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3.0 RESULTS AND DISCUSSION �I The results of the bench tests are discussed In the absence of soil, both Fe(II) and Cascade° decreased the concentration of Cr(VI) in groundwater to below the detection limit of 1 gg/L at the doses used in this study Both compounds decreased the Cr(VI) concentration in GW in the presence of soil, but the degree of removal was lower 3.1 Characterization of Soil and Groundwater The results of the preliminary characterization on homogenized, untreated soil and groundwater are shown in Tables 3 and 4 Based on the results of the characterization and upon consultation with ATC Associates, Soil SB-10-3 was chosen for bench-scale testing Table 3. Characterization of Untreated Site Soils. Analyte Units Sample ID SB-10-1 SB-10-2 S13-10-3 15-175 25-27 35-375 Hexavlaent chromium m kg 0 002 0 002 0 006 <0 001 0 002 0 006 Chromium Total mg/kg 45 65 60 25 46 44 Alkalinity m L CaCO3 1200 3 800 12 000 n a n a n a Metals Arsenic mgtkg 36 3 53 na na na Copper mg/kg 28 43 45 n a n a n a Iron,Total mg/kg 27,000 1 32 000 33 000 n a n a n a Manganese Total mg/kg 940 49Q 700 n a n a n a Zinc mg/kg 56 1 72 70 n a n a n a Niiro en Ammonia,total mg/kg N 086 <0 2 <0 2 n a n a n a Nitrate rn9,Lk9 N <25 <25 57 na na rta TQC %4 289 1 435 476 1 na na n a 3.2 Effect of Reducing Agents on Aqueous Cr(VI) Concentration The results of the batch tests to evaluate the effectiveness of each reducing agent and estimate the amount required to achieve Cr(VI) reduction are shown in Table 5 In the absence of soil, all treatments decreased the concentration of Cr(VI) to below the ' detection limit of 1 gg/L However, in the presence of soil, complete removal was only seen with the higher dose of iron (GWS High Fe)—the lower dose of iron (GWS Low Fe) still contained 700 gg/L Cr(VI), while the low and high doses of Cascade® contained 1500 and 120 gg/L of Cr(VI), respectively The concentration of Total Cr in the tests using only groundwater ranged from 2,300 to 5,700 gg/L Cr This indicates that although the Cr(VI) can be reduced, it did not precipitate or form large particles (samples were filtered through a 0 45 µire filter prior to preservation and analysis) PRIMA Environmental 7 Eva]of Reductants January 19 2005 ATC-Diamond Walnut