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E A kT H C 0 N"I <br /> A.2 Purpose of Well Abandonment Project <br /> Monitoring well MW-7 does not access the same water bearing zone as down-gradient wells MW- <br /> 2A, MW-3A, and MW-9A as identified previously in the report titled Technical Report and <br /> Groundwater Monitoring Well Investigation Workplan (Technical Report - Miller Brooks <br /> Environmental, Inc. (Miller Brooks), 2008) and as discussed in the following Section A.3. Upon <br /> review of the Technical Report the Central Valley RWQCB did not concur with the abandonment of <br /> MW-7 at that time due to the reported concentrations of TPH-g, acetone, and chloroform. The last <br /> reported concentrations of TPH-g and acetone in MW-7 were in March 2008. An isolated <br /> occurrence of a J-flagged concentration of toluene was reported in the most recent 1St Quarter 2014 <br /> monitoring event; however, toluene was previously detected at J-flagged concentrations in the off- <br /> Site up-gradient wells (EarthCon, January 2014). In addition, the presence of chloroform <br /> concentrations reported historically in MW-7 was assumed to be due to a previous irrigation leak on <br /> the adjacent property. The problem was addressed and after that the chloroform concentrations <br /> exhibited a decreasing trend as identified in Figure 3. Additionally, chloroform was not reported <br /> above the associated laboratory detection limit in the two most recent groundwater monitoring <br /> events. Upgradient monitoring well MW-11 was added to the monitoring well network representing <br /> an upgradient well, accessing the same water bearing zone as down gradient wells MW-2A and <br /> MW-3A as well as cross/down-gradient well MW-9A. As discussed further below, MW-11 is an <br /> appropriate replacement for MW-7. Therefore, due to the location of MW-7 and the groundwater <br /> analytical results, EarthCon requests the removal of MW-7 from the monitoring network and <br /> approval for its abandonment. <br /> A.3 Local Geological and Hydrogeologic Conditions <br /> Monitoring well MW-7 is located in the upper most water bearing unit, identified as Zone III in the <br /> Technical Report(Miller Brooks, 2008) and summarized in the table below. <br /> Monitoring Well <br /> Zone Hydrologic Layer Lithology Screened in <br /> Interval <br /> I Vadose Zone Clay and Silt <br /> II Vadose Zone (Semi-Confining Unit) Clay <br /> MW Abandonment Workplan MW-7 Stockton,Ca <br /> Cove Contractors,Inc. 2 Project No.04.20090407.00 <br />