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t10 May 2004 <br /> AGE-NC Project No. 98-0520 <br /> Page 5 of 6 <br /> The contaminates began to migrate laterally as well as vertically in Layer 2; the direction of lateral <br /> ' migration was dominantly towards the northwest,in the preferred ground water flow direction. The <br /> lateral and vertical extent of soil and ground water contamination has been defined(Figures 3 and 4, <br /> and in the CAP). <br /> Significant petroleum-hydrocarbon impact to soil in the vadose zone is present in borings B2-20.25, <br /> ' B4-20,MW2-25 and MW4-20, in the area-of the former USTs, and off-site well MW9-20. TPH=g, <br /> TPH-d and TPH-mo are present at maximum concentrations of 670 mg/kg (B2-20.25),' l 50 mg/kg <br /> (MW-9-20) and 120 mg/kg(B-2-20.25),respectively. Most of the contamination appears to reside <br /> ' at the top of the clay layer, at approximately 20 feet bsg. <br /> 6.0. SUMMARY AND CONCLUSIONS <br /> Based upon the findings of this site investigation, AGE concludes: <br /> • The vertical soil profile consisted of generally medium- to coarse-grained sand from the,. <br /> surface to approximately 15 feet bsg,silt with clay from 15 to approximately 30 feet bsg,and, <br /> fine- to coarse-grained sand from approximately 30 feet bsg to total depth. <br /> • Contaminants of concern were not detected in the analyzed soil and grab ground water <br /> samples' collected during this investigation. The vertical and lateral extent of petroleum hydrocarbon-impacted soil and groundwater has been defined: vertically, contaminants do <br /> not extend below 45 feet bsg; and laterally, contaminants do not extend beyond down- <br /> gradient soil boring locations B5 and B6, monitoring well location MW-7 to the west- <br /> 'southwest, and well location MW-10 to the east-southeast. <br /> 7.0. RECOMMENDATIONS <br /> ' Based upon the site assessment activities to date, AGE recommends EHD's approval and <br /> implementation of the AGE-prepared Corrective Action Plan, dated ll February 2003. <br /> 8.0. LIMITATIONS <br /> ' Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities. The findings were based upon <br /> ' analytical results provided by an independent laboratory. <br /> ' Advanced GeoEnvironmental,Inc. <br /> 1 <br />