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i QUARTERLY GROUNDWATER MONITORING REPORT SECOND QUARTER 2005 QUIK STOP MARKET NO. 132 3555 WEST HAMMER LANE STOCKTON, CALIFORNIA !Y I 1� 1.0 INTRODUCTION ATC Associates Inc. (ATC) is pleased to present this report for the Second Quarter 2005 groundwater monitoring conducted at the subject site in Stockton, San Joaquin County, California(Figure 1). The site plan (Figure 2) shows the location of the station building, adjacent streets, monitoring wells, and other site-specific features. The monitoring wells have been sampled quarterly to monitor two shallow groundwater aquifers f underlying the site. The program scope of work is as follows: f P • Measure depth to groundwater in site wells; 0 Analyze groundwater samples for select petroleum hydrocarbon constituents; • Construct groundwater elevation contour maps within the study area boundaries; and _ • Compare current and past data. ATC has adopted the San Joaquin County Environmental Health Department's recommendations for discontinuing the monitoring of wells MW-3, MW-6, MW-7 and MW-8, and modifying the sampling program for the remaining wells as per letter received February 15, 2005 (see Appendix D). The existence and degree of petroleum hydrocarbons in groundwater underlying the site is evaluated by (1)the presence of free-floating product and(2)laboratory analysis of groundwater samples analyzed for total petroleum hydrocarbon compounds in the gasoline range (TPH-G), and benzene, toluene, ethyibenzene and total xylenes (BTEX). Included with this report and in compliance with the March 24, 2004 request of the San Joaquin County Environmental Health Department, are results of analyses for the fuel oxygenates methyl-tertiary-butyl ether (MTBE) (a non-metallic antiknock and oxygenating compound used in gasoline), di-isopropyl ether (D1PE), ethyl-tertiary-butyl ether (ETBE), tertiary-amyl l methyl ether (TAME) and tertiary-butanol (TBA) by United States Environmental Protection Agency (USEPA)Method 8260B for samples collected from selected groundwater monitoring wells. 1 i 2.0 GROUNDWATER SAMPLING On May 24, 2005, in accordance with ATC's field protocol (Appendix A), groundwater samples were collected from on-site groundwater monitoring wells MW-IR, MW-2, MW-4, MW-5, and off-site t groundwater monitoring wells MW-9 and MW-10. Groundwater purged from the wells and equipment decontamination water was placed in Department of Transportation (DOT) approved 17H drums and � i. stored on site. The volume of groundwater removed from the wells and other measured sampling j-. parameters are noted on the field sampling logs included in Appendix B. Quarterly GW Monitoring Report---2nd Qtr 2005 NATC Quik Stop No. 132 Quik Stop Markets, Inc. � ATC Project No.75.62503.3205 June 13,2005 Page 1 of 4