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19. <br /> <br />20. <br /> <br />21. <br /> <br />22. <br /> <br />23. <br /> <br />24. <br /> <br />Detectable levels of VOCs at the water table are restricted to within approximately 800 <br />feet of the landfill boundaries. Total VOC concentrations detected at the water table <br />range from about 28 ug/l to near 1,000 ug/1 with the highest concentrations occurring in <br />wells east of the landfill (MW-8, MW-16A, MW-1AR). Aromatic and ether compounds <br />were only detected in the area east of the landfill at the water table, while the halogenated <br />compounds were present in all samples collected from water table wells in which VOCs <br />were detected. Ether compounds were present in significantly higher concentrations than <br />the aromatic compounds and were detected within a larger area than the aromatics. <br /> <br />The aromatic compounds are generally associated with petroleum products or paint <br />solvents. Aromatics are low molecular weight, highly volatile compounds that are <br />moderately soluble in water from an environmental chemistry definition. These <br />compounds also possess specific gravities less than a value of one which indicates the <br />compounds are less dense than water. <br /> <br />Ether compounds, such as ethyl ether and tetrahydrofuran, are normally associated with <br />industrial solvents, particularly solvents for PVC products. Tetrahydrofuran can also be <br />found in low levels in food packaging. Ether compounds are lighter than water <br />compounds and are highly volatile and extremely soluble in water (Remedial <br />Investigation). <br /> <br />Halogenated VOCs include chlorinated alkanes and alkenes and fluoroalkanes. <br />Chlorinated compounds are generally associated with industrial and household solvents. <br />Fluoroalkanes, more commonly known as freon, are associated with aerosol spray cans, <br />polyurethane foam and refrigerants. Halogenated compounds are more dense than water, <br />with the exception of chloroethane and vinyl chloride, and are highly to extremely <br />volatile. These compounds range in aqueous solubility's from slight to highly soluble <br />(Remedial Investigation). <br /> <br />Trace heavy metals have only been detected sporadically at downgradient well locations <br />nearest to the landfill. Concentrations have not been significantly greater than those <br />detected at ambient locations. Metals detected, with the exception of zinc, have had <br />concentrations less than 10 ug/l and, in most cases, concentrations have been nearer to the <br />detection limit of 1 ug/1. Zinc ranged in concentrations up to about 40 ug/1 at impacted <br />downgradient wells. However, upgradient concentrations for zinc were significantly <br />higher than those zinc concentrations detected downgradient. Metals do not appear to be <br />migrating from the landfill in the groundwater because of the neutral or slightly basic pH <br />conditions of the aquifer. The high bicarbonate content (alkalinity) of the neutral <br />groundwater buffers the acidic leachate generated at the landfill to keep the pH of the <br />groundwater near neutral, thereby immobilizing metals. <br /> <br />Limited inorganic water quality data are available for private wells. From the available <br />water quality data, it appears that the private wells sampled, whether bedrock, lower sand, <br />or unknown screened position, are free of any impact from landfill operations (Remedial <br />Investigation). <br /> <br />RESOLUTION #97-05-136 <br /> Page 4 of 6 <br /> <br /> <br />