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08 September 2005 <br /> AGE-NC Project No 97-0333 <br /> Page 10 of 11 <br /> • Based on the overall trend of increasing PCE concentrations observed at the pump-and-treat <br /> influent since July 2004 and from increasing PCE concentrations reported from monitoring <br /> wells MW-2,MW-3 and MW-7A,it would appear as though the core-area of the PCE plume <br /> has migrated west towards the northwest section of the Rainwater Car Wash site, and may <br /> have been Induced by a ground water cone of depression created by the ongoing ground <br /> water extraction activities (Figure 10) <br /> 5.0 RECOMMENDATIONS <br /> Based upon data collected from the site, AGE recommends <br /> ' • Continued quarterly ground water monitoring and sampling of monrtonng wells MW-1 <br /> through MW-13 <br /> • Continued ground water extraction(interim ground water remediation) from well EW-1 <br /> • The most intense MTBE-impacted ground water was reported in water samples collected <br /> ' from monitoring wells MW-2, MW-3, MW-6 and MW-7A with MTBE concentrations as <br /> high as 5,600 µg11 Wells MW-6 and MW-7A are located less than 10 feet from extraction <br /> well EW-1,and appear to be sufficiently located within the capture zone ofEW-1 However, <br /> wells MW-2 and MW-3 are located 20 feet and 50 feet,respectively,from well EW-1 AGE <br /> recommends Installing two-inch diameter pneumatic ground water pumps in wells MW-2 <br /> (12-32 feet) and MW-3 (12-32 feet) to augment interim ground water remediation efforts, <br /> 1 extracted ground water from wells MW-2 and MW-3 would be routed to the existing ground <br /> water pump-and-treat system <br /> ' i Generally,the core of the dissolved MTBE plume appears to located In the First Zone within the area <br /> of wells EW-1, MW-1, MW-2, MW-3, MW-6, and MW-7A, outside of the dissolved MTBE core <br /> 1 area, only low to very low MTBE concentrations have been detected on-site and off-site toward the <br /> north (MW-12B) in Second Zone Based on the data collected during the first quarter 2005, <br /> additional ground water monitoring wells are not warranted at this time and the existing monitoring <br /> ' well network may be sufficient to complete a site Problem Assessment Report(PAR) <br /> i6.0. 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 mainly <br /> �. upon analytical results provided by an independent laboratory Evaluations of the hydrogeologic <br /> 1 Advanced GeoEnvironmental,Inc <br />