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CLEARWATER £nvironm rnlal Srrv�crs QUARTERLY GROUNDWATER MONITORING REPORT FIRST QUARTER 1997 Boettcher Western Properties 4555 North Pershing Avenue, Stockton, California March 27, 1997 BACKGROUND The site is currently unoccupied and is used primarily as a two-lane driveway providing access to an adjacent shopping center The site was formerly operated as a card lock refueling station Nine soil borings were drilled in June 1991 Analysis of soil samples collected from the borings indicated the presence of gasoline contamination at a depth of approximately 25 feet bgs Three underground storage tanks (UST's) containing leaded gasoline, unleaded gasoline, and diesel fuel were excavated and removed from the site by TreaTek, Inc on January 8, 1992 In November 1992, McLaren/Hart installed five groundwater monitoring wells (MW-1 through MW-5) to a maximum depth of 40 feet bgs Clearwater began quarterly groundwater monitoring and sampling at the site in December 1994 GROUNDWATER MONITORING FIELD ACTIVITIES Date of field activities March 6, 1997 Wells monitored/sampled MW-1, MW-2, MW-3, MWA, and MW-5 Analytes tested TPHg, BTEX, and MTBE Analytical methods EPA Methods 8015/8020 (modified) . Laboratory American Environmental Network, Inc of Pleasant Hill, CA GROUNDWATER MONITORING RESULTS Depth to water 16 31 to 16 88 feet below grade Flow directon/gradient East northeast at 0 6% (0 006 ft/ft) TPHg concentration range 60 ppb (MW-1) to 90 ppb (MW-5), <50 ppb in all other wells Benzene concentration range 13 ppb (MW-2) to 9 4 ppb (MW-3), <0 5 ppb in all other wells MTBE concentration range <5 0 ppb in all wells Remarks The direction of groundwater flow is generally consistent with previous measurements, depth to groundwater is approximately four feet higher than on December 17, 1996 PROJECT STATUS Quarterly groundwater monitoring will be continued ATTACHMENTS • Site Location Map (Figure 1) • Site Plan (Figure 2) • Groundwater Elevation Contour Map-3/6/97(Figure 3) • Hydrocarbon Distribution Map-3/6/97(Figure 4) • Groundwater Elevations and Analytical Results (Table 1) • Clearwater Gauge/Purge Calculations and Well Purging Data (Appendix A) • Laboratory Report and Chain-of-Custody Form (Appendix B) • Clearwater Groundwater Monitoring and Sampling Protocols (Appendix C)