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13 December 1999 <br /> AGE-NC Project,No. 98-0433 <br />' Page 12 of 13 <br /> 5.0. SUMMARY AND CONCLUSIONS <br /> The following conclusions were drawn from the results of this investigation: <br />' Ground water at the site was encountered at approximately 17 to 20 feet bsg. The prevailing <br /> ground water flow direction in this area of.limco is generally toward the west and somewhat <br /> northwest. ; <br /> • The most intensely hydrocarbon-impacted soil was encountered in the area of the former <br /> USTs. Soil contaminated with petroleum-hydrocarbons was limited to depths of 3'0 feet bsg,' <br /> except for fuel additives, and the highest hydrocarbon concentrations were encountered at <br /> depths of 10 to 20 feet bsg. However, MTBE was detected at reduced concentrations in soil <br /> collected from a depth of 30 feet bsg near the former UST area. <br /> • The highest concentration of dissolved hydrocarbons quantified as TPH'g,TPH-d and overall <br /> BTEX compounds extends northward -of the former UST area. Hydrocarbons were <br /> ' encountered in the presumed down-gradient direction from the UST to the location.of grab . <br /> water sample B14. TPH-g and BTEX concentrations in ground water decrease eastward in <br /> the area of well MW-7 and decrease'solith of the former USTs, in the area of well MW-8. <br /> • The lateral extent of the dissolved phase plume can be approximated. Figure 4 depicts an <br /> approximate areal distribution of impacted ground water. <br /> • Analytical data from the initial site assesslrient indicates that remediation of soil and/or <br /> ground water may be required at the,site. <br /> 6.0. RECOMMENDATIONS <br /> ' Based on the results of this investigation, AGE recommends the following: <br /> ' Quarterly monitoring at the site should be initiated to coincide with the monitoring <br /> performed at the Ripon Farm Service site. <br /> ' The next monitoring event should be scheduled for January 2000 and should include <br /> sampling of on-site domestic wells for analysis for constituents of concern.' <br /> • A work plan for installation of necessary wells and procedures to assess feasibility of various <br /> ' corrective action alternatives should be prepared. <br /> • A Corrective Action Plan (CAP) should be prepared upon completion of the feasibility <br /> ' testing. The CAP should include remediation feasibility studies (e.g. in-situ air sparging pilot <br /> Advanced GeoEnvironmental,Inc. <br />