

2. Cleaning shall not be considered complete unless the primary clearance levels are achieved (see Table 2). The apartment will be re-cleaned and retested if the primary clearance levels are not achieved. These clearance levels may be re-evaluated and revised if determined necessary based on field conditions and ’analytical limitations. ^Secondary clearance levels shall be considered in determining the need for additional cleanup, however failure to meet the secondary clearance levels does not automatically trigger the re-cleaning. In the event re-cleaning is required, re-sampling shall be performed immediately upon completion of the cleaning.

5 of? 2/7/03

NYC-WTC_000155427