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composition of this gaseous mixture. However, limited studies of earlier land- fill operations indicate that under ideal conditions, each pound of refuse could, theoretically, generate up to seven cubic feet'of gas consisting mainly of methane (CH4) and carbon Dioxide (CO2) and lesser amounts of nitrogen, hydro- gen, argon, ammonia, hydrogen sulfide, and complex hydrogen gases. However, in real situations the total amount of gas generated could be as little as three to four cubic feet due to incomplete decomposition. The studies further indi- cate that on the average, three months after solid wastes were placed in fill, (CO2) accounted for approximately 88 percent and (CH4) five percent of the mix- ture. Whereas, four years later, the ratios shifted 51 percent for (CO2) and 48 percent for (CH4). The rate of gas production appears to range from 0.1 to 0.6 cubic feet per pound of refuse per year with a commonly used "rule of thumb" value of 0.16 cubic feet per pound per year. This could continue for up to 100 years. Figure 8 illustrates, in principle, decomposition gas production and composition as related to time. As decomposition gas is produced, it exits the landfill either upward through the landfill surface or it migrates horizontally or downward into the surrounding soils. It is anticipated that most gas produced at the proposed site would harmlessly enter the atmosphere through the surface. In order to qualify the significance of decomposition gas production, it should be noted that these gases have been produced for millions of years by natural decomposition processes. There also exists within our ecosystem natural, bio -chemical processes which recycle these gases to "purify" our atmosphere and maintain background concentrations at their present levels. These gases occur naturally within our atmosphere and become a hazard only when they are not allowed to disperse and are permitted to accumulate and concentrate to many times that of their natural background concentrations. For example, hydrogen sulfide gas (H2S), which can be extremely toxic at high concentrations of 600 to 900 parts per million (ppm), is reduced to no more than an odor nuisance (odor of rotten eggs) at .07 ppm. Based on monitoring data from other landfill operations, it is anticipated that atmospheric con- centrations of (H2S) would never exceed .006 ppm anywhere within the study area. Methane (CH4) is of particular concern since it can be explosive under certain conditions. There have been a number of cases where methane gas, escaping through surface cracks at a landfill site, has been ignited. There have also been cases of flash fires occurring in the basement of homes and various other subterranean structures adjacent to landfill sites. Natural gas, which has been used for cooking and heating for decades, is nearly pure methane gas. As unknown amount of dust may be produced at the proposed landfill site, but it is not anticipated to be a significant amount. Presently, the site is used for grazing cattle, and surrounding land uses are agricultural in nature as well. Consequently, to some degree, dust production is a problem common to all lands in the general area. If properly operated by periodically sprinkling as appropriate to control dust, the landfill should not generate dust signifi- cantly different from that created by the current use of the site. The potential for a nuisance odor problem is, again, dependent upon the operation of the landfill facility. If the daily soil cover is applied to J