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t• it Biwa . Mr Harlin Knoll November 29, 1995 (9347-0085) Benzene and TPH-G were not detected above the method detection limits in the samples collected from the two borings In August 1990, additional borings SB-9, SB-10, and MW-1 were drilled at the site Borings SB-9 and SB-10 were advanced to 71 5 and 41 5 feet bg Monitoring well MW-1 was constructed to a total depth of 40 5 feet bg to determine if a perched water table existed above the clay layer encountered at 37 feet bg This work is summarized in Delta's Problem Assessment Report, dated January 9, 1991 Groundwater has not been observed in the well since installation in August 1990 Ground water measurements taken on October 5, 1989, from a onsite domestic water supply well indicate depth to ground water is approximately 68 feet bg Pertinent excerpts of reports containing the laboratory results of the previous investigations are included in Attachment 2 Soil Boring Advancement and Sampling On September 20 and 21, 1995, Fugro personnel supervised the advancement and sampling of soil borings GEO1 through GE04 (Figure 2), by Gregg Drilling of Martinez, California, using a GeoProbe sampling system The mobile hydraulically-driven GeoProbe sampling system advanced 1-1/4 inch diameter push rods up to 38 feet bg (GE02) Borings • GE02 and GE03 were advanced at angles of 25 and 15 degrees, respectively Boring GE02 was advanced 42 linear feet while boring GE03 was advanced 26 linear feet Actual vertical depths of borings GE02 and GE03 were 38 and 26 feet bg GEO1 is approximately 7 feet southeast of the location TS-2 and GE04 is approximately 5 feet northwest of the current UST basin GE02 was advanced at an angle beneath the northwest fuel dispenser island, approximately 5 feet northwest of the location of PL-5 GE03 was advanced at an angle beneath the southwest fuel dispenser island, approximately 8 feet south of the location of PL-6 Undisturbed soil samples were collected at 5-foot intervals beginning at 5 feet bg using a 1 1/16-inch diameter split spoon This process does not generate soil cuttings Soil samples were field screened using a portable organic vapor monitor Ground water was not encountered in borings GEO1 through GE04 Boring logs and the SJCPHS Boring Permit are included in Attachment 3 Laboratory Analysis Ten soil samples collected from borings GEO1 through GE04 were submitted to Sequoia Analytical, of Sacramento, California for the following chemical analysis • TPH-G using EPA Method 8015 -3- 9347-0085 ARP