ARCHIVED REPORTS_XR0012706 - Laserfiche WebLink

Home Browse Search

Mr` 1 Clayton EMC)N%I["tAt C01,SI.L1, T5 Y4.1.3 Se�t1e TSL xcuvation and Removd Prior to the septic tank removal on August 17, 1990, about 8 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 oil and resulting rinsate were sent to an oil recycling facility, Domino Kordoon, in Compton, California, accompanied by a hazardous waste manifest. Ms. Diane Hinson of the SJC/EHD oversaw the septic tank removal and soil sampling. 4.2 SOIL AERATION The excavated soils were divided into four piles. The first 2 feet of soil from the excavation, which appeared to be clean,was piled on the east and west sides of the excavation. The soil excavated from between 2 feet and 12 feet below ground surface (bgs)was spread out in a 1-foot layer east of the excavation. The soil excavated from below the septic tank was piled east of the excavation, separate from the rest of the soil. Aeration of the excavated soils was accomplished by spreading it in thin layers (approximately 1 foot thick) on a polymeric liner. The liner was used to prevent the contaminants in the excavated soil from mixing with surface soil. The excavated soils were periodically rototilled to expose additional soils to aeration. Eight confirmation soilsamples were collected from the locations shown in Figure 4 at the direction of SJC1/EHD. 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 :. protocols described iso Appendix A. Table 5 summarizes the laboratory results I obtained from composite samples. j Based on the results of the confirmation soil samples, on September 28, 1990, Clayton recommended backfilling the excavation. SJC/EHD concurred with this recommendation. 4.3 EXCAVATION BACIFICLL E Fuel Oil Polishing Company began backfilling the excavated pit on October 18, 1990. Because the groundwater table was shallow (10.5 to 12 feet bgs), Fuel Oil Polishing placed a layer of clean imported gravel in the bottom of the excavation. This gravel established a suitable base for operation of soil compaction equipment. Fuel-_Oil Polishing placed_a 2-foot layer of clay, obtained from the walls of the - ' excavation, on top of the gravel. This clay was compacted with a vibratory sheepsfoot roller. This clay layer was ins.kalled to provide a barrier between groundwater and d shallow mils that:h6ve a low level of hydrocarbon contamination. The aerated soil piles were transferred to the excavation,and were compacted in 2- foot layers. Field activities onsite were completed on October 20, 1990. _.., 7