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L <br />u <br />6.0 SUMMARY OF OBSERVATIONS <br />EMCON reviewed and evaluated the screening -level data obtained from <br />ambient air samples, integrated surface walk samples, gas probe, <br />samples and landfill gas well samples collected on February 16, 17, <br />and 18, March 2 and 3, April 7, and May 25, 1988. The objective of <br />this evaluation was to (1) characterize the gas stream within the <br />landfill, (2) determine whether specified VOC contaminants are present <br />in ambient air at the site boundaries, and (3) whether subsurface gas <br />is migrating off site. The data obtained during this ASWAT study are <br />intended to be used only for screening. <br />EMCON has assumed steady-state conditions prevailed at the site during <br />sampling (i.e., no unusual dumping or landfill activities occurred), <br />and the integrated surface walk area is representative of the entire <br />active landfill area. Summaries of salient observations follow. <br />6.1 LANDFILL GAS CHARACTERISTICS <br />In areas of buried municipal refuse, the major gas components detected <br />in the gas wells were methane, nitrogen, and carbon dioxide. Methane <br />concentrations ranged from 6.6 to 40 percent by volume. Vinyl chlor- <br />ide, benzene, 1,2-dichloroethane, methylene chloride, tetrachloro- <br />ethylene, 1,1,1 -trichloroethane, trichloroethylene, and chloroform <br />were detected in one or more gas wells. <br />The results of the integrated surface walk indicate that total organ- <br />ics measured as methane were detected at 4.4 ppm. Benzene, methylene <br />chloride, tetrachloroethylene, and 1,1,1 -trichloroethane were detected <br />in the surface walk sample. Benzene and tetrachloroethylene <br />concentrations were at or below their respective regulatory detection <br />limits. <br />PJ9 9390304.00D 6-1 Rev. 0 09/20/88 <br />