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SECOR <br /> Ms. Lori Duncan <br /> San Joaquin County EHD <br /> May 24, 2005 <br /> Page 2of4 <br /> hydrocarbons as gasoline (TPH/g); and total petroleum hydrocarbons as diesel (TPH/d). <br /> Analysis of two wellhead vapor samples will be included on a semi-annual basis. <br /> GROUNDWATER MONITORING <br /> Quarterly groundwater monitoring will be completed in June, September, and December <br /> 2005, and March 2006. Monitoring well locations are shown in attached Figure 1. <br /> Groundwater sampling will include up to twelve on-site wells (MW-9, MW-11, MW-12, <br /> MW-13, MW-14, MW-16, MW-19, MW-20, MW-24, MW-25, VM-1 and VM-2) and two <br /> QA/QC samples per event. Groundwater monitoring will include measurement of the <br /> depth-to-water in each well to prepare a groundwater elevation contour map of the site. <br /> From the groundwater contour map, the groundwater flow direction and hydraulic gradient <br /> can be calculated. Groundwater purging of three well casing volumes will be completed <br /> prior to sampling and pH, conductivity, and temperature will be measured after each <br /> purge. <br /> Groundwater samples will be collected in laboratory-approved containers using <br /> disposable bailers or dedicated sampling pumps and tubing, and transported under chain- <br /> of-custody for laboratory analysis. Electronic files of the water quality data in electronic <br /> deliverable format (EDF) will be uploaded to the State Water Resources Control Board <br /> (SWRCB), in accordance with §2729 and 2729.1 of Title 23, California Code of <br /> Regulations. Purge water generated during well purging will be containerized in properly <br /> labeled 55-gallon Department of Transportation (DOT) approved drums and stored on-site <br /> pending laboratory analyses. <br /> ANALYTICAL REQUIREMENTS <br /> Vapor and groundwater samples will be transported to Advanced Technology <br /> Laboratories (ATL) in Signal Hill, California for analysis using appropriate U.S. <br /> Environmental Protection Agency (USEPA) methodologies. ATL is certified through the <br /> California Department of Health Services Environmental Laboratory Accreditation <br /> Program, for the appropriate test methods. Two quality assurance/quality control <br /> (QA/QC) samples, a travel and equipment blank, will be analyzed with each groundwater <br /> event. Concentrations detected between maximum detection limit (MDL) and the practical <br /> quantitation limit (PQL) values will be reported with a "J° flag indicator. <br /> Groundwater samples will be analyzed for BTEX, TPHg, TPHd, dissolved oxygen, <br /> oxidation/reduction potential, and ferrous iron. Sulfate and nitrate analysis will be <br /> IACALTRANS1Stockton-Shop 101GW Monitohng\Letter to SJ County_Final.doc May 24,2005 <br /> Project No.9407.43148.00 SECOR international Incorporated <br />