ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study are or have been amenable to biodegradation in the area beneath the City of Ripon wastewater lagoons. 6.2 Vertical distribution of VOCs in Groundwater Historically, the subsurface beneath the Study Area has been divided vertically into the vadose zone and five water-bearing units named B, A, C1, C2, and D, with increasing depth. In a 2001 assessment, IT Corporation" combined these water-bearing units as follows: • Upper Aquifer, consisting of the B and A subunits, generally ranging from 25 to 120 feet below ground surface (bgs); The B subunit generally ranges from 25 to 70 feet bgs, with the A subunit ranging from approximately 85 to 120 feet bgs. • Intermediate Aquifer, consisting of the C1 and C2 units, generally ranging from 120 to 190 feet bgs; and • Lower Aquifer, consisting of the D unit, extending from 210 feet bgs to at least 390 feet bgs. For the purposes of this Revised FS, with remedial approaches and objectives as a primary focus, ECM has utilized the above vertical designations when referring to the primary water bearing units. These vertical units have been selected in order to provide a useful division of the subsurface for the purpose of outlining possible remedial alternatives in Sections 10 and 11. A description of these subsurface intervals, and the current understanding of the distribution of VOCs within each Zone, is provided below: 6.2.1 Upper Aquifer (25 to 120 feet bgs) The highest TCE concentrations in the Upper Aquifer were reported during sampling performed in August 2005 using a Cone Penetrometer Test (CPT) boring procedure""'. Historically, the highest TCE concentrations (greater than 1,000 fag/L) have been reported in groundwater samples from wells offsite in the B subzone of this aquifer at wells M-613 and M-81B. TCE concentrations have decreased substantially since 1987 at M-813, in part, due to groundwater extraction although decreasing trends are apparent prior to initiating groundwater extraction in 2001 . An increase in TCE concentrations was observed at M-613 between 1987 and 1993, followed by a decreasing trend through October 2010. A similar increase in concentration (from 1987 to 2005), followed by a decreasing trend has been observed at well M-1 B. Lower TCE concentrations have been reported in samples taken from off-site well M-22B and onsite well M-1 B. These trends indicate that the Upper Aquifer TCE plume appears to be limited in extent and has been attenuated over time. 6.2.2 Intermediate Aquifer (120 to 190 bgs) Intermediate Aquifer groundwater is affected by TCE, cis-1,2-DCE, and VC (VC and cis-1,2-DCE are breakdown products of TCE). The highest COC concentrations in 2007/2008 were reported in samples from well M-31 C1 (TCE, 16