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Table 1. Summary of Groundwater Monitoring Data: Water Elevations and Analyses <br /> ARCO Facility 2093, Tracy, California <br /> Floating Change Concentrations in µg/L ingfL <br /> Top-of-casing Depth-to- product Water-level since last <br /> Well number elevation, water, thickness elevation, measurement, Total <br /> and date in feet (a) in feet in feet in feet(b) in feet Benzene Toluene Etlr lbenzene Xylenes TPH-G MTBE DO <br /> TEX-1 (c) <br /> 10/26/95 12.86 -- -- -- <5 <0.5 <0.5 <0.5 <350 -- -- <br /> 2/12/96 10.90 - -- 1.96 -- -- -- __ _- -- _- <br /> 4/18/96 11.35 -- -- -0.45 <0,5 <0.5 <0.5 <0.5 <50 -- -- <br /> 7/18/96 11.52 -- 1.34 -- -- -- -_ -_ -- <br /> 11/15/96 12.30 -- -1.40 -- -- -- -- -- -- -- <br /> 3/14/97 -- -- — <br /> (a) All elevations corrected to an arbitrary datum based on a Notes: Dash indicates not measured or sampled. <br /> temporary on-site benchmark with an assigned elevation of 50 feet. TPH-G=Total Petroleum Hydrocarbons as Gasoline by EPA Method 8015, <br /> (b) Corrected water levet elevation value(Wlc=Wlni+(b)(p)),where Wlc=water-level Modified. <br /> elevation corrected, WIm=►eater-level elevation measured,b=hydrocarbon thickness BTEX Distinction by EPA Method 8020. <br /> p=specific gravity(0.7) of hydrocarbon. MTBE=Methyl Tertiary Butyl Ether by EPA Method 8020. <br /> (c)Tap of well casing altered. Well casing has not been resurveyed. Vater-level meas DO-Dissolved Oxygen <br /> from the highest point of well casing. Wells ATR-1, ATR-3,ATR-6, ATR-9, ATR 10,and ATR-11 on a <br /> serni-annual sampling schedule. Sampled during thelst and 3rd quarters <br /> of each year. <br /> 4747Q'ABLLS12093 MAR7.XLS <br />