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11 April 2003 <br /> AGE-NC Project No 01-0865 <br /> Page 5 of 9 <br /> Physicochemical analysis of four selected soil samples (B12-26, B12-38, B13-14 and B13-23) <br /> determined a pH range of between 7 1 and 7 2, mtrate-nitrogen range between 6 and 9 ppm,nitrate <br /> ion range between 26 4 and 39 6 ppm, ammonia-nitrogen range between 17 and 24 ppm, ammonia <br /> ion range between 21 93 and 30 96, ortho-phosphate range between 34 and 38 ppm and potassium <br /> range between 56 and 64 ppm <br /> Microbial enumeration determined the populations of general microbes (heterotropic,nonspecific) <br /> at(12 Ito 17 8 ) x 105 and specific microbes(gasoline/diesel specific) at(2 4 to 3 5) x 105, specific <br /> microbes comprised between 16 88% and 19 83 % of the microbe population <br /> Analytical results of soil samples are summarized in Table 1 The laboratory reports(CTEL Lab IDs <br /> 0210-178-1 through 0210-178-15,0210-178-18 through 0210-178-21,and 0210-178-27 and BioJet <br /> Lab IDs BJ-AGE-HHM-2-4) and chain-of-custody forms are included in Appendix D and E <br /> 3 3 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> TPH--g was detected in the ground water samples collected from borings B11, B12, and B13 at <br /> concentrations of 5,300 µg11, 7,900 µg/1 and 6,500 µg/l, respectively <br /> BTEX compounds were detected in the ground water samples collected from the borings at <br /> concentrations as high as 330 µg/1 benzene (B12), 670 µg/1 toluene (1313), 330 µg/1 ethylbenzene <br /> (B 12) and 1,520 µg11 total xylenes (B 12) <br /> Fuel additives, including MTBE, were not detected at or above laboratory reporting limits in the <br /> ground water samples Analytical results of ground water samples are summarized in Table 2 The <br /> laboratory report (CTEL Lab IDs 0210-178-22 through 0210-178-24) and chain-of-custody forms <br /> are included in Appendix D <br /> 4.0. SITE CONCEPTUAL MODEL <br /> Based on the data collected to date from soil borings and monitoring well installations and sampling, <br /> AGE has developed a site conceptual model for the release, migration and distribution of the <br /> contaminants in the subsurface as described below <br /> The site is essentially flat land,with a 20-foot high levee on the western edge (Figure 3) The levee <br /> is composed essentially of anthropomorphic, built-up levee material ranging fromm clay and silt <br /> adjacent to the slough to coarser-grained sands and road-base material A peat layer ranging from <br /> 40 6 to 20 feet thick underlies the levee deposit and forms the surface layer of the flat land (Unit 1) <br /> Advanced GeoEnvaronmental,Inc <br />