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SECOR www.secor.com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C O R INCORPORATED Rancho Cordova,CA 95670 <br /> 916-861.0400 TEL <br /> 916-861-0430 Fax <br /> April 9, 2004 <br /> 1-D <br /> Mr. Harlin Knoll APR 12 2004 <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor ENVIRON[ViLNT HEALTH <br /> Stockton, CA 95201 PERMIT/SERVICES <br /> RE: Groundwater Monitoring and Sampling Reduction Requests <br /> 7-Eleven Store#19976 ,r�✓" <br /> 1399 North Main Street fr+ 1y} <br /> Manteca, California r ry, <br /> SECOR Project No.: 77EL.19976.04.0104 <br /> Dear Mr. Knoll: <br /> SECOR International Incorporated (SECOR) submits this letter requesting the reduction of the <br /> monitoring and sampling frequency of monitoring wells MW-4 and MW-4A. Groundwater samples <br /> are currently collected quarterly during groundwater monitoring and sampling for the above- <br /> referenced site (Figure 1 and 2). <br /> Groundwater monitoring and sampling have been conducted since the third quarter 1998 to <br /> determine water table elevation and the distribution of dissolved hydrocarbons in the site-related <br /> t groundwater monitoring wells. MW-4 and MW-4A have been monitored and sampled since the <br /> v� second quarter 1999. Historical groundwater analytical results and monitoring data are summarized <br /> in Table 1. <br /> Groundwater samples are currently collected from a total of ten on and off-site wells. SECOR <br /> proposes reducing sampling MW-4 and MW-4A from quarterly to annually. Wells MW-4 and MWS, <br /> have not contained petroleum hydroc bons above laboratory reporting limits since the send J�tq1'O� <br /> quarter 2001 and second quarter 200 , respectively. Mt has never been reported above the <br /> California Primary Maximum Contaminant Level (MCL) of micrograms per liter since monitoring <br /> and sampling of these wells began in 1999. Annual analysis of groundwater samples collected from <br /> MW-4 and MW-4A in the first quarter of each calendar year will consist of total petroleum <br /> hydrocarbons as gasoline, benzene, toluene, ethylbenzene, and total xylenes, and fuel oxygenates <br /> m ethyl-tert-butyl ether (MtBE), tert_-butyl alcohol, diisopropyl ether, ethyl-tert-butyl ether, and tert- <br /> amyl-methyl ether, and tert-butyl alcohol. Wells MW-4 and MW-4A will continue to be monitored <br /> quarterly for groundwater flow direction and gradient calculation. A summary of the proposed <br /> monitoring and sampling plan has been included in Table 2. <br /> Sincerely, <br /> SECOR International Incorporated <br /> Jaff Auchterlonie <br /> Senior Geologist <br /> cc: File, 7-Eleven Inc. <br /> Mr. James Barton, RWQCB, Central Valley Region <br /> 19976 MW-4 M&S reduction request.doc <br />