ARCHIVED REPORTS_XR0005922 - Laserfiche WebLink

Home Browse Search

R A 08 June 2002 AGE-NC Project No 98-0433 ' Page 7 of 8 location ground water flows towards the north,whereas from the UST location southwards, ' ground water flows towards the south-southeaster �A Ah -TU 1AI the r. P 0, • The highest concentrations ofq-P -&and TPH-d were deter ed in water samples collected 'Y ' from well MW-1, located adjacent to the former UST area TPH-g concentrations decreased from the previous quarter in all wells except MW-6, where the concentration increased by a factor of four, TPH-d concentrations also decreased In all wells except MW-1, where the ' concentration increased by almost a factor of three • Generally,BTEX concentrations decrease in samples from wells MW-1 and MW-2 since the ' last sampling event • Benzene was detected in water samples MW-1 and MW-2 The dissolved benzene plume is ' currently constrained by well MW-4 to the north, wells MW-3 and MW-5 to the west, well MW-8 to the south and well MW-7 to the east / • Except for TPH-d,the lateral extent of dissolved hydrocarbons is defined by the current well network • MTBE was detected In wells MW-1 at a significant concentrations above the CaliforniafA • maximum contaminant levels The lateral extent of the dissolved 1p plume is defined,but the vertical extent has not been defined �0 -' 1' � 4� f, m J ' • DIPE and TBA were detected in well MW-8, the TBA concentration(27 µg/1) exceeds the DHS drinking water action level of 12 pg/l ' 5.0. RECOMMENDATIONS ' Based on the results of this investigation, AGE recommends • Continued quarterly monitoring at the site, the next monitoring event should be scheduled ' for May 2002 • Performance of additional assessment to delineate the vertical extent of MTBE-im acted , ground water and the lateral extent to the east of dissolved TPH-dt50 -1" • Preparation of a Corrective Action Plan(CAP)upon completion of vertical assessment and ' analysis of feasibility testing analysis The CAP should include remediation feasibility studies (e g In-situ air sparging pilot test, soil vapor extraction, soil excavation and bio- enhanced remediation or attenuation)to determine appropriate remedial options for the site ' The CAP should also include a well receptor survey to determine if local domestic water wells (beyond the domestic well that serves the Jimco site)maybe at risk from the dissolved petroleum-hydrocarbon plume at the site ' Advanced GeoEnviron mental,Inc