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6. Hydrogeologic Conditions at the Site. The following discussion of hydrogeologic conditions is based on the results of a Hydrogeologic Assessment of the quarry area performed in 1998. A copy of that report is attached. As part of that investigation, three (3) new ground water monitoring wells, MW-5, -6, & -7, were installed at the site. Ground water at the site flows through the interbedded limestone and shale of the Fort Hayes Limestone and the underlying Codell Sandstone. Field observations ofcuts in the limestone indicate that the ground water flows primarily under perched conditions along the horizontal bedding planes in the undisturbed limestone upgradient of the areas that have been mined. In the areas which have been mined, the hydraulic conductivity increases significantly as a result of the nature of the backfill method (i.e., dumping) and material (i.e., broken shale/argillaceous limestone). In addition, the hydraulic gradient is likely to be very steep where the ground water flows out of the face of the undisturbed limestone, as observed along the north wall of Cuts 5 and 7 near monitoring well MW-6, through the crushed backfill material and down to the undisturbed Codell Sandstone. At this point the hydraulic gradient becomes more flat and appears to generally reflect the southwesterly dip of the stratigraphic units at the site. The ground water contours for both the upgradient undisturbed limestone and the mined areas of the site are depicted on Figure 2. The bottom of the CICD/sludge landfills are reportedly approximately ten (10) feet above the top of the Codell Sandstone. In addition, based on ground surface elevations of monitoring wells IviW-1 through MW-4 at the time of their installation (1991) and current estimated ground water elevations, it appears that ground water flowing through the Codell Sandstone may be on the order of 30 to 50 feet below the bottom of the CKD/sludge landfilled in Cut 6. Therefore, it appears that ground water does not currently flow through the CKD/sludge material. Cut 6, located in the south-central portion of the mine, was recently used for landfilling the CICD. Ground water monitoring wells (MW-1,-2,-3, and -4) were installed in the bottom of this cut in 1991 (see Figure 2). These wells were installed by the Fremont Sanitation District to evaluate the potential impact of the sewage sludge disposal on the local ground water. Wells MW-1, -2, and -3 were installed in the western half of Cut 6 which was subsequently backfilled with mining waste/overburden (i.e., Smoky Hill KS-9903-02 Page 8 K-S &Compon7 August 16, 1999 Copyrightl999