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SECOR 5.0 "B" ZONE 5.1 "B" Zone Groundwater Gradient Groundwater elevations in "B" zone wells ranged from 4.20 feet below MSL in well SP/WC-1M to 3.05 feet above MSL in well PS/MW-1M. Groundwater flow in the "B" zone during the first quarter 2006 was generally to the southeast with hydraulic gradients ranging from 0.004 ft/ft to 0.007 ft/ft. Historical groundwater flow direction and hydraulic gradient data are included in Table 3. A groundwater elevation contour map for the "B" zone on February 6, 2006 is presented as Figure 7. 5.2 "B" Zone Groundwater Quality Data During the first quarter 2006, groundwater samples were collected from 16 "B" zone wells between February 6 and February 9, 2006 (Table 1). Analytical results are presented in Tables 4 and 5 and are summarized below. "B" zone TPHg, TPHd, benzene, and MTBE isoconcentration maps are provided as Figures 8, 9, 10, and 11, respectively. • SPH: SPH was not present in any of the "B" zone wells during the first quarter 2006. • • Analytical Results Summary: Number of Number of Minimum Maximum Wells Detections Concentration in Concentration in Constituents Analyzed above Lthe pg/L (Well ID) pg/L (Well ID) MR TPHg 16 7 260 (AR/MW-9B) 22,000 (TO/WC-2B) TPHd 16 6 61 (AR/MW-12B) 7,100 (TO/WC-2B) Benzene 16 9 0.5 (AR/MW-12B) 9,900 (TO/WC-2B) Toluene 16 5 1.1 (AR/MW-9B) 48 (AR/MW-14B) Ethylbenzene 16 1 --- 27 (TO/WC-2B) Xylenes 16 5 4.1 (TS/MW-1B) 61 (AR/MW-14B) MTBE 16 10 1.2 (TO/WC-1 M) 1,100 (AR/MW-14B) TBA 10 8 5.3 (AR/MW-18B) 2,300 (AR/MW-11 B) DIPE 9 3 0.60 (AR/MW-9B) 2.8 (AR/MW-1B) TAME 8 0 not detected above MRL not detected above MRL ETBE 8 0 not detected above MRL not detected above MRL Ethanol 6 0 not detected above MRL not detected above MRL Methanol 7 0 not detected above MRL not detected above MRL Definitions: MRL = Method Reporting Limit pg/L = Micrograms per Liter • = Not applicable STTC 1Q06 Final Report 9 May 1,2006 770T.43673.12.0002