ARCHIVED REPORTS_XR0006950 - Laserfiche WebLink

Home Browse Search

12 December 2005 AGE-NC Project No 97-0333 ' Page 10 of 11 • Minor to significant PCE and/or TCE concentrations were detected in ground water monitoring wells located in First Zone,Second Zone,Third Zone,and Primary Aquifer Zone aquifers(Figure 10,Table 4) The highest concentrations of dissolved PCE were detected in ' the samples collected from First Zone well MW-3 at a concentration of 250 pg/1, from Second Zone well MW-10B at concentrations as high as 1,400 µg/l, and from Third Zone wells MW-SD at a concentration of 1,100 µg/l ' PCE and TCE are chlorinated solvents often associated with dry cleaning operations Based on the July 2005 PCE iso-concentration map in First Zone water(Figure 10),AGE interprets the PCE/TCE plume to have originated from the dry cleaner's facility located immediately east of the Rainwater Car Wash • Based on the overall trend of increasing PCE concentrations observed at the pump-and-treat influent since July 2004 and from PCE concentrations reported from monitoring wells MW-2, MW-3 and MW-7A, it would appear as though the core-area of the PCE plume has migrated west towards the northwest section of the Rainwater Car Wash site The plume may may have been induced by a ground water cone of depression created by the ongoing ground water extraction activities(Figure 10),however,the majority of the dissolved PCE/TCE has currently migrated vertically to a depth below water table to the Second Zone and Third Zone ' and now the Primary Aquifer Zone 5.0 RECOMMENDATIONS Based upon data collected from the site, AGE recommends • Continued quarterly ground water monitoring and sampling of monitoring wells MW-1 ' through MW-13 • Continued groundwater extraction(interim groundwater remediation)from well EW-1 The ' general increase of dissolved MTBE north of well EW-1 provides ,justification for the installation and operation of an additional ground water extraction well, within the First Zone The SJCEHD has previously denied the recommendation that additional shallow ' ground water extraction would be beneficial and would cause the migration of the dissolved PCT/TCE onto the Rainwater site Currently the dissolved PCE/TCE is 0 3% as compared to the current dissolved MTBE concentrations, within the First Zone, therefore additional ' ground water extraction north of well EW-1 (down gradient of the current extraction well) would be focused on the increased TP1 /BTEX and MTBE plumes AGE recommends the installation and operation of an additional shallow, ground water extraction well near well MW-3 to prevent the off-site migration of dissolved hydrocarbons(MTBE)in the First Zone •, and to increase the mass removal(extracted batch volumes) from the site Advancer!GeoEnvironmental,Inc