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Forward, Inc. -5- 23 April 1982 <br /> [The figures for single concentrations are used as upper limits <br /> for pesticides discharged at Class II-1 sites in the San Francisco <br /> Bay area (Harold Singer, Region 2) . Halogenated organic limit <br /> compares well with those obtained by applying specification <br /> I.E.6. , above. Organophosphate and carbamate limits are lower due <br /> to their higher relative acute toxicities . Cumulative limits <br /> reflect the possible additive or synergistic toxicities of chemi- <br /> cals within each group.] <br /> 8. Total nonhalogenated organic solvent concentrations shall not <br /> exceed 500 ppm. <br /> [Nonhalogenated organic solvents are generally less toxic and more <br /> readily degraded in the environment than halogenated organics. <br /> Some solvents cause clays to shrink and crack, thereby allowing <br /> breakthrough and bulk transport through liners. There is little <br /> data on which solvent chemicals, other than benzene, xylene, and <br /> carbon tetrachloride, cause clay liner breakdown and no data on <br /> which concentrations of solvents in wastes or water cause this <br /> problem. However, it is reasonable to assume that relatively <br /> dispersed or dilute organic solvents aould not pose a threat to <br /> the integrity of clay liners . Halogenated organic solvents such <br /> as carbon tetrachloride are covered more strictly in specification <br /> I.E.7 . , above.] <br /> 9. Acidic materials shall be pH 3 or higher, and caustic materials <br /> shall be pH 11 or lower. <br /> [Strong acids and caustics cause chemical degradation of clays by <br /> altering ionic balances. They can thereby increase the permeabil- <br /> ity of clay liners.] <br /> 10. Acidic and caustic materials shall be neutralized before disposal <br /> whenever practical . <br />