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1 ' 20 October 200 • AGE-NC Project No 95-0111 ' Page 4 of 8 Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and ' generally consist of moderate to poorly drained fine-textured soils The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from ' mixed rock sources The Modesto, Riverbank,Turlock Lake Formations and overlying recent alluvium are the principal ' source of domestic ground water in the 13,500-square-mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primanly by the San Joaquin River The nearest surface water feature in the vicinity of the property is the Old River approximately 1,300 feet north of the site 1 2 5 GROUND WATER DEPTH AND GRADIENT ' Based on seven years of quarterly monitoring, the depth to ground water has consistently been approximately 6 to 10 feet bsg at the site,and has consistently had a northerly flow direction Ground t water occurs in a generally silty clay extending from surface grade to the total depths of the wells on-site Off-site in well MW-4 and MW-5,ground water also occurs in gravel extending from 10 feet to 15 feet bsg lie 3.0 GROUND WATER MONITORING EVENTS: JANUARY 1994 TO JUNE 2003 ' Ground water monitoring has been performed on wells MW-1, MW--2 and MW-3 at the site on a quarterly basis since January 1994,on well MW-4 since December 1994,on wells MW-5 and MW-6 ' since March 1996, and on wells MW-7 and MW-8 since March 1999 During this time, depths to ground water from wells MW-1 through MW-8 were measured between 5 97 and 1147 feet below ' the top of well casings Groundwater at the site has consistently had a northerly flow direction under an average gradient of approximately 0 008 foot/foot (Figure 3) Ground water elevation data are summarized on Table 2 4.0. WATER WELL RECEPTOR SURVEY ' Drinking water at and near the site is not currently supplied by the City of Tracy or San Joaquin County On 08 September 2000, a representative of AGE performed a reconnaissance of visually ' observable potential receptors within a 2,000-foot radius of the above referenced site Four domestic water wells were observed during the visual search Two domestic water wells were observed at 2450 and 2480 Toste Road The remaining two domestic water wells were observed at 2040 and ' 2120 Grant Line Road Additionally, 18 ground water monitoring wells were observed at 3 different . locations ' Advanced GeoEnvironmental Inc 1