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approved by DTSC and the Central Valley Regional Water Quality Control Board for a <br /> PG&E Former MGP site,located in downtown Stockton. <br /> The decision tree organizes the monitoring wells as upgradient,downgradient, <br /> crossgradient,or within the plume as follows: <br /> • Upgradient wells:MW-DIS-4,-5,-6,-7S,-71),-8S,and--8D. <br /> • Downgradient wells:Currently,no downgradient wells exist. <br /> • Crossgradient:MW-DIS-3,-9,and—10 <br /> 0 Within Plume:MW-DIS-1,-2,NP-1-70',-80',-90',SVE-South,and SVE-North. <br /> Table 7 presents the recommended sampling frequency for all wells at the Disco site. Due to <br /> the recently discovered presence of 1,2-DCA,EDB,and TBA,we recommend that'all wells <br /> be sampled for these compounds on a quarterly basis to assess the extent of these <br /> compounds at the site.Modifications to the sampling plan will be made after four rounds of <br /> sampling for these compounds.Monitoring wells MW-DIS-1,MW-DIS-2,NP-1-70,-80,-90, <br /> SVE-South,and SVE-North will continue to be sampled semi-annually for TPH-gas and <br /> BTEX compounds. <br /> Note:In order to continue the accurate assessment of the groundwater flown direction, <br /> water level measurements in all wells and evaluation of the groundwater gradient will <br /> continue to be performed on a quarterly basis. <br /> 4 <br />