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DQp~~ 7. Management practices for CKD disposal are appropriate and no changes in the current method of disposal are believed to be necessary. Periodically capping the disposed CKD with a layer of compacted shale or clay soils would further isolate the CKD from precipitation and infiltration of rain and snowmelt. Southdown has committed to doing this in cells that are built to 7 acres in size and in approximately 20 ft. lifts. 2.0 Introduction and Regulatory Background Southdown, Inc. and its predecessors have operated a cement plant and associated quarries in Boulder County near Lyons since about 1969. Cement kiln dust (CKD), baghouse dust, and plant clean-up dust have been properly disposed of in the quarries since the inception of the cement plant. There are no known adverse impacts to groundwater. The quarries south of the cement plant (referred to as the Lyons quarries) received a 112 permit for the Colorado Mined Land Reclamation Board in 1977. {Permit No. M-77-208). The permit is active and in good standing, the financial warranty is in place, and the facility is in compliance with the CMLRB permit. There are currently over 300 acres under active reclamation. Waste materials generated at a permitted mine site (the cement plant is within the permit area) may be disposed at the mine site without a Certificate of Designation pursuant to the requirements of the Colorado Department of Public Health and the Environment (CDPHE). Disposal of the CKD in the quarries is in compliance with the requirements of both the Division of Minerals and Geology (DMG) and the CDPHE. This report has been prepared at the request of DMG staff pursuant to Rule 3.1.7 of the Construction Materials Rules and Regulations of the Colorado Mined Land Reclamation Board (effective January 1996). That Rule allows the DMG staff to request information on existing, permitted operations (for permits issued prior to September 1, 1993) to assure that the operation is not affecting current or potential future use of surrounding groundwater resources. On January 20, 1999 Carl Mount and Christina Kamnikar of the DMG inspected the facility. The inspection report requested a characterization of the chemical constituents of the CKD, a characterization of the local geology and hydrology, and an analysis of potential groundwater impacts. This report responds to that request. Groundwater quality standards used in this analysis are either human health standards, secondary standards, agricultural standards or Federal drinking water standards, whichever is most restrictive. The groundwater quality standards were supplied to Southdown by Harry Posey of the DMG (for unclassified