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Project No.034-98081 Page No. 9 4.0 HYDROCARBON VAPOR HAZARD CRITERIA Exposure to elevated levels of hydrocarbon vapors presents potentiai health risks that must be addressed. Work practices and methods will be used to limit exposures. Where elevated exposures persist, respiratory protection will be used to protect personnel from inhalation of hydrocarbon vapors. The hydrocarbon vapors expected to be encountered during the field portion of this investigation are composed 40. of a variety of volatile refined petroleum constituents. Most of these chemicals have limited toxicity thus ` requiring minimal controls at the concentrations that are anticipated to be encountered.. There are certain components, such as benzene vapors, that present significant toxicological hazards and must be properly * controlled. Water, soil, and vapor samples collected near the point of release commonly contain benzene at 1%of the total hydrocarbon constituents. Criteria for the use of respiratory protection is based on limiting potential exposures to benzene. s... A limit of 100 ppmv total hydrocarbon is proposed as the maximum acceptable hydrocarbon level of exposure without respiratory protection. An H-nu® photoionization detector (FID) will be used to measure total hydrocarbon levels of the sample. When levels of the sample are above 50 ppm, breathing zone concentrations will be monitored and documented every 15 minutes. When a persistent level of 50 ppmv is noted to exist at the breathing zone, an appropriate respirator will be donned by that field team member. in a typical situation,with 1%of the hydrocarbon vapors being benzene, a 50 ppmv concentration [•• of total hydrocarbon would result in a breathing zone level of 0.5 ppmv benzene. This level is one half of the current Permissible Exposure Limit(PEL) of 1 ppm for an 8-hour occupational exposure to benzene. When possible,to assure benzene exposures are below a 1 ppmv limit,Drager®benzene detector tubes will be used if PID measurements of the breathing zone concentrations indicated persistent *.. hydrocarbon levels above 50 ppmv. These detector tubes are not compound specific and may respond to other less hazardous petroleum hydrocarbons such as toluene,xylene and ethylbenzene. In the event that benzene detector tube measurements indicate that levels exceed 0.5 ppmv in the breathing zone; respirators will be required. This is considered a conservative approach since the Drager®detector tubes may respond to several hydrocarbons other than benzene. Table I summarizes the various hydrocarbon vapor concentration and appropriate responses to i6w prevent exposure to these potential vapor hazards. KRAZAN & ASSOCIATES,INC. Offices Serving the Western United States