ARCHIVED REPORTS_REMEDIATION COMPLETION REPORT

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3.0 FIELD ACTIVITIES the excavated soil and ambient air.The construction superintendent used the field screening observations to manage the excavation activities and to determine the excavation limits. Excavation slopes were benched and sloped as necessary to maintain slope stability along the boundaries of the excavation and to retain support below existing underground utilities to the west and east (Figure 4). Localized areas within the excavation were deepened to a maximum depth of 14 feet bgs. Based on initial sidewall sample results collected along the northern perimeter of proposed excavation Area 1 (Figure 3),soil between excavation Areas 1 and 2 was removed and the combined excavation area was expanded to the northwest to form a single large excavation. Verification soil samples were collected and analyzed to confirm the extent of source removal in the base of the excavation and to document the concentration of petroleum hydrocarbon concentrations in excavation sidewalls. Verification sampling results are discussed in Section 3.7.3. Groundwater was observed to enter a portion of the excavation at a depth of approximately 12 feet bgs. Minor petroleum sheen was observed on the water surface.Groundwater was not removed prior to backfilling the excavation with drain rock. The quantity of soil removed was 2,590 tons(approximately 1,620 in-place cubic yards).Soil removed was directly off-hauled by PG&E's subcontractor,DenBeste Transportation,to Forward Landfill in Manteca,California. Copies of the non-hazardous waste manifests for soil are included in Appendix D. 3.7 Results 3.7.1 Sampling for Disposal Pre-acceptance Two pre-acceptance soil samples were collected for disposal pre-acceptance criteria as discussed in Section 3.2. Both samples were analyzed for benzene,toluene,ethylbenzene and total xylenes (BTEX) (U.S. Environmental Protection Agency [USEPA]Method 8021) and total petroleum hydrocarbons(TPH) (USEPA Method 8015 Modified) within 24 to 48 hours of sampling.TPH results were reported in the gasoline range (TPH-g,C6-C>o),the diesel range (TPH-d,C10-C24),and the motor oil range (TPH-mo,C24-C36).These samples were also analyzed for CAM-17 metals as required by the disposal facility. BTEX was not detected in either sample.TPH-g was detected at concentrations of 3.6 and 6.1 milligrams/kilograms (mg/kg) in samples 20-MW-2-5-10-11-04 and 20-MW-2-10-10-11-04 at 5 and 10 feet,respectively. TPH-d was detected at 16 and 49 mg/kg at 5 feet and 10 feet bgs, respectively,and TPH-mo was detected at 13 and 25 mg/kg collected at 5 and 10 feet bgs, respectively. Results for BTEX,TPH,and metals met Forward Landfill's acceptance criteria.The results are summarized in Table 1.The analytical laboratory reports and COC documents are provided in Appendix E. 3.7.2 Northern Perimeter Soil Sampling As discussed above in Section 3.5, six soil samples were collected and five analyzed from the northern perimeter of the excavation prior to general excavation activities.These soil samples were submitted to APPL Laboratories, Inc. for analysis for BTEX and TPH. As with SF01(THORNTON COMPLETION REPORT_6-21-05.DOC) 34