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21 March 2006 AGE-NC Project No 97-0290 ' Page 14 of 15 ' directions Ground water elevation at the site decreased an average of 0 5 feet between the fourth quarter 2005 and the first quarter monitoring events Ground water levels were within the screen interval of the all wells monitored ' Historically, the highest concentrations of contaminants have been detected in the area of wells MW-2,located at the former UST location,and MW-4,located directly down-gradient of the former USTs However,the concentrations of dissolved BTEX and TPH have steadily ' and significantly declined in these areas since remediation at the site began The BTEX plume appears to be stable and declining, with the core of the plume limited to the southern portion of the site The detections of BTEX compounds were limited to the on-site well ' MW-2 and TPH-g was not detected during this monitoring event(Appendix F) • The thermal oxidation and carbon-based SVE system operated for approximately 4 years,and ' removed a calculated total of 19,512 6 lbs, or 3,122 gallons, of gasoline (TPH-g) (Appendix G) ' TPH-g was detected in soil samples collected from 20 feet bsg in both confirmation soil borings at a maximum concentration of 400 mg/kg (B101-20), lower concentrations were also detected in the soil collected from 50 feet and 55 feet bsg BTEX compounds were detected in the soil samples collected from borings B101 and B102 at depths of 20 feet, 50 feet,and 55 feet bsg The remaining mass of hydrocarbons reside within silty sand above silt (82 7 lbs TPH) and within sand at the water table level (2 5 lbs TPH) The estimated ' remaining mass near the soil borings established is 85 lbs of TPH-g (Appendix G) • Shallow soil samples collected and analyzed from the site prior to remediation, from locations under the current Lodi Theater structure, were non-detect at depths ranging from 15 feet,20 feet, and 30 feet bsg Shallow vapor intrusion into and under the slab foundation of the theater is not likely or probable based on 30 feet of non-impacted soil beneath the ' structure Volatilization of low BTEX concentrations detected near 20 feet bsg(B 1 01/B 102), into the ambient air surrounding wells MW-2 and VW-1 should be naturally attenuated within the soil structures above 20 feet bsg (clean backfill sand) or dispersed into the atmosphere with considerable dilution 10.0. RECOMMENDATIONS Based on the findings of the environmental activities recounted in this report, AGE recommends • Based on the declining concentrations of dissolved hydrocarbons in ground water and low dissolved hydrocarbon concentrations remaining in the core of the contaminant plume,AGE believes the site should be certified for closure Advanced GeoEnvironmentsl,Inc