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PH k ,y S'• _ -..tet <br /> 3L _ f °kS-t T H .mob Y Y� f M <br /> dsYY:.�, ,rt^rs�� .itx rte, <br /> 1 _ e C � � <br /> Brown and Caldwell ter, <br /> y� SacramY,hl <br /> i" - (:=Cdiun;1 fi.57111'ti9.' <br /> 19161 4J.;UWJ <br /> fhX+,51G;d 1J;Sf;)i <br /> March 9, 1'990 <br /> HAR 1 3 171 <br /> Mr. Kyle Christie <br /> ARCO Products Company <br /> 2WO Alameda de las Pulgas <br /> Post Office Box 5811 <br /> San Mateo, California 94402 017-32I4-15/I <br /> Subject: Report on October 1989 Quarterly Groundwater Sampling <br /> at ARCO Station 434,501 Kettleman Lane,Lodi, California <br /> Dear Mr. Christie: <br /> This letter report describes the October groundwater sampling of eight on-and off-site monitoring <br /> wells at ARCO Products Company(ARCO)Station 434 in Lodi. A total of ten on-and off-site <br /> I groundwater monitoring wells were installed between April 1987 and,Tune 1988. The purpose <br /> V of the monitoring wells is to characterize hydrocarbon occurrence in groundwater beneath the site <br /> resulting from a December 1986 gasoline Ieak at Station 434. <br /> Figure 1 shows the location of monitoring wells,benzene concentrations in groundwater samples <br /> collected from these wells during October 1989, groundwater contours, and the direction of <br /> groundwater flow. Figure 2 shows the design of each monitoring well,the installation dates,and <br /> t: the depths to groundwater beneath the site in April 1987, and October 1989. <br /> Between July and November I987, and again between May and July 1988, free product . <br /> accumulated in monitoring wells W-2 and W-3. The maximum product thickness measured <br /> during these time periods was 3.18 feet of free product in monitoring wrll W-2. A total of 52 <br /> gallons of gasoline were recovered from these two wells during these two time periods, product <br /> has not been detected in monitoring wells W-2 or W-3 since August 1988. <br /> To track the dissolved h/drocarboi-trends systematically, in the fall of 1988,ARCO authorized <br /> - <br /> quarterly groundwater mpling and analysis for benzene, ethylbenzene, toluene, and xylenF <br /> (BETX). At the request of the California Regional Water Quality Control Board,Central Valley <br /> _ - e ----_ Region,-in_May-1989-ARCO began-monthly-sampling and-analysis-of-groundwater from the-____ T ----- T—--� T <br /> deeper monitoring well (W-2B) for BETX. Groundwater samples from monitoring well W 2B . <br /> were collected for analysis on September 12, 1989. Groundwater samples from monitoring wells <br /> -, W-2, W-2A, W-2B,W-3, W-4, W-5, W-6, and W-7 were collected for analysis on October 17 <br /> ` and 18, 1989. Monitoring W-1 was not sampled due to lack of water in the well. Monitoring <br /> d <br />