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Beacon Cardiock Station Number 610 SSB 92-1001-01 3300 Waterloo Road Stockton, California Page 10 4.0 HYDROCARBON VAPOR HAZARD CRITERIA Exposure to elevated levels of �P hydrocarbon vapors presents potential 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 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. A limit of 100 ppmv total hydrocarbon is proposed as the maximum acceptable hydrocarbon level of P exposure without respiratory protection A photoionization detector (PID)will be used to measure real- time breathing zone concentrations for comparison with the 100 ppmv limit. When a persistent level of 100 ppmv is noted to exist, an appropriate respirator will be donned by that field team member. In ' a typical situation,with 1% of the hydrocarbon vapors being benzene, a 100 ppmv concentration of total hydrocarbon would result in a breathing zoite level of less than 1 ppmv benzene This level is one tenth ' of the current Permissible Exposure Limit (PEL) for an 8-hour occupational exposure to benzene tTo assure benzene exposures are below a 1 ppmv limit, Sensidyne benzene detector tubes will be used if PID measurements indicated persistent hydrocarbon levels above 30 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 1 ppmv, respirators will be required If benzene concentrations exceed 10 ppmv, work will cease The field crew will be instructed to say ' upwind of the borehole until the concentrations subside This is considered a conservative approach since the Sensidyne detector tubes may respond to several hydrocarbons other than benzene Table 1 summarizes the various hydrocarbon vapor concentration and appropriate responses to prevent exposure to these potential vapor hazards SSB ENVIRONMENTAL CONSULTANTS, INC