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Beacon Station No.474 August 2, 1996 Stockton,California Assessment Report Drilling, Soil Sampling, and Groundwater Sampling Between May 8 and May 10, 1996, a Horizon geologist observed the drilling of soil borings B-1 through B-4, MW-4, and MW-5. The location of the borings and wells were selected to attempt to delineate gasoline hydrocarbons in the soil and groundwater beneath the site and in the area adjacent to the site as proposed by AMV in the work plan. The borings were drilled and sampled using a truck-mounted a CME-75 drill rig equipped with 8-inch diameter hollow-stem augers. Drilling was performed by Mitchell Drilling Environmental Corporation of Rancho Cordova, California. Borings B-1, B-3, and B-4 were advanced to a depth of approximately 461/2 feet bgs and boring B-2 was advanced to a depth of approximately 751/2 feet bgs. Borings MW-4 and MW-5 were advanced to depths of approximately 86 feet to 86%2 feet bgs. The approximate Iocation of the borings are shown on Figure 2 and identified as B-1 through B-4, MW-4, and MW-5. Groundwater was initially encountered in the borings at depths of approximately 80 feet bgs and rapidly rose to a depth of approximately 71 feet to 72 feet bgs. During drilling, soil samples were collected from the borings at 5-foot intervals from the ground surface to the total depth of the borings. Soil samples and cuttings were evaluated for the presence of petroleum hydrocarbon vapors with an organic vapor meter (OVM). Evidence of petroleum hydrocarbons are noted during drilling and are included in the soil boring logs. The soil boring logs containing soil descriptions are included in Appendix C. Upon completion of drilling, a 2-inch ID groundwater monitoring well was constructed in borings MW-4 and MW-5. Borings B-1 through B-4 were backfilled to grade using a "6-sack" neat cement slurry. Sediments encountered during drilling consisted primarily of clayey silt and silty sand from approximately surface grade to .the. total .depth..of. the .borings. The sediments from the borings were classified using the Unified Soil Classification System (USCS). A copy of the USCS is shown on the Boring Log Symbol Key in Appendix C. 3 1474.11-RPT HORIZON ENVIRONMENTAL.INC.