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values of each formation. The values fall between accepted representative values for pure shale <br />and pure limestone formations. While <br />While the test conducted was not a conventional slug test all indications are that the hydraulic <br />conductivity results are valid and are consistent with results reported by other investigators. <br />Attached to this letter (Attachment 2) is Figure 2 from the June 21, 1999 Banks & Gesso report <br />titled "Report on Storage of Cement Kiln Dust, Southdown, Inc. Lyons Plant ". This figure indicates <br />that the shale units above and below the Fort Hays Limestone have hydraulic conductivities ranging <br />from 2 x 10 to 1 x 10 cm /sec. Further, page 3 from the October 29, 2004 URS Corporation <br />report titled "Evaluation of the Potential Impact of Ponded C -Pit Water on Groundwater Quality in <br />the Dakota Sandstone" reports that packer tests conducted in the bedrock shales of the present - <br />day Dowe Flats quarry area by Morrison Knudsen Corporation and others arrived at conductivities <br />ranging from less than 1 x 10 to 4 x 10 cm /sec. These packer tests were conducted at relatively <br />high hydrostatic head pressures (up to 230 feet of head, or 100 psi), which likely forced water <br />transport along bedding planes, joints and fractures, and therefore the resulting hydraulic <br />conductivity calculations were viewed as likely high estimates. (These two reports are in the DRMS <br />files for the Lyons plant.) <br />We conclude from the preceding discussion that C -Pit is effectively contained within a fractured <br />bedrock system that has low hydraulic conductivity. As such, we think continued monitoring of <br />CEM -001 is not warranted. However, we propose to continue monitoring CEM -004 in the nearby <br />alluvial system to the northeast of C -Pit. <br />