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N Site Background Information - Grewal's Market Page 6 of 6 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 ground water monitoring data collected at the site since February 2000, ground water levels steadily declined from 46 feet bsg in May 2000 to 61 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-8, MW-1 through MW-3), but was encountered at depths between 60 feet and 65 feet bsg following 2002 from soil borings P-10 through P-12, P-15, P-15B, P-16, CPT-1 and CPT-2. 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. 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 between surface grade and 45 feet bsg (approximate depth to historic ground water high). Comprised primarily of less permeable, confining to semi-confining silty clay/clayey silt and sandy silt. • Hydrogeologic Unit 9 (HU1) - Located between 45 feet and 63 feet bsg, characterized by variable low to medium pore pressures. Comprised primarily of less permeable, confining to semi-confining, silty clay/clayey silt and sandy silt. • Hydrogeologic Unit 2 (HU2) - First `flow unit' located between 63 feet and 72 feet bsg. Generally characterized by low to medium pore pressures and comprised primarily of permeable, silty sand and fine to medium sand. • Hydrogeologic Unit 3 (HU3) - Located between 72 feet and 80 feet bsg. Generally characterized by variable low to medium pore pressures and comprised primarily of less permeable, semi-confining to confining, stiff fine grained silt and clay. • Hydrogeologic Unit 4 (HU4) - Second `flow unit' located between 80 and 95 feet bsg. Generally characterized by low and medium pore pressures and comprised primarily of semi- permeable silty sand, sandy silt and permeable fine to medium sand. Advanced GeoE nviron mental,Inc.