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r <br /> oe- <br /> 00� GROUNDWATER <br /> ��l0❑ TECHNOLOGY, INC. 4057 Port Chicago Highway,Concord.CA 94520(415)671-2387 <br /> FAX:(415)685-9148 <br /> October 19, 1991 <br /> _y <br /> Job No. 020301211OCT <br /> Mr. Steven K. Schneiderjll�, <br /> Public Health Services <br /> San Joaquin County <br /> P.O. Box 2009 <br /> 445 N. San Joaquin Street <br /> Stockton, CA 95201 <br /> RE: SOUTHLAND CORPORATION STORE NO. 20680; 9110 THORNTON ROAD; STOCKTON, CA <br /> Dear Mr. Schneider: <br /> This letter is provided to notify you of the positive analytical results we have received for the Ivy Motel <br /> domestic well (#9172) located cross-gradient of the subject site. A map is attached depicting the <br /> location of domestic well #9172. <br /> Well #9172 is sampled monthly as part of the routine monthly domestic well sampling program. <br /> Detectable concentrations were not detected since early 1988 in well #9172, until the sampling event <br /> for August 26, 1991 as reported in our September 30, 1991 correspondence to you. <br /> Concentrations of petroleum hydrocarbons were detected again in samples collected from well #9172 <br /> on September 26, 1991. The detectable concentrations were reported as follows: <br /> • Ethylbenzene at 0.4 ppb <br /> • Xylene at 7.0 ppb <br /> • TPH-as-gasoline at 230 ppb <br /> The laboratory results reported below detection limits for benzene and toluene. Copies of the <br /> laboratory reports are enclosed for your review. <br /> The maximum contaminant level (MCL) for ethylbenzene is 680 ppb, and the MCL for xylene is 1,750 <br /> ppb (22 CCR 64444.5). Despite the fact that the reported results are far below the state drinking <br /> water standards, the repeated appearance of detectable concentrations of dissolved petroleum <br /> hydrocarbons in the cross gradient domestic well warrant reporting. <br /> Domestic well #9172 will continue to be sampled as part of the routine monthly sampling program. <br /> I would like to take this time to point out that the September 30, 1991 correspondence sent to you <br /> regarding the August detection erroneously reported the total petroleum hydrocarbon (TPH) <br /> concentration for the September 12, 1991 confirmation sample as 10 ppm. The result should have <br /> been reported as 10 ppb, as confirmed by the laboratory report included with the correspondence. <br /> Of/rces throughout the U.S..Canada and Overseas <br />