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ENMS <br /> ENSR International <br /> 10411 old Placerville Road <br /> Suite 210 <br /> I Sacramento,CA 95827-2508 <br /> (916)362-7100 <br /> August 25, 2005 FAX (916)362-8100 <br /> www ensr com <br /> I <br /> Mr James Barton <br /> Regional Water Quality Control Board U " <br /> ICentral Valley Region pUG 2 9 20fl5 <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670 �NVIRON� T HEALTH <br /> RE: Air Sparge Well Installation Report <br /> Former Unocal Facility No. 5098 <br /> I 5400 and 5606 Pacific Avenue, Stockton, California <br /> ENSR Project No 06940-293-120 <br /> Dear Mr Barton <br /> ENSR Corporation (ENSR) was authorized by Union Oil Company of California (Unocal), to <br /> conduct an additional hydrogeologic investigation at the subject site (Figure 1) that consisted of <br /> the installation of one air sparge well (Figure 2) The new air sparge well, AS-33 is intended to <br /> further remediate the central mass of a petroleum hydrocarbon plume located within a deeper <br /> I. water bearing zone The work was conducted in accordance with ENSR's Amendments to <br /> Monitonng and Reporting Program CAO No 5-00-707 and Work Plan to Install an Additional Air <br /> Sparge Well within the Deeper Aquifer Zone (near MW-3) and Convert Mondonng Well MW-23S into <br /> an Air Sparge Well dated March 31, 2005 The Regional Water Quality Control Board — Central <br /> Valley Region (RWQCB) approved the workplan to install the proposed monitoring wells, with <br /> conditions, as specified in RWQCB letter dated May 3, 2005 A copy of the RWQCB letter is <br /> included in Attachment A <br /> Permits <br /> A well installation permit was obtained from San Joaquin County Environmental Health <br /> IDepartment (SJCEHD) A copy of the permit is included as Attachment B �I <br /> Soil Borings and-Sampling <br /> On July 11, 2005, a ^eatji�nin e-ftf­ fr^m PMCZP nhccnjorl r'act-aria nrilling int- of Rannhn (-nrHnva <br /> California advanced soil boring AS-33 to an approximate depth of 91 feet below ground surface <br /> (bgs) The boring was advanced using a truck mounted drill rig equipped with 8%-inch diameter <br /> hollow stem augers The soil boring was completed as air sparge well AS-33 (Figure 2) <br /> Soil samples were collected from AS-33 using a modified California split-spoon sampler at a <br /> minimum of 5-foot intervals and at changes in lithology to the total depth of the boring The soil <br /> IJ 1Prolects10694015098-2931WorkinglReports15098 Well Installation Report AS-33 doc <br /> Celebrating Over 35 Years of Excellence in Environmental Services <br />