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Well Installation Report San Joaquin County Environmental Health Department February 17, 2006 . Page 3 of 5 area the valley floor consists of Quaternary age alluvial sediments deposited by the 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 Area and Hydrology and Hydrogeology 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 Diversion Channel, and exists at approximately 50 to 100 feet bsg 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 % mile northeast of the site Permits Drilling permits for the monitoring wells were obtained from the San Joaquin County Environmental Health Department (END) An encroachment permit for the well installations was obtained from the County of San Joaquin Department of Public Works Copies of these permits are included in Enclosure A Soil Borings On November 30, 2005 Delta observed the drilling of two off-site soil borings using a truck-mounted, hollow-stem auger drilling rig Soil borings MW-18S and MW-18D were advanced to 65 and 90 feet bsg, respectively Both soil borings were completed as groundwater monitoring wells with the same name recognition Due to their close proximity, soil samples were only collected from soil boring MW-18D Soil samples were collected at five-foot intervals and the lithology of each was recorded on a soil boring log using visual and manual methods Samples were screened for the presence of organic vapors using a photoionization detector (PID) and the measurements recorded on the boring logs The soil boring logs are presented in Enclosure B Field methods and procedures used during the installation of these wells are summarized in Enclosure C Soil Sample Laboratory Chemical Analyses The soil samples collected at the groundwater interface and at 90 feet were submitted for chemical analysis The samples were sent to Kiff Analytical LLC for analyses of benzene, toluene, ethylbenzene and total xylenes (collectively referred to as BTEX), total petroleum hydrocarbons (TPH) in the gasoline range, and the compounds methyl tertiary butyl ether (MTBE), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), methanol, and • ethanol using EPA Method 8260B Also, one soil sample was analyzed for total lead using EPA Method 6010B for disposal purposes The laboratory analytical results are summarized in Table 1 and the laboratory report is presented in Enclosure D W 1RPMS-CAMorkinoroject Files\]00966 Stockton 2537 Waterloo RoadUnveshgation