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GeolagccalTechntcslru Page 7 <br /> Groundwater Monitoring Report <br />' Project No 724 2 <br /> November 21,2005 <br /> 1 <br /> Conclusions <br /> 0 The groundwater plume does not display a typical "core" but exhibits wide variations <br /> in contaminant concentration in both vertical and lateral planes as shown in Figures 6 <br /> - 11 Generally the plume has migrated down gradient of the source and is displaced <br />' east of the former UST <br /> o The highest MTBE concentrations detected in the intermediate and deep aquifers <br /> were in wells MW-106 (20 µg/1) and MW-209 (13 [.g/1), respectively <br />' o Water table well MW-7 contains 2 ug/L MTBE <br /> o The contaminated shallow, intermediate and deep wells are down gradient from <br /> the former UST and dispenser locations areas in the predominant groundwater <br />' direction to the east <br /> o The highest TPH-G concentrations were detected to the east of the site in wells <br /> MW-106 and MW-208, and the highest Benzene concentrations were detected to <br /> the east and northeast in wells MW-106 and MW-109 in the intermediate wells, <br /> and MW-209 in the deep wells, respectively <br /> 0 In their correspondence dated September 3, 2002, the San Joaquin County <br /> ' Environmental Health Department (SJC/EHD) identified two LUFT sites (701 E <br /> Charter Way and 749 E Charter Way) as being up gradient of the subject site The <br /> contamination detected in the MW-108/208 location may be partly or entirely <br /> originated from an offsite source <br /> U The SJC/EHD also stated in their above letter that a sandy interval at 70 -- 80 bgs <br /> t could be acting as lateral conduit for contaminant migration The presence of <br /> contamination in deep wells MW-208 and MW-209 support this theory However, <br /> GTI still suggests that the low concentrations of TPH-G & MTBE in these wells do <br /> ' not warrant an engineered clean up <br /> • The data shows that a relatively stable, wide spread, low concentration plume of <br /> petroleum hydrocarbon compounds are present in the groundwater at this site The <br /> ' deeper TPH-G plume is not defined to the north and the deeper MTBE plume is not <br /> defined to the east <br /> ' Recommendations <br /> • Maintain the current quarterly monitoring schedule to determine contaminant and <br /> gradient trends <br /> ' • To further define the lateral extent of the groundwater plume, the work as outlined in <br /> the April 18, 2005 letter from San Joaquin County should be performed This work is <br /> ' in progress <br /> �c <br /> 1 <br />