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C A M B R I A Mr.Jeffrey Wong <br /> April 20, 2006 <br /> TECHNICAL RATIONALE FOR PROPOSED SCOPE OF WORK <br /> • No groundwater monitoring wells are placed downgradient of the USTs. _ <br /> • The groundwater flow direction beneath the site is predominantly northeasterly. <br /> • Shell proposes installing two groundwater monitoring wells to further assess the lateral <br /> extent of petroleum hydrocarbons and fuel oxygenates in groundwater beneath the site. <br /> © WORK TASKS <br /> Permit: Cambria will obtain an appropriate permit for drilling from SJCEHD. <br /> Site Safety Plan: Cambria will prepare a site safety plan for field work. . <br /> Utility Clearance: Cambria will mark the proposed drilling locations, and the locations will be <br /> cleared through Underground Service Alert prior to drilling.�'.Cambria will also retain a private <br /> utility locator to clear the drilling locations. <br /> Site Investigation: Two monitoring wells (MW-5 and MW-6) are proposed at the locations <br /> shown on Figure 2. The exploratory borings will be drilled using hollow-stem auger equipment <br /> and converted to groundwater monitoring wells. Well MW-5 will be'located east of the USTs, <br /> and well MW-6 will be located northeast of the USTs, behind the station building, to monitor <br /> groundwater concentrations in the downgradient direction. <br /> A Cambria geologist will supervise the drilling and describe encountered soils using the Unified <br /> Soil Classification System. Cambria will collect soil samples from the borings a[.5-foot intervals <br /> for soil description, .possible chemical analyses, and organic vapor screening with a photo- <br /> ionization detector (PID). Cambria will prepare an exploratory' boring log for each well and will - <br /> record PID measurements on the boring logs. <br /> Cambria will retain soil samples designated for chemical analyses in stainless steel or brass j <br /> sample tubes. Cambria will cover the tubes on both ends with Teflon sheets and plastic end caps, <br /> label the soil samples, enter them onto a chain-of-custody record, and place them into a cooler <br /> with ice for transport to a State-of-California-certified laboratory for analyses. We will request a <br /> standard 2-week turn-around time for laboratory results. <br /> I <br /> i <br /> 3 <br /> i <br /> i <br />