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SECTION 2 HAZARD ASSESSMENT The hazard classifications expected to be encountered during the referenced tasks include physicochemical, chemical, physical, and biological hazards. Most of the hazards found on site emanate from the UST and associated contents. However, project location, site operations, and climatic conditions contribute to the overall hazard assessment. '2.1 PHYSICOCHEMICAL HAZARDS In gasoline UST removal activities, flammability and explosion hazards are of paramount concern. Vapors from stored products are likely to remain in the tank at high concentrations even after the contents and residues have been removed. Furthermore, vapors may be present in the excavation and the work area at concentrations sufficient to support combustion. Therefore, precautions will be taken to eliminate build-up of combustible vapors by properly purging or inerting tanks and venting displaced vapors. During these operations, all potential sources of ignition will be removed from the area. Frequent monitoring with a combustible gas indicator (CGI) is required. Additional explosion potential is present during drilling operations near buried natural gas lines. Due to lower vapor pressures and higher flashpoints, diesel fuel and heating oils do not present the extreme explosion hazard as that of gasoline. However, vapors from these fuels can accumulate in confined or low-lying spaces and, in the presence of an ignition source, cause an explosion. Table I presents the chemical properties of the components and/or products of concern. 2.2 CHEMICAL HAZARDS Although petroleum products are blends of numerous hydrocarbon compounds, most present relatively minor health hazard during UST related activities. However, benzene, toluene, ethyl benzene, and xylenes are regular constituents of gasoline, and do present the potential for ill health affects. Routes of exposure include inhalation, ingestion, and absorption through the skin and eyes When high concentrations of these chemicals are inhaled, symptoms of intoxication may result. These symptoms, ranging from simple dizziness to excitement or unconsciousness, are similar to those produced by alcohol or anesthetic gases. If such effects occur, the Individual should be removed to fresh air. Benzene and tetraethyl lead, an additional fuel additive, require special toxicity considerations and are discussed below. Benzene is a known animal carcinogen and human leukemogen, as well as a suspected human carcinogen. The present exposure limit for benzene is 1 ppm as set by the Occupational Safety and Health Administration (OSHA) with a Short Term Exposure Limit (STEL) of 5 ppm SEACOR has developed a special protocol for monitoring and responding to situations involving benzene (see Section 4 3 2) Rev 1/93 2.2 corp-h&sl blank ust h&s