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ATC Associates lnc <br /> 1117 Lone Palm Avenue, Suite B <br /> Modesto, Califomia 95351 <br /> 209-579-2221 <br /> ASSOCIATE%T 4: <br /> s INC fax 209-579-2225 <br /> ft/ft or approximately 116 ft/mde A summary of groundwater monitoring data is presented in <br /> Table 1 <br /> ANALYTICAL RESULTS <br /> The groundwater sample collected from well MW4 contained detectable concentrations of TPHg, <br /> benzene, and ethylbenzene [1,100 mtcrograms per hter (ug/L), 44 ug/L, and 31 ug/L, <br /> respectively] Groundwater samples collected from wells MW 1 through MW3 and MW5 through <br /> MW8 contained no detectable concentrations of TPHg or BTEX constituents <br /> Groundwater samples collected from wells MW i, MW2, MW4, MWS, MW6, MW7, and MW8 <br /> contained detectable concentrations of MTBE at, 3 1 ug/L, 10 ug/L, 780 ug/L, 330 ug/L, 820 <br /> ug/L, 11 ug/L and 3,900 ug/L, respectively The groundwater samples from well MW5 contained <br /> detectable concentrations of TAME at 5 9 ug/L <br /> Analytical results of groundwater samples are summarized in Table 2 Laboratory data sheets and <br /> chain-of-custody documentation are contained in Attachment 2 An isoconcentration map <br /> depicting the MTBE concentrations in on-site wells during the third quarter 2004 is shown on <br /> Figure 4 <br /> GEOTRACKER DATA UPLOAD <br /> The depth to water data was submitted electronically to the State Water Resources Control.Board <br /> (SWRCB) Geotracker database (confirmation number 260146099) and the laboratory data was <br /> also submitted electronically to the: SWRCB Geotracker database (confirmation number <br /> 9295738816) Documentation of the data submittal is contained in Attachment 3 <br /> CONCLUSIONS <br /> Chemical contaminant concentrations from wells MW1 through MW8 generally remain consistent <br /> with the results from the previous sampling event The direction of groundwater flow was fairly <br /> consistent with respect to the previous monitoring event The gradient on December 1, 2004 was <br /> 0 0022 ft/ft or approximately 116 ft/mile Groundwater elevations have increased since August <br /> 2004 <br /> RECOMMENDATIONS <br /> Based on the results of the fourth quarter 2004 monitoring episode, we recommend the following <br /> • Conduct the first quarter 2005 groundwater monitoring and sampling of wells MW1 and <br /> MW4 through MW8 and analyze samples for TPHg and BTEX by EPA Method <br /> . 8015M/80� d MTBE, ETBE, DIPE, TBA, TAME, 1,2-DCA., and EDB by EPA <br /> Method 8260B y�41m f U&"{ fj i 4'a m n1,ett 4 <br /> 5 tienvunm=M\2584710437+repoM\3gr-2004 doe4 - <br />