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i x Mr. Harlin Knoll,SJCEHD June 18, 2007 Well Installation Work Plan A. Teichert and Sons Property, Stockton,CA Page 7 1,200 feet north-northwest of the site. Historical data appear to indicate the groundwater flow beneath the site has not been toward the Fremont Street wells. Given the distance of j these wells from the subject site and the apparent lack of groundwater flow in this direction, it appears unlikely dissolved petroleum hydrocarbons originating from the Teichert property will impact these water supply wells. Water service in the vicinity of the subject site appears to be provided by California Water Service. SCOPE OF WORK The objectives of the proposed work are to: • Establish a well network that will allow for repeatable groundwater sampling across areas of the site impacted with 1,2-DCA. • Additionally characterize the geology beneath the site. • Evaluate current groundwater flow direction. To accomplish these objectives, Stratus is proposing the following activities: • Drill and install three (3) shallow screened monitoring wells (MW-15 through MW-17) to approximately 75 feet bgs using hollow stem augers. • Complete one (1) deeply screened" roundwater monitoring well (MW-1$) to approximately 95 feet bgs using the sonic drilling method. • Collect soil samples for lithologic comparison and chemical analysis. • Develop and sample the newly installed wells. • Update the monitoring well survey for the site. Rationale The locations of the proposed monitoring wells are illustrated on Figure 2 and included, as appropriate, on Figures 3 and 5. Information regarding the lateral and vertical extent of 1,2-DCA impact is largely known from data collected during the 2006 CPT investigations completed on-site and off-site. The well depths and screening intervals will target water bearing sandy intervals in areas where 1,2-DCA impact has previously been identified. The exact depths and screening intervals of each well proposed in this document may need to be adjusted, based on field conditions observed at the time of the investigation, to ensure that the monitoring wells are appropriately screened across discrete zones of saturated strata. Based on historical analytical results 1,2-DCA impact to groundwater predominately extends east, southeast, and south from the site. The highest concentrations of 1,2-DCA KATeichcrt\Stockton-1031Work Plansltcichert-well install work plan 06-2007.doe 5771'ATUS