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metric average of the on-site and local water-table gradients, i1 <br /> and i2 (see Section 2.1 .1) . Thus, <br /> vavg = K il. i2 /n <br /> = 10_3 0.004 x 0.0006 /0. 30 <br /> 5.2 x 10-6 m/s = 21 m/yr <br /> The plan diameter of the source is estimated to be 24 feet (8 m) , <br /> which is the diameter of the circle enclosing the two tanks be- <br /> neath which contaminated soil was found (Table 3; Figure 5) . It <br /> is important to note that th4 deep soil samples from three <br /> borings (C1, C2, C3) located just beyond the tank field peri- <br /> meter, had no detectable hydrocarbons (Table 3; Figure 5) . The <br /> source depth is assumed to be a 10-foot thick sandy layer just <br /> beneath the water table (68-78 feet deep) . Hence, the cross- <br /> sectional area is 240 ft (22 m2) . The source volume flow rate <br /> is <br /> Qs = 22 m2 x 27 m/yr = 594 m3/yr <br /> = 0.068 m3/hr <br /> The receptor well (Broadway Hatchery) is assumed to pump at a <br /> rate of 10 gpm; its distance from the source is 250 feet (76 m) . <br /> It has a depth of 180 feet and a diameter of 12 inches (0 .30 m) . <br /> The aquifer thickness is taken to be 140 feet (43 m) , the <br /> interval between the water table and the well bottom. Porosity <br /> is assumed to be 0.3, typical of sand. As a source waj.er- <br /> contamination level, 1 mg/L was used in the computer model, but <br /> this is not important; the dilution factor (C-CO) / (CD-CO) , <br /> appearing in the RESSQ output is important. <br /> RESSQ (see Appendix C) predicts a dilution factor of 0 .0214 as a <br /> maximum (steady-state) value, which is reached 2 . 9 yeari after <br /> contaminant release. The appropriate chemical concentrations in <br /> ground water at the source are taken as the geometric average of <br /> 20 <br />