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Canepa s Car Wash 6230 Pacific Avenue Stockton CA _ - Second Quarter Groundwater Monitoring Report,May 2006 _ - I - Page 2 of 8 Table 1-Summa of Mal 20062uarterll Groundwater Monitoring Results ©' Field Activity Number of groundwater monitoring 11 Number of wells sampled 7* wells(not including soil vapor ---' - -—--- -extraction well SV-4) - - - - -- _ Number of groundwater monitoring _ 11 Date(s)monitored and sampled 05/18/2006 wells measured for water level -Site-Hydrology Average depth to groundwater below 35 60 feet Average increase(+)/decrease(--)in -1 64 feet shallow monitoring well measuring depths to groundwater since last (shallower) Dints(excluding MW-1 and-11) samrilinR -Approximate flow direction - - -Generally north-northwest with a cone of depression centered at MW-1-3- - Groundwater Contamination Monitoring wells containing free None Monitoring wells with petroleum 3 product(not-including SV-4) hydrocarbon odor noted(not tncludin SV-4 Number of monitoring wells with 3 Number of monitoring wells with 4 concentrations below both the concentrations at or above either or benzene and MTBE MCLS both the benzene and MTBE MCLs Nature of contamination BTEX, Range of analyte concentrations Gasoline detected in the monitonng wells Oxygenates/ Benzene(µg/L) <0 5- 11,400 Additives, Toluene(pg/L) <0 5-4,540 TPH-G Ethyl Benzene(pg/L) <0 5- 1,790 Total Xylenes(gg/L) <1 0-4,403 MTBE(gg/L) <0 5-6,650 1,2-DCA(pg/L) <0 5-28 3 EDB(gg/L) <05- 34 TPH-G m <0 05-36 3 Notes Pumping well MW-1 was active *Monitoring wells MW-5,MW-6,MW-7 and MW-10 are sampled annually during the third quarter j FIELD OBSERVATIONS �On-May-18,2006,a Condor representative made-field�b6§efvations-and collected-depth to groundwater _ measurements at the 11 Site monitoring wells(MW-1 through MW-7, and MW-9 through MW-12D) and at one soil- apor extraction well (SV-4) MW-1 and MW-11 are used for groundwater extraction related to the operation of the groundwater treatment system Field observations included appearance of samples (color, clarity, and presence of petroleum product sheen or phase in samples), collection of water quality field parameters, and any other conditions of note Depth to groundwater measurement data is provided in Table 2, on the following page, field observations are included in the field forms (Attachment E) A spotty sheen was noted in the bailed field inspection samples collected from monitoring well MW-2 and soil vapor extraction well SV-4 No separate phase petroleum was noted in the bailed field inspection samples from any of the on-Site wells A moderate petroleum hydrocarbon odor was noted in monitoring well MW-2 A slight petroleum hydrocarbon odor was noted in monitoring wells MW-3 and MW-12D A strong hydrocarbon odor was noted in soil vapor extraction well SV-4 -µGROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation contours estimated for the shallow monitoring wells (MW-1, MW-2, MW-3 MW- 4, MW-5, MW-6, MW-7, MW-9, MW-10, and MW-11) on May 18, 2006, indicate a groundwater gradient generally toward the north-northwest (consistent with historic gradients) but with a localized k CONDOR