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also pose a fire and explosion hazard from gases and vapors trapped beneath the ground surface. Soil samples will be collected with the backhoe/excavation bucket or a pole drive sampler. At no time will personnel be allowed in the excavation. The most significant risk associated with petroleum fuels is exposure to aromatic compounds. Skin contact will be eliminated by use of clothing, eye wear, and gloves; and the inhalation hazard will be minimized using appropriate respiratory protective devices as determined by on-site air monitoring using a PID calibrated to the benzene molecule with isobutylene gas. The Safety Coordinator/Project Manager will establish an exclusion zone encompassing a conservative 50 foot radius from the work area. Limits of the exclusion zone may be modified based on field measurements taken during the course of investigative activities. Access within this zone will be limited to required personnel. Excavation equipment will be set up in the upwind direction, if possible, to reduce the exposure to any aromatic hydrocarbons. Current enforceable and recommended exposure limitations for potential site contaminants are presented in Table 1 . Also presented in Appendix I is additional hazard information on these compounds. Table 1 Hazard Exposure Guidelines Substances OSHA 1989-90 ACGIH PEL TLV ------------------------------------------------------------- Benzene 10 ppm (TWA) 10 ppm (TWA) 25 ppm (Ceiling) Toluene 100 ppm (TWA) 100 ppm (TWA) 150 ppm (STEL) 150 ppm (STEL) Ethylbenzene 100 ppm (TWA) 100 ppm (TWA) 125 ppm (STEL) 125 ppm (STEL) Xylene 100 ppm (TWA) 100 ppm (TWA) 150 ppm (STEL) 150 ppm (STEL) Gasoline 300 ppm (TWA) 300 ppm (TWA) 500 ppm (STEL) 500 ppm (STEL) * Possible contaminants that could be encountered as presently known.