ARCHIVED REPORTS XR0007835 - Laserfiche WebLink

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Ms Lori Duncan Page 3 of 3 • No petroleum hydrocarbons or gasoline additives were detected above method detection limits in groundwater samples collected from any site well, except well MW3 Well MW3 contained TPHg at 880 ppb, benzene at 17 µg/L, toluene at 37 µg/L, ethylbenzene at 15 pg/L, and xylenes at 88 µg/L Well MW3 also contained several other VOCs associated with petroleum hydrocarbons Groundwater analytical results are summarized on Table 3 Attachment 3 contains laboratory reports and chain of custody documentation The distribution of dissolved PCE beneath the site is presented on Figure 3 The figure was created by plotting the average concentration of the target analyte over the last four sampling events, the results of which are noted on the figure Although the contours are based on the composite value, the contours for a given sampling round would be very similar if plotted separately The concentration of dissolved PCE to all site wells over time is illustrated on Figure 4 4.0 CONCLUSIONS Although groundwater beneath the site has consistently flowed northeast (Figure 2), the highest concentrations of PCE In groundwater were detected in well MW7, located northwest(cross-gradient)of the former UST Further, no PCE has been detected in well MW3, which was completed through the former UST's location The distribution of dissolved PCE in site wells (Figure 3) strongly suggests that the primary source of PCE In groundwater is off-site Although measurable free product remains in well MW3 in the form of oily hydrocarbons, no dissolved petroleum hydrocarbon constituents have been detected in any other site well Please feel free to contact John Lane of Ground Zero at (209) 838-9888 if you have any questions regarding this submittal Respectfully, Ground Zero Analysis, Inc V o— �� PEp GAO Joseph L Vasquez Staff Geologist Q� JOHN P LANE a No 6/95 17. John P Lane CA Registered Geologist No 6795 7�cs`QP C P,Ll�O�p Attachments cc Mr John Gabbard Mr James L L Barton, RWQCB-Central Valley Region Mr Patrick Riddle, Attorney at Law G 1GROUNbZE1(iABBARI)V ports\QMR1200511QM2005 doe