Laserfiche WebLink
t01 October 2404 <br /> AGE-NC Project No 97-0333 <br /> ' Page 10 of 11 <br /> - Second Zone,Third Zone and Primary Aquifer groundwater flow was inferred to be towards <br /> ' the north-northwest and north-northeast at approximate gradients of 0 001 ft/ft or less <br /> (Figures 5, 6 and 7, respectively) <br /> - Due to the low ground water gradient at the site, small variations in ground water <br /> measurements or changes of recharge/discharge of the local ground water could greatly <br /> modify the inferred ground water flow direction ' <br /> - The highest on-site concentrations of dissolved MTBE were detected in the samples <br /> collected in the area of First Zone monitoring wells MW-2, MW-3 and MW-7A at <br /> ' concentrations as high as 47,000µg/1 Lower concentrations of on-site MTBE were detected <br /> in water samples from First, Second, Third and Primary Aquifer Zone monitoring wells <br /> MW-1, MW-7 (B-E) and MW-8 (A and C), generally, moderate to significant MTBE <br /> increases were reported this quarter from most oftlie on-site wells(Figures 8 and 9,Table 3) <br /> - Off-site MTBE was not detected from any of the above wells <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 39 of 46 ground water monitoring wells <br /> 10 located in First Zone, Second Zone, Third Zone and Primary Aquifer Zone Aquifers <br /> (Figure 10, Table 4) The highest concentrations of dissolved PCE were detected in the <br /> ' samples collected in the area of on-site wells MW-2,MW-3,MW-10B (upper Second Zone) <br /> and offsite well MW-12A(First Zone) at concentrations as high as 1,600 µg/l (MW-3) <br /> - PCE and TCE are chlorinated solvents often associated with dry cleaning operations Based <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 <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 /> i <br /> through MW-13 <br /> ' - Continued groundwater extraction (interim groundwater remediation) from well EW-1 <br /> ' Generally,the core of the dissolved MTBE-plume appears to located in the First Zone Aquifer within <br /> 0 the area of wells EW-1;-MW-2;MW-3,-MW-6 and MW-7A,.outside of the dissolved MTBE-care <br /> Advanced GeoEnviron mental,Inc <br />