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' Mr Barton <br /> September 29, 2006 <br />' Page 3 of 5 <br />' During the quarterly monitoring event, groundwater elevations ranged from 25 89 feet (MW-8) to 23 30 <br /> feet (MW-5) below mean sea level at the site Since the first quarter of 2006, groundwater elevations <br /> have increased an average of 0 44 feet at the site The groundwater flow direction was generally to the <br />' east-southeast as shown on the potentiometnc map (Figure 1) and the horizontal hydraulic gradient was <br /> calculated at approximately 0 016 foot per foot (ft/ft) The predominant groundwater flow direction has <br /> been towards the east-southeast at the site, as depicted on the groundwater flow direction rose diagram <br />' (Attachment 2) <br /> Analytical Results <br />' Analytical results for the quarterly groundwater monitoring event are presented in Attachment 1 - Tables <br /> 1 through 4 Figure 2 presents an isoconcentratyon map for PCE Results for groundwater samples are <br /> summarized in the table below <br />' Frequency <br /> Range of <br /> of Detected California Frequency of Concentration of <br />' Constituent Detection Primary <br /> Concentrations 3 Exceedances Exceedances(ug/L) <br /> Above the (ug/L)z MCL <br />' Benzene 2113 1 -2 1 1/2 2(MW-5) <br />' • MTBE 1/13 100 13 1113 100(MW-8) <br /> 20(MW-6), 8(MW-3), <br /> TGE 9113 1-20 5 4/9 8(MW-7),7(MW-8), 7(MW- <br /> IID) <br /> 4,800(MW-6),3,700(MW-7), <br /> 3,500(MW-3), 550(MW-2), <br />' PCE 13113 2-4,800 5 12/13 650(MW-13), 380(MW-5),270(MW-4),270(MW-11D), <br /> 130(MW-14), 100(MW-9), <br />' 28(MW-10),280(MW-8) <br /> Notes <br />' 1 MDL=method detection lmut <br /> 2 ug/L=micrograms per liter,equivalent to parts per billion <br /> 3 MCL =maximum contaminant level <br />' Detected concentrations of benzene, TCE, and PCE are consistent with detected concentrations from the <br /> first and second quarters of 2006 TPH was not detected above method detection limits (MDLs) to <br /> groundwater samples, and MTBE was detected above the MDL at one location (MW-8) BTEX <br />' compounds were not detected above MDLs with the exception of benzene at two monitoring locations at <br /> low concentrations (MW-5 and MW-11D) Benzene was detected above the California Primary MCL in <br /> well MW-5 at a concentration of 2 µg/L MTBE was detected above the California Primary MCL in <br /> I <br /> monitoring well MW-8 at a concentration if 100 Ag/L Monitonng well MW-8 had not been sampled <br /> since October 2003 due to the well being dry <br /> 1 <br /> 047603054 doe <br />' BLASLAND, 13OUCK&LEE, INC <br /> an ARCADIS company <br />