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IWO Site Background Information: Larry's Auto Page 7 of 8 PRELIMINARY SITE CONCEPTUAL MODEL • AGE interpreted the CPT data to identify three potential hydrogeologic flow units informally identified as HU2-First Flow Unit, HU4-Second Flow Unit and HU6-Third Flow Unit . Generally,permeable to semi-permeable lithology was observed in the units that consisted of gravelly sand, fine to medium sand and silty fine sand. • AGE interpreted the CPT data to identify semi-confining/confining units informally identified as HUl, HU3 and HUS. Generally, semi-confining, silty fine sand and isolated intervals of silty clay/clayey silt was observed from HUI and less permeable, semi- confining to confining, stiff fine grained silt and clay observed from HU3. • Petroleum hydrocarbons were detected at three of the six CPT locations:CPT-1 at the former gasoline UST area at the northwest corner of the site and CPT-5 and CPT-6 at the eastern and southeastern end of the block. The lateral extent of petroleum hydrocarbon contamination is defined to the west by soil boring CPT-8,to the north by soil boring CPT-9, and to the southwest by CPT-7; the lateral extent appears undefined to the northeast, east, southeast, and south. • The vertical extent of petroleum hydrocarbon-impacted ground water is undefined at the former gasoline UST location(CPT-1)and at the eastern end of the block on Aurora Street (CPT-5); however, it should be noted that CPT-5 was a shortened boring, encountering refusal at 115 feet bsg. Based on the November 2001 CPT investigation,the vertical extent of petroleum hydrocarbon-impacted ground water also is undefined at the former diesel fuel UST location along Miner Avenue. • Two soil samples were collected for laboratory analysis, one at 60 feet bsg (HUl/HU2 boundary)in CPT-7 and at 155 feet bsg(HU6)in CPT-8.No petroleum hydrocarbons were detected at or above laboratory reporting limits. Based on the data collected to date from CPT borings, soil borings and ground water monitoring wells, AGE has developed a preliminary site conceptual model for the release, migration and distribution of the contaminants in the subsurface as described below. The transportation of the migrating hydrocarbons originated at the former UST areas.One UST was located near the northwestern edge of the parking lot at the site and an additional set of tanks were located on the southern sidewalk of the site. The former UST dispenser area was above to each of the UST system, thus the release locations were generally centralized to the UST locations. The release occurred separately at each UST set, the northern and the southern area, and then migrated vertically to a depth likely near 60 feet bsg,based on soil impact. Free product was encountered in MW-4 and removed. The hydrocarbons dissolved at a depth near 50 feet bsg, that created a significant smear zone or possible a highly-saturated hydrocarbon impacted soil, as depicted in water samples collected from boring VWS. Advanced GcoEnvironmental,Inc