ARCHIVED REPORTS_STOCKTON AVENUE SYSTEM WELL E-2 POST-SHUTDOWN EVALUATION

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Stockton Avenue System Well E-2 Post-Shutdown Evaluation November 21, 2012 Former Nestle USA, Inc. Facility, Ripon, CA EVALUATION 1. Well E-2: • This is an extraction well operating since 1999. The maximum TCE concentration observed in this well prior to shutdown was 150 microgram per liter (µg/L) in January 2000. • Following the shutdown of E-2 in October 2010, the concentration of TCE increased from 1.3 pg/L in November 2010 to 2.5 pg/L in April 2011. Since April 2011, the TCE concentration decreased to 0.87µg/L in August 2012. • The TCE concentrations follow a decreasing trend since shutdown in October 2010 (Figure 1). • Data trends, as well as the magnitude of concentrations, indicate that there is no rebound of TCE concentrations in Well E-2. 2. Well M-813 (located immediately south of E-2): • TCE and cis-1-2DCE data for this well since September 19901, as well as data collected since initiation of extraction from well E-2 in 1999, show a concentration decrease of more than 96% for both CDCs (Figure 2). This suggests significant mass removal due to the operation of extraction well E-2 before shutdown in October 2010. • The concentration of TCE decreased from 9.7 µg/l_ in November 2010 to 8.9 µg/l_ in August 2012. Though there are some variations in concentrations between November 2010 and August 2012, TCE concentrations remained the same or below the post- shutdown concentration (Figure 1). • Post-shutdown data indicates either a stable/decreasing trend (Figure 1). 3. Well 52B (located approximately 70 feet north of E-2): • The concentration of TCE increased from 1.5 µg/L to 3.7 pg/L after shutdown of well E-2, within a four-month period. This is a typical trend for a downgradient well. • The highest post-shutdown TCE concentration was observed in April 2011 (3.7 µg/L). Since that time, TCE has decreased to 3.2 µg/l_ (August 2012). • The concentration of TCE in this well shows a stable/decreasing trend since the observation of highest post-shutdown concentration. 4. Well 53B (located approximately 150 feet northwest/downgradient of E-2): • As observed in well M-52B, TCE concentrations in this well increased after shutdown, from 3.6 µg/l_ to 7.4µg/l_ after approximately six months. As stated, this is typical for a downgradient well. • Since the highest concentration observed in this well during the April 2011 event, TCE concentrations decreased from 7.4µg/L (in April 2011)to 3.0 µg/l_ in August 2012. Monitoring data for well MW-81B is available since October 1, 1987. Data prior to September 1, 1990 includes variable reporting limits and thus were not included in Figure 2. Page 2 of 3