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Beacon Station No 419 August 2, 1996 <br /> Stockton,Califomia Assessment Report <br /> Sediments encountered during drilling consisted primarily of clayey to sandy silt and silty <br /> sand from approximately surface grade to the total depth of the borings The sediments from <br /> the borings were classified using the Unified Soil Classification System (USCS) A copy of <br /> the USCS is shown on the Boring Log Symbol Key in Appendix C <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 4-inch (ID) groundwater monitoring <br /> wells Boring MW-6 was completed as 2- inch ID groundwater monitoring well The <br />• groundwater monitoring wells were completed to a depth of approximately 68 feet bgs The <br /> lower portion of the groundwater monitoring wells were constructed of 20 feet of 4-inch ID <br /> schedule 40 polyvinyl chloride (PVC) well screen with 0 020-inch slots (MW-4 and MW-5) <br /> or 20 feet of 2-inch ID schedule 40 PVC well screen with 0 020-inch slots (MW-6) Four- <br /> inch ID blank PVC casing was extended to the surface to wells MW-4 and MW-5, and 2- <br /> inch ID blank PVC casing was extended to the surface in well MW-6 The annular space <br /> 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 2 to 3 foot thick bentonite seal was <br /> placed at the top of the sand pack in all the wells, and a mix of "6 -sack" neat cement was <br /> used to complete the annular seal to the surface The wells were completed with a flush- <br /> grade, water-tight well box at the surface The top of the well casings were secured with a <br /> locking watertight expansion cap and lock Well construction details are shown on the <br /> boring logs in Appendix C <br /> 1419 11-RPT 4 HORIZON ENVIRONMENTAL INC <br />