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rn Mr. Kyle Christie April 4, 1995 Page 2 Because of the obstruction, monitoring well W-2 was replaced on December 29, 1994. The replacement well was installed in the same borehole as the original well. A well replacement report will be prepared in the first quarter of 1995. The well was developed, and samples were collected and analyzed for TPH-G and BTEX by EPA Methods 503018020, and 8015 Modified. Results and Discussion 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. 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. The general groundwater flow direction beneath the site on December 19, 1994, was to the south under a hydraulic gradient of approximately 0.002 (Figure 1). Well W-2B was not used for contouring because it is completed in a deeper zone than the other wells. Well W-4 was not used in contouring because it was dry, well W-10 was not used because it was inaccessible, and well W-2 was not used because it was obstructed. Since groundwater monitoring began in 1988, the general groundwater flow direction has ranged from southwest to southeast at this site. The hydraulic gradient measured this quarter is within the range of previously reported gradients. Depth-to-water on December 19, 1994 ranged from 63.02 in well W-8 to 66.10 in well W-9. Well W-4 was dry. Since the last quarterly monitoring event (September 28, 1994), water-level elevations in all the measured monitoring wells have increased an average of 2.35 feet. I Benzene concentrations this quarter were nondetectable in all the sampled wells (W-1A, W- 2A, W-2B, W-3, W-6 through W-9, W-11, and W-12)except well W-5. Benzene in well W-5 is reported to be 2.2 micrograms per liter (µg11). These concentrations are within the range of previously reported values. TPH-G concentrations were nondetectable in all sampled wells. These concentrations are consistent with previous values. The detection limit for benzene is 0.5 pg/1 and for TPH-G is 50 pg/l. The reason for the presence of benzene in the sample from well W-5 is unknown at this time. BTEX and TPH-G have not been detected in well W-5 since February of 1992, with the exception of 1.1 pg/l of toluene on September 28, 1994. As discussed in the third quarter 1994 report, the presence of toluene on September 28, 1994 may be the result of laboratory •� Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document. 13194ZEPORTS\4TH94QTRM T