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Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan <br />Former Countryside Market, Stockton, California April 30, 2015 <br />with a total area of 35,000 fe extending from 50 to 60 feet bgs with an average TPHg concentration <br />of 1,976 mg/kg. The formula and calculations are presented below: <br />(28317 crfl3 ) kg \ x ( it \ Masssou = (C„ii ) x (Bd) x x (Voi soll ) x , , <br />1 f t - 10-mg \ 0 4536kg) <br />Where: <br />Masssoil = Pounds of TPHg in soil <br />Cs0i1 = Average TPHg concentration in soil <br />Bd = Average bulk density of soil <br />Vo/s ,,ii = Volume of impacted soil <br />Inner zone: <br /> <br />x <br />1 f t 3 <br />(28,317 cm3) <br />) 5,965 lb s = (4,333mg /kg ) x (0.00147 "/ x (15,000 ft 3 ) x C7113 X 10 6 mg l.0.4536kg) <br />Outer zone: <br />6,347 lbs = (1,976 7719/kg) x (0.00147 "/cm 1 f t 3 3 ) x <br />( ) <br />10 6 mg) <br />\ 28,317 cm 3 X (35,000 ft 3 ) x kg X <br />( <br />( itb <br />k0.4536kg) <br />Calculations indicate approximately 12,312 pounds of petroleum impacted soil remain in the <br />vadose zone. <br /> <br />5.8 Helium Tracer Monitoring <br />During injection testing at AS-1 and AS-2, helium was detected within the casing of observation <br />well OBS-1. The helium concentrations in OBS-1 generally increased with increasing injection flow <br />rates during both tests. Helium was not detected in vapor monitoring well VW-1 during testing at <br />AS-1 and AS-2. <br /> <br />5.9 AS Effectiveness and Estimated AS ROI <br />Based on the AS testing observations discussed above, including the significant decrease in <br />dissolved-phase petroleum related constituents that occurred over the course of testing, SGI <br />concludes that air sparging is a viable approach to remediate dissolved-phase petroleum <br />hydrocarbons in groundwater beneath the Site and that the average AS zone of influence extends <br />at least 15 feet. A greater zone of influence may be achieved by an increased duration of air <br />injection. Pulsed/cyclic operations should be implemented to prevent mounding, groundwater <br />displacement, and possible diversion of the dissolved-phase hydrocarbon plume which could occur <br />with continuous high-flow injection. <br />5.10 SVE Effectiveness and Estimated SVE ROI <br />A full scale SVE pilot test was not completed at the Site, but based on mass calculations presented <br />in Section 5.7.1, a significant petroleum hydrocarbon mass remains in the vadose zone near the <br />former USTs. SVE is thus recommended as a precautionary measure to remove residual vadose <br />5-3 The Source Group, Inc.