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ii <br /> CONESTOGA=ROVERS Mr. Michael Infuma <br /> & ASSOCIATES November 26, 2008 - <br /> The background levels for all organic chemicals are assumed to be less than the typical analytical <br /> reporting limit. The COC are total petroleum hydrocarbons as gasoline (TPHg), benzene, <br /> toluene, ethylbenzene, and xylenes (BTEX), methyl tertiary butyl ether (MTBE), and TBA. The <br /> current maximum concentrations of TPHg, BTEX, MTBE, and TBA exceed the water quality <br /> objectives. CRA proposes that the groundwater cleanup goals equal the established water quality <br /> objectives. <br /> Table A <br /> Constituent Background Water Reference Historical Current <br /> of Concern Level Quality for Maximum Maximum <br /> (pg/L) Objectives Objective Detected Concentration <br /> (pg/L) Concentration (pg/L) <br /> (pg/L) <br /> TPHg <50.0 50 Reporting 900,000 75,000 <br /> Limit <br /> Benzene <0.5 1 CCR 22 MCLS 23,000 51200 <br /> Toluene <0.5 150 CCR 22 MCLS 28,000 4,400 <br /> Ethylbenzene <0.5 300 CCR 22 MCLS 3500 2,000 <br /> Xylenes <0.5 1750 CCR 22 MCLS 19,000 124000 <br /> MTBE <0.5 13 CCR 22 MCLS 590,000 6,400 <br /> TBA <5.0 5 Reporting 30,000 13,000 <br /> Limit <br /> Significant reductions in groundwater concentrations of COCs can be attained by various <br /> remedial alternatives. However, attainment of the approved clean-up levels may not be <br /> technically or economically feasible. Actual clean-up levels may be restricted by these <br /> limitations. <br /> Remediation Objectives <br /> The objective of active remediation will be to reduce hydrocarbon concentrations within the <br /> source area by one to two orders of magnitude. To meet this objective, CRA recommends <br /> 240783 3 <br /> NEWEEMENNO <br /> Worldwide Engineering, Environmental. Construction, and IT Services <br />