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i <br /> Mr. Kyle Christie %no., <br /> June 29, 1989 <br /> Page 3 <br /> February 1989 Analytical Results <br /> All of the samples were analyzed for BETX and TPH using U.S. Environmental Protection <br /> Agency (EPA) Method 8015, modified. The analytical results of the groundwater samples <br /> collected in the previous four quarters and February 1989 are summarized in Table 1. <br /> Complete laboratory results for the February groundwater sample analysis are included in this <br /> report as Appendix A. <br /> BETX Results. BETX concentrations in wells ATR-3 and ATR-4 are generally lower in <br /> the February 1989 samples than in the September 1988 samples, particularly well ATR-3. <br /> Nevertheless, BETX concentrations are highest in well ATR-4 and exceed the action level <br /> for drinking water as established by the California Department of Health Services (DHS). <br /> With the exception of benzene, all of the constituents were below DHS action levels in wells <br /> ATR-1, ATR-2, and ATR-4. <br /> BETX were identified in minor amounts in wells ATR-1 and ATR-2. Well ATR-2 has not <br /> previously contained BETX, based on detection limits of 0.5 parts per billion (ppb). During <br /> February 1989, the BETX concentrations ranged from 0.6 to 3.4 ppb. <br /> Well ATRA has contained variably low BETX concentrations during the 15-month monitoring <br /> period. In December 1987, benzene and ethylbenzene were present at relatively low <br /> concentrations (5.9, and 0.9 ppb). In June 1988, ethylbenzene, toluene, and xylene were <br /> present at somewhat higher concentrations (1.3, 4.3, and 2.2 ppb, respectively). BETX were <br /> not present in samples collected during March and September 1988, based on a detection limit <br /> of 0.5 ppb. In February 1989, benzene and xylene were present at lower concentrations (1.4 <br /> and 1.8 ppb, respectively). <br /> TPH Results. Petroleum hydrocarbon concentrations in the gasoline range, have increased <br /> from 57.4 parts per million (pptn) to 110 ppm in well ATR-3, and 1.4 ppm to 220 ppm in <br /> well ATR-4. Gasoline was identified in well ATR-2 for the first time (0.37 ppm) since <br /> quarterly sampling began in December 1987. Groundwater from well ATR-1 did not contain <br /> petroleum hydrocarbons in the February 1989 samples based on a detection limit of 0.1 ppm. <br /> Groundwater Flow <br /> Groundwater levels at the site are measured in each well on a quarterly basis. The water <br /> levels are measured relative to the top of well casing with an electronic water/oil interface <br /> probe. The groundwater flow direction in June and September 1988 was approximately north, <br /> under a hydraulic gradient of 12 feet per mile or 0.2 percent. In February 1989, the <br /> groundwater flow direction shifted to the northeast under a hydraulic gradient of 0.2 percent. <br /> Conclusions <br /> Based on field observations and analytical results, the following conclusions are presented. <br /> Analytical results of groundwater samples collected during February 1989 show that benzene <br /> and toluene have been identified in well ATR-1 in minor amounts. Well ATR-1 has contained <br /> BROWN AND CALDWELL <br /> 723 S STREET SACRAMENTO.CALIFORNIA 95814-7092.(916)444-0123 <br />