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SECOR www secorcam R INTERNATIONAL 3017 Kilgore Road Suite 100 . S E R Q INCQRPORATED 916 6Ranch1 0400 Cordova ECA 95970 818-1161040 wuc August 31, 2004 Mr James Barton Central Valley Regional Water Quality Control Board 11020 Sun Center Drive, Suite 200 Rancho Cordova, CA 95670-6114 RE Field Test Program for Evaluation of Oxidation Capacity of Groundwater 7-Eleven Store#14117 2725 Country Club Boulevard Stockton, California 95204-3937 SECOR Project No 77EL 14117 04 0104 Dear Mr Barton SECOR International Incorporated (SECOR) on behalf of 7-Eleven presents the analytical results of a groundwater sample collected at 7-Eleven Store ##14117 in support of the planned field test program for evaluation of groundwater oxidation capacity (Table 1), the laboratory data sheets are presented as Attachment A Sample collection, analysis, and , . data evaluation were completed to comply with the Regional Water Quality Control Board's request during a meeting conducted August 5, 2004 to discuss the planned field test program The groundwater sample was collected from monitoring well MW-1 (Figure 1) and analyzed for general inorganic constituents and dissolved metals to provide baseline chemistry data for the site prior to initiation of the oxygen infection field test program The depth to water was measured to within 0 01 feet bgs from the top of casing (TOC) using a water level indicator The dissolved oxygen concentration was also measured in the well using a YSI Model 550A dissolved oxygen meter equipped with a down-hole sensor Sampling equipment was thoroughly cleaned prior to purging and sampling the well The sampling procedure included measuring the water level and purging three casing volumes of water using a bailer During purging, temperature, pH, and electrical conductivity were monitored to document that these parameters were stable prior to collecting the sample In addition, ferrous iron concentration (Fe+2) was measured during purging using a HACH Model 1R-18C ferrous iron test kit After purging, the water level was allowed to recover to 80% of the original level prior to collection of the water sample The groundwater sample was collected using a disposable Teflon® bailer, placed into appropriate Environmental Protection Agency (EPA) approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a California state-certified laboratory The groundwater is a Na-HCO3 type water of low ionic strength, saturated with respect to calcite and iron oxyhydroxides It is well buffered relative to pH, therefore, the system should remain at or near neutral even with precipitation of iron oxyhydroxides Oxygen demand is almost entirely due to the presence of organic compounds, i e , petroleum 117 ElevenW-11 Stores1141171Correspandence114117 Baseline Chemistry IU RWQCB doe