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• <br /> July 30, 1992 <br /> Former Unocal Station 2859, Stockton, California Working To Restore Nature <br /> • <br /> Laboratories in Stockton,California,using Standard Methods, 15th Edition,American Public <br /> Health Association Cumulative results of analyses are summarized in Table 3 Copies of <br /> the Chain of Custody Records and laboratory analysis reports are attached. <br /> TPHg was detected in the samples collected from wells MW-4, MW-5, and MW-6 at <br /> concentrations of 160 parts per billion(ppb), 130 ppb, and 110,000 ppb, respectively BTEX <br /> were detected 1n the water sample collected from well MW-6 at concentrations of 85 ppb, <br /> 1,100 ppb, 1,200 ppb, and 7,400 ppb, respectively TPHg and BTEX were not detected in <br /> the sample from well MW-7 Concentrations of TPHg and benzene in ground water are <br /> • shown on Plate 4 and Plate 5, respectively Results of bacteriologic analysis of the sample <br /> collected from well MW-7 indicated that the sample met the public health standard for <br /> drinking water <br /> RECOMMENDATIONS <br /> • <br /> The highest concentrations of dissolved hydrocarbons were detected in well MW-6, in the <br /> southwest corner of the site, upgradient of the former tank pit, product lines and dispensers <br /> We recommend conducting a records search for possible upgradlent sources We <br /> recommend continuing quarterly monitoring We have scheduled the next sampling for the <br /> •. third week of August 1992 <br /> We recommend a copy of this report be forwarded to Ms. Diane Hinson of the San Joaquin <br /> Local Health District, P O Box 2009, Stockton, California 95201, and Ms Elizabeth A <br /> Thayer of the California Regional Water Quality Control Board, Central Valley Region, <br /> . 3443 Routier Road, Sacramento, California 95827-3098 <br /> • <br /> • <br /> • D528bbou <br /> 38012-9 3 <br /> • <br />