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Advanced <br /> G_ eoEtiviron mental , -Inc. <br /> 02 March 2005 <br /> AGE-NC Project No. 96-0235 <br /> Mr. Jeff Wong <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, 3`d Floor <br /> Stockton, CA 95202 <br /> Subject: Monitoring Well Schedule <br /> WEST CLAY PROPERTY <br /> 639 West Clay Street,Stockton, California <br /> Dear Mr. Jeff Wong: <br /> At the request of West Clay Property(WCP)at the direction of the Underground Storage Tank Clean <br /> Up Fund(USTCF),Advanced GeoEnvironmental,Inc.(AGE)has prepared a sampling schedule for <br /> the monitoring well network at 639 West Clay Street,Stockton,California.As noted by the USTCF <br /> and based on analytical data from continual and bi-annual sampling of the monitoring well network, <br /> a reduced monitoring schedule for non-impacted wells is justified; and a minimal monitoring of <br /> wells with low or reduced contamination should also be supported to reduce project costs. <br /> Monitoring wells within the central areas of the dissolved plumes of total petroleum hydrocarbons <br /> and fuel additives required quarterly monitoring for attenuation purposes.Monitoring wells MW-1 <br /> and MW-2 at the southern UST release have demonstrated continual hydrocarbon-impact,with low <br /> detections of the fuel additive 1,2-DCA.Monitoring wells near the northern UST removal area have <br /> demonstrated only detections of methyl tertiary butyl ether(MTBE);all these wells have no current <br /> benzene, toluene, ethyl-benzene or total xylene (BTEX), while TPH-g (gasoline) detections have <br /> been identical in concentrations to the detections of MTBE.Four monitoring wells near the northern <br /> UST removal area have demonstrated low detections of 1,2-DCA. <br /> The southern plume analysis should continue to include TPH-g, TPH-diesel BTEX and 1,2-DCA; <br /> conversely analysis of the northern UST area should not included TPH-d(not recently detected)and <br /> limit the analysis to TPH-g, BTEX, MTBE with fuel additives and 1,2-DCA. <br /> Monitoring wells MW-3,MW-4,MW-5,MW-6,MW-7,MW-8AB MW-I IA, 12A, 13A and 14A <br /> have been non-detect. These wells should be monitored annually or until needed to monitor <br /> corrective action. Monitoring wells I IB, 1213, 13B and 14B have demonstrated low and stable <br /> concentrations of fuel additives MTBE and low concentrations of 1,2-DCA in wells I IB, 12B and <br /> 13B and greater in well MW-1413. Monitoring well MW-1, MW-2, MW-9, MW-10 have <br /> demonstrated significant concentrations requiring quarterly monitoring. <br /> 837 Shaw Road,Stockton,California 95215 <br /> Telephone(209)467-1006 Fax(1209)467-1118 <br />