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• a <br /> • Beacon Station No.474 August 2, 1996 <br /> Stockton,California Assessment Report <br /> Soil cuttings generated during drilling operations were stockpiled on and covered with <br /> plastic and left onsite until subsequent disposal by Ultramar. Four soil samples were <br /> collected from the stockpile, composited at the laboratory, and analyzed for gasoline <br /> hydrocarbons. <br /> Monitoring Well Installation <br /> The borings MW-4 and MW-5 were completed as 2- inch ID groundwater monitoring wells. <br /> The groundwater monitoring wells were completed to a depth of approximately 85 feet bgs. <br /> The lower portion of the groundwater monitoring wells were constructed of 20 feet 2-inch <br /> ID schedule 40 polyvinyl chloride (PVC) well screen with 0.020-inch slots. Two-inch ID <br /> blank PVC casing was extended to the surface in wells MW-4 and MW-5. The annular <br /> space adjacent to the well screen portion of the wells was backfilled with #8 Omega sand to <br /> approximately 2 feet above the screened intervals. A 3-foot thick bentonite seal was placed <br /> at the top of the sand pack in the wells, and a mix of "6 -sack" neat cement was used to <br /> complete the annular seal to the surface. The wells were completed with a flush-grade, <br /> water-tight well box at the surface. The top of the well casings were secured with a locking <br /> watertight expansion cap and lock. Well construction details are shown on the boring logs <br /> in Appendix C. <br /> Wellhead Elevation Survey <br /> On June 6, 1996, the wellheads for all the groundwater monitoring wells at the site were <br /> surveyed to a local National Geodetic Vertical Datum benchmark by a licensed land <br /> surveyor (Ron Archer Civil Engineering Inc.). The results of this wellhead survey data are <br /> included in Appendix D. <br /> 4 <br /> 1474.11-RPT HORIZON ENVIRONMENTAL INC. <br />