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GA-ROVERS Mr. Michael lnfurna 1 H_ l.4/r""" & ASSOCIATES November 26, 2008 ` sodium persulfate injection with a hydrogen peroxide catalyst. Once the objective has been 7 - achieved or it has been determined that the objective can not be achieved within reason by the selected remedy, active remediation will cease. Natural attenuation can then further reduce hydrocarbon concentration until the WQOs are achieved. _ J ISCO WITH SODIUM PERSULFATE Persulfate (S20s) directly oxidizes carbon-containing material including non-aqueous phase liquids. The persulfate oxidation potential is 2. 1 volts and the sulfate radical (SO4) oxidation potential is 2.6 volts. Persulfate typically reacts with carbonaceous material for a few hours to a few weeks. Persulfate is injected as sodium persulfate (Na2S208) which has a high solubility of 73g/100g water and a density greater than water at 25 degrees Celsius. At high sodium persulfate concentrations, density driven transport occurs. Persulfate can be catalyzed to the sulfate radical to increase the oxidation potential. The oxidant can also be consumed by non-petroleum organic matter and metals in the sediments, which can increase the mass of oxidant required to remediate residual hydrocarbon mass. Byproducts of persulfate injection may include solubilization of naturally occurring metals within the soil matrix, carbon dioxide, sulfate and hydrogen ions. However, it is expected that these compounds will be generated slowly and will attenuate naturally. This remedial method would be in compliance with applicable laws and regulations if applied properly. SYSTEM DESIGN AND INSTALLATION n Sodium persulfate with a hydrogen peroxide catalyst will be injected to target the sand and silty- rW sand layer between 15 and 20 feet below grade (tbg) containing the highest on-site dissolved- phase concentrations of TPHg, BTEX, MTBE, and TBA. Historical soil analytical data are summarized in Table 1 . The preliminary design proposes twelve 20400t deep 4-inch diameter injection wells placed in a three by four grid (Figure 2). Sodium persulfate with hydrogen peroxide would be injected quarterly for a period of one to two years. During each injection event, a 350 gallon mixture of a 40-percent sodium persulfate solution and a 10-percent hydrogen peroxide solution will be gravity fed into each well. This anticipated dosage will be validated or adjusted based on a bench-test treatability study. Bench-test Treatability Study: A bench-test treatability study will be performed to determine the optimum dosage of oxidant required to effectively oxidize the hydrocarbon compounds present 240783 4 Worldwide Engineering, Environmental, Construction, and IT Services