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Mr. Mike Desso Is - 2 - • 19 September 2007 <br /> Nestle USA Inc. <br /> modified to improve the capture of dissolved-phase VOCs in groundwater within the sand <br /> immediately beneath the clay layers.), <br /> 2. In situ reductive dechlorination by zero-valent iron, <br /> 3. Enhanced in situ bioremediation, and <br /> 4. In situ chemical oxidation by activated persulfate injection and ozone sparging. <br /> Nestle proposes to proceed with the first method listed above: Groundwater extraction and <br /> treatment exclusively from upper zone extraction wells. Treated water would continue to be <br /> conveyed to the City of Ripon wastewater treatment plant. Regional Water Board staff <br /> concurs with this proposal. In compliance with Required Action No. 14 of the 24 July 2006 <br /> Cleanup and Abatement Order, and in consideration of the Regional Water Board staff <br /> comments listed below, Nestle must proceed with implementation of the TRAP. <br /> Regional Water Board Review Comments <br /> 1. The installation of shallow extraction wells screened within the sandy material with <br /> elevated concentrations of VOCs should be implemented in such a way as to <br /> maximize gradient control. Nestle should utilize the groundwater model developed for <br /> the site. <br /> 2. The monitoring well network should be configured to monitor horizontal and vertical <br /> groundwater flow gradients. A monitoring well should be installed across the <br /> groundwater table at well nest M-6. This should enhance the vertical flow gradient <br /> monitoring capabilities. <br /> 3. The additional objective to reduce concentrations of VOCs dissolved in groundwater <br /> could be enhanced with implementation of an in situ remediation technology. Nestle <br /> should continue their evaluations of the other three technologies evaluated in the <br /> IRAP as well as other possible technologies not yet evaluated. <br /> Nestle must implement the IRAP and submit a report documenting installation of the revised <br /> groundwater extraction and treatment system components to the Regional Water Board on or <br /> before 21 January 2008. If you have any questions or concerns, please contact me at <br /> (916) 464-4675 or jbrownell(o)waterboards.ca.gov. <br /> R. <br /> James R. Brownell, P.G. <br /> Engineering Geologist <br /> cc: Attached Distribution List <br />