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15 October 2000 AGE-NC Project No 96-0232 Page 7 of 11 to flus depth,despite the presence of a fine-grained sedimentary unit between 74 feet and 86 feet bsg, may have been facilitated by the gravel pack around the casing of RDW-1 repotted to be between 50 feet and 150 feet bsg Further westward from RDW-1, the plume of water impacted by oxygenates and ethanol, appears to extend to P-17 at the west end of the Rocky's Restaurant parking lot, with a vertical extent from possibly 10 feet bsg to possibly 105 feet bsg(MTBE),TBA was detected from 111 to 114 feet bsg; the low ethanol concentrations detected to these samples may be valid data as the coated bentonite pellets had not been utilized prior to or during installation of P-17 MTBE was detected to the samples between 37 and 83 feet bsg The plume may or may not extent to MW-13 at the west side of the Three B's site Contaminants in ground water at MW-13 include TPH-d, benzene, MTBE and TAME at shallow depth (10 to 20 feet bsg), TPH-d and MTBE at intermediate depth (50 to 60'feet bsg), ethanol at deeper depth (90 to 100 feet bsg), and less than detectable concentrations near total depth (130 to 15d feet bsg) Ethanol detected at tugh concentrations in the upper three samples is believed to be the result of localized contamination introduced during well construction The TPH-d, benzene and higher concentration of MTBE in the shallow sample suggest that most of the contaminants are from a source other than the Flag City plume as TPH-d and benzene were not detected at shallow depth to the RDW-t area and the MTBE concentrations are higher in the shallow MW-13 arca than in the shallow P-17 of RDW-1 areas Relative to the inferred source area near MWA, the northern extent of the plume appears to have reached MW-4 at depths between 55 and 65 feet bsg, the eastern extent of the plume appears to have migrated slightly past MW-2 at depths between 45 and 55 feet bsg, and the southern extent of the plume appears to have migrated slightly past MW-6 at depths between 10 and 50 feet bsg Based on the site conceptual models, the average thickness of impacted ground water ort-sttc (s , approximately 45 feet near the Flag City Chevron site and 55 feet offsite near"MW-11, the dimensions of the plume were estimated to have a short radius of 105 feet and a long radius of 215 feet' 24 Potential Impact Of The Wastewater Discharge On, The Contatmnent And Rate Of Movement Of The Ground Water Plume . t . Contamxnarits will be removed from the water to be discharged, discharge into the conveyance ditch anticipated to have minimal infiltration. Furthermore, point of discharge will be well beyond the plume margins 2 5 Effects Of The Ground Water Extraction System On The Gradient And Plume Generally, ground water gradient at the site is low, varying from 0 001 to 0 003 Once the ground Advanced Geo Environments!,Inc