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' Mr Terry ardi <br /> . ry Ta <br />' July 15, 2003 <br /> Page 3 <br /> rsummarizes the historical analvtical results for petroleum hydrocarbon <br /> constituents Laboratory reports for the groundwater samples collected for these <br /> sampling events are included as Attachment B <br /> Discussion <br /> Based on the second quarter's data, the groundwater hydraulic gradient remains <br /> basically flat, as shown in Figure 2 <br /> AnaIvtical constituents for each well from the 2nd quarter is shown on Figure 3, <br /> and a MTBE isoconcentration map is shown on Figure 4 <br /> BTEX BTEX concentrations remained consistent with the previous quarters in <br /> all four monitoring wells The reporting limits for all constituent concentrations in <br /> 1\4-W-1 were decreased due to known high concentrations of MTBE in the sample <br /> The cWutions were necessary because the MTBE concentrations were out of the <br /> calibration range for the target analvte Samples from MW-1 are analyzed multiple <br /> tunes by the analvtical laboratory to bring the correct dilution into the calibration <br /> range <br /> TPH-G TPN-G concentrations are below the method reporting hn-ut of 50 µg/l- <br /> in <br /> g/Lnn MW-2 and the supply well As in the case of benzene concentrations described <br /> above for MW-1 and MW-4, the TPH-G reporting Jum>,t was decreased to 10,000 <br /> and 200 �xg/L for TPH-G, respectively, which makes it difficult to determine if <br />' TPH-G concentrations are present TPH-G concentrations in MW-3 remain <br /> similar to 1 st quarter 2003 concentrations <br /> MTBE In MW-1, MTBE concentrations increased from 44,000 µg/L to 53,000 <br /> n/L MTBE was not detected above reporting limits in MW-2 and the supph <br /> well MTBE concentrations in MW-3 and 1\7W-4 increased from 10 µg/L to 33 <br />' �ig/L and 500 }ig/L to 760 }tg/L, respectively Despite increased concentrations in <br /> 1\4W-3 and 1\4W-4 these values remain within historical ranges <br /> Other Oxygenates ETBE, DIPS and TAME were not detected in samples from <br /> any of the monitoring wells Tert-Butanol was detected in MW-3 and MW-4 at <br /> concentrations of 9 6 �ig/L and 77 µg/L, respectively Dilutions within the MW-1 <br /> sample increased ieporung limits, which makes it difficult to determine of <br /> o%ygenate concentrations are present <br />' P\21106\21417\14port,\2nd(byt doc <br />