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6.0 SUMMARY OF OBSERVATIONS EMCON reviewed and evaluated the screening -level data obtained from ambient air samples, integrated surface walk samples, gas probe sam- ples, and landfill gas well samples collected February 23 through 26, 1988. The objective of this evaluation was to (1) characterize the gas stream within the landfill, (2) determine whether the specified VOC contaminants were present in ambient air at the site boundaries, and (3) determine whether subsurface gas is migrating off site. The data obtained during this ASWAT study are intended to be used only for screening. EMCON has assumed steady-state conditions prevailed at the site during sampling (i.e., no unusual dumping or landfill activities occurred) and the integrated surface walk area is representative of the entire active landfill area. Summaries of salient observations follow. Appendix J contains summary reports for the regulatory agencies. 6.1 LANDFILL GAS CHARACTERISTICS The major gas components detected in the gas wells were methane and carbon dioxide, which are refuse decomposition by-products. Methane concentrations were 63 to 76 percent by volume, and carbon dioxide concentrations were 24 to 31 percent. Vinyl chloride, benzene, 1,2-dichloroethane, methylene chloride, tetrachloroethylene, 1,1,1 -trichloroethane, trichloroethylene, and chloroform were detected in one or more gas wells. The results of the integrated surface walks indicated total organics measured as methane were detected at 3 ppm in the active landfill area on the west side of the landfill site, and at 23 ppm in the active landfill area near the evaporation pond on the northwest side. Benzene and 1,1,1 -trichloroethane were detected in both surface walk samples. The concentrations were below their respective regulatory detection limits. PJ9 9390405.00D 6-1 Rev. 0 09/07/88 Emon Associates