ARCHIVED REPORTS_QUARTERLY REPORT - THIRD QUARTER 2005

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Appendix A - Historical Background River City Petroleum and Connell Motor Lift Truck Page 10 of 13 Based on the CPT results, AGE has developed a preliminary site hydrogeologic model comprised of seven informal zones,a vadose(unsaturated)zone and six hydrological units;the model presented is interpretational and will be modified as more data is collected. The seven zones are as follows (depths are approximate and can vary by several feet across the site): • These characteristics allowed construction of a site geologic/hydrogeologic model of the vadose zone extending from surface grade to approximately 50 feet bsg or the current water table level which fluctuates with seasonal recharge in the area. The hydrologic units defined are informal units and vary considerably based on the direction and content. The units are designated to aide in the clarification of flow pathways and to designate migration pathways. • The first hydrologic unit from 50 feet or the water table to 75 feet bsg; a second hydrologic unit from 75 feet bsg to 85 feet bsg;and a third hydrologic unit from 85 feet to approximately 100 feet bsg; a fourth hydrologic unit from 100 feet to 110 feet bsg, a fifth hydrologic unit from 110 feet to 145 feet bsg,the sixth hydrologic unit at 145 to 185 feet bsg. The second, fourth locally and sixth are presumed to have a greater ground water velocity and therefore may conduct more ground water.The seventh hydrologic unit begins vertically at 160 to 185 feet bsg, and extends vertically,unmodified to the depth of the current investigation limits. • First Quarter 2004. This unit is consistently composed of sand,with gravel locally present. SITE CONCEPTUAL MODEL Based on the data developed to date,including all soil borings,monitoring wells installed and CPT soundings,AGE has developed a site subsurface model for the release, migration and distribution of the varying contaminants in the subsurface as described below: • The subsurface from site grade to approximately 240 feet bsg is composed primarily of fine-grained soil with a coarse-grained interval of variable thickness and semi-consistent lateral distribution. A major coarse-grained sand and gravel interval in the vadose zone occurs between 20 and 35 feet bsg;a laterally continuous coarse-grained sand interval occurs at approximately 75 to 85 feet bsg and approximately 150 feet bsg;a vertically and laterally significant sand/gravel unit begins at 165 to 185 feet bsg, and is present across the site#o a depth of 240 feet bsg. A laterally discontinuous, yet significantly thick sand unit extends from 100 feet to 110 feet bsg. • Overall high pore-pressure was documented in the CPT sounding of the coarse-grained sand below the water table. The remaining stratigraphy of the site is comprised of silt with clay inter-channel fill areas. A laterally continuous clay, locally silt at CPT9, unit is present ibeginning at 120 feet bsg across most of the distribution of the contaminate plumes. Advanced GeoEnvironmental,Inc.