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...n 0,1 A rr ', . Ciavton Clayton discovered significant concentrations of oil and grease and gasoline in samples MN-1, ME-1, and NE-1. These samples were collected from the north and cast walls of the excavation. Clayton recommended additional excavation of soil in these areas. Additional samples were collected after overexcavation was completed (Figure 3). These samples were NE-2, MN-2, ME-2, and SME-1. These samples did not show any significant contamination. Laboratory results of all samples collected from the excavation pit are presented in Appendix C. 5.2 SEPTIC TANK REMOVAL On August 9, 1990, during the soil excavation, a septic underground concrete tank was encountered. PHS/EHD and Mr. Lewis, land owner, were informed of the tank's existence. Clayton obtained a septic tank closure permit from the PHS/EHD on August 10, 1990. Ms. Diane Hinson of the PHS/EHD oversaw the septic tank removal on August 17, 1990. Prior tothe septic tank removal, about S inches of waste oil and about 30 inches of solid sewage were removed from the tank. The tank was then steam cleaned. The removed waste oft and resulting rinsate were sent to an oil recycling facility, Domino Kordoon in Comptoa, California, accompanied by a hazardous waste manifest. A copy of the manifest is included in Appendix A. Two soil samples were collected from under the former location of the removed septic tank. The analytical results for these samples are presented in the next section. 5.3 AERATED SOIL SAMPLING AND ANALYSIS The soi)'s excavated from the pit were divided into three piles. The first 2 feet of soil, which appeared to be clean, was piled on the east and west sides of the excavation. The soil excavated from between 2 feet and 10.5 feet below ground surface (bgs) was spread out in a 1-foot layer east of the excavation. The soil excavated from be;ow the septic tank was separated from the rest of the soil and was piled east of(.he excavation. Eight soil samples were collected from the locations shown in Figure 4. Five of these samples were collected from the aerating soil, and one soil sample was collected from each of the remaining piles. These samples were collected in brass cylinders and handled in accordance with the sampling instructions described in Appendix C. Table 4 summarizes the iaboatory results obtained from composite samples. Figure 4 shows locations where�samples were collected. Laboratory results are ._......._.....included.in.Appendix.D._... _ .._.._ -5-