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Page 1 of 2 <br /> Vicki McCartney [EH] <br /> From: Tamorah Bryant[TamorahB@gtienv.com] <br /> Sent: Wednesday, March 10, 2010 9:42 AM <br /> To: Vicki McCartney[EH] <br /> Cc: Jenny Weese <br /> Subject: RE: Marci Property <br /> Vicki, <br /> Further to our conversation a few days ago, I wanted to provide more information regarding what would <br /> be involved in a hydro-geologic evaluation at the 2969 Loomis Road, Stockton site. <br /> A review of historical groundwater elevations and comparison to MW-5 and MW-7 TPH-D <br /> concentrations indicates over time, TPH-D concentrations have fallen as the average groundwater <br /> elevation has increased at the site, as shown in the following figure: <br /> MW-5 & MW-7 TPH-Q & Average GW Elevation Over <br /> 120,000 - Time _ _ _ ___ -20 <br /> 100.000 - - -25 <br /> g80,000 -30 <br /> y 60,000 -35 <br /> C <br /> c 40,000 - - 40 —lw—MW-5 <br /> 4 <br /> 20,000 __ .- ,45 Mw-7 <br /> 0 - -50 --+—Ave GW <br /> N <br /> Ln N t_!f Gii N <br /> The predominant groundwater bearing has been estimated as easterly, with MW-7 being located close <br /> to the former LISTs and MW-5 being slightly up-gradient. As described in the Revised Work Plan - <br /> Additional Dual Phase Extraction Pilot Test, GTI anticipates extracting groundwater from the newly <br /> installed extraction wells, and monitoring the impacts on MW-4, MW-5 and MW-7. As part of the <br /> effectiveness evaluation, GTI will estimate the radius of influence of the DPE system by comparing the <br /> changes in pressure and depth to water at various monitoring wells. <br /> Following the pilot test, GTI has recommended that a hydrogeologic evaluation be performed, <br /> incorporating the results of the pilot test findings, to develop a conceptual understanding of <br /> groundwater flow patterns and recharge areas. The pilot test may provide sufficient data to evaluate <br /> the site, or further investigation may be required based on the results of the pilot test. The evaluation <br /> may also include an estimate of TPH-D concentrations in groundwater over time, and explore natural <br /> biological degradation at the site. <br /> I apologize for the delay in responding to your inquiry. Please let me know if you have any questions, <br /> or require further information. <br /> Thank you, <br /> 3/10/2010 <br />