SITE INFORMATION AND CORRESPONDENCE

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Mr. Mike Desso -3- 31 August 2011 resume monitoring and sampling of M-13A on a quarterly basis beginning with the fourth quarter 2011 event. Nestle Monitorinq Well Nest M-28: Well nest M-28 is a guard well nest for City water supply well MW-3. The nest is located approximately 2,310 feet west of the former facility and approximately 1,050 feet southwest of well nest M-13. Central Valley Water Board staff notes that TCE and cis-1,2-DCE were detected in 2009 in monitoring well M-28C1 which is screened in the C Zone between 148 and 158 feet bgs. Both CDCs were detected during all seven subsequent events through the second quarter of 2011. The attached graph shows the TCE and cis-1,2-OCE concentration trends between January 2004 and June 2011. As is the case with M-1 3A, the COC concentration trends are increasing. Also, staff notes that TCE was detected for the first time during the fourth quarter of 2010 in the adjacent C Zone monitoring well M-28A/C, screened between 127 and 132 feet bgs. TCE was detected during both subsequent sampling events during the first and second quarters of 2011. As with M-1 3A, the well screen is near the boundary of the A and C Zones. The COC concentration trends in M-28A/C are, as yet unknown. Nestle should begin discussions with the City regarding recent detections of COCs in the M-28 nest guard wells and in City water supply well MW-3. City Water Supply Well MW-3: Water supply well MW-3 is located approximately 1,120 feet west of guard well nest M-28. It is a 156 feet deep, opened bottom well, utilized by the City for supply of potable water. The well casing is likely perforated within sandy units of the A and C Zonesr.but this is unknownbecause the well completion report is unavailable. Therefore, it pumps from the C Zone, and possibly the A Zone, if perforated within A Zone sandy units. TCE and cis-1,2-DCE were first detected in MW-3 during the first quarter of 2007, and have been detected during every quarter from the fourth quarter 2007 through the second quarter 2011. The trends are increasing with the highest concentrations reported during the third quarter 2010. The attached graph shows the TCE and cis-1,2-DCE concentration trends between January 2004 and June 2011. Nestle should begin discussions with the City regarding MW-3 pumping rates and any available information on the perforation intervals within MW-3. School Water Supply Well RPS-1: RPS-1 supplies irrigation water to the Ripon USD school at 304 North Acacia Avenue. Attached Figure 5 of the Report shows the geologic cross section along transect B'-B extending from the southeast end of Pine Street (CPT-21) west to Locust Avenue (CPT-30). Concentrations of TCE were detected in CPT-30 groundwater samples collected from two of the three sandy units of the A Zone. Central Valley Water Board staff note that TCE and cis-1,2-DCE were detected on 20 July 2006 in water supply well RPS-1, located approximately 1,190 feet west of transect B'-B and 1,610 feet west of well nest M-10. TCE or cis-1,2-DCE were detected in RPS-1 during 31 of the 37 subsequent monthly sampling events through August 2009. Between September 2009 and June 2011, TCE and cis-1,2-DCE have both been detected during all 21 monthly sampling events. The attached graph shows that concentration trends for both CDCs are increasing; the highest TCE concentration of 4.4 pg/L was detected during the April 2011 sampling event. The well's casing is 149 feet deep, but the screen intervals are not available. Therefore, it is unknown whether the well is screened within the A or C Zones, or both. It is possible that TCE and cis-1,2-DCE have migrated from the former facility within sandy units of the A or C Zones to RPS-1. Additional investigation soil borings between CPT-30 and RPS-1 are needed to