ARCHIVED REPORTS_2013 ANNUAL REPORT

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A1.6 SOIL AND GROUNDWATER INVESTIGATION Between 1986 and the present, Nestle conducted several investigations to delineate the impact of TCE and its daughter products at the Site and within the Study Areaa. As a result of these investigation S21,22,23,24,25. Nestle installed monitoring wells, guard wells, and replacement wells, and properly destroyed unused domestiC26 and irrigation wells. Nestle completed the Lower Aquifer Zone investigation in 2007.27 In 2010, ECM conducted a search to gather more information on wells within the City of Ripon as part of the regional Water Management Plan under preparation. The resulting Well Inventory Report summarizes historical well searches and the results of recent findings intended to exhaust all reasonable efforts to: 1. Locate and map all documented wells, including: a. the source of the well information; b. investigation and verification of the well information; 2. Identify the status of all wells, including: a. Identifying wells which are of immediate concern as potential receptors or conduits of contaminants of concern; b. Determining short-term and long-term effect of wells on groundwater remediation efforts; c. Recommending action plans for the wells that may directly or indirectly affect remediation efforts. ECM and AMEC Geomatrix conducted investigation activities jointly in September 2010 in accordance with the M-10A Investigation Work Plan 28 to assess the causes of recent increases in concentrations of TCE and associated byproducts observed in monitoring well M-10A. ECM presented a description of the field activities, a summary and discussion of the analytical results, conclusions, and recommendations in the M-10A Investigation Report29. A1.7 HYDROGEOLOGY The Study Area is located in the Eastern San Joaquin County Groundwater Basin (ESJCGB), which is located in the northeastern San Joaquin Valley. The major physical features in the ESJCGB include the Sierra-Nevada foothills, the alluvial plain, and the Stanislaus River,30 which divides San Joaquin County from Stanislaus County. The Stanislaus River, located in the southern portion of the Study Area, flows to the west/southwest into the San Joaquin River. The San Joaquin River then flows northwestward to the inverted river delta of the Sacramento-San Joaquin Delta, which forms the largest estuary on the Pacific Coast of the United States31 The Study Area is underlain by fluvial deposits associated with the Stanislaus River and alluvial fan deposits. Detailed information regarding the physiographic setting and geology of the region is presented in the Updated Site Conceptual Model (SCM) prepared by AMEC-Geomatrix32. Groundwater is first encountered at a depth of 20 to 40 feet below ground surface (bgs) beneath Ripon. Groundwater is locally affected by recharge and discharge areas and fluctuates with precipitation cycles and the stage of the Stanislaus River. Groundwater generally flows away from recharge areas. The recharge areas include the City municipal WWTP lagoons, irrigation fields currently located on property formerly owned by Neenah Paper Company, and the a The term"Study Area"refers to a wider area of investigation in the larger Ripon vicinity.