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GROUND ZERO ANALYSIS, INC. <br /> 1714 Main Street <br /> Escalon, California 95320 <br /> 'telephone: (209)838-9888 L <br /> Facsimile: (209)838-9883 <br /> February 15, 2006 [t��II " lLl, <br /> EN v FO!`.,il� 11 I S <br /> Mr. Nuel Henderson p�!';��.i;; r�F ;;,��GES <br /> San Joaquin County Environmental Health Department <br /> 304 E. Weber Ave., 3rd Floor <br /> Stockton, CA 95202 <br /> ` Subject: Fourth Quarter 2005 Groundwater Sampling Report <br /> 102 South Wilson Way, Stockton, California (Figure 1) <br /> Dear Mr. Henderson: <br /> Ground Zero Analysis, Inc. (Ground Zero) has prepared this report to summarize fieldwork <br /> i conducted at the subject site during the fourth quarter of 2005. Groundwater related activities <br /> included monitoring groundwater elevations in all site wells and sampling groundwater from <br /> select site wells. <br /> Groundwater analysis consisted of total petroleum hydrocarbons as gasoline (TPHg), benzene, <br /> toluene, ethylbenzene and total xylenes (BTEX), 1,2 dichloroethane (1,2-DCA), ethylene <br /> dibromide (EDB), and gasoline oxygenate additives [methyl-tert-butyl ether (MTBE), ethyl- <br /> tert-butyl ether (ETRE), di-isopropyl ether (DIPE), tert-amyl methyl ether (TAME) and tert- <br /> butyl alcohol (TBA)]. <br /> GROUNDWATER ACTIVITIES <br /> Groundwater Monitoring and Sampling <br /> In conjunction with Stratus Environmental, Inc., who monitored and sampled wells at the <br /> adjacent ARCO site, depth to groundwater was measured on December 8, 2005 in monitoring <br /> wells MW1 through MW16B and in vapor wells VW1 through VW6. Depth to groundwater <br /> was then subtracted from each respective wellhead elevation to determine groundwater <br /> elevation. On November 11, 2005, Morrow Surveying changed the elevation datum on our <br /> wells from NAVD 88 to the City of Stockton Benchmark No. 92 to be consistent with the <br /> adjacent ARCO and Top Filling Station wells. Copies of the survey map and associated data <br /> are included in Attachment A. Water levels at the site fell an average of 0.77 feet since the <br /> third quarter event in August 2005. The potentiometric surface was above the top of the <br /> screened intervals in monitoring wells MW4 through MW 13B, MW 1513, MW 15C, MW 16B <br /> and vapor wells VW1 and VW4. Vapor well VW5 was dry. <br /> G:%GROUNU)ZE1ROEK%QMR12005 Wgm2005.doc <br />