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7.1.2 Air Abatement Technology Evaluation <br />' EMCON Associates has identified several alternatives for abating the <br /> petroleum hydrocarbon-impacted soil vapors. These alternatives include <br /> adsorption onto granular activated carbon (GAC), combustion in an internal <br />' combustion (IC) engine, thermal oxidation, and catalytic oxidation. <br /> A preliminary evaluation of these technologies has indicated that each one <br /> is technically feasible for abating the petroleum hydrocarbon-impacted soil <br /> vapors at this site. Additionally, EMCON Associates believes that each is <br /> capable of meeting the previously described performance criteria. <br />' Therefore, EMCON Associates' recommendation of an air abatement <br /> technology is based on cost and implementability of each technology. <br /> Because of high estimated capital costs, EMCON Associates has eliminated <br />' combustion in an 1C engine, thermal oxidation, and catalytic oxidation. <br /> Based on the SVET results and preliminary cost estimates, EMCON <br /> Associates believes that a SVE system with GAC abatement will effectively <br />' and efficiently remediate the residual petroleum hydrocarbons in the <br /> extracted soil vapors. <br /> 1 7.2 Ground-water Remediation Alternatives <br /> Ground-water remediation alternatives considered for this site included <br /> G in situ enhanced biodegradation <br /> C extraction and treatment with discharge to the sanitary <br />' sewer, storm sewer, or a reinjection system <br /> 4 physical containment with extraction and treatment <br />' G vapor extraction <br />' Given the relatively low magnitude and extent of ground-water impact and <br /> technical complexity and costs to implement the first three alternatives, <br /> vapor extraction is recommended. <br />' Specifically, this recommendation is based on the fact that (1) the dissolved <br /> plume has had at least 5 years to migrate off site and has not, (2) the <br /> ground-water gradient is very low (0.003 foot per foot), (3) the SVE system <br />' will be drawing vapors from a depth of 80 feet (within 5 to 7 feet of the <br /> ground-water table) over a radius of potentially up to 60 feet, and (4) the <br /> capital costs for installing a pump and treat system are high. <br /> EMCON Associates recommends continuing ground-water monitoring on a <br /> quarterly basis. If there are significant increases in the concentrations of <br /> dissolved petroleum hydrocarbons in wells MW-10, MW-11 , or MW-13, or <br /> if dissolved petroleum hydrocarbons are detected in well MW-12, EMCON <br /> pjo\Of9O\Of9OOO2O.1 ag 7 - 3 Rev. 0 December 15, 1992 <br />