NYC-WTC_000210694

NYC 9/11 Public Portal Document

Scope of Work

2.1 Air Sampling Procedures

ALC's licensed technician collected air samples using the TEM Methodology

The air samples were collected usmg high volume air samplmg pumps Once the pumps were in place the air sampling techmcian recorded the location, time, date, sample numbers, pump number. flow rate, start and stop times and his imtials

The air cassette was independent of the pump motor This is to prevent the vibrations of the motor from affecting the fibers m the cassette A separate stand or tnpod was used to hold the cassette in place The cassette was angled 45 degrees downward from the horizontal stand This is to insure that no asbestos will drop into the cassette while samplmg

Using a rotameter, we calibrated each pump to the required flow rate, notmg this rate on the sample record After calibranng the pumps, the end cap from the cassette was removed, the pump was turned on and run for the required amount of time

The samplmg pumps were checked periodically to ensure they were still operatmg, the cassettes were still m place, and no one has disturbed the equipment. If at any time the area being sampled was suspected of havmg high fiber counts, the filter inside the cassettes were examined for “overloading”, or an excessive amount of fibers and/or debns on the filter

When the pre-determined volume of air has been collected, the technician then calibrated the samplmg pump agam to determme the current flow rate This rate will often be different from the flow rate measured at the beginmng of the samplmg penod. That difference is usually due to the cloggmg of the filter, thereby addmg mcreased resistance to the flow of air

Once the pre-determined volume of air has been reached, the time was recorded as well as on the cassette. Before the pump was turned off, the cassette was angled upward and the cap replaced and the end plug. The cassettes were placed m sealed contamers, labeled with an identifying code and a sample log was kept. The samples were then submitted to the laboratory to be analyzed for asbestos content. A cham of custody record was prepared and accompamed the samples to the laboratory.

2.2 Asbestos Analysis and Methodology

Each air sample is cross-referenced by field designation and lab mtemal code to ensure proper, consistent handling through a cham of custody. Sample preparation takes place within a HEPA Filter clean bench to avoid any possible contamination. Air samplmg was conducted at a level approximatmg the breathmg zone of persons anticipated to be present in the area durmg normal operations. Samples collected represent the typical aubome fiber concentration of the area.

3. Findings and Conclusions

Thirty six (36) air samples were collected and analyzed via TEM Methodology. The results indicated that the areas achieved the acceptance cnteria below <70 structures per mm2 set by the above regulations

CITY_21MC1OO_OO2861954

NYC-WTC_000210695