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U <br /> October 5, 2005 ZC05 OCT -6 AM 9: 39 <br /> SAN SC. <br /> r3lJ4 T Y <br /> ENYIr Ol!`1Etd7AL <br /> HEAITN UEPAkTHENT <br /> Ms. Lori Duncan,REHS 2168 <br /> Unit IV-Site Mitigation 06a4 <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue,Third Floor <br /> Stockton, California 95202-2708 <br /> RE: Workplan for the Abandonment of a Groundwater Monitoring Well,Installation of an <br /> Interim Soil Vapor Extraction/Air Sparge Groundwater Treatment System,and <br /> Installation of Groundwater Monitoring Wells—Addendum II <br /> Former ARCO Station No. 2168 <br /> 441 West Charter Way <br /> Stockton, California 94570 <br /> Dear Ms. Duncan: <br /> On behalf of Atlantic Richfield Company (ARCO, a BP-affiliated company), URS Corporation <br /> Americas (URS) has prepared this second addendum to the URS submitted Workplan for the Abandon- <br /> ment of a Groundwater Monitoring Well, Installation of an Interim Soil Vapor Extraction/Air Sparge <br /> Groundwater Treatment System, and Installation of Groundwater Monitoring Wells dated June 9,2005, <br /> to address comments in the San Joaquin County Environmental Health Department's (SJCEHD) letter <br /> dated September 26, 2005 (Attachment). <br /> The following paragraphs present the unapproved scope of work changes described in the SJCEHD <br /> letter, and the URS justifications for these modifications. <br /> Groundwater Monitoring Well Installation <br /> One additional groundwater monitoring well will be installed in the northeast portion of the site to <br /> provide additional lateral assessment of contaminant migration in the downgradient direction. This <br /> additional well completes a monitoring network surrounding the eastern portion of the site. Well <br /> locations are shown on the attached figure. <br /> SVE/AS Well Completions <br /> At the request of the property owner, Mr. Bill Halverson, remediation wells will be completed below <br /> grade so the surface can be made to match the surrounding landscape. Each well will be completed at <br /> least 1-foot below grade, with a steel plate placed over the top, and then covered with material to match <br /> the surrounding ground surface. The wells will be inaccessible from the surface. The location of each <br /> well will be surveyed to ensure that they can be easily located for repairs or destruction. <br /> URS Corporation <br /> Crown Corporate Center <br /> 2870 Gateway Oaks Drive,Suite 300 <br /> Sacramento,CA 95833 <br /> Tel:916.679.2000 <br /> Fax: 916.679.2900 KAWprocess\15 BP ARCO\02168\2005 System lnstallauon\SVE-AS SyslnsWP Addendum n.doc <br />