Agenda - Council - 10/14/1980 - Laserfiche WebLink

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II. MElHANE GAS HAZARD Landfilled refuse is subject to bacterial decomposition under anaerobic conditions in a complex biological process which produces gaseous end pro- ducts. Methane and carbon dioxide are the primary landfill gases, being pro- duced in approximately equal amounts; trace amounts of other gases are also 'produced. Carbon dioxide has negligible effects on human or animal life at the concentrations normally observed near landfills. ~t is conceivable that carbon dioxide and/or methane could accumulate in an enclosed space to exclude oxygen to the point that it would create a risk of as.phyxiation to persons entering the space. The maximum acceptable level of carbon dioxide as an asphyxiant is 5,000 ppm in air based on an 8-hour exposure (4D hours per week). Methane gas, when considered as an asphyxiate, has a maximum accept- able level of 1% by air volume (10,000 parts per million) based on an 8-hour exposure or 40-hour per week exposure. The maximum acceptable level of methane when considered as an explosive (in a confined area) is 20% (~0,000 ppm) of the lowest explosive limit (LEL) of the explosive gas in air. The LEL is approximately 5% methane in air. We know of no reports of illnesses due to the exposure to landfill gases among the many thousands of workers in and around landfill operat'ions. The greatest hazard to persons and property from landfill gases is posed by the possible accumulation of methane gas and the potential for fire and explosion to occur under certain conditions. This is essentially the same gas utilized throughout our county for cooking and heating in our homes and offices. The range of combustible concentrations of methane is app~roximately 5 to ]5 percent by volume in air. Since methane is usually present within the landfill at a concentration of approximately 50 percent, the gas almost always passes through the combustion range as it migrates away from the landfill and becomes diluted with air. This dilution normally occurs in the soil cover as the gas vents harmlessly into the atmosphere. Fortunately, a source of igni- tion is seldom present as the methane passes through the combustion range. 2