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URS DDDS1V oD <br /> FEB '41, 1 2.006 <br /> February 17, 2006 ENVIRONiv1ENT HEALTH <br /> PERNIMSERVICES <br /> Ms. Lori Duncan, RENS 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 III <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 third addendum to the URS submitted Workplan for the <br /> Abandonment of a Groundwater Monitoring Well, Installation of an Interim Soil Vapor Extraction/Air <br /> Sparge Groundwater Treatment System, and Installation of Groundwater Monitoring Wells dated June <br /> 9,2005, to present the following modifications to the scope of work: <br /> • Abandonment of one groundwater monitoring well (MW-2); and <br /> • Installation of one replacement groundwater monitoring well (MW-2R); <br /> MODIFIED SCOPE OF WORK <br /> Well Destruction <br /> Due to construction activities of an equipment compound on site, groundwater monitoring well MW-2 <br /> will be property abandoned by a licensed drilling contractor at the direction of a URS geologist. The <br /> groundwater monitoring well will be destroyed by pressure grouting and then overdrilling the top five <br /> feet below ground surface (bgs) with 10-inch, outside-diameter (OD), hollow-stem augers (HSAs) and <br /> filling with a Portland cement grout containing<5%bentonite powder(grout)to the surface. <br /> Groundwater Monitoring Well Installation <br /> One replacement groundwater monitoring well (MW-2R) will be installed approximately 10 to 20 feet <br /> to the south-southwest of the original well location (Sheet 1). The final location of the well will be <br /> determined in the field. The boring will be drilled with an 8-inch OD HSA-equipped drill rig. Soil <br /> URS Corporation <br /> Crown Corporate Center <br /> 2870 Gateway Oaks Drive,Suite 150 <br /> Sacramento,CA 95833 <br /> Tel:916.679.2000 KAWprocessV5 BP ARC0\02168\2005 System Installation\SVE-AS SyslnsWP Addendum IB.doc <br /> Fax:916.679.2900 <br />