ARCHIVED REPORTS_XR0007692 - Laserfiche WebLink

Home Browse Search

1 ' GeoHydrologic Consultants, Inc may not be actually achieved for many days to weeks of constant pumping Sediment ' types would be characterized as silt and clay sized particles according to these values, which are consistent with the sediments encountered within the borehole from depths within the screened zone of well EW-5S ' Based on the results of the pump test on well EW-51), it appears that a steady decline in water levels of all observation wells was observed during the first third (235 minutes) of ' the 12-hour test indicating that a constant pumping rate of approximately 2 3 gallons per minute would effectively result in measurable drawdown of the water table A pumping rate less than this would not effectively draw the water table down below the screened interval of EW-5, therefore, not exposing the soil to vapor extraction Conversely, the results of the pump test on well EW-5S indicated a rise in water table in ' the nearby observation wells Approximately five hours into the pumping test on EW-5S, a significant rise in the water table was reported for all gauged observation wells In this case, drawdown data and recovery data from the extraction well was the only usable data ' for the pump test analysis This may be attributed to the low groundwater extraction rate sustainable in EW-5S (approximately 0 25 gpm) coupled with possible changes in atmospheric pressure and adjustment of the aquifer to these changes once the well lids ' were opened TPHg and benzene concentration in groundwater extracted from EW-5S and EW-51) ' were significant and averaged 92,700 gg/L and 15,850 pg/L, respectively, from EW-5S and 82,250 gg/L and 4,145 gg/L, respectively, from EW-513 In addition MTBE was present in the extracted groundwater from well EW-5S at an average concentration of ' 3,925 gg/L Based on these results, it is concluded that pumping groundwater with onsite treatment is ' a feasible technology for remediating groundwater at the Site, with a projected extraction rate of 2 30 to 2 50 gpm for EW-513, and 0 25 to 0 40 gpm for EW-5S, or approximately 2 55 to 2 90 gpm for the combined two wells 1 9.0 FINAL REMEDIAL ACTION PLAN Based on the available data including the recentilot test results it appears P pp ars that soil vapor/groundwater extraction and treatment (multi-phase extraction (MPE)) is a very ' effective remedial approach for the Site and will therefore be considered the primary methodology for treatment of petroleum hydrocarbons including TPHg, BTEX, and MTBE in soil and groundwater at the Site In addition, this methodology was previously ' proposed as a viable option in GHC's Aquifer Testing Report and Remedial Action Plan dated July 11, 2002, and the Site is currently undergoing soil vapor extraction with a fixed permanent remediation system It should be noted that groundwater extraction alone ' appeared to be more applicable for extraction well EW-5D since this well is screened below the water table and only yielded low vapor concentrations during pilot testing activities TOC 171 Punt study Page 24