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I ' San Joaquin River and its tributaries Soil lithology in the Stockton area includes sands, silty sands, silts, clayey silts and clays ' The site lies at an elevation of approximately 25 feet above mean sea level Sediment deposition in the area has produced nearly horizontal topographic features in the vicinity of the site Soils encountered beneath the site during the previous assessment activities consist of inter-bedded alluvial deposits, ' including clays, silts, sands, and fine gravels ' 4.6 Area Hydrology and Hydrogeology According to BC, the San Joaquin River is the mayor surface drainage within the Stockton area of the San ' Joaquin Valley The river flows approximately 40 miles from its point of origin, in the central San Joaquin Valley to Suisun Bay Groundwater in the valley flows west, from the Sierra Nevada Mountain range, and east from the Coastal Ranges, towards the center of the valley, then north towards the Central Valley Delta area The general groundwater flow direction in the Stockton area is reportedly to the northwest, towards the Stockton Divertion Channel, and exists at approximately 50 to 100 feet bgs ' Shallow groundwater is considered unconfined and has been designated as a beneficial water use unit Groundwater is used for farming and ranching (irrigation of crops and watering of farm animals), municipal and industrial water supply, and as a drinking water supply for the general public ' The San Joaquin River is located approximately 4 miles southwest of the site However, the nearest body of surface water, a water transportation and irrigation canal, is located approximately '/2 mile northeast of ' the site Within the last 10 years groundwater beneath the site has risen from approximately 80 to 50 feet bgs Based on the groundwater monitoring event conducted by ATC on November 6, 2001, the calculated groundwater hydraulic gradient and flow direction indicates a north-northeastern flow direction at a gradient of 0 007 ft/ft beneath the site I5.0 SCOPE OF WORK This work plan for additional assessment, remediation well installation, and performance of feasibility studies was prepared in accordance with the recommendations contained in the Clearwater Site Investigation and Well Installation Report, dated August 28, 2001 Based on the results of the previous site characterization activities, the most recent groundwater monitoring data, ATC proposes the following 1 Resume quarterly groundwater gauging and sampling activities 2 Install replacement monitor wells in the proximity of MW-6 through MW-8 (MW-13 through MW- 15) In addition, install MW-16 off-site on the adjacent property to the west, and install MW-17 off- site on the property east of the site across Auto Avenue These wells will be installed to a total depth of approximately 65 feet and be screened from 40 to 65 feet bgs EZ 100966SAFSWP ATC Associates Inc S TZ ServclEZ 1009WReports1100966SAFSWP ATC Project No 43 25827 0026 5