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Site Background Information: Former Ocampo Property Page 4 of 6 xylenes (MW5-15). TPH-g and one or more BTEX compounds were reported in soil samples collected from MW6-5, -35,-40-45,-50,-55, and -60 at maximum concentrations of 2,000 mg/kg TPH-g, 3.2 mg/kg, benzene, 52 mg/kg toluene, 39 mg/kg ethylbenzene, and 273 mg/kg total xylenes, in sample MW6-40. TPH-d was reported in samples collected from MW6-35,-40,- 45,-55, and -60 at a maximum concentration of 230 mg/kg in sample MW6-40. Soil samples collected from boring VW2-10 and VW2-5 reported TPH-g at a maximum concentration of 6.6 mg/kg in sample VW2-10. One or more BTEX compound were reported in soil sampled collected from VW2-10, -15, and -20 at maximum concentrations of 0.048 mg/kg benzene (VW2-10), 0.22 mg/kg toluene (VW-10), 0.064 mg/kg ethylbenzene (VW2-20), and 0.680 mg/kg total xylenes (VW2-15). Petroleum hydrocarbons were reported in soil samples collected from boring MW5, MW6 and VW2, adjacent to the former UST excavation area. The lateral extent of petroleum hydrocarbon-impacted soil is defined to the south and north by MW3 and MW1, respectively. Lateral extent appears undefined to the east by boring VW2 and west of the former UST location. The vertical extent of petroleum hydrocarbon-impacted soil is undefined within the former UST location (borings for B5 and MW5 impacted at depth). STRATIGRAPHY Brown to yellow-brown and reddish-brown clays, silty clays, and clayey silts were encountered throughout the majority of each boring to a depth of approximately 50 feet. Brown to yellow-brown clayey sands and silty sands were encountered at 5 feet bsg in the northeast and southeast of the borings completed. More clayey sand was encountered at 10 feet bsg in MW-1. This may be a continuation of that encountered in MW-2. Orange- brown silty sand was encountered at 20 and 25 feet bsg in MW-2. Brown to yellow-brown fine sands and clayey fine sands were encountered around 50 feet bsg. HYDROGEOLOGIC MODEL A hydrogeologic, or hydrostratigraphic, unit (HU) is defined as a body of rock or sediment that has hydrogeologic characteristics (i.e. hydraulic conductivity, pore pressure, etc.) that make it distinct from surrounding bodies of rock or sediment (Sanders, 1998), or a part of a body of rock that forms a distinct hydrologic unit with respect to the flow of ground water (Maxey, 1964). A 'flow unit' may be defined as a hydrogeologic unit and is characterized by significantly greater hydraulic conductivity values than overlying and underlying units; a flow unit is capable of serving as a preferred migration route, and could potentially allow migration of large contaminant masses over great distances. Advanced GeoEnvironmental, Inc.