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I <br /> ATC Associates Inc. <br /> TC 1117 Lone Palm Avenue, Suite 201 <br /> (YVAModesto, California 95351 <br /> 209-579-2221 <br /> fax: 209-579-2225 <br /> j 4.0 CONCLUSIONS <br /> The predominant mass of TPHg is located within the saturated zone soil. An estimated <br /> l 11 , 862.52 lbs of TPHg have impacted the vadose zone soil and 24, 506.94 lbs have impacted the <br /> - saturated zone soil. The overall estimated mass of petroleum hydrocarbon impacted soil is <br /> approximately 36,369.46 lbs. Since December 19, 2002, the SVE system has removed an <br /> ' ! estimated 8,811 .95 lbs of TPHg from the subsurface and the groundwater treatment system has <br /> removed and treated approximately 10.292 lbs of TPHg from groundwater. The estimated mass <br /> of TPHg remaining in groundwater beneath the site is approximately 10.64 lbs. <br /> n <br /> The current remediation system could continue to remediate soil and groundwater beneath the <br /> site, however the remediation system could be optimized by implementing ozone sparging <br /> combined with soil vapor extraction to expedite the remediation process . <br /> 5.0 RECOMMENDATIONS <br /> As a result of mass calculations prepared for the site, ATC recommends the following: <br /> • Continue quarterly groundwater monitoring of MWI through MWIO. Analyze samples <br /> for TPHg by EPA Method 8015M and for BTEX, MTBE, TBA, and TAME by EPA <br /> Method 8260B . <br /> ( � • Reduce the sampling of MW4, MW5, MW6, MW8, MW9, MWIO, and CW to a semi- <br /> annual schedule. <br /> jl <br /> j • Perform monthly remediation system O&M activities. <br /> • Implement the workplan dated to conduct a feasibility study for ozone pilot testing upon <br /> approval from the EHD. <br /> '- J <br /> r . <br /> S:Environmental\62596\Reports\Mms Calcs 2009.doe 7 <br /> {i_i <br /> 4I <br />