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SC&D Boyett Petroleum October 23, 1998 419 South Main Street, Manteca, California Page 2 Underground Storage Tank Preliminary Investigation-ROF All drilling equipment was thoroughly steam-cleaned before drilling began to prevent the introduction of contamination from off site, and between borings to prevent cross contamination. The borings were logged under the direct supervision of a registered professional using the Unified Soil Classification System (Appendix A). The color, texture, moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil or bedrock characteristics were noted (Appendix B). All water-bearing zones and the depths at which they were encountered were also noted on these logs. Upon termination, the borings were backfilled with a bentonite/cement mixture and sealed with a neat concrete grout. 3.2 Soil Sampling Soil sampling were taken in 1 1/16" by 24" plastic sleeves from relatively undisturbed soil. The soil samples were taken using a Geo-Probe system with plastic sleeves. The laboratory samples did not have head space and were immediately sealed in their liners using Teflon® lined caps. They were then labeled and placed in an ice chest cooled with Blue Ice®. The samples were then delivered to the State- certified laboratory, Geo-Analytical Laboratories, Inc., in Modesto, California. The remaining samples were removed from their liners and used as an aide to the on-site specialist in logging the material at the depth. ' The soil samples collected at SB-1 (SB-1@4-6', SB-1@9-11', and SB-1@16'), SB-2 (SB-2@4-6', SB-2@9-11', and SB-2@16'), and th stockpile (SP-1 ) for laboratory analysis were analyzed using EPA method 8020 for BTX&E and MTBE and EPA method 5030/LUFT for total Petroleum Hydrocarbons as Gasoline. EPA method 8260 was used to confirm the presence of MTBE if ' MTBE was detected by EPA method 8020. A Chematograph was also performed on all the samples. Chain of Custody records were maintained at all times (Appendix Q. ' 3.3 Groundwater Sampling All water sampling equipment was thoroughly steam cleaned before and between sa.rnpnug to prevcni cross contamination. One wafer sampie was coiiected from • the termination point at each boring using the Geo-Probe sampler.