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S E C O R Second Quarter 2004, QuarterlyProgress Report July 13, 2004 g p Page 1 1.0 INTRODUCTION SECOR International, Incorporated (SECOR), on behalf of Chevron Environmental Management Company (Chevron), presents second quarter 2004 (2Q04) groundwater monitoring and sampling results, and operational data for the groundwater extraction and treatment (GWET) system at 301 West Kettleman Lane, Lodi, California (Figure 1). This report covers the period from March 10, 2004 through June 14, 2004, and was prepared in accordance with Cleanup and Abatement Order (CAO) No. 5-00- 704, dated April 20, 2000 (Appendix A). 2.0 GROUNDWATER MONITORING AND SAMPLING On April 30, 2004, Gettler-Ryan Incorporated (G -R), conducted 2Q04 groundwater monitoring and sampling. Certified laboratory analytical reports and chain -of -custody documentation and sampling field data sheets, are included in Appendices B and C, respectively. A brief summary of results is presented below. �. 2.1 Monitoring Well Gauge Data Monitoring well gauge data indicates the approximate depth to groundwater in A, B, and C -zones ranges x from 57.74 to 63.69 feet below ground surface (bgs). Groundwater gauging data is presented in Table 1. The potential for groundwater in the A -zone near the site appears to be radially inward toward extraction well EX -3 (Figure 2). The potential for groundwater flow in the B -zone appears to be variable (Figure 3). Insufficient monitoring wells in the C -zone prevent evaluation of the potential for groundwater flow in this zone. 2.2 Sample Analytical Results During the 2Q04, groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethyl -benzene, and total xylenes (BTEX), methyl tertiary butyl ether (MtBE), tertiary butyl alcohol (TBA), di -isopropyl ether (DIPE), ethyl tertiary butyl ether (EtBE), tertiary amyl methyl ether (TAME), ethanol, methanol, ethylene di -bromide (EDB), and 1,2-dichloroethane (1,2 -DCA). Sample analytical results are summarized in Table 2. Maximum concentrations of detected constituents for A, B, and C -zones are presented in the table below. An A -zone isoconcentration map for MtBE is presented as Figure 4. lAChevron1957751Periodic Monitoring\Q P R1200412nd Quarter -2004 QPR.doc Maximum Constituent Concentrations (µg11) Zone TPHg Benzene Toluene Ethyl- benzene Xylenes MtBE TBA EtBE TAME A- zone 240 <1 1 <1 <1 3,200 <10 180 43 B- <50 < < n <5 <0.5 <0.5 C- zone <50 <0.5 0.8 <0.5 <0.5 <0.5 <5 <0.5 <0.5 Explanations: µgll = Micrograms per liter < Indicates the constituent was not present at or above the method detection limit shown lAChevron1957751Periodic Monitoring\Q P R1200412nd Quarter -2004 QPR.doc