Laserfiche WebLink
9000562C, Page 6 <br /> B.5.2 Air Monitoring <br /> B.5.2.1 Organic vapor/gas concentrations in the work area must be measured to <br /> determine whether or not respiratory protection, area evacuation, or other action is needed. <br /> Measurements shall be made with a Foxboro OVA (model 108 or 128) and taken near the <br /> borehole and whenever the borehole is open. <br /> B.5.2.2 If vapor/gas concentrations exceed an OVA reading of 100 ppm, <br /> measurements shall be taken again in the breathing zone of the person(s) working closest to <br /> the borehole (usually the drill rig operator and assistant). If the concentrations of <br /> vapors/gases in the breathing zone exceed 25 ppm total hydrocarbons, then half- or full- <br /> face respirators with organic vapor cartridges (color coded black) shall be donned by <br /> personnel working near the source of contamination. <br /> B.5.2.3 If vapor/gas concentrations in the breathing zone exceed an OVA reading of <br /> 100 ppm work shall be suspended. If work is suspended, the Site Safety Officer shall <br /> direct individuals in his charge to a safe point upwind of the bore hole, inform the Project <br /> Manager that work has been suspended, and return periodically to the bore hole to <br /> remeasure vapor/gas concentrations. If the vapor/gas concentrations fall to 100 ppm or <br /> less, work may be resumed. If necessary, the Health and Safety Officer may be contacted <br /> for advice. <br /> B.5.2.4 The Level C action level of 25 ppm and the evacuation level of 100 ppm are <br /> conservative. Given a protection factor of 10 for a half-face respirator, the concentration <br /> inside the mask would be 2.5 ppm (at 25 ppm detection). The relative response of the <br /> OVA to TCE and PCE ranges from 70% to 100%. Thus, the actual airborne concentration <br /> inside the mask at an OVA reading of 25 ppm could range from 2.5 to 3.5 ppm (based on <br /> relative responses of the OVA), which is significantly less than the PEL's for TCE and <br /> PCE. <br /> B.5.2.5 All air monitoring measurements are to be recorded on the air monitoring <br /> data sheet and included in the safety completion report. <br />