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•' QUARTERLY GROUNDWATER MONITORING REPORT <br /> ' THIRD QUARTER 2005 <br /> QUIK STOP MARKET NO. 132 <br /> 3555 WEST HAMMER LANE <br /> �. STOCKTON, CALIFORNIA <br /> 1.0 INTRODUCTION <br /> ATC Associates Inc. (ATC) is pleased to present this report for the Third Quarter 2005 groundwater <br /> monitoring conducted at the subject site in Stockton, San Joaquin County, California(Figure 1). The site <br /> plan (Figure 2) shows the location of the station building, adjacent streets, monitoring wells, and other <br /> site-specific features. Sampling this quarter employed two different styles: low-flow / low-purge <br /> '. sampling using a peristaltic pump,and conventional sampling using a power pump and bailers. This was <br /> done in an effort to determine if conventional sampling of the wells with low contaminant concentrations <br /> results in fluctuating analytical results. The results of this comparison are discussed in the Conclusions <br /> ' and Recommendations. <br /> The monitoring wells have been sampled quarterly to monitor two shallow groundwater aquifers <br /> �. underlying the site. The program scope of work is as follows: <br /> • Measure depth to groundwater in site wells; <br /> • Analyze groundwater samples for select petroleum hydrocarbon constituents; <br /> • Construct groundwater elevation contour maps within the study area boundaries; and <br /> ' • Compare current and past data. <br /> ATC continues to follow the San Joaquin County Environmental Health Department's recommendations <br /> for a modified sampling program as per the letter received February 15,2005. <br /> The existence and degree of petroleum hydrocarbons in groundwater underlying the site is evaluated by <br /> (1)the presence of free-floating product and (2) laboratory analysis of groundwater samples analyzed for <br /> total petroleum hydrocarbon compounds in the gasoline range (TPH-G), and benzene, toluene, <br /> ethylbenzene and total xylenes (BTEX)and selected fuel oxygenates. <br /> 2.0 GROUNDWATER SAMPLING <br /> On August 24, 2005, in accordance with ATC's field protocols (Appendix A), two sets of groundwater <br /> samples were collected from on-site groundwater monitoring wells MW-1R, MW-2, MW-4, MW-5, and <br /> off-site groundwater monitoring wells MW-9 and MW-10. Groundwater purged from the wells and <br /> equipment decontamination water was placed in Department of Transportation (DOT) approved 17H <br /> drums and stored on site. The volume of groundwater removed from the wells and other measured <br /> sampling parameters are noted on the field sampling logs included in Appendix B. <br /> Quarterly GW Monitoring Report-3rd Qtr 2005 <br /> Quik Stop No. 132 <br /> CMATC <br /> Quik Stop Markets, Inc. <br /> ATC Project No.75.62503.3206 <br /> �. <br /> September 30,2005 <br /> Page 1 of 4 <br />