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_ Stantec Consulting Corporation I <br /> 3017 Kilgore Road Suite 100 <br /> Ran <br /> Rancho Cordova CA 956770 <br /> Tel: (916) 861 -0400 �S ! <br /> Fax: (916) 861 -0430 ) til <br /> StanWc ° ✓ <br /> July 9, 2010 to <br /> Mr. Mike Infurna li , l5 4n PIP <br /> San Joaquin County Environmental Health Department <br /> 600 East Main Street ( ' <br /> Stockton, California 95202 <br /> RE: Remediation System Removal <br /> ARCO Service Station 2130 <br /> 7906 North EI Dorado Street <br /> Stockton, California <br /> File No. : 211601033. 300.521 <br /> Dear Mr. Infurna: <br /> This letter, prepared by Stantec Consulting Corporation (Stantec) on behalf of Atlantic Richfield <br /> Company (ARC), a BP Affiliated Company, proposes changes to the existing remediation <br /> system at the site referenced above. The proposal has been prepared to address concerns <br /> raised by San Joaquin County Environmental Health Department (SJCEHD) in an email dated <br /> May 26, 2010. The email requested a Feasibility Study and recommendations for cleaning up <br /> the site in a timely manner. ( /407— j d�«ln� <br /> C0I u,� t� .Q !0 - afr - /a <br /> REMEDIATION HISTORY n 4rS• <br /> An SVE system that utilized 12 vapor extraction wells began operating in August 1995 and was <br /> operated continuously through November 1997. In August 1995, four soil borings (B26 through <br /> B29) were drilled and converted into two AS wells (AS-2 and AS-3) and two vapor wells (VW-11 <br /> and VWA2) to be used as part of the SVE system operation. EMCON Associates of <br /> Sacramento, California (EMCON) performed monitoring, operation, and maintenance of the <br /> system . During the operation of the system, EMCON reported that extraction rates for TPHg <br /> and benzene decreased by 78% and 99.9%, respectively. <br /> In June 1998, the system was shutdown due to low influent concentrations. EMCON concluded <br /> that insufficient screen was available to effectively operate the SVE system. During operation, <br /> the SVE system removed approximately 9, 100 pounds (Ibs) of TPHg . <br /> Remediation of groundwater continued by injecting ambient air at low flow rates into selected <br /> wells to enhance biodegradation [URS Corporation of Sacramento, California (URS) , 2004] , with <br /> air being injected into VWA0 until failure of the blower in October 2009, <br /> 2130 Response Letter - Remediation System Removal .doc 1 <br />