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conditions in the vicinity of the Site in 1987. Nestl6 currently monitors and samples municipal, <br /> irrigation, industrial supply, groundwater extraction and treatment, and groundwater monitoring <br /> wells in the Study Area in accordance with the RWQCB's Monitoring and Reporting Program <br /> R5-2010-08104 (MRP) issued April 19, 2010. This MRP supersedes the 2005 MRP (R5-2005- <br /> 0829). <br /> The RWQCB issued a Cleanup and Abatement Order (CAO) in 1993. The RWQCB issued a <br /> revised CAO in 2006. Some of the requirements in the CAO have been challenged, and the <br /> State Water Resources Control Board has accepted a petition to hold the CAO in abeyance. <br /> Other regulatory authorities involved with this project are the San Joaquin County <br /> Environmental Health Department, Stanislaus County Environmental Resources, San Joaquin <br /> Unified Air Pollution District, and the City of Ripon. <br /> A1.5 SOIL VAPOR INVESTIGATION <br /> Nestl6 investigated soil gas in 19875, 19896, 19917, and 19958 to delineate the vadose zone <br /> source and for remediation planning. The details of the investigations and remedial action taken <br /> based on the investigation results were discussed in other reports9,10,11 submitted to the <br /> RWQCB. <br /> Because soil gas investigations indicated that the highest concentrations of volatile organic <br /> compounds (VOCs), primarily TCE, in soil and groundwater were present near the Industrial <br /> and Stockton Avenue properties, ECM investigated the potential for vapor intrusion into <br /> residential, commercial and industrial buildings in 2007 and 2008 on behalf of Nestl6. ECM <br /> conducted shallow soil gas surveys 12 to assess soil vapor intrusion potential in accordance with <br /> California Department of Toxic Substances Controls (DTSC) protocol. Follow-up indoor air <br /> sampling at an industrial facility located northwest of the site on Stockton Avenue verified that <br /> soil vapors presented no significant risk to human health 13. ECM collected quarterly soil vapor <br /> samples at the Stockton Avenue property and at other locations west of the Site in 2008 to <br /> assess any seasonal variations of soil gas emissions from impacted groundwater 14. The data <br /> analyses did not reveal any significant seasonal variation. <br /> A1.6 SOIL AND GROUNDWATER INVESTIGATION <br /> Between 1986 and the present, Nestl6 conducted several investigations to delineate the impact <br /> of TCE and its daughter products at the Site and within the Study Area a. As a result of these <br /> investigations, Nestl6 installed monitoring wells, guard wells, replacement wells, and closed <br /> domestic and irrigation wells. <br /> Nestl6 completed the Lower Aquifer Zone investigation in 2007.15 <br /> In 2010, ECM conducted a search to gather more information on wells within the City of Ripon <br /> as part of the regional Water Management Plan under preparation. The resulting Well Inventory <br /> Report summarizes historical well searches and the results of recent findings intended to <br /> exhaust all reasonable efforts to: <br /> 1. Locate and map all documented wells, including: <br /> a. the source of the well information; <br /> b. investigation and verification of the well information; <br /> a The term"Study Area"refers to a wider area of investigation in the larger Ripon vicinity. <br /> Appendix A <br /> Page A2 of A7 <br />