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1 <br /> CLEARWATER <br /> i <br /> G R O U P, I NC. <br /> Euvirunmentel Seeai ces <br /> QUARTERLY GROUNDWATER MONITORI=NG REPORT <br /> FOURTH QUARTER 1996 <br /> Boettcher Western Properties <br /> 4555 North Pershing Avenue, Stockton, California <br /> January 2, 1997 <br /> BACKGROUND <br /> The site is currently unoccupied and is used primarily as a two-lane driveway providing access to an <br /> adjacent shopping center. The site was formerly operated as a card lock refueling station. Nine soil <br /> borings were drilled in June 1991. Analysis of soil samples collected from the borings indicated the <br /> presence of gasoline contamination at a depth of approximately 25 feet bgs. Three underground storage <br /> tanks (USTs) containing leaded gasoline, unleaded gasoline, and diesel fuel were excavated and <br /> removed from the site by TreaTek, Inc. on January 8, 1992. In November 1992, McLaren/Hart installed <br /> five groundwater monitoring wells (MW-1 through MW-5) to a maximum depth of 40 feet bgs. <br /> Clearwater began quarterly groundwater monitoring and sampling at the site in December 1994. <br /> GROUNDWATER MONITORING FIELD ACTIVITIES <br /> Date of field activities: December 17,1996 <br /> Wells monitored/sampled: MW-1, MW-2, MW-3, MW-4, and MW-5 <br /> Analytes tested: TPHg, BTEX, and MTBE <br /> Analytical methods: EPA Methods 8015/8020 (modified) <br /> Laboratory: American Environmental Network, Inc. of Pleasant Hill, CA <br /> GROUNDWATER MONITORING RESULTS <br /> Depth to water: 20.51 to 21.08 feet below grade <br /> Flow direction/gradient. East northeast at 0.54% <br /> TPHg concentration range: 130 ppb (MW-5); <50 ppb in all other wells <br /> Benzene concentration range: 2.0 ppb (MW-3); <0.5 ppb in all other wells <br /> MTBE concentration range: <5.0 ppb in all wells <br /> Remarks: The direction of groundwater flow is generally consistent with previous measurements; <br /> analytical results.indicate continued attenuation of the contaminant plume. <br /> PROJECT STATUS <br /> Quarterly groundwater monitoring will be continued. <br /> ATTACHMENTS <br /> • Site Location Map (Figure 1) <br /> • Site Plan (Figure 2) <br /> • Groundwater Elevation Contour Map-12/17/96(Figure 3) <br /> • Hydrocarbon Distribution Map-12/17/96 (Figure 4) <br /> • Groundwater Elevations and Analytical Results (Table 1) <br /> • Clearwater Gauge/Purge Calculations and Well Purging Data (Appendix A) <br /> • Laboratory Report and Chant-of-Custody Form (Appendix B) <br /> • Clearwater Groundwater Monitoring and Sampling Protocols (Appendix C) <br />