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-.Z _ <br /> r <br /> _ Unocal Refining&Mark Division RDS 1.92 <br /> Unocal C rporation ` <br /> i 2000 Cro N Canyon Place,Suite 400 <br /> P.O.Box 155 <br /> San Ram n,California 94583 <br /> Telephone(510)867-0760 RECEIVED <br /> UNOCAL19 <br /> OCT 0 9 1992 . <br /> ENVIRONMENTAL HEALTH <br /> October 7, 1992 PERMIT/SERVICES <br /> Northern Division Mr. Steve Schneider <br /> San Joaquin County Public Health Services <br /> 445 North San Joaquin Street <br /> P.O Box 2009 <br /> Stock-ton, California 95201 <br /> SEVICE STATION NO. 6015 <br /> 60E. KETTLEMAN LANE <br /> L01:11. CALIFORNIA <br /> PARTIAL SITE CLOSURE REQUEST <br /> Dear Mr. Schneider: <br /> Unocal is in the process of divesting this service station site and has pending escrow with the <br /> existing operator. In order to facilitate the closing of escrow, the lending institution is <br /> requesting a partial (soils) closure of the service station site. <br /> After discussions with our consultants (Kaprealian Engineering, Inc.) and a review of the latest <br /> quarterly monitoring results (KEI-P91-0202.QR2), L nocal respectfully requests a partial (soils) <br /> site closure on the Unocal Service Station at 601 East Kettleman Lane, Lodi. The sources of <br /> contamination were successfully remediated through overexcavation in 1991. Low levels of <br /> groundwater contamination are believed to be residua and localized. In support of this request, I <br /> we offer the.following.discussion. <br /> Unocal retained Kaprealian Engineering, Inc. (KEI) to collect soil samples during the removal <br /> and replacement of the underground tanks at the site in early 1991. Six samples were initially <br /> collected from beneath the tanks, and 11 additiona. samples were collected within the pipe <br /> trenches. All of the samples that were analyzed fo TPH as gasoline showed non-detectable <br /> concentrations, except for the sample that was collec ed beneath the former eastern fuel tank at <br /> a depth of about 16 feet below grade, which showed oncentrations of TPH as gasoline at 3,900 <br /> ppm and benzene at 7.4 ppm. However, the contaminated portion of the tank pit was <br /> overexcavated to a depth of about 26 feet below grade, when one bottom and four sidewall <br /> samples were collected. The analytical results of these five additional samples showed levels <br /> of TPH as gasoline ranging from non-detectable to &1 ppm. It should be noted that of the 17 <br /> initial samples that were collected, 15 showed level of benzene ranging from 0.011 to 0.018 <br /> ppm. However, based on the close proximity of thes results, the fact that the analytical results <br /> were just above the detection limits (0.0050 ppm), and the fact that no TPH as gasoline was <br /> detected in any of these 15 samples, Unocal and KEI believe that these analytical results for <br />