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Subsurface Investigation Report <br /> Installation of Wells MWS,MW6,and MW7 <br /> 640 N El Dorado Street, Stockton, CA <br /> 3.0 RESULTS OF INVESTIGATION <br /> 3.1 Subsurface Conditions <br /> Soil encountered in borings SB9 (MW5), SB 10 (MW6), and SBI l (MW7)consisted of the following <br /> DEPTH SOIL TYPE <br /> (feet,bsg) SB9(MWS) SB10 MW6 SB11 MW7 <br /> 0-16 Clay and silty clay CL CUM) Clay CL Clay and silty clay CL CL/ML <br /> 16-25 Silty clay and silt CUML,ML Clay and silt CL, ML Silt ML <br /> 25-27 Silt ML Well graded sand 5 Well graded sand S <br /> I 27-29 Silt ML �kqSilt ML Well graded sand S <br /> 29-30 Well graded sand S Silt ML Well graded sand (SW) Z d <br /> 30-36 Silt ML Silt clay and silt CL/ML,ML Well graded to clayey sand SW SC <br />' 36-40 Silt and silt wlsand ML Fat clay and silt CH, ML Silty clay(CL/ML) <br /> 40-43 Sil to well graded sand SM, S Silt ML Silt ML <br /> 43--48 Silt and clay ML CL Silt and silty clay ML CUML Silt and silty,clay ML, CL/ML <br />' �48---51 Clay ML Well graded sand(SM Clay CL <br /> —51-55 Not logged (boring terminated at 50 Clay CL Not logged (boring terminated at 50 <br /> First groundwater at 29 feet First groundwater at 25 feet First roundwater at 25 feet <br /> PID readings from all samples collected were less than 1 0 part per million(ppm) No hydrocarbon odors <br /> or soil discoloration were noted in borings SB9 through SBII All recorded PID readings as well as <br />' noted odors or soil discoloration are included on the boring/well logs included in Appendix 2 <br /> 5&-!o 1, <br /> Groundwater was first encountered' gatgapproximately 25 feet bsg in borings SB9 and SBI 1 and approximately 29 feet bsg in boring S431[twhich corresponds t, o the first sand unit in each of the borings S6-7 ,7 <br /> Groundwater appeared to be semi-confined,as groundwater in the wells subsequently stabilized at depths <br /> ranging from approximately 21 9 to 22 6 feet bgs Figure 3 shows the locations of soil borings and <br />' monitoring wells Figures 4 and 5 show subsurface lithology along sections A-A' and B-B' Figure 6 <br /> presents a groundwater gradient map generated using the June 2003 data Groundwater elevations were <br /> calculated by subtracting the measured depth to groundwater in each well from the respective wellhead <br />' elevation The depth to groundwater in the wells on June 3, 2003 ranged from 24 21 feet below the top <br /> of the well casing (btoc) in well MW3 (corrected for the presence of free product) to 25 24 feet btoc in <br /> well MWS Groundwater flowed in a northeasterly direction with a calculated gradient of 0 0034 feet per <br />' foot(approximately 18 feet per mile) <br /> 3.2 Soil Analytical Results <br />' Based upon previous analytical results and field observations only soil samples collected from the <br /> capillary fringe zone and-the bottom-o£each boring_were submitted for analysis _ No detectable <br /> concentrations of BTEX, TPHg, TPHd, TRPH, or VOCs were detected in any soil sample Soil <br />' analytical results from borings SB9, SB 10, and SBI I are summarized in Table 6 Laboratory reports and <br /> chain of custody documentation are included in Appendix 4 <br /> 1 <br /> -4- <br />