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rr • Ms Margaret Logono August 30, 2001 Page 5 the soil samples Only trace concentrations of benzene,toluene, ethylbenzene, and total xylenes (BTEX) were detected in sample B1-25 5-26 0 Figure 1 shows the location of cross-section A-A' Figure 2 shows the cross-section of A-A', borehole location and depths, and TPHd concentration of each sample Table 2. Summary of Soil Sample Depth and Analytical Results Sample Total Depth :Benzene Toluene Ethylbenzene Xylenes, MTBE TPHd Sample ID feet bgs) m /Km /K m /K (mg/K (mg/K (mg/Kg) B1-25 5-26 0 25 5-26 0 0 030 0 033 0 055 030 <00050 <10 B1-29 5-30 0 29 5-30 0 <00050 <00050 <00050 <00050 <00050 <10 B1-31 5-32 0 31 5-32 0 <00050 <00050 <00050 <00050 <00050 <10 B2-20 5-210 20 5-21 0 <00050 <00050 <00050 <a0050 <00050 <10 B2-23 5-24 0 23 5-24 0 <00050 <00050 <00050 <00050 <00050 <10 B3-19 5-20 0 19 5-20 0 <00050 <00050 <00050 <00050 <00050 <10 B3-22 5-23 0 1 22 5-23 0 1 <00050 <00050 <00050 <00050 <00050 <10 Notes bgs—below ground surface mg/Kg—millrgram per lulogram 3.0 SOIL CHARACTERIZATION POST EXCAVATION Based on the most recent soil investigation analytical results and previous excavated and over-excavation soil sample results only residual amounts of petroleum hydrocarbons remain in the soil Soil investigation boring samples dict not contain any detectable levels of TPHd and only residual concentrations of BTEX in one soil sample Residual BTEX concentrations remain in a localized area on the east side of the former UST and extend no deeper than 29 5 feet bgs The amount of benzene remaining in the soil can be conservatively estimated by assuming the areal extent as a cylinder with a 10-foot-diameter, centered on B-1, the only boring with reportable a benzene concentration The mass was calculated by estimating the areal extent of the impacted area, estimated the thickness of contannnated soil and assigning a concentration of benzene from sample data within the area Benzene was chosen due to non-detectable concentrations of TPHd and because it is commonly the driving constituent of concern for soil and groundwater remediation Based on the conservative assumptions outlined above, approximately 0 030 pounds of benzene remain in the soil 4.0 SUMMARY AND RECOMMENDATIONS After the May 1999 removal of the diesel UST,TPHd impacted-soil was removed during excavation activities Based on stockpile sample analysis results,the excavated soil contained approximately 6,201 pounds TPHd Based on soil boring P%I 60001162711Dtesel tankTinal Diesel UST Rpt doc