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1 <br /> 50TA F. <br /> Environmental Technology Inc — <br /> zo <br /> However, this high concentration of TPH-g found at MW-4 (i e , an eight (8) fold <br /> increase), has never been evidenced at MW-4, in the past <br /> Based on the general increase in concentrations found at all five monitoring <br /> wells, with the exception of MW-3, the question is raised regarding the <br /> unknown source(s) of contamination Taking into account that the historical <br /> groundwater flow direction has been in the directions west, northwest to north, <br /> it may be possible that a contaminant plume is corning on-site from an <br /> unknown off-site source(s) The evidence of MW-4 . which is located upgradient <br /> from the former dispensing island area, displaying very high concentrations, <br /> further suggests this possibility From Figure 3, a potential contaminant plume <br /> from off-site can be interpreted However, it should be noted that the dotted <br /> lines, do not represent actual contours they are merely possible projections of <br /> an off-site plume At this time, SOTA cannot conclusively define the off-site <br /> plume, if any, which may have impacted the U-Haul center <br /> SOTA had earlier proposed further delineation of the groundwater <br /> contamination plume as was also required by San Joaquin County SOTA <br /> submitted a workplan detailing the proposed additional site assessment on <br />' November 29, 1994 SOTA's workplan was conditionally approved by San <br /> Joaquin County in their letter dated February 3, 1995 U-Haul International <br /> has authorized SOTA to proceed with the additional site assessment <br /> investigation which will include drilling two off-site monitoring wells and one <br /> on-site monitoring well SOTA is submitting well permit applications to the San <br /> Joaquin County, Environmental Health Division for all three proposed <br /> monitoring wells After obtaining the well permits. SOTA will submit an <br /> application to the San Joaquin County, Public Works Department to obtain an <br /> Encroachment permit to drill in the County's right of way Upon obtaining the <br /> Encroachment permit, SOTA will proceed with field activities, which is <br /> anticipated in the next three to five weeks These proposed off-site monitoring <br /> wells scheduled to be installed will provide information to assist in the <br /> delineation of a potential off-site plume <br /> Should there be any questions regarding this transmittal please contact us at <br /> (619) 485-8100 <br />' Sincerely, <br /> SOTA Environmenta gy, Inc , <br /> 1 ►�u�r <br /> , <br /> AO <br /> Dakshana Mur EF7-P E Greg Alyanakian <br /> Project Manage /��p Staff Scientist <br /> O <br /> cc Doug Dunham, U- au International, Phoenix, AZ <br />