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Antonia Vorster -5- 25 August 1989 <br /> needed to determine if contamination has resulted. The need for C and <br /> D-zone wells is dependent upon the extent of A and B-zone contamination. <br /> It should be noted, as in other plume areas, that the potential for <br /> deeper contamination is dependent on downgradient distance from the <br /> source, the potential increasing with distance. <br /> e. Plume 5 - the agricultural wells southwest of this area have obviously <br /> had a significant effect on contaminant movement. From the data <br /> available, it appears that contamination has been drawn from the source <br /> near BC-103 southwest and downward toward agricultural wells AGW-6 and <br /> 7. It would then appear that contamination has moved west/northwest <br /> again with the natural gradient in times of no pumping. <br /> Wells need to be placed in the A, B, and C-zones to define the lateral <br /> extent of contamination to both the southwest and northwest. Hunter/ESE <br /> states that proposed wells 12A-C will aid in definition. These wells <br /> ( in addition to not being shown on the Work Plan map) were also proposed <br /> for definition of Plume 3. These plumes are on opposite sides of AGW- <br /> 6 and 7, thus one well location cannot be utilized for both plumes. <br /> The need for D-zone wells is again dependent upon the downgradient <br /> (well-induced and natural ) extent of C-zone contamination. Placement <br /> of wells should only be made after a thorough review and contouring of <br /> all water level data, which applies to all the plumes, but is especially <br /> crucial in this area. <br /> f. Plume 6 - in addition to proposed wells 8A and B in the source area, <br /> additional lateral definition in the B-zone to the southwest, northwest, <br /> and downgradient of well 444 is needed. Well placement should, again, <br /> be determined only after careful review of water level data considering <br /> the proximity of the agricultural wells. The need for additional A, <br /> C, or D-zone wells can be made after additional A and B-zone wells are <br /> completed. <br /> g. North Balloon - this plume is two-lobed; the primary plume extending <br /> to the northwest from the main source area near 439 and a secondary <br /> plume extending east from 439 to 421 and SHAD-1. The secondary plume <br /> may be from a potential source near SHAD-1 or, more probably based on <br /> the data, from movement of contamination from 439 toward SHAD-1. <br /> Possibly, both sources may be responsible. However the plume was <br /> formed, it will move to the northwest with the natural gradient when <br /> SHAD-1 is not pumping, as has been the case for substantial periods <br /> of time. The lateral extent of this plume in the A, B and C-zones has <br /> not been defined along its northern boundary. Proposed well 10C may <br /> accomplish this in the C-zone if its accurate location was known. <br /> Whether contamination exists in the D-zone needs to be determined. This <br /> would probably best be accomplished with a D-zone well at location 421. <br /> In the primary plume, the leading edge in the A and B-zones, and the <br /> northern lateral extent in the A, B, and C zones needs to be determined. <br /> The lateral and downgradient extent of contamination in the C/D zone <br />