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27 October 2006 AGE-NC Project No. 02-0950 Page 2 of 4 2.2. SOIL EXCAVATION Hydrocarbon-impacted soil from beneath the former UST area (Figure 2) will be excavated to facilitate an overall mass reduction of contaminants. Petroleum hydrocarbon-impacted soil in the vadose zone appears to be limited to the area containing well MW-2 and soil borings B 1 through B4. Impacted soil at the site has an estimated north-south diameter of approximately 50 feet,an east-west diameter of approximately 40 feet, and appears to extend downward to maximum depths between 35 feet and 40 feet below surface grade (bsg). The greatest concentrations of impacted soil are present at depths between approximately 5 feet and 20 feet bsg (Figures 3 and 4). Soil will be removed to a depth of approximately 24 feet bsg using an excavator, with an estimated 550 to 600 yards of impacted soil to be removed and disposed. The proposed extent of soil excavation is depicted on Figure 2. During excavation activities, soil will be screened for organic vapors using a organic vapor meter (OVM). Saturated soil will be piled within piles of dry impacted soil for disposal and excavated soil that appears visibly stained or has a petroleum hydrocarbon odor will be considered impacted. 2.3. SOIL SAMPLE COLLECTION AND ANALYSIS A total of five soil samples will be collected from the excavation and submitted for laboratory analysis. Following State of California Regional Water Quality Board, Tri-Regional Board recommendations,soil samples will be collected from the base and each side wall of the excavation at a minimum interval of every 20 linear feet. Soil samples will be collected from the base of the excavation at a minimum of one sample for every 400 square feet of excavation area. Field procedures for collection of soil samples are presented in Section 3.2.. Soil samples will also be collected from the stockpiled soil from the excavation. For soil disposal characterization, a 4:1 composite soil sample will be collected from every 100 yards of soil excavated. Each soil sample will be analyzed by a State of California Department of Health Services (DHS)- certified laboratory for the following constituents: • Total petroleum hydrocarbons quantified as gasoline (TPH-g) and diesel (TPH-d) in accordance with EPA Method 8015 Modified; • Benzene,toluene,ethylbenzene,and total xylenes(BTEX)and fuel additives methyl tertiary- butyl ether(MTBE),tertiary-butyl alcohol(TBA),di-isopropyl ether(DIPE),ethyl tertiary- butyl ether(ETBE),tertiary-amyl methyl ether(TAME), 1,2-dichloroethane(1,2-DCA),and 1,2-dibromoethane(EDB) in accordance with EPA Method 8260B. Advanced GeoEnvironmental,Inc.