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3� ' <br /> ti Golden Grain Company <br /> January 11 , 1989 <br /> s 202/799-5045.01 <br /> == bentonite/cement mixture tremied in up to just above the tap of <br /> the clay layer to seal the lower zone from the upper one. The <br /> second well would be placed beside the first, screened from the <br /> top of the bentonite/cement seal to 10 feet below grade. The 12- <br /> inch casing would be removed as sand was poured into the annulus <br /> to a depth of 8 feet. The well would be sealed by a bentonite <br /> plug topped by cement grout to the surface. A traffic-raced <br /> street box would be installed to protect both wells, which would <br /> also be fitted with locking caps. <br /> MONITORING WELL LOCATIONS <br /> Five of the eight existing wells (MW-1 through MW-4, MW-7) <br /> are located within 30 feet of each other and therefore are not <br /> very helpful in defining the hydraulic gradient and estimated <br /> flow direction. The data from MW-5 and NW-6 could be more <br /> useful, but the gradient generally appears to be so shallow <br /> - (often less than 1%) that no definitive gradient direction is <br /> ! indicated. Only MW-8 .is located far enough away from the other <br /> _ wells to provide useful gradient information. <br /> Only MW-8 contains water free from hydrocarbon contamina- <br /> tion. The lateral extent of the contaminant plume is not defined <br /> by the existing well locations. The vertical extent of con- <br /> tamination is shown only in MW-7, the only well screened in the <br /> inferred second aquifer. <br /> The existing wells, with the exceptions of MW-4, MW--7, and <br /> MW-8, are only 25 feet deep. This past dry season, one well {MW- <br /> 3} went dry and water levels in others were within a foot of the <br /> bottoms of the wells (Appendix VI} . <br /> _. 19 <br />