2023-04-19_PERMIT FILE - C1981010 (97)

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A significant difference in concentration of barium was observed in the leachate from the ash compared to the ash -gypsum. This can be seen in Figure 4.3-11. The high concentrations of barium (10-90 mg/1) observed.in the ash leachate were con- siderably above the primary drinking water limit of 1 mg/1. The concentration of barium in the ash gypsum leachate was typically below the drinking -water limit of 1 mg/1. This significant reduction in barium concentra- tion due to the presence of calcium sulfate in the leachate may be due to the limited solubility of barium sulfate. Concentrations of aluminum (30-100 mg/1) in the ash leachate were slightly higher than those observed in the ash -gypsum leachate (5-20 mg/1). The high concentra- tions of aluminum were more likely the result of the high pH's. The leaching behavior of chromium and molybdenum for both the ash and ash -gypsum columns were comparatively equal. The concentrations of chromium and molybdenum were initially quite high (approximately 2-5 mg/1) then dropped off rapidly to levels which approximated or were below applicable water quality limits of 0.05 and 0.01 mg/1 for chromium and molybdenum, respectively. This leaching behavior is graphically presented in Figure 4.3-12. The concentration of vanadium leached from the ash -gypsum mixture was approxi- mately 0.3 mg/1, slightly above the irrigation limit of 0.1 mg/1. The concentra- tion of vanadium in the ash leachate was slightly lower than the limit (approxi- mately 0.02-0.1 mg/1) as shown in Figure 4.3-13. As expected, significant differences in sulfate concentration were observed between the two materials as shown in Figure 4.3-13. The concentration for sul- fate in the ash -gypsum mixture was equivalent to that predicted by the solubility of gypsum. The small quantities of sulfate present in the ash appear to be leached from the ash during the passage of the first aliquot of water. The con- 4-75 centration for sulfate in all the ash -gypsum leachates and in the first leachate from the ash column are significantly above the 250 mg/liter secondary drinking water limit. 4-75