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' 29 March 2004 . AGE-NC Project No. 97-0327 ' Page 5 of 12 ' feet bsg and at depths greater than 65 feet bsg. General lithology beneaththe it e in cross-sectional view is depicted in Figures 3 and 4; boring logs are included in Appendix o" OS 4I I Permeability and porosity characteristics were tested at 35 feet bsg and at 55 feet bsg in soil samples-� ' collected at the site in February 2002 (Quarterly Report-First Quarter 2002, dated 17 July 2002). Analysis of the 35 foot soil sample reported an average permeability in a clayey sand (lower vadose ' zone) at 3.0 x 10-6 cm/s, porosity at 40 percent and moisture at 23 percent. Analysis of the 55 foot soil sample reported an average permeability in a silty clay-with sand (upper hydrogeologic unit 1) at 6.0 x 10-6 cm/s, porosity at 49 percent and moisture at 34 percent. ' Physicochemical &microbial characteristics were tested at 40 feet bsg in a soil sample collected at the site in February 2002 (Quarterly Report-First Quarter 2002, dated 17 July 2002). Analysis of ' the 40 foot soil sample reported the general microbial enumeration was 9.9 x 105 CFU (colony forming units)per gram,and hydrocarbon-degrading microorganisms were present at 1.2x 105 CFU, or approximately 12.12 percent of the sample. Physicochemical laboratory analysis detected ' concentrations of nitrate at 48.4 mg/kg, nitrate as nitrogen at 11 mg/kg, ammonia as nitrogen at 22 mg/kg, phosphorus at 31 mg/kg and potassium at 46 mg/kg. ' • Based on groundwater monitoring data collected at the site since February 2000,groundwater levels have steadily declined from 45 feet bsg in May 2000 to.62 feet bsg in September 2003. The depth at which saturated soil was encountered in soil borings reflects the declining water level; saturated ' soil was encountered at approximately 55 feet bsg in years 1999 and 2000 soil borings (P-S,MW-1 through MW-3), but was encountered at between 60 feet and 65 feet bsg in year 2002 soil borings . (P-10 and P-11). Based on the subsurface soil distribution and depth to water table,AGE has developed a preliminary ' subsurface model of the hydrostratigraphy consisting of a vadose zone and one informal hydrogeologic zone (Figures 3 and 4). Hydrogeologic units are defined as significant vertical intervals of soil having significant lateral extent and having similar-hydrologic characteristics with respect to ground water flow (i.e. hydraulic conductivity, transmissivity, etc.) over its vertical and - '. horizontal extent. The hydrogeologic'model is identified as follows(depths are approximate and can vary by several feet across the site): • Vadose Zone - Located from surface grade to the water table at approximately 60 feet bsg, and consists primarily of laterally continuous less permeable fine grained, silts and sandy TT $} silt; two Iaterally continuous silty sand intervals were generally identified, at depths of between 20 and 35 feet bsg and between 50 and 60 feet bsg. 1 .