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,R -�.r +'r1.�Tkf Y �.r' y:` r• �-h'..-f'.rt-S�J'�" S.�•h�s Y Jr�'.* -.=bPx nr-r 4� _.`w:'a.: <br /> r„ <br /> n1l: L REMEDIATION PIAN <br /> Shell Oil Company <br /> 620 West Cliarter'Nay,Stockton,California <br /> E Delta Project No.4048-586 <br /> Page 15 <br /> F u Benzene concentrations in ground water samples coilcct-,A from monitoring wells MW-1 through MW-9 <br /> ranged from nondetectable in monitoring well MW-6 (located upgradient) to 20 ppm in monitoring well <br /> i, MW-9(located in the area of the former pump islands).Free-phase petroleum product has been identified <br /> on the water table surface in monitoring Well MW-2,located in the area beneath the former undergroun. <br /> [ee[ upgtadicat, 6a fcl <br /> storage_tanks, and in monitoring wg4,MW-3,MW-4, andI W.7, Iocated 3{1 <br /> approximately downgradient, aiad 85 feet downgradient, respectively. Figure�8 illustrates the inferred <br /> distribution of free-phase petroleum product and the concentrations of dissolved benzene in ground water. <br /> f � <br /> Original laboratory data sheets from the October 1990 quarterly sampling event are included in Appendix D <br /> of this report. Previous ground water quality data sheets were included in previous reports listed in <br /> t ' Section 1.3. <br /> k <br /> 3.5 Soil Vapor Extraction and Ground Writer Pumping Test <br /> s Qa,1Glareh 21l,and"21, 1990,Delta conducted t<soil,vapor eartractiou and ground waw.pumping°test at the' <br /> 1 site: The information obtained from this test was used for the design of the proposed remedial system,and <br /> will also be used in the permitting of the remedial technologies that will be implemented at the site. <br /> 3.5.1 Ground Water Pumping Test <br /> Monitoring well MW-7 was pumped for approximately 35 hours with a submersible pump in order to <br /> determine the specific flow rate of water that the well would produce per foot of drawdown(gpm/ft.).The <br /> �•,� <br /> well was then pumped under the influence of a vacuum in order to--mpare the stabilized pumping rates. <br /> A data summary of this initial pumping test is included in Appendix B of this report. <br /> Ir.general,stabilised purt ping rate;for the well were low,ranging from 0.1 galln,CVer.minute(gpm)during <br /> "Eaturai:pumping to 0.6 gpm during vacuutn-enhanced pumping?The resr,iis of the pumping tests on <br /> monitoring well MW-7 show that the average specific capacity of this well was approximately 0.06 gpm/ft <br /> of drawdown. Calculations for analysis of the pumping test results are presented in Appendix F of this <br /> report. <br />