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ARCADIS Sulfate and fluorescein: indicators of injection solution distribution Total petroleum hydrocarbons quantified at gasoline (TPH-GRO), total petroleum hydrocarbons quantified as diesel (TPH-DRO), and TPH-DRO analyzed using silica gel cleanup method • Benzene, toluene, ethylbenzene, and xylenes (BTEX)and naphthalene Secondary by-products (magnesium,total dissolved solids[TDSj,and additional biogeochemical indicators(dissolved iron and manganese) Observations To date,the data demonstrate the following: • Sulfate was effectively delivered to the treatment area, including hydrostratigraphic units with limited permeability and elevated petroleum hydrocarbon concentrations(A'and B'), as indicated by increased sulfate and fluorescein concentrations in the targeted dose response monitoring wells. • Sulfate utilization is occurring within 2 months of injection,as indicated by more rapid decreases of sulfate compared with fluorescein (e.g., U-27A and U-27A'). In samples collected during the 6 month post-injection event, sulfate concentrations were near or below baseline and were less than the secondary maximum contaminant limit of 250 mg/L, in the wells with the exception of U-27A(273 mg/L). In samples collected from U-27A, sulfate concentrations have been steadily decreasing since injection and according to linear regression analyses, most likely reached baseline levels within a month following the most recent monitoring event. • TPH-DRO and TPH-GRO concentrations are generally decreasing in locations where delivery of sulfate was most effective(i.e., U-27A, U-27A',and U-27B').The TPH-DRO concentrations analyzed with silica gel decreased to a greater extent than the total TPH-DRO concentrations, indicating that non-polar petroleum hydrocarbons are transforming into polar, less-toxic degradation products. The decreases in total TPH-DRO concentrations suggest that polar degradation products are also being degraded. • Additional constituents are also decreasing, including toluene, ethylbenzene,xylenes and naphthalene in U-27A,and benzene, toluene and xylenes in U-27A'. • As expected, secondary by-products associated with the injections, such as sulfide, magnesium, TDS, iron,and manganese temporarily increased following the first injection and are attenuating through intrinsic geochemical reactions. glaprojecPenNdieumnup'al5eisaYQ ammuniratlmbxaspoMan®Yma rden®cfeMlwmm Page: �o a/aosaiswmmby n�miomn da 2/4