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1117 Lone Palm Avenue, Suite 201B <br /> Modesto, California 95351 <br /> ATC 209-579-2221 <br /> Fax:209-579-2222 <br /> Shaping the Future <br /> 4075 East Main Street, Stockton, California, dated January 15, 2008. This work was approved by the <br /> San Joaquin County Environmental Health Department(SJCEHD)in a letter dated January 18, 2008. <br /> �I A sensitiveTeceptor surveyTL_s was conducted for the site and surrounding area during August 2008 <br /> reported in ATC's Sensitive Receptor Survey Report for Jamar Service Station, 4075 Eas MainStreet, <br /> U� Stockton. <br /> In February 2009, ATC submitted the Supplemental Subsurface Investigation Work Plan dated February <br /> 27, 2009. This workplan proposed the advancement of one CPT boring with accompanying <br /> hydropunch borings to collect discrete grab groundwater samples below the "C" zone on site, and the <br /> installation of two deep, discretely screened groundwater wells to monitor the lateral extent of the <br /> groundwater contamination reported in the "C" zone grab groundwater samples collected from previous <br /> CPT borings. <br /> In March 2009, ATC submitted Interim Remediation Implementation Work Plan dated March 5, 2009. <br /> This workplan proposed the installation of one shallow groundwater monitoring well to define the <br /> shallow plume to the north, installation of two additional ozone infusion points and connecting them to <br /> the ozone remediation system (piping is already installed), trenching and piping to connect the SVE <br /> wells on site to the remedial compound, and initiation of interim soil remediation by SVE. <br /> In a letter dated April 2, 2009, the SJCEHD stated that it believes that the C-zone monitoring wells <br /> should be installed to verify the reported concentrations of contamination from the CPT borings in the <br /> deeper zone before any additional CPT work is done. The SJCEHD also requested an additional C-zone <br /> monitoring well be installed in the northeast corner of the property, near the locations of CPT-2/MW-1. <br /> The EHD did not approve installation of additional ozone infusion points in the C-zone until the new <br /> deep monitoring wells confirm contamination on site in that zone. <br /> Between November 22 and December 6, 2010, ATC supervised the installation additional C-zone <br /> monitoring wells MW11C to approximately I I I feet bgs,MW1C to approximately 110 feet bgs,MW3C to <br /> approximately 110 feet bgs. These wells were installed to further evaluate the vertical migration of the <br /> plume both on and off site. ATC supervised the installation of A-zone monitoring well MW12A to <br /> approximately 75 feet bgs to evaluate the extent of the plume in the northern part of the site. Additionally, <br /> ATC supervised the installation of ozone injection wells IW6 and IW7 to approximately 77 feet bgs. <br /> From January to April, 2011, ATC supervised modification and expansion of the existing remediation <br /> compound and installation of a SVE system that included a Mako 250 thermal-catalytic oxidizer <br /> (TCAT)unit. <br /> In 2013 and 2014, a neighbor contacted the County and registered repeated complaints about the <br /> remediation system's effects on the air, her city-supplied water, and alleged illegal activities by another <br /> neighbor. Above-ground measurements and sampling by Cardno ATC, San Joaquin County, the <br /> regional AQMD,and the SWRCB have found no basis for the complaints to date. <br /> S9268234epdaUamer-2015 SUIS M.doc 3 Cardno ATC <br />