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•� _07 March 2003 <br /> AGE-NC Project No.'95-0106 <br /> Page 3-of 4 <br />' 4.0,: SUMMARY AND CONCLUSIONS m <br /> The following-cone lusians-were drawn from the-resultsof the site.izivestigation: <br /> ' The ground water was generally northward on 19 December 2002;,and gradients,were ' <br /> calculated to range from 0.005 toward the north-northwest to 0.003 toward the northeast-' <br /> Dissolved petroleum hydrocarbons'were detected in ground water samples from monitoring <br /> well MW4; located down-gradient off-site from the former UST excavation, and MW-I <br /> ',.located just north of the former UST area. <br /> BTE&X compounds were detected in the water samples'collecied from MW-4 and MW-1. <br /> The concentrations of benzene iii the samples exceeded-the State of•California maximum` <br />' contaminant lever(MCL) of 1 pg/l for drinking water. <br /> • Analytical data from monitoring wells MW-2 and MW-7 limits the horizontal extent of <br /> dissolved hydrocarbons south and east of the site, respectively. Analytical data from wells <br />' MW-3 and MW-'6 limits the extent of dissolved hydrocarbons northeastward of the site. <br /> Analytical data from monitoring well MW-5 limits the extent,of dissolved hydrocarbons <br />' north westward' of the .site. The extent of dissolved hydrocarbons to the west"is' not <br /> completely defined at this time. <br /> ,.Continued detection of TPH�-g and BTE&X in ground water samples collected from the off-- <br />' , site well MW4 indicates that the plume of impacted ground water has migrated off-site <br /> towards'the north, however, the general lack of detection of hydrocarbons in the MW-7,'' <br /> MW-6, MW-5' and MW-3 'wells shows that the. plume is not wide-spread and has not <br />' migrated northeast of MW-4 or northwest of the.former UST excavation. <br /> The extent of the plume around MW-4 is constraine&by data from MW-6.toward the north- <br /> northeast, MW-5•toward the southwest and MW-7.toward the.east relative to MW-4. The ; <br /> northwestern extent of the"plume'frorn MW-4 is not well constrained. <br />' The.results of this and previous monitoring events and previous soil investigations leads AGE to ' <br /> conclude that: <br /> The hydrocarbons encountered in' ground water,samples from MW-1 and MW-4 represent <br /> a northward extension of the hydrocarbon-impacted ground water that had already reached <br /> its current extent at,the time the monitoring well,system was-installed beginning in 1996. <br /> Advanced GeoEnvironmental,Inc. ' <br />