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MAY-01-67 17:00 Frem:1.T. OORPORATIOH 5102282501 T-620 P.08f08 Joh-685 <br /> i <br /> 2.2. /Residual Masi of Diesel in Snit <br /> To estimate the residual mass of diesel in soil, a statistical method was used since an extrema <br /> variation in the diesel concentration was measured at the site (5 orders of magnitude). The <br /> following method was followed to ensure a rWistie, yet conservative estimate of the rcidual <br /> mass of diesel in soil.: <br /> A histogram was plotted to dewmine the distribution of TPH as diesel in the soil <br /> (Figure 1). All the available data from sail'borings drilled at the site betwa= 1987 <br /> and 1995, totalling seventy (70) data paints. The resulting histogram exhibited a log- <br /> normal distribution with an extreme left skew spanning five orders of magnitude ([1 <br /> mg/kg to 130,CWDO mg/kg), A log-normal distribution of TPH as diesel in the soil is <br /> consistent with oontaminant distributions typically observed in tho sail and <br /> groundwater (USEPA 1989, 1992, 1994). More than 80 percent of the data yietded <br /> concentrations of TPH as diesel less than 100 mg/lig, and 50 percent of the data <br /> yielding non-detect concentrations. <br /> ■ Data analysis used procedures recommended by Ott (Ott, 1995) to determine the <br /> residual mass of diesel in the soil. A log-normal distribution of TPH as diesel in the <br /> soil was anumed. The residual mass of diesel in the soil at the site was calculated to <br /> be 1203 16s, corresponding to 160 gallons. Table 2 provides the squential method <br /> that was employed when calculating the residual mass. <br /> 2.3 Mass Ralaure Calculation <br /> The treated mass of diesel was calculated to be 2,482 tbs in 8,910 fe of impacted soil. This <br /> was treated by excavation of impacted sail in the source area. The residual mass of diesel in <br /> the sail was calculated to be 1,203 tbs in 17,030 ftof soil at the site. Therefore the total <br /> mass of diesel in the soil prior to treatment was: <br /> 2,482 lbs + 1,203 lbs = 3,68S las. <br /> Therefore approximately 67 percent of mass was treated at the site, only by excavating the <br /> heavily impacted material. 'Therefore if intrinsic bioremediation is considered at the site, it <br /> is likely that the treated mass will increw significantly. <br /> 3.0 Concl Wons <br /> Based OSI the calculations that were performed with the data from the site at least 67 percent <br /> of the diesel ma-m at the site has been rcmediabW by excavation and disposal of impactod <br /> soil. <br /> MZ/0S-01-97NDEFW-OW4.j11 2 <br />