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EXECUTIVE SUMMERY <br /> Bench-scale laboratory testing was performed on soil and water collected from the <br /> Diamond Walnut Growers site in Stockton, California Four soils (SB-10-1, SB-10-2, <br /> SB-10-3 and SB-11) and 2 waters (MW-3 and site tap water) were received for testing <br /> MW-3 water contained approximately 4 2 mg/L of hexavalent chromium [Cr(VI)], while <br /> the soils contained 0 006 mg/kg or less of Cr(VI) Bench testing evaluated the <br />' effectiveness of two potential reducing agents—ferrous iron solution and calcium <br /> polysulfide (Cascade°)—to chemically reduce Cr(VI) to trivalent chromium [Cr(IH)] <br /> Tests were conducted in the presence and absence of soil to assess the potential for in situ <br />' remediation <br /> Laboratory testing demonstrated that both Fe(II) and Cascade° could decrease the <br />' concentration of Cr(VI) in groundwater in the presence and absence of soil Soil <br /> decreased the efficiency of each treatment, but complete removal was still achieved with <br /> the higher dose of Fe(H) and could probably be achieved with Cascade° if a higher dose <br />' than used in this study were employed <br /> Treatment with Fe(II) solution affected more secondary water quality parameters than did <br />' treatment with Cascade° Specifically, Fe(II) affected pH, dissolve iron, dissolved <br /> manganese, sulfate, conductivity and TDS Cascade® affected manganese The <br /> magnitude of the changes may be different in the field than in the laboratory due to <br /> difference in soil to liquid ratio and other factors Neither treatment affected ammonia, <br /> nitrate, arsenic, copper or zinc, and neither generated methane <br />' The amount of acid needed to decrease the pH of site tap water to pH 3 (in order to <br /> prepare Fe(II) solution) is about 300 mL 98% H,,SO4/1000 gallons of water <br />' Site soil can neutralize about 100 mmoles H'/kg soil and about 10 mmoles OH-/kg soil <br /> Acid must eventually be neutralized if Fe(H) is used, while base must eventually be <br /> neutralized if Cascade® is used <br /> 1 <br /> i <br /> PRIMA Environmental i Eval of Reductants <br /> January 19 2005 ATC-Diamond Walnut <br /> i <br />