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r r d. Breathing zone vapor concentrations that reach or exceed 50 ppm at the drilling area, as detected <br /> t{.. by the OVA, requires site activities to be stopped until concentrations decrease. Site manager <br /> should continuously monitor site perimeter. <br /> e. If breathing zone vapor concentrations are detected at the site perimeter, the site manager shall <br /> monitor the perimeter at 30 minute intervals. <br /> f. If the vapor concentrations continue to reach or exceed a value of 10 ppm at the site perimeter for <br /> Lr 15 minutes, drilling activities shall be stopped. Appropriate regulatory agencies should be <br /> contacted (see contact sheet). Site manager shall continue to monitor conditions until levels are <br /> rreduced to background conditions. <br /> L <br /> TABLE 5-1 <br /> L Benzene Exposure Limits <br /> C Compound OSHA-PEL TLV-TWA TLV-STEL ppm REL ppm Odor threshold Odor Characteristic Maximum Soil <br /> ppm ppm values,ppm Concentration to date, <br /> ppm <br /> Benzene 1 10 5 0.1 4.65 aromatic,sweet NA <br /> (Ca) <br /> Toluene 100 100 150 100# 1.74 sweet,pungent NA <br /> Xylene 100 100 150 100# 0.27 aromatic,sweet NA <br /> i� <br /> PEL OSHA Permissible Exposure Limit <br /> TLV -ACGII3 Threshold Limit Values. <br /> TWA Time Weighted Average. <br /> STEL Short Term Exposure Limit. <br /> REL NIOSH Recommended Exposure Limit. <br /> Ca Suspected carcinogen,1988-89 ACGIH TLV, <br /> # -60 minute ceiling,10 hour TWA,200 ppm 10 minute ceiling. <br /> L <br /> Lo <br /> L <br /> L <br /> Li <br /> LI <br /> Li I <br /> L, <br />