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Figure 12 shows these calculations for a solid waste containing soluble arsenic. The water <br /> quality goal has been chosen to be equal to the Primary MCL of 0 05 mg/l and the site- <br /> specific environmental attenuation factor has been determined to be equal to "n". The <br /> concentration of arsenic in the "initial leachate" that has the potential to degrade ground <br /> water quality is calculated from equation [2], to be (0.05 x n) mg/l of leachate. The <br /> concentration of soluble arsenic in the waste that has the potential to degrade water quality <br /> is calculated from equation [31 to be(0 05 x n) mg/kg of waste. The Soluble Designated <br /> Level for arsenic in the solid waste at this site is calculated, from equation [4], to be(0.05 x <br /> n -t- 10) mg/1 of extract from the WET or (0.005 x n) mg/l. A solid waste for which the <br /> concentration of arsenic in the WET extract exceeds (0.005 x n) mg/1 would be classified as <br /> a 'designated waste' and the landfill or waste pile would be required to provide Class H <br /> containment under Subchapter 15. <br /> Leachability Factors and Total Designated Levels <br /> If extractable concentrations of a solid waste cannot be determined for particular <br /> constituents, such as volatile organics, analyses for total constituent concentrations are <br /> usually possible. Under these circumstances,Total Designated Levels must be calculated <br /> for comparison with total constituent concentrations in the waste,using available <br /> information on the leachability of the constituents under worst-case conditions at the site of <br /> waste discharge. As shown in Figure 13,only a certain fraction of the total constituent - <br /> "` concentration is available for leaching from the waste and for uptake by organisms upon <br /> which the constituent would have a toxic or deleterious effect. The remainder of the <br /> constituent concentration is immobile or unavailable for leaching due to such factors as <br /> encapsulation in the waste matrix,chemical bonding,or other molecular interactions <br /> within the waste. Information on the fraction of leachable constituent under reasonable <br /> worst-case conditions at the proposed site of discharge may be used to derive a <br /> --"leachability factor":The-leachabchty factor is equal=to the total-constituent-concentration- <br /> (leachable plus non-leachable) divided by the leachable constituent concentration,in other <br /> words, the reciprocal of the fraction of the constituent concentration that is leachable. <br /> ' Leachability Factor = Total Constituent Concentration <br /> Leachable Constituent Concentration <br /> 1 / (Leachable Constituent Fraction) (5] <br /> For example,if it is known that for a particular constituent in a waste,reasonable worst- <br /> case <br /> orstcase conditions at the proposed-site-of-discharge are-able to mobilize one tenth-(1/10)of the - <br /> total concentration of the constituent, the leachability factor would be equal to ten (10). <br /> Usually,when extractable concentrations of solid waste constituents cannot be determined, <br /> information on the leachable fraction is also unavailable. In these cases,the leachability <br /> factor must be approximated. The CAM SOR,in deriving TTLCs from STLCs.for <br /> "Persistent and bioaccumulative toxic substances",uses a leachability factor[called the <br /> "bioavailability factor" in that document] of 100 for toxic inorganic constituents and 10 for .� <br /> } toxic organic constituents. The reason for this difference is explained as follows: <br /> Designated Level Methodology Page 37 <br />