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UST Closure Report Sharpe Defense Distribution Region West Lathrop,California Page 12 4.1.6 Excavation Groundwater Sample (GW-1-P) A sample of the groundwater was collected from the floor of the UST excavation by CAL INC on January 11, 1999. The sample, GW-1-P, was collected after 350 gallons of groundwater that had flowed into, and accumulated in the excavation had been purged from the excavation. The groundwater was purged with a vacuum truck supplied by American Valley Waste Oil, Inc. The water sample was analyzed by GeoAnalytical Laboratories, Inc. on January 11 and 12, 1999. 4.1.7 Stockpile SPA Samples (SPA-1 to—12 and SPB Samples SPB-1 to—10) Mr. Craig Soares of GeoAnalytical Laboratories, Inc. collected 26 soil samples from stockpiles SPA and SPB under the direction of Mr. Sasson (SJCEHD), on January 13, 1999. The samples were collected on a grid pattern, at a rate of about one sample per 30 cubic yards of stockpiled material (see Figure 4). All 26 samples were analyzed by GeoAnalytical Laboratories, Inc. on January 15 to 23, 1999. On January 26, 1999, Mr. Steve Sasson of the SJCEHD told CAL INC by telephone that he had learned that the SJCEHD did not have the authority to grant approval to CAL INC to use the excavated materials in stockpiles SPA and SPB for backfill in the UST excavation. The authority, he said, rests with the Central Valley Regional Water Quality Board (CVRWQB) because groundwater was intersected in the excavation. The CVRWQB inspector, Ms. Bessett, told CAL INC that the stockpile samples (SPA and SPB series) were not representative because they had not been collected with an auger. On February 2, Ms. Bessett instructed CAL INC to move, mix and aerate the stockpiled soil then collect samples from the new stockpile. 4.1.8 Pigg Excavation Stockpile SPC Samples SPC-1 to SPC-5) Mr. Richard Chrun of GeoAnalytical Laboratories, Inc. collected five soil samples from stockpile SPC of fill materials excavated from the piping trenches. The samples, SPC-1 to SPC-5, were collected under the direction of Mr. Sasson (SJCEHD) on February 5. They were taken at a depth of 3 feet, at 5-foot long intervals along the centerline crest of the 5 feet high and 30 feet long stockpile. The stockpile was estimated to contain about 50 to 60 cubic yards from its dimensions. Each sample therefore represents about 11 cubic yards of stockpiled material. Mr. Sasson also directed that the laboratory make a composite of samples SPC-2 and SPC-4 and analyze it. In addition, the discrete sample SPC-3 was analyzed, but only for oxygenates. The two samples were analyzed by GeoAnalytical Laboratories, Inc. on February 8 and 10. 4.1.9 Product Piping Excavation Samples PL-1 to PL-11) Mr. Richard Chrun of GeoAnalytical Laboratories, Inc. collected 11 soil samples from the floor of the trenches excavated to remove the product piping between the USTs and the fuel dispensers ® on February 6. The samples, PL-1 to PL-11, were collected at depths of 3 to 6.7 feet below grade, and at approximately 20-foot long intervals along the trenches (Figure 5). Mr. Sasson (SJCEHD) directed that samples be collected at depths of only 0 to 6 inches below the floor of NAPR0JECTS\3546\Reports\3546 UST Closure Report Draft.doc March 24,1999