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r r • • <br /> r, <br /> ENVIRONMENTAL COST MANAGEMENT INC <br /> 3525 Hyland Aventj .Snin,200 <br /> Costa Mesa Calitorna'3262b <br /> Mile;(714)662 2759 F,. J714)662 2758 <br /> November 5, 2009 <br /> James Brownell, P.G. IUvU� v I� <br /> Central Valley Regional Water Quality Control Board NOV d 9 2009 <br /> 11020 Sun Center Drive, #200 <br /> Rancho Cordova, CA 95670 ENVIRONNIEN1 HEALTH <br /> PERMIT/SERVICES <br /> Ref.: Stockton Avenue Groundwater Extraction System Shut-down Request <br /> Extraction wells E-2 and E-6 <br /> Former Nestle USA, Inc. <br /> 230 Industrial Avenue <br /> Ripon, CA 95366 <br /> Dear Mr. Brownell: <br /> On behalf of Nestle USA, Inc. (Nestle), Environmental Cost Management, Inc. (ECM) <br /> requests your approval to shut-down the Stockton Avenue groundwater treatment <br /> system. This letter follows our discussion during an October 1, 2009, meeting at which <br /> Nestle, ECM, AMEC/Geomatrix, and Central Regional Water Quality Control Board <br /> (RWQCB) representatives participated. A follow up telephone discussion was held on <br /> October 22, 2009. <br /> Groundwater treated at the Stockton Avenue System is extracted from two extraction <br /> wells, E-2 and E-6. The groundwater treatment system at Stockton Avenue (Stockton <br /> Avenue System) consists of an air stripper, catalytic oxidizer (cat-ox) to destroy the air <br /> stripper's off-gases prior to discharge to the City of Ripon's (the City's) non-potable <br /> water system (NPS). Additional details and the rationale for recommending system <br /> shut-down are provided below. <br /> STOCKTON AVENUE GROUNDWATER EXTRACTION SYSTEM HISTORY <br /> Nestle installed the Stockton Avenue System in 1999 at 519 South Stockton Avenue in <br /> Ripon, California (Figure 1). Extraction well E-2 was installed in 1999 to address <br /> trichloroethylene (TICE) in the uppermost portion of the Upper Aquifer referred to as the <br /> B-zone, which is the water table aquifer. Extraction well E-6 was added in 2004 to <br /> address TCE and its daughter products reported in groundwater samples from the <br /> deeper Intermediate Aquifer. <br /> Extraction well E-2 was installed to control migration of TCE and its breakdown products, <br /> hereafter defined as chemicals of concern (CDCs), in shallow groundwater at the Stockton <br /> Avenue location. Well E-2 is screened from 47.8 to 65.5 feet below ground surface (feet <br /> bgs). Groundwater extracted from well E-2 is treated using activated carbon prior to <br /> discharge to the City of Ripon wastewater lagoons. <br /> In 2001, a numerical groundwater model suggested potential for migration of volatile <br /> organic compound (VOC)-impacted groundwater in the Intermediate Aquifer in the north <br /> and northwest direction. To arrest any migration, extraction well E-6, screened from 143 <br />