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December 22, 1995 Wright Project No. 4123-S Site Closure Report 6.0 . FIELD, ACTIVITIES - SOIL EXCAVATION, STOCKPILING, AND SAMPLING .6.1 Exploratory Test Pits Wri ght,excavated and observed two test pits(Test Pit 1 and Test Pit 2) on August 18, 1995, within the area of staining at the site. The test pits were excavated with a backhoe through the center.of the stained area and intersected one another. Test Pit 1 was oriented in a northwest-southeast direction through the center of the stained area and Test Pit 2 was oriented in a northeast-southwest direction through the center of the stained area. Both test pits extended to a depth of approximately 4 feet below grade and were approximately 20 feet in length. Obvious staining was encountered within the soil exposed in each test pit. Two HandbyTM field screening samples were collected, one from each test pit, which indicated that the soils had been affected by petroleum hydrocarbons. Some of the overburden soil within the area of the test pits was not found to be affected and was stockpiled at a different location for reuse. The locations of the test pits are shown on Figure 2. 6.2 Excavation and Stockpiling of Contaminated Soils Wright began excavating the overburden and affected soils on August 21, 1995, and completed the excavation work on August 25, 1995. Noticeable staining was observed at the base and sidewalls of the excavation. HandbyTM field screening tests were conducted on the exposed soils until determined to be free of staining and petroleum hydrocarbons. The final dimensions of the excavation were approximately 41 feet long by 37 feet wide by 13 feet deep. The affected soils were removed and placed on sheets,of visquene at a location west of the excavation, designated as Stockpile on Figure 3. The location of the excavation is also shown on Figure 3. 6.3 Confirmatory Soil.Sampling -Excavation Area Wright utilized the services of Blaine Tech Services, Inc. (BTSI) to collect confirmatory soil samples from within the base and sidewalls of the excavation. BTSI collected a total of six soil samples designated as ESW-1, ESW-2, ESW-3, ESW-4, ESW-5, and EBS-1 from the base and sidewalls of the excavation on August 25, 1995, under the direct oversight of Wright personnel and Ms. Linda A. Turkatte, of the San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD). Soil samples ESW-1, ESW-2, ESW-3, and ESW-4 were collected at a depth interval of.approximately 10.5 to 11.0 feet below the existing grade. Soil Sample ESW- 5 was collected at a depth interval of approximately 9.0 to 9.5 feet below grade and sample EBS-1 was collected at a depth interval of approximately 13.0 to 13.5 feet below grade. Sample FSW-1 was collected from the easternmost sidewall;sample ESW-2 was collected from the northernmost sidewall; sample ESW-3 was collected from the westemmost sidewall; and samples ESW-4 and ESW-5 were collected from the southernmost sidewall of the excavation. Soil sample EBS-1 was collected from the base of the excavation. A summary of the soil sample depths and brief descriptions are presented in Table 1. The locations of the soil samples collected are shown on Figure 3. A copy of the BTSI report showing the soil sample locations, descriptions of sample locations, sampling methodology, and associated chain-of-custody documentation, is included in - Appendix A. 6.4 Confirmato Soil Sampling - StockRile Wright personnel collected a total of eight soil stockpile samples (COTSP-1, COTSP-2,COTSP-3, COTSP-4, COTSP-5, COTSP-6, COTSP-7, and COTSP=8) on August 25, 1995, for chemical analyses and disposal at a landfill. Stockpile samples COTSP-1, COTSP-3, COTSP-5, and COTSP-7 were collected at a depth of approximately 18 inches into the stockpile. Similarly, samples COTSP-2, COTSP-4, COTSP-6, and COTSP-8 were collected at a depth of approximately 36 inches into the stockpile. A summary of the soil sample depths and brief descriptions are presented in Table 2. The locations of the stockpile and associated soil samples are shown on Figure 3. 5