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-- Clayton <br /> t\'INU%%i1%T"L <br /> C J\51.11 \11 <br /> 4.1.3 Se tip a lank_Excavation and Removal <br /> Prior to the septic tank removal on August 17, 1990, about 8 inches of waste oil and <br /> about 30 inches of solid sewage were removed from the tank. The tank was then <br /> steam cleaned. The removed waste oil and resulting nnsate were sent to an oil <br /> y recycling facility, Domino Xordoon, in Compton, California, accompanied by a <br /> hazardous waste manifest. Ms. Diane Hinson of the SJC/EHD oversaw the septic <br /> tank removal and soil sampling. <br /> 4.2 SOIL AERATION <br /> s The excavated soils were divided into four piles. The first 2 feet of soil from the <br /> excavation, wluch appeared to be clean, was piled on the east and west sides of the <br /> excavation. The sod excavated from between 2 feet and 12 feet below ground surface <br /> b _ <br /> (bgs)was spread out in a 1-foot layer east of the excavation. The soil excavated from <br /> below the septic tank was piled east of the excavation, separate from the rest of the <br /> .z, <br /> sod. <br /> Aeration of the excavated sods was accomplished by spreading it in thin layers <br /> (appr6oinately 1 foot thick) on a polymeric liner. The liner was used to prevent the <br /> s e 5 a <br /> � contaminants in the excavated sod from mixing with surface soil The excavated soils <br /> y> t 'Y werekpenodically rototilled to expose additional soils to aeration. <br /> r a�1 *ns <br /> Eight confirmation soil samples were c1 1 <br /> ollected from the locations shown in Figure 4 at <br /> r theidirection of SJC/EHD. Five of these samples were collected from the aerating <br /> soil, and one,soil sampleAwas collected from each of the remaining piles These <br /> sai6iplesS-were_c6llected in brass cylinders and handled m accordance with the sampling <br /> q s priifocols described:in Appendix A. Table 5 summarizes the laboratory results <br /> obtained fromeotripa5ite samples. <br /> r$ rxf <br /> �Based�onJ'the results of the confirmation soil samples, on September 28, 1990, Clayton <br /> t <br /> recoinrnendead backfilling the excavation. SJC/EHD concurred with this <br /> -reconiuiefidation <br /> 4.3, EXCAVATION BACKFILL. <br /> ry' � Fuel Od;Polishing�Company began backfiWng the excavated pit on October 18, 1990 <br /> NP. <br /> i �y $pause`the groundwater table was shallow {l0 5 to 12 feet bas), Fuel Oil Polishing <br /> r placed'as layer+af clean imported gravel m the bottom of the excavation This gravel <br /> established a suitable base for operation ofsod=compaction equipment. <br /> ,' '�'•;; Fuel'Oil Polishing placed a 2-foot layer of clay, obtained from the walls of the <br /> excavation;on.top of the gravel. This clay was compacted with a vibratory sheepsfoot <br /> f<_ roller. This clay layer was installed to provide a homer between groundwater an <br /> shallow soils that have a low level of hyi:roearbon contamination. <br /> The aerated soil piles were transferred to the excavation, and were compacted in 2- <br /> foot layers. Field activities onsite were completed on October 20, 1990. <br /> ' 7 <br /> prtl+ k <br /> S <br />.r.. i <br /> w <br /> y J k <br /> t <br />]� a <br />