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1.. Site Assessment Work Plan Advanced Environmental Concepts,Inc. 1.3 Schedule Advanced Environmental Concepts,Inc. anticipates beginning the services described in this work plan within one week upon approval by SJCPHS-EHD and authorization to proceed from Mr. Brian Hauss of CAPS. Drilling will commence only after applicable permits have been obtained. The borings will be completed within one day of mobilization on the site. 6d A final report will be prepared summarizing all field operations and laboratory results. The report will be provided within 30-days of completion of the field work. V 2.0 BACKGROUND At the request of Prudential q Agricultural Investments,AEC performed a Preliminary Site Assessment(PSA) on a 729 acre agricultural parcel located approximately 6 miles southeast of Tracy, California during August and September, 1996. Two former underground storage tank (UST) emplacements containing a total of three �.. UST's were identified in the compound area south of the residential dwelling in the central portion of the property. The three UST emplacements were investigated on January 7, 1997. The analytical results indicated that significant soil and groundwater contamination existed in the area of the gasoline USTs. From October 6-10, 1997 AEC excavated gasoline impacted soil and groundwater from the former gasoline UST location, and finished the excavation during July 6 through the 15th of 1998. Our confirmation sampling indicated that all accessible gasoline impacted soil and groundwater had been removed from the former tank emplacement, land farmed, and the excavation backfilled. This workplan is being prepared to confirm that adequate mitigation of the groundwater has occurred. 3.0 SITE CHARACTERISTICS w San Joaquin County is part of four separate physiographic regions in California. The majority of the county is located within the lower San Joaquin Valley,which extends from north to south through the eastern portion of �. the county. Most of the remainder of the county,in the western area, is located in the Sacramento-San Joaquin Delta. Foothills of the Sierra Nevada occupy the easternmost edge,and portions of the Coastal Ranges occupy the southwestern portion. Landforms of the lower San Joaquin Valley include flood plains, alluvial fans, fan terraces, basins. dunes, and low and high terraces. Surface topography is generally flat, although relief in �+ some areas ranges from undulating to hilly due to dissection and erosion. Nearly level flood plains are located along the Stanislaus, Calaveras, San Joaquin, and Mokeiumne Rivers. All of these tir_.od plains were subject to regular flooding prior to development of levees and reservoirs. Natural drainage ways in San Joaquin County generally flow from east to west;the San Joaquin River, largest in the county, flows from south to north. Flood plair!s are also located along Hospital, Lonetree, and Corral Hollow Creeks. Flood waters in these areas dissipate on leveled alluvial plains before reaching the San Joaquin River. The Stanislaus and Mokelumne Rivers deposit alluvial material originating the Sierra Nevada Mountains, forming extensive alluvial fans and �+ fan terraces. 1.114ind-deposited sand dunes were once common along the Stanislaus River. Many of these dune areas have been artificially leveled and reclaimed for agricultural use. Many low and high terraces along the eastern edge of the San Joaquin Valley have developed complex surface drainage patterns and microrelief. One of these drainage patterns occurs as a meandering or disarranged pattern of intermittent channels which double back or, each other. In some areas,short segments terminate at small closed basins that commonly �... Project: AEC 9SC-1917 2 • ENVOC NMENTAL CONCEPTS WITH DESIGN W MWD 4400 ASHE ROAD.*208 • BAKERSFIELD.CA 93313 805/831-1646 • FAX 805/831-1771 V