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aquifer which shalt be cemented off top and bottom.", and 2) the House Bill 1195, which states <br />"Drill holes which have encountered an aquifer in volcanic or sedimentary rock.. Shall be sealed <br />utilizing a seating procedure which Is adequate to prevent fluid communication between <br />aquifers." <br />The boreholes were drilled into the stratigraphic horizon that contains the Laramie-Fox Hills <br />aquifer, a regional hydrogeologic unit that spans the base of the Laramie Formation and the top <br />of the l=ox Hills Formation. In a letter to Mr. Kenneth Holmes (Mobil), dated February 23, 1982 <br />(Attachment E), Ms. Walker expressed concerns over the use of drilling mud In an interval of an <br />aquifer, and the potential for contaminants in the upper Laramie Formation to enter the Laramie- <br />Fox Hills aquifer. <br />However, in the area of the Project, the Laramie-Fox Hills interval appears to have low potential <br />as a significant aquifer. Mr. Faulhaber's memo cites numerous reports describing the interval <br />as consisting of Gay rich siltstone and sandstone. Mr. Faulhaber concluded that "it would <br />appear that the Laramie-Fox Hills interval, although potentially water bearing, does not possess <br />sufficient permeability to constitute a significant aquifer." Based on this conclusion, the use of <br />drilling mud in borehole abandonment is appropriate and consistent with the standards <br />previously discussed. <br />The Project reclamation activities described above are consistent with the standards described <br />in the Notices of intent to Conduct Prospecting Operations reports, and House Bill 1195. <br />Therefore, Exxon Mobil requests that the Prospecting Permit be cancelled and the Project be <br />released from financial surety provided under Statewide Prospecting Bond No. 17-003-193. <br />It you have any questions about the attached information, please call me at (703) 846-1150. <br />Sincerely, <br />W. ?, W <br />Mark E. Hoffman, P.E. <br />Project Manager <br />MEHips <br />Attachments <br />c: P. Sorek -- MFG <br />file