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1.0 Conclusions ~. As requested by the Colorado Division of Minerals and Geology, Southdown conducted an evaluation of their CKD management practices at the Lyons cement plant. This evaluation included a review of historical and current mining permits, characterization of cement kiln dust, assessment of local geology and hydrology, and an analysis of potential ground water impacts. Conclusions from the above studies are summarized as follows: 1. Disposal of the CKD in C-Pit is allowed under CMLRB Permit No. M- 77-208 DisposaTOfitiKU m L-h'rt presents little or no impact to ground water resources in the area. 3. Although the laboratory CKD samples showed several parameters which exceeded ground water standards, the two background samples (pasture soil and North 59~' St.) also had parameters above the ground water standard. 4. There were five parameters from the laboratory CKD sample that exceeded applicable ground water standards by small levels. The parameters are: ` - selenium - thallium - total dissolved solids ' - pH - gross beta ~, Geochemical computer modeling of the transport and fate of these five parameters over distance and time indicates compliance with all ground water standards before they could potentially migrate off of ' Southdown's property to the locally utilized aquifers. 5. The only useable ground water sources in this area are in the alluvial deposits of St. Vrain Creek and in the Dakota Sandstone. There is no hydraulic pathway from the C-Pit limestone and shale units to either of these ground water sources 6. The rock formations adjacent to and beneath C-Pit have relatively low permeability. The bedding planes in these sedimentary rocks do not provide a hydraulic connection with the alluvial or Dakota Sandstone aquifers. Permeability perpendicular to or across bedding planes is ~'