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Water Quality Site Assessment -6- <br /> • D R' S November 1992 <br /> i. If the calculated degree of attenuation is available between the base of the <br /> contaminated soil and highest ground water, then the soil constituent <br /> does not threaten ground water quality. No further action is required for <br /> that constituent in that lithology,provided that the concentration does not <br /> present a risk to human health. <br /> ii. If the calculated degree of attenuation is not available between the base of <br /> the contaminated soil and highest ground water, then the soil constituent <br /> threatens ground water quality, and the soil must be remediated to the <br /> lowest level that is achievable, considering both technological and eco- <br /> nomic factors. <br /> iii. If the same contaminant is present both ground water and in overlying <br /> soils, contaminant breakthrough has occurred and no attenuative capacity <br /> is available for that constituent within overlying soils. <br /> 5. When the background ground water concentration is greater than the numerical <br /> water quality limit for a constituent, the assessment site soil leachate concentration is <br /> only compared to the background ground water concentration to determine both the <br /> threat to beneficial uses and the threat of degradation,following the steps in Section <br /> 4.b. above. <br /> To aid in understanding and applying this narrative discussion for determining back- <br /> ground, and conducting a water quality site assessment for ground water and soils, the <br /> following attachments have been included: <br /> Attachment A (Narrative) Environmental Leachate vs. WET Extract <br /> Attachment B (Flow Chart) Water Quality Site Assessment: Ground Water <br /> Attachment C (Flow Chart) Water Quality Site Assessment: Soil <br /> Attachment D (Narrative) Water Quality Site Assessment Methodology <br /> Attachment E (Table) Water Quality Site Assessment Table <br />