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ATC <br />ENVIRONMENTAL • GEOTECHNICAL <br />BUILDING SCIENCES • MATERIALS TESTING <br />_7 Lone Palm Avenue, Suite 201B <br />Modesto, CA 95351 <br />Telephone 209-579-2221 <br />Fax 209-579-2225 <br />wwvv.atcgroupservices.com <br />January 6, 2017 <br />Z054000033 <br />Mr. Alan Buehler <br />Central Valley Regional Water Quality Control Board <br />11020 Sun Valley Drive, Suite 200 <br />Rancho Cordova, California 95370 <br />Subject: Revised Workplan for Additional Site Investigation, Farmer Property/Former Toyota <br />Town Inc., 610 North Hunter Street, Stockton, California <br />Dear Mr. Buehler: <br />ATC Group Services LLC has prepared this revised workplan, on behalf of Ms. Linda Wilson, for soil <br />gas sampling and additional investigation at the subject site. The purpose of the soil gas sampling <br />addendum is to address requested conditions provided by the Regional Water Quality Control Board <br />(RWQCB) in correspondence dated October 13, 2015 and November 18, 2016 in response to ATC's <br />Workplan for Soil Gas Investigation, Farmer Property, 610 North Hunter Street, Stockton, California <br />dated September 17, 2015. The original workplan was submitted at the request of the San Joaquin County <br />Environmental Health Department (SJCEHD) in correspondence dated July 22, 2014. <br />The scope of work described by this revised workplan includes advancing four borings and finishing each <br />boring as a permanent soil vapor sampling point; advancing nine hydropunch borings to groundwater <br />between 40 and 60 feet below ground surface (bgs) to delineate deeper groundwater; advancing four <br />additional shallow soil borings to evaluate direct exposure risks and background metals concentrations; <br />and advancing a boring in the vicinity of the former waste oil UST to a depth below the reported 1988 <br />over-excavation. <br />SCOPE OF WORK <br />LONG TERM SOIL VAPOR PROBES <br />Installation of Long Term Soil Vapor Probes <br />This task includes mobilization to the site, advancing four soil borings, and completing the borings as <br />permanent soil vapor probes. The soil vapor probes are planned to be located between the identified <br />source area and the on-site structure, near the eastern corners of the on-site structure and along the <br />southern wall of the on-site structure. Estimated soil vapor probe locations are shown on Figure 2. <br />The soil vapor probes will be advanced to approximately six feet bgs using truck mounted direct push <br />drilling rig employing narrow diameter, direct push technology. Drilling will be conducted by a State- <br />licensed C57 drilling company. A field geologist will be present to log soil samples. Descriptions of soil <br />S: \62596\reports\SVIS_WP_ADD-2016.doc <br /> 1 ATC