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r L'� .•4 _r <br /> PACIFIC <br /> ENVIRONMENTAL ,y <br /> GROUP INC. . <br /> .9 <br /> March 27, 1995 <br /> Project 310-001.1B R <br /> Ms. Penny Silzer <br /> Unocal Corporation <br /> 2000 Crow Canyon Place, Suite 400 <br /> San Ramon, California 94583 <br /> Re: Revised Groundwater Monitoring Program Recommendations <br /> Former Unocal Bulk Plant 0788 <br /> 8203 East 1 Ith Street <br /> Tracy, California <br /> Dear Ms, Silzer: <br /> This letter, prepared by Pacific Environmental Group, Inc. (PACIFIC), for Union Oil <br /> Company of California, recommends revisions to the groundwater monitoring program for <br /> the site referenced above. <br /> PACIFIC recommends that the groundwater monitoring program for the subject site be <br /> modified to reflect the amount of historical data available. The most recent quarterly <br /> groundwater monitoring report which presents a site map, groundwater elevation data, and <br /> historical groundwater analytical data is presented as Attachment A. The proposed <br /> groundwater monitoring program is described below. <br /> • Semiannual gauging of all monitoring wells to determine groundwater <br /> elevation and product thickness. The wells will be gauged during <br /> seasonal groundwater highs and lows, in February and October_ <br /> • Semiannual sampling of Monitoring Wells U-1. U-2, U-5, and U-6 for <br /> total petroleum hydrocarbons (TPH) calculated as gasoline, benzene, <br /> toluene, ethylbenzene and xylenes (BTEX compounds), and TPH <br /> calculated as diesel (TPH-d). The wells will be sampled during seasonal <br /> groundwater highs and lows, in February and October. <br /> • Annual sampling of Monitoring Wells U-3, U-4, U-7, U-8, U-9, and U- <br /> 10 for TPH-g, BTEX compounds, and TPH-d. The wells will be <br /> r <br /> sampled during seasonal groundwater highs in February. <br /> • Semiannual submittal of groundwater monitoring reports. <br /> a <br /> 2025 Gateway Place, Suite 440, San lose, California 95110 (408) 441-7500 FAX (408) 441-7539 ' <br />