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Quik Stop Station No:39 April 10,2008 <br /> Stockton, of 'a -..Wofk Plan for Additional Groundwater Invest' ation <br /> The sole gasoline hydrocarbon constituent of concern remaining in groundwater from,wells <br /> MW 1 and.MW2-is DCA. First quarter analytical results indicate DCA concentrations in <br /> wells MW-1 and:MW-2, are 0.60 micrograms` per liter (parts .per'biIlion). Groundwater <br /> monitoring data I,ndicate. that wells- MW=3 through ,'MW-8 are not . impacted With <br /> hydrocarbons. Historical qukarterly monitoring.-indicates; that -hydrocarbon impacts to <br /> groundwater have not extended to the outer.monitoring wells MW4 through MW-8. The <br /> SJCEHD requested the additional groundwater investigatioh in-response to review of the <br /> third and fourth quarter 2007 groundwater monitoring-reports. <br /> Proposed Scope of Work <br /> P P <br /> The purpose of the proposed work is to,,collect grab,groundwater samples south -and <br /> southwest of wells MW-1 and.i:MW-2 to evaluate the lateral"extent of DCA in.groundwater. <br /> Proposed-grab groundwater sample locations, HP=I -and AP'-2, are.shown on Figure 3. <br /> Groundwater samples shall be;collected.utilizing a hydropunch tool advanced by a Geoprobe <br /> direct-push rig. Fieldwork shall be conducted according to the attached Horizon's Field <br /> Methods and Procedures. Horizon proposes:the following tasks: <br /> Task 1 Retain and schedule Va. C57=licensed driller to conduct soil boring: and <br /> hydropunch groundwater sampling services; obtain required-boring permits <br /> from- the SJCEHD; update; the Site .Health )and Safety Plan; notify <br /> Underground Service Alert (USA) to.identify and locate underground utilities <br /> h in the site ares. <br /> Task Advance 254inch;diarneter hydropunch tools to 3_feet below,groundwater; <br /> (approximately,47-feet bsg collect grab 'groundwater .samples; record field <br /> boring operation and groundwater sampling information; backfill borings with <br />'E a bentonite-neat''cement grout mixture,to the surface. <br /> k Task 3 :Submit groundwater samples,`; under COC documentation, to Kiff Analytical <br /> LLC (Kiff) of Davis, ' California (California ELAP #12236); analyze <br /> j groundwater sam1 ples for total petroleum hydrocarbons as gasoline (TPHg),the <br /> volatile aromatic compounds<`benzene; toluene, etliylbenzene; total xylenes <br /> .(13TEX), the five,fuel•'oxygenates methyl=t-butyl ether (MTBE); diisopropyl <br /> ether (DIP E); ethyl-t-butyl ether (ETBE); tert-amyl methyl ether (TAME), <br /> DCA and 1;2=dibromoethane~(EDB)by EPA Method 8260B. <br /> j <br /> Task 4 Survey hydropunch locations to GeoTracker specifications. <br /> l Task 5 Upload new field point names, updated site map, hydropunch location survey <br /> data, analytical data and reports to-the GeoTracker data base; prepare a report <br /> docuritenting the investigation fieldwork and groundwater analytical: results; - <br /> I and evaluate the lateral extent of DCA in groundwater in the context of an <br /> E updated site conceptual model, <br /> GW=HP WPApr08 <br /> Project No.7039.1.9 2 HORIZON ENVIRONMENTAL INC. <br />