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Beacon Station No 419 August 2, 1996 Stockton,California Assessment Report groundwater monitoring wells (copies are included in Appendix A) The Horizon Field Methods and Procedures are included in Appendix B Drilling, Soil Sampling, and Groundwater Sampling Between May 6 and May 8, 1996, a Horizon geologist observed the drilling of soil borings SB-4, SB-5, and MW-4 through MW-6 The location of the onsite boring and wells were selected to attempt to delineate gasoline hydrocarbons in the soil and groundwater beneath the site and the area east of the site as proposed in the AMV 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, except for wells MW-4 and MW-5 which were subsequently reamed using 10-inch diameter hollow stem augers Drilling was performed by Mitchell Drilling Environmental Corporation of Rancho Cordova, California Barings SB-4 and SB- 5 were advanced to a depth of approximately 561/2 feet bgs Borings MW-4 through MW-6 were advanced to depths of approximately 70 feet to 71 feet bgs The approximate location of the borings are shown on Figure 2 and identified as SB-4, SB-5, and MW-4 through MW- 6 Groundwater was encountered in the borings at depths of approximately 50 feet to 57 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 4-inch inside-diameter (ID) monitoring well was constructed in borings MW-4 and MW-5, and a 2-inch ID groundwater monitoring well was constructed in boring MW-6 Borings SB-4 and SB-5 were backfilled to grade using a "6-sack" neat cement slurry 1419 11-RPT 3 HORIZON ENVIRONMENTAL INC