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April 11, 1996 �.- Page 5 If groundwater is encountered within the trench excavation, groundwater samples will be collected by the use of disposable bailers. The samples will be decanted irkto 40 milliliter volatile organic analysis (VOA) containers, preserved with a volume of hydrochloric acid sufficient to produce a 10% solution in the filled containers. Groundwater samples will be labeled, sealed in plastic bags; placed on ice, and transported to the laboratory accompanied by the appropriate chain-of-custody documentation. Excavation Backfill Upon completion of tank closure and soil and groundwater sampling activities, the trench will be backfilled with clean, imported backfill material. The backfill will be appropriately compacted, and the asphalt surface of the site restored. Laboratory Analytical Procedures Soil and groundwater samples will be analyzed for total purgeable petroleum hydrocarbons calculated as gasoline (TPPH-g), benzene, toluene, ethylbenzene, and xylenes (BTEX compounds), and lead. All analyses will be performed by a state- certified analytical laboratory. Sample extraction for TPPH-g and BTEX analyses will be performed by the purge-and- trap method, EPA Method 5030. Analyses for TPPH-g and BTEX compounds will be performed by modified EPA Methods 8015 and 8020. These analytical methods utilize gas chromatography and flame-ionization detection or photo-ionization detection. The detection limit for TPPH-g is 1.0 part per million (ppm). The detection limit for each of the BTEX compounds is 0.005 ppm. Sample extraction for lead analyses will be performed by acid digestion= EPA Method 3005. Analyses will be performed by the inductively coupled plasma(ICP) method, EPA Method 6010. The detection limit for lead by this method will be 5.0 ppm. Disposal of Excavated Soils For each 50 cubic yards of stockpiled soil, four soil samples will be collected. These soil samples will be submitted to an analytical laboratory and composited four-into one prior to chemical analysis. The resulting composite soil samples will be analyzed for TPPH-g, BTEX compounds, and total lead. The results of these analyses will be used to determine an appropriate disposal site for the stockpiled soils. The analytical data for the composite stockpile samples will be submitted to Unocal and the PHS/EHD. Upon approval by the PHS/EHD, PACIFIC will arrange to have the soils hauled to an appropriate landfill. The stockpiled soils will be manifested, 3100971B\TANKWP.DOC