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Clayton Co`5UITAN T5 The concentration of TRPH in the water sample collected from the excavation pit was 2 ppm. The groundwater sample was not analyzed for gasoline or BTEX. 4.1.2 Overrexcavation Based on the initial excavation, Clayton recommended additional excavation of soil from the north and east walls. The excavation in the vicinity of the north and east walls was deepened to approximately 12 feet below grade, where soil appeared to be clean based on visual observation and readings from the OVM. In some areas, the excavation was deepened below the water table,. The walls of the excavation were expanded to the north and to the east. On August 9, 1990, a concrete, underground septic tank was encountered. SJC/EHD and -` Interland Corporation were informed of the tank's existence. Clayton obtained a septic tank closure permit from the SJC/EHD on August 10, 1990. Ms. Diane Hinson of the SJC/EHD oversaw the septic tank removal and soil sampling on August 17, 1990. New confirmation samples were collected from the north and east walls after any soil i that showed evidence of potential contamination was excavated. The excavation was deepened to approximately 13 feet below grade in the vicinity of the former septic tank (4 feet below the bottom of the tank). This overexcavation included the area where soil sample ME-1 was collected. Clayton sampled the soil at 13 feet below j grade (IT-4'-BT). In total, the following six soil samples were collected from the overexcavation: Au,gust L7. 1990: N&2, ME-2, SME-1, IT-6"-BT, and IT-4'-BT ' : I • Au st 2$ 1990: MN-2 The soil samples were analyzed by EPA Method 418.1, for TIZPII. Only samples ME- '" 2 and MN-2 were analyzed by EPA Method 5030/8015-8020,for gasoline and BTEX, . Additionally, sample IT-6"-BT, collected from 6 inches below the former septic tank, was analyzed by the following methods: EPA Method 8010,for purgeable halocarbons I EPA Method 6010, fortotal and soluble lead The sample locations are n►dicated on Figure 3. Table 4 summarizes iaborato ry results. Notable results are Usted below.. • None of the organic canstituentsfor which analyses.wereconducted were detected: 5 _:_:.. ...:.. _._._... ......... .. = Sample TI'-6"-BT had lead concentrations well }} - _ within background levels for soil. . total of about 1,650 cubic yards of soil were excavated to achieve removal of soils with concentrations exceeding 3.6 mg/kg of gasoline and 80 mg/kg of oil and grease. 6