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Mr Kyle Chnstie May 12, 1995 Page 2 • xylenes (BTEX) and total petroleum hydrocarbons as gasoline (TPH-G) by U S Environmental Protection Agency (EPA) Method 503018020, and 8015 Modified Field data sheets and chain-of-custody documentation are included in Exhibit A Results and Discussion The general groundwater flow direction beneath the site on February 28, 1995, was to the northeast under a hydraulic gradient of approximately 0 002 (Figure 1) Since groundwater monitoring began in April 1987, the general groundwater flow direction has ranged from north to east at this site The hydraulic gradient measured this quarter is within the range of previously reported gradients Depth-to-water on February 28, 1995 ranged from 8 45 feet in Well ATR-8 to 12 65 feet in Well ATR-I Since the last quarterly monitoring event (December 16, 1994), water-level elevations in all the measured monitoring wells except ATR-1, ATR-3, ATR-1 I, and SMW-I have decreased an average of 0 09 feet The water- level elevation in well ATR-3 did not change, and increased an average of 0 1 feet in wells ATR-I, ATR-11, and SMW-1 Summaries of depth-to-water measurements and calculated groundwater elevations are presented in Table 1 Table 2 lists past and present groundwater flow directions and hydraulic gradients for this site. Benzene concentrations this quarter were nondetectable in all sampled wells except ATR-4 and SMW-1 Benzene was 180 micrograms per liter (pg/1) in well ATR-4, and 1000 pg/l in well SMW-I The detection limit for benzene is 0 5 pg/l These concentrations are within the range of previously reported values, with the exception of well SMW-1 The concentration of benzene in well SMW-1 has increased this quarter, in comparison with previously recorded values TPH-G concentrations ranged from nondetectable in wells ATR-1, ATR-2, ATR-6, ATR-7, ATR-9, ATR-10, and ATR-11 to 8300 pg/I in well SMW-i The detection limit for TPH-G is 50 pg/1 These concentrations are consistent with previous values, with the exception of SMW-1 TPH-G concentrations in well SMW-1 increased this quarter, in comparison with previously recorded values. Analytical results of groundwater samples are summarized in Table 3 The complete laboratory report for the sampling event is presented in Exhibit A. Figure 2 shows TPH-G and BTEX concentrations for this sampling event A soil vapor extraction and treatment/air sparging (SVET/AS) system has been designed for this site An Authority-to-Construct permit (Permit No N-3413-1-0, issued March 10, 1995 and expiring March 10, 1997) has been obtained from the San Joaquin Valley Unified Air Pollution Control District for this site The: system design has been submitted to the City of Tracy and is currently under review by the City Planning Department Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document 204NZEPORTSM ST95gMAPT