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29 October 2003 AGE-NC Project No. 96-0235 Page 2 of 4 3.2. Soil Excavation and Backfilling Soil removal activities will consist of excavating and stockpiling both potentially uncontaminated shallow subsurface soil and petroleum-impacted soil at the site. Based on the findings of previous investigations, the vertical extent of contaminated soil appears to be approximately 55 feet bsg (Figure 3). However, ground water at the site is at approximately 20 feet bsg. Therefore, AGE proposes excavating impacted soil to a depth no greater than 20 feet bsg. The proposed area of soil to be excavated is illustrated in Figure 2. During excavation activities, excavated soil will be screened for volatile organic compounds using an organic vapor meter(OVM)equipped with a photo-ionization detector(PID).Excavated soil wil l be segregated into either "clean" or impacted soil stockpiles. Excavated soil that appears visibly stained, has a petroleum hydrocarbon odor, or OVM readings above background readings will be considered impacted. It is anticipated that approximately 340 cubic yards (500 tons) of petroleum-impacted soil and approximately 340 cubic yards(500 tons)of potentially uncontaminated shallow subsurface soil will be excavated and stockpiled at the site. Uncontaminated "clean" shallow subsurface soil and contaminated soil will be segregated to allow differing disposal alternatives. It is proposed that "clean" soil with no observed petroleum hydrocarbon staining, odor, or OVM readings will be used to backfill the excavation. The remainder of the excavation will be backfilled to original surface grade with imported clean soil and/or AB road base material. Backfill material will be compacted with the excavation equipment.Field procedures for soil excavation activities are presented in Section 5.1. 3.3. Sol] Sample Collection and Analysis Approximately 9 soil samples will be collected from the excavation and submitted for laboratory analysis. Following RWQCB Tri-Regional Board recommendations, soil samples will be collected from each side wall of the excavation at a minimum interval of every 20 linear feet and from the base of the excavation at a minimum of one sample for every 400 square feet of excavation area. Soil samples collected from the sidewalls of the excavation will be obtained from the depth interval of previously identified petroleum hydrocarbon impacted soil (approximately 10 to 15 feet bsg). Soil samples will be collected from the impacted soil stockpile at a minimum frequency of one four- point composite soil sample for every 100 cubic yards of soil; the proposed sampling frequency is the minimum sampling frequency required for waste profiling and landfill disposal.It is anticipated Advanced GeoEnvironmental,Inc.