ARCHIVED REPORTS_SITE CONCEPTUAL MODEL 2009

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amec�9 Nestle Groundwater Extraction Wells Nestle pumped groundwater from four extraction wells at 230 Industrial Avenue, and from two extraction wells at 519 Stockton Avenue, at a combined annual flow rate of approximately 600 gpm in 2007. Extraction well E-6, located at 519 Stockton Avenue, is an Intermediate Aquifer extraction well constructed with a screen interval from approximately 143 to 158 feet bgs, and was pumped at an annual average rate of 380 gpm in 2007. Nearby B-zone (Upper Aquifer) extraction well E-2 (screened from 47.5 to 65.5 feet bgs) was pumped at an average rate of 67.6 gpm in 2007. Onsite extraction wells EW-1 (99— 120 feet bgs) and EI-1 (pumped from the A-zone of the Upper Aquifer, (96 — 116 feet bgs) at average annual rates of 10.9 and 142.5 gpm, respectively. Approximately 63% of the pumping by Nestle wells is from the offsite Intermediate Aquifer extraction well at 519 Stockton Avenue (E-6), and the remainder from the Upper Aquifer (approximately 25.5% from the A-zone and 11.2% of total pumping from the B-zone). Total pumping by Nestle decreased to 382 gpm in 2008 (Table 3) with 66% of extracted groundwater derived from offsite Intermediate Aquifer extraction well E-6. 4.4 AQUIFER PROPERTIES AND GROUNDWATER FLOW 4.4.1 Upper Aquifer The Upper Aquifer likely contains alluvial and fluvial sediments of both the Riverbank and Upper Turlock Lake Formations. According to Burow et al. (2004), moderate groundwater yields are associated with the Riverbank Formation, but high groundwater yields are associated with the Turlock Lake Formation. Production wells drawing from this formation are often capable of pumping rates exceeding 2,000 gpm with specific capacities greater than 50 gpm/foot of drawdown. Average hydraulic conductivity values are on the order of 27 to 54 ft/d (Burow et al., 2004). The horizontal groundwater flow direction in the Upper Aquifer (based on both A- and B- zones) had a radial pattern based on measured water levels in January and July 2008, where the highest water levels are measured in monitoring wells north and northeast of the WWTF lagoons (Appendix F). The position of the apparent water level mound appears to be different during the Q1 and Q3 2008 monitoring events. Groundwater flow beneath the WWTF was generally to the south in 2008, towards the Stanislaus River, and was northward from Doak Boulevard in July 2008, near M-17B/A, but westwards along Doak Boulevard in January 2008, and northward along Stockton Avenue. The water level mounding observed in this area is likely related to industrial water disposal by irrigation at the Neenah Paper Company facility, and the recharge of treated wastewater and untreated industrial process water at the WWTF. Farther north, the groundwater flow direction in the Upper Aquifer was approximately north- AMEC Geomatrix, Inc. I:\Doc_Safe\9000s\9837.005\4000 REGULATORY\SCM_01.30.09\1_text\SCM Report Final.doc 34