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GROUND ZERO ANALYSIS, INC. <br /> 1714 Main Street <br /> Escalon, California 95320-1927 <br /> Telephone: (209)838-9888 <br /> Facsimile: (209) 838-9883 r <br /> June 28, 2002- � /7:;N rr=��f-,--P <br /> Mr. Jeffrey Wong <br /> San Joaquin County Environmental Health Department JUL 0 12002 <br /> 304 E. Weber Ave., 3rd Fl. ENVIRORMENT HEALTH <br /> Stockton, CA 95202 PERMIT/SERVICES <br /> Subject: Workplan for Monitoring Well Installation <br /> Harry's Auto Mart, 2662 N. Wilson Way, Stockton, CA(Site Code: 1306) <br /> Dear Mr. Wong: <br /> This Workplan is submitted on behalf of John and Maxine Ferraiolo in response to your directive dated <br /> April 3, 2002. This Workplan describes the proposed methodology to further define the extent of <br /> groundwater contamination at the subject site (Figure 1). <br /> I <br /> BACKGROUND <br /> Four groundwater monitoring wells have been installed at the site to investigate gasoline hydrocarbon <br /> contamination associated with leaking underground storage tanks. In addition to monitoring and <br /> sampling these four wells, Ground Zero has incorporated U-Haul well MW7 into the monitoring and <br /> sampling program. The locations of the wells are shown on Figure 2. <br /> Large seasonal fluctuations in groundwater levels have been'noted at the site and elevations currently <br /> f�° ,e' appear to be in a period of decrease. Historic high water levels of approximately 36 feet below grade <br /> kV, <br /> (1999) and historic low water levels of approximately 86 feet below grade (1992) have been recorded at 1 <br /> SeA� the adjacent U-Haul site. Water levels in the site vicinity appear to be especially sensitive to annual <br /> precipitation. Water level data are summarized in Table 1. <br /> Groundwater flow direction at the site has been extremely inconsistent and irregular. On none of <br /> the monitoring occasions has a consistent flow direction been observed. Rather, flow has always <br /> been radial, either toward or away from the central portion of the site. Because of this radial flow a <br /> rose diagram cannot be constructed. Potentiometric surface maps from February 2001 to present <br /> are included in Attachment A. <br /> I <br /> Elevated levels of gasoline hydrocarbons have been consistently present in each monitoring well at <br /> the site. Groundwater analytical data are presented in Table 2. San Joaquin County Environmental <br /> Health Department has directed the responsible party to define the extent of groundwater <br /> contamination. <br /> i <br /> I <br /> t <br /> \\GZA_FS\SYSO1\Data\GROiJNDZE\HARRYS\Reports\Workplans\WKPLAN 3MWS_RFS.doc f <br /> 1 <br />