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22 May 1998 AGE-NC Project No. 95-0152 Page 6 of 7 Appendix D. 5.0. SUMMARY AND CONCLUSIONS Based on data collected from soil probe borings PI through P5, AGE concludes the following: • It is assumed that first encountered ground water is between 75 and 85 bsg; review of historical depth to ground water maps dating back to 1971 indicates that ground water depth near the site has fluctuated between 50 and 90 feet bsg. • A total of nineteen soil samples collected from P1 through P5 and beneath the former tank cavity were submitted for laboratory analysis of petroleum hydrocarbons (Table 1). The laboratory detected substantial TPH-g,toluene,ethylbenzene and xylenes beneath the former tank cavity at approximately eleven feet bsg. Trace concentrations of toluene, ethylbenzene and xylenes were detected from P I at depths of fifteen and forty feet bsg. • Laboratory analysis of the domestic water well grab ground water sample did not detect any VOCs. • A total of thirty-one domestic and irrigation wells were located within a 2,000-foot radius during a reconnaissance search for visually observable potential receptors (Figure 3). • Laboratory and field data suggest the majority of petroleum hydrocarbon-impacted soil at the site is limited to the area beneath the former UST area to depths of approximately 15 feet bsg. • Figure 4 depicts general lithology beneath the site in cross sectional view. Figure 5 depicts selected soil sample locations and the estimated extent of TPH-g impact beneath the site in cross sectional view. Figure 6 depicts the estimated extent of TPH-g impact in plan view. When the data collected at the site is calculated from both plan and cross sectional views,the apparent volume of petroleum impacted soil remaining at the site is approximately 12.5 cubic _ yards (Appendix E). • Based upon data collected during investigation of the former UST area, approximately 11.4 gallons of gasoline remain in soil to a depth of 15 feet bsg (Appendix E); only residual concentrations of hydrocarbons are present between depths of 15 and 40 feet bsg. Since ground water depth at the site is in excess of 75 feet bsg, it is unlikely that this small volume of hydrocarbons remaining in soil poses a significant threat to ground water. Advanced CeoEnvironmenlal.Inc.