ARCHIVED REPORTS_XR0012072 - Laserfiche WebLink

Home Browse Search

03 July 2003 AGE-NC Project No 95-0130 Page 5 of 6 • Significant concentrations of 1,2-DCA were detected or have consistently been detected from wells MW-2, MW-3, MW-6B, MW-6C, MW-7A, MW-7B, VW-1B, VW-1C, VW-2A, VW-2B and VW-3A suggesting a significant 1,2-DCA-impact to ground water at the site • TBA was not detected in any of the analyzed water samples,however, TBA was previously detected at wells MW-1, MW-2, MW-3, MW-5, VW-1C, VW-2A, VW-2B and VW-3A suggesting a significant TBA-impact to ground water at the site • EDB was detected in a water sample collected from VW-I C, however, EDB has previously been detected at wells MW-7B, VW-1B and VW-2A in concentrations significantly above I the DHS's Maximum Contaminant Level (MCL) in drinking water • The high concentrations ofpetroleum hydrocarbons detected in samples collected from wells MW-6 (A and B),MW-7 (A and B), VW-1 (B and C), VW-2A and VW-3A, indicating that ' these wells are within or near the dissolved petroleum hydrocarbon"core area"of the plume (Figures 4 and 5) • The lateral and vertical extent of the dissolved petroleum hydrocarbon plume is not known toward the northwest,north, northeast, east and southeast of the area bound by wells MW-1 through MW-5 (Figures 4 and 5) 5.0. RECOMMENDATIONS Based upon the results of the first quarter 2003 investigation, AGE recommends • Installation of well MW-8 and ground water extraction wells EW-1 and EW-2 to provide adequate ground water elevation data from on-site wells • AGE recommends that a well-head elevation survey be performed by a state-certified surveying engineer following the well installation, so that reported ground water elevations are relative to a City of Stockton benchmark datum and accurately comparable to ground Iwater elevation from wells of the adjacent UST investigations • Continued quarterly ground water monitoring of wells VW-1 (B and C),VW-2A, VW-3 A, ' MW-6 (A-E) and MW-7 (A-E), the next two quarterly ground water monitoring event are tentatively scheduled for June 2003 and September 2003 • Continued quarterly depth-to-water measurements in all monitoring wells at the site, but ' reduced ground water sampling frequency from a quarterly to a semi-annual program, AGE believes that continued quarterly ground water sampling from these wells at this stage of the ' investigation is not cost effective and will not provide enough useful information to supplement the ongoing investigation Semi-annual sampling events should be adequate to Advanced CeoEnvironmental,Inc