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i Fire, Electrical and Noise Hazards: * Underground gas and product lines, and * excessive machinery noise. Due to the nature of drilling or excavating, there is a risk for electrical shock from overhead and underground electrical lines. There is also a risk of physical injury from moving machinery and heavy drilling or excavating equipment. 4. DISCUSSION OF POTENTIAL CHEMICAL HAZARDS The Material Safety Data Sheets (MSDS) for compounds that are potentially present on site are included in Appendix A. 4. 1 Hydrocarbon Vapors Hydrocarbon vapors expected to be encountered consist of gasoline or gasoline constituents, however the levels of these vapors are expected to be at levels which should cause no deleterious effects. Exposure to elevated levels of hydrocarbon vapors presents potential health risks that need to be properly controlled. Hydrocarbon vapors will be measured using a calibrated "MiniRAE Portable Pid. Work practices and methods will be instituted to limit exposures. Where elevated exposures persists, respiratory protection will be the primary control method to protect personnel from inhalation of hydrocarbon vapors. The hydrocarbon vapors expected to be encountered during project activities are composed of a variety of volatile refined petroleum compounds. The majority of these have limited toxicity requiring minimal controls at the concentrations expected. Petroleum fuel and solvents consist of hundreds of chemical compounds. There are certain compounds such as Benzene that present significant hazards and must be properly controlled. To do so, a working limit of 100 ppm total hydrocarbon is proposed as the maximum acceptable level of exposure without respiratory protection. In a typical situation with 1% of the hydrocarbon vapors being benzene, a 100 ppmv concentration of total hydrocarbon will result in a breathing zone of less than 1 ppmv benzene. This level is one tenth of the current occupational Permissible Exposure Limit (PEL) for an 8 hour exposure to benzene. 4.2 Action Levels of Hydrocarbon Components in Petroleum Fuel Hydrocarbons >100ppm PEL LEL >10% If hydrocarbon vapors are indicated an evaluation of the levels will be made and work will continue or not based on this evaluation. If hydrocarbon vapors exceed 1000 ppmv or 10 ppm benzene, work will be stopped. The field crew will be instructed 4