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i <br /> i <br /> 23 December 2003 ' <br /> AGE-NC Project No 97-0333 <br /> Page 10 of 11 i <br /> ' from First,Second,Third and Primary Aquifer Zone monitoring wells MWA,MW-3,MW-7 <br /> (A-E) and MW-8 (A-C), generally, significant MTBE decreases were reported this quarter <br /> in most of the on-site wells (Figures 8 and 9, Table 3) <br /> , r <br /> ' • Off-site MTBE was reported only in the water sample from Second Zone monitoring well <br /> MW-12B at a concentration of 32 µg/1 <br /> ' • Concentrations of PCE and/or TCE have been detected in water samples collected from all <br /> well locations associated with the Rainwater Car Wash investigation Minor to significant <br /> PCE and/or TCE concentrations were'detected in 44 of 47 ground water monitoring wells <br /> ' located in First Zone,`Second Zone,Third Zone and Primary Aquifer Zone Aquifers(Figure <br /> 10, Table 4) The highest concentrations of dissolved PCE.were detected in the samples <br /> s collected in the area of on-site well MW-8C('lower Second Zone)and offsite well MW-12A <br /> k (First Zone) at concentrations as high as 1,100 µg/1 i <br /> • PCE and TCE are chlorinated solvents often associated with dry cleaning operations Based i <br /> ' on a August 2003 PCE iso-concentration map in First Zone water (Figure -10), AGE <br /> interprets the PCE/TCE-plume to have originated from the dry cleaner's facility located " I <br /> immediately east of the Rainwater Car Wash <br /> 5.0 RECOMMENDATIONS <br /> Based upon data collected`from the site, AGE recommends <br /> • Continued quarterly ground water monitoring and sampling of monitoring wells MW-1 <br /> through MW-13 r <br /> ' •' Continued,ground water extraction(interim ground water remediation) from well EW-1 <br /> ` I <br /> Generally,the core ofthe dissolved MTBE-plume appears to located in the First Zone Aquifer within <br /> ' I the area of wells EW-1', MW-2, MW-3,MW-6 and MW-7A, outside of the dissolved MTBE-core <br /> area,only low to very fow MTBE concentrations were detected on-site and off-site towards the north <br /> in`Second Zane; Third Zone &Primary Aquifer Zones Based on the data collected during the third <br /> quarter'2003 'additional ground waterkmonitonng wells are not warranted at this time and'the <br /> l f existing monitoring well network maybe sufficient to complete alsite Problem Assessment Report <br /> (P A h I ''.I <br /> , I <br /> I <br /> I ! <br /> L ( n € <br /> i <br /> Advant'd GeoEnvironmental,inc I'�k <br /> I F <br /> J EI <br />