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• Unocal Refining!r Fling Division <br /> Unocal Corporation <br /> 2000 Crow Canyon Place,Suite 400 <br /> San Ramon,California 94583 <br /> Telephone(415)867-0760 <br /> F p � <br /> UNOCAL 76 JAN 2 1 1992 <br /> ENVIRONMENTAL HEALTH <br /> January 13, 1992 PERMIT/SERVICES <br /> Mr. Mike Infurna <br /> Northern Division San Joaquin County <br /> Department of Public Health <br /> P. O. Box 2009 <br /> 1601 East Hazelton Avenue <br /> Stockton, California 95201 <br /> RE: Subsurface Investigation at <br /> Former Unocal S.S. #5098 <br /> 5606 Pacific Avenue <br /> Stockton, California <br /> Mr. Infurna: <br /> Per our conversation, this letter is intended to provide you a <br /> summary of the work performed at the subject site to date, along <br /> with the next proposed phase of work. Two Site Vicinity Maps, one <br /> well Location Map, and four Site Plans are attached to this letter. <br /> The Unocal service station that formerly occupied the subject site <br /> was closed and demolished in mid-1985. An office building is <br /> presently constructed on the site. <br /> Two fuel storage tanks, one waste oil tank, and the associated <br /> underground piping were removed at the time of station demolition. <br /> Contaminated soil was encountered beneath the tanks. Unocal <br /> subsequently retained Kleinfelder and Associates (KA) to conduct a <br /> subsurface environmental site investigation. Between August of <br /> 1985 and March 1988, KA installed 19 exploratory borings (seven of <br /> which were converted into vapor extraction wells in anticipation of <br /> the operation of a soil vapor extraction system) and 10 monitoring <br /> wells. The locations of these monitoring wells and exploratory <br /> borings are shown on the attached Site Plans, Figures 5, 6, and 7. <br /> Due to problems and delays in the design of the proposed <br /> remediation system at the site, Unocal retained Kaprealian <br /> Engineering, Inc. (KEI) to complete the soil remediation at the <br /> site. KEI began soil remediation in September of 1988, which <br /> consisted of (extensive soil excavation and aeration) and completed <br /> the project in December 1988. Soil was excavated to a depth of <br /> approximately 53 feet below grade (where ground water was <br /> encountered) . During excavation, two of the monitoring wells (MW1 <br /> and MW7) and all seven vapor extraction wells were destroyed. Six <br /> of the seven remaining monitoring wells (MW2 , MW3 , MW4 , MW5, MW8, <br /> r-- <br />