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v A s s O C I A T E S I N C presented in Table 3-3 Refer to PRIMA'S Evaluation of Reductanis for the In Sitar Stabilization of Hexavalent Chromium included in Appendix B for detailed information Table 3-3 Summary of Baseline Groundwater Sample Analytical Results ' Analyte Units Sample ID MWA MW-2 MW-3 MW4 MW-5 MW-6 I MW-7 MW-8 MW-9 Chromium, Total ug/L 83 36 6,300 43 110 150 190 86 23 ' Manganese, Total ug/L 750 21 < 10 270 800 880 1,400 490 61 Manganese, Dissolved ug/L 780 < 5 < 5 76 < 5 < 5 < 5 < 5 < 5 Copper ug/L < 10 < 10 < 10 19 59 70 120 52 < 10 Zinc ug/L < 100 < 100 < 100 < 100 110 120 200 < 100 < 100 Arsenic ug/L < 5 < 5 < 5 7 15 16 19 13 98 Iron, Total ug/L 950 1,500 2,600 14,000 47,000 54,000 97,000 42,000 2,300 ' Iron, Dissolved ug/L 790 810 2,400 360 700 760 520 600 410 Alkalinity mg/L 680 630 250 390 280 270 440 360 270 ' CaCO3 Ammonia mg/L N 017 < 0 10 < 0 10 < 010 0 12 < 010 < 010 < 010 < 010 Nitrate mg/L N 55 97 35 2 2 18 16 42 99 77 Sulfate mg/L 29 31 38 91 90 74 13 42 26 TOC mg/L 42 1 1 8 1 3 14 1 1 4 1 1 2 1 14 1 1 3 1 1 ' 4.0 SUMMARY OF BENCH SCALE TESTING RESULTS Detailed methodology and results of the bench scale treatability study for reducing hexavalent ' chromium (CrVI) 3n the subsurface are presented in PRIMA's report presented in Appendix B In summary, bench scale laboratory testing was performed on soil and water collected from the ' site to evaluate the effectiveness of two potential reducing agents — ferrous iron solution and calcium polysulfide (Cascade°) — to chemically 2educe CrVI to divalent chromium (CrIII) Tests were conducted in the presence and absence of soil to assess the potential for in situ ' remediation via infection of solution into the subsurface Both the ferrous iron solution and Cascade were effective in decreasing the concentration of CrVI in groundwater in the presence and absence of soil Soil decreased the efficiency of each treatment, but complete removal of ' CrVI was achieved with ferrous iron solution and appears to be achievable with Cascade° if a greater concentration of Cascade" than used in the bench scale study were employed Both the ferrous iron solution and Cascade° affected secondary water quality parameters Manganese was affected significantly by both reducing agents resulting in high concentrations of this constituent The resultant high concentrations of manganese are likely attributable to the reducing agents reacting with naturally occurring manganese dioxide in the soil S lenvaronmuit d\625831rLP0Ftslbu1ch test rpt doc 7