SITE INFORMATION AND CORRESPONDENCE

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Mr. Mike Desso 0 - 3 - • 3 October 2006 7. Text errors Page 6, last bullet item. Monitoring well M-34D, not M-32D, has had VOC concentrations less than 3.3 micrograms per liter. 8. Southerly migration of the VOC plume in the Lower Aquifer along Stockton Avenue. Starting in July 2002, VOC concentrations have been detected during every quarter in monitoring well M-81D. Starting in April of 2005, VOC concentrations have been detected during every quarter in monitoring well M-20D. It would appear that the VOC plume in the Lower Aquifer has migrated south from M-8D to M-20D between 2002 and 2005. However, VOC plume isoconcentration maps prepared for Nestle have shown the area between the two wells as non-detect for VOCs. If Nestle believes that the occurrence of VOCs in the area of M-20D is not related to southerly plume migration, it should install a monitoring well in the Lower Aquifer between the two wells, perhaps at the M-11 well nest. 9. Monitoring frequency at Lower Aquifer wells M-21D and M-23D. Nestle should increase the frequency of monitoring and sampling of wells M-21 D and M-23D to quarterly because the VOC plume in the Lower Aquifer has expanded in areas up- gradient of these wells (at M-8D and M-20D). 10.1ntermediate Aguiferplume capture with MW-9. Nestle and the City of Ripon have entered into an agreement that requires the City to maintain a pumping rate of no less than 600 gallons per minute in MW-9. However, the monitoring well network in the Intermediate Aquifer is not sufficient to evaluate the affect of this pumping. Nestle should install monitoring wells or piezometers in the Intermediate Aquifer to monitor the affect that pumping of MW-9 is having on the aquifer potentiometric surface If you have any questions, please contact Jim Brownell at (916) 464-4675, or by email at jbrownell@waterboards.ca.gov R James R. Brownell, M.S., P.G. Engineering Geologist cc: Distribution list