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19 November 1999 AGE-NC Project No. 99-0604 Page 2 of 10 Three unpermitted dry wells were installed at the site in 1996 for discharge of the excess wastewater. The design characteristics for the dry wells are not known, but according to Mr. Warren Snider of WSI,each dry well was approximately 42-inches in diameter and was excavated to a depth of 25 feet bsg. A 4-inch PVC casing was located near the center of each excavation and the remaining void space was backfilled with pea grave and river rock. The entire area around the dry well was then covered with approximately 5-inches of concrete. The dry wells were connected to the clarifier by 2-inch PVC piping. hi early 1999, the clarifier system failed and was replaced with a sanitary sewer hook-up to the City y of Stockton. Currently, all excess wastewater, not to exceed 400 gallons per day, is disposed under permit, into the City of Stockton sanitary sewer. 2.2. SHALLOW DISPOSAL WELL EXCAVATION AND SAMPLING _ The three shallow disposal wells were excavated on 07 September 1999 under the supervision of AGE and observation of the PHS-EHD. Discrete soil samples were collected beneath each dry well and from beneath the former drain line. Significant concentrations of petroleum hydrocarbons, low concentrations of several volatile organic compounds(VOCs)and elevated concentrations of several target metals were detected in soil samples collected beneath each dry well. No contamination was detected in the sample collected beneath the drain line. Details of the excavation and sampling are discussed in the "Shallow Disposal Well Closure Report" dated 02 November 1999, prepared by AGE. Upon completion of excavation and sampling, each well was backfilled to approximately 4 feet below surface grade with concrete. 2.3. DISPOSAL OF HYDROCARBON-IMPACTED SOIL On l 1 November 1999, soil excavated from the disposal wells was transported to BFI - Vasco Road Landfill for disposal. The soil was transported by Lutrel Trucking, Inc. wider Non-Hazardous Waste Manifest 2.3. GROUND WATER DEPTH AND FLOW DIRECTION Based upon the San Joaquin County Flood Control Map Lines of Equal Depth in Water Wells- 1996, ground water depth in the area of the site is approximately 55 to 60 feet below surface grade. Regional ground water flow direction is east-northeast; however, flow direction and ground water Advanced GeoEnviron mental,Inc.