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ow, GROUNDWATER MONITORING WEL%T!�NSTALLATION WORKPLAN
<br /> SJCEHD requested that UOP conduct an investigation to determine the lateral and vertical extent
<br /> MTBE impact in soil and groundwater.
<br /> ESA obtained eleven soil and five groundwater samples from five soil boring locations on July 5,
<br /> 2000. As documented in ESA's Subsurface Soil and Groundwater Assessment Report,dated
<br /> August 25,2000,laboratory analyses did not identify concentrations at or above the laboratory
<br /> detection limits of total petroleum hydrocarbons as gasoline (TPH-g),benzene,toluene,
<br /> ethylbenzene and xylenes(BTEX),di-isoproyl ether(DIPE),ethyl tertiary butyl ether(ETBE),
<br /> tertiary amyl methyl ether(TAME),or tertiary butyl alcohol(TBA)in any soil and groundwater
<br /> samples collected. The soil sample obtained from boring TP-4 at 15 feet below ground surface
<br /> (bgs)contained MTBE concentrations of 11 milligrams per kilogram(mg/kg). MTBE was also
<br /> detected in groundwater samples collected from borings TP-4 and TP-5 at concentrations of 1,300
<br /> micrograms per liter(µg2)and 1.4 µg2,respectively. Based on these findings,ESA concluded
<br /> r that MTBE impact to soil and groundwater was localized with minimal lateral extent.
<br /> Following receipt of ESA's August 25, 2000 report, SJCEHD requested that additional
<br /> groundwater data to further delineate MTBE concentrations detected in groundwater near the
<br /> northern end of the former UST. ESA obtained twelve groundwater samples from multiple
<br /> sampling locations in and around the former UST location on January 10 and 11, 2001,as shown
<br /> �. on Figure 3. No concentrations, at or above the laboratory detection limits, of TPH-g,BTEX,
<br /> MTBE, DIPE,ETBE,TAME,TBA,ethanol,methanol,ethylene di-bromide (EDB),and 1-2
<br /> dichloroethane(1-2 DCA) were detected in any of the twelve groundwater samples. Based on
<br /> these findings,ESA concluded that the occurrence of MTBE in groundwater is localized at the
<br /> north end of the former UST excavation, and does not appear to have migrated laterally or
<br /> vertically. The results of this investigation were detailed in the Additional Groundwater
<br /> Assessment Report dated March 26,2001.
<br /> In a letter dated April 25,2001,SJCHED subsequently requested that a workplan be submitted
<br /> for the installation of groundwater wells to establish the direction of groundwater flow and further
<br /> evaluate the extent of MTBE impact in groundwater in the presumed down-gradient direction of
<br /> the former UST site. On behalf of UOP,ESA held a telephone conference with SJCEHD and the
<br /> RWQCB on May 16,2001 to discuss potential future investigative approaches to further define
<br /> the extent of MTBE in soil and groundwater. ESA has prepared this workplan based on the
<br /> approaches discussed in the May 16, 2001 telephone conference, and comments in Ms. Dot
<br /> Lofstrom of SJCEHD's facsimile response to ESA's letter dated July 26, 2001 regarding
<br /> proposed groundwater well locations.
<br /> SAMPLING AND ANALYSIS PLAN
<br /> The objective of this investigation is to confirm the direction of groundwater flow, and to further
<br /> define the localized extent of MTBE in groundwater in a presumed down-gradient groundwater
<br /> flow direction. Proposed activities include the installation of five soil borings,collection of one
<br /> grab groundwater sample,collection of soil samples from each soil boring,installation of four
<br /> groundwater monitoring wells, and subsequent development and sampling of the newly installed
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<br /> Environmental Science Associates 2 University oftbe Pacific
<br /> September 25,2001 Groundwater Monitoring Well Installation Workplan
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