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October 16, 1995 UEC Document No.: R -1659510A UEC Job No.: 165040-9510C 3.1.2 Selection of Air Sample Collection Locations Area air pump locations are to be strategically positioned to determine if the abatement /excavation activities are unduly emitting unacceptable levels of airborne fibers into the atmosphere. Due to the fact that airborne fibers are carried and remain aloft as a consequence of air currents, it is reasonable to suppose that the atmosphere downwind of the excavation activities will have the greatest probability of being adversely impacted by the cleanup activities. Therefore, at least one area air sample collection pumps will be established downwind of each area of operation. It is understood that the prevailing wind in the southeast portion of Stockton, California blows from the west -northwest to the east -southeast. It can therefore be expected that the area air sample collection pumps will be set up to the east -southeast of the excavation and /or loading areas. Of course, conditions existing at the time of abatement will dictate the specific air sample collection pump locations. See Figure 1 for representative locations where area air sample collection points will be established. 3.1.3 Air Quality Analytical Data: Airborne Fiber Concentration Timeline The airborne fiber concentration timeline is a graphical tool which allows for the non -formal correlation between specific cleanup phases /activities and recorded airborne fiber concentrations. In order to establish the necessary analytical data, area air samples must be collected prior to, during, and upon completion of all cleanup activities. The air samples collected prior to the start of cleanup activities are referred to as "baseline" air samples. The baseline sample set is a measure of the airborne fiber concentration of the ambient air in the proximity of the site; the ambient airborne fiber concentrations, if greater than 0.01 fibers /cubic centimeter (f /cc), will establish the acceptable level of airborne fiber concentration during cleanup activities. By including the baseline air sample results as part of the airborne fiber concentration timeline, any variation in airborne fiber concentration during cleanup activities can be viewed in context of the ambient conditions as opposed to an arbitrary, possibly non -applicable airborne fiber concentration datum. UEC proposes to collect three (3) baseline air samples from the approximate locations identified in Figure 1. During cleanup activities, air samples will be collected from outside of the work area and plotted versus a linear time scale; cleanup activities occurring at the time of sample collection shall be included on the same chart. However, during cleanup activity, if the UEC CAC observes any increase in airborne fiber concentrations, the abatement /excavation crew will be advised to apply the engineering control deemed appropriate to attenuate the observed airborne fiber concentrations. It is expected that the UEC staff will have the air sample analytical results available within 24 hours from the time of collection, in order to give 7