NYC-WTC_000219925

NYC 9/11 Public Portal Document 1 Search -1 Result - APPENDIX A TO SUBPART E - INTERIM TRANSMISSION EL... Page 37 of 38

C. Interpretation of Results

1. The response action shall be considered complete if either:

a. Each sample collected inside the abatement area consist of at least 11,199 L of air for a 25 mm filter, or 2,799 L of air for a 37 mm filter, and the arithmetic mean of their asbestos structure concentrations per square millimeter of filter is less than or equal to 70 s/mm <2>; Or

b. The three blank samples have an arithmetic meean of thee asbestos structure concentration on the blank filters that is leess than or equal to 70 s/mm (2) and the average airborne asbestos concentration measured inside the abatement area is not statistically higher than the average airborne asbestos concentration measured outside the abatement area as determined by the Z-test. The Z-test is carried out by calculating

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where Y[l] is the average of the natural logarithms of the inside samples and Y[O] is the average of the natural logarithms of the outside samples N[l] is the number of inside samples and N[o] is the number of outside samples. The response action is considered complete if Z is less than or equal to 1.65.

NOTE; When no fibers are counted, the calculated detection limit for that analysis is inserted for the concentration.

2. If the abatement site does not satisfy eeither (1) or (2) of this Section C, the site must be recleaned and a new set of samples collected.

D. Sequence for Analyzing Samples

It is possible to determine completion of the response action without analyzing ail samples. Also, at any point in the process, a decision may be made to terminate the analysis of existing samples, reclean the abatement site, and collect a new set of samples. The following sequence is outlined to minimize the number of analyses needed to reach a decision.

1. Analyze the inside samples.

2. If at least 1,199 L of air for a 25 mm filter or 2,799 L of air for a 37 mm filter is collected for each inside sample and the arithmetic mean concentration of structures per square millimeter of filter is less than or equal to 70 s/mm<2>, the response action is complete and no further analysis is needed.

3. If less than 1,199 L of air for a 25 mm filter or 2,799 L of air for a 37 mm filter is collected for any of the inside samples, or the arithmetic mean concentration of structures per square millimeter of filter is greater than 70 s/mm<2>, analyze the three blanks.

4. If the arithmetic mean concentration of structures per square millimeter on the blank filters is greater than 70 s/mm<2>, terminate the analysis, identify and correct the source of blank contamination, and collect a new set of samples.

5. If the arithmetic mean concentration of structures per square millimeter on the blank filters is less than or equal to 70 s/mm<2>, analyze the outside samples and perform the Z- test.

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