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1 1 regulation for facilities that currently have mining permits; therefore, the site does not have a solid waste permit foc landfilling CKD. The location of the cuts previously used for landfilling CKD are indicated on Figures 3 thru 7, Appendix B. CKD is currently being disposed in the cut adjacent to monitoring well MW-70. The bottoms of these cuts coincide with the top of the underlying Codell sandstone, which is the primary water-bearing unit in the quarry azea. Approximately ]0 feet of shale was reportedly placed in the bottom of these cuts ptfor to the placement of any CKD. ' On July 3Q 1999 the EPA proposed rules for the management of CKD under RCRA (Resource Conservafion and Recovery Act). The proposed Wile was published in the Federal Register on August 20, 1999 and comments were accepted anti[ Febntary t8, 2000. These proposed rules include technical standards for the management of CKD. However, in Colorado, the regulatory responsibility for the new requirements has been relegated to the Department of Natural Resources, DMG. ' Therefore, the requirements for CKD management may be incorporated into each facility's Mined Land Reclamation Permit. These requirements would include specific requirements for ground water as described in Rule 3.1.7 of the "Construction Material Rules and Regulations" and the Water Quality Control Commissions' Regulation No. 41, "Basic Standazds for Ground Water". Holnam submitted a request for a Technical Revision (No. 006) to its pernvt on August 16, 1999 for the landfilling of CKD. ' It its response, dated January 18, 2000, DMG requested that Holnam install two (2) additional monitoring wells, MW-8 and MW-9, and monitor the ground water quality for five (5) quarters from the two new wells and from MW-7. Most recently, monitoring well MW-10 was installed down gradient of historic CKD landfills. This well was also requested by the DMG. The stated purpose of the five quarters of sampling was to "characterize the ambient ground water quality". ' WeU Drillin¢ and Installation The quarterly sampling requested by the DMG began after the installation of monitoring wells MW-8 and MW-9. Monitoring well MW-10 was installed prior to the fifth quarter of sampling. All of the monitoring wells included in the sampling were drilled with anair-rotary drilling rig. The wells were constructed of 4-inch diameter PVC casing and filter packed with Colorado Silica sand. A bentonite seal was then placed on top of the filter pack to help prevent grout from penetrating the filter pack ' material. A cement/bentonite grout seal was then placed in the annulus of each of the wells from the Yop of the bentonite seal to the ground surface. Aiezometers installed to help better characterize the ' ground water flow were constructed in the same way except with 1,5-inch PVC instead of 4-inch PVC casing. Due to the ]ow hydraulic conductivity of the formations, it typically took several days, and sometimes several weeks (e.g., MW-10), before ground water was observed in the newly constructed wells. Construction details for these wells are included in Table 1, Appendix A. The locations of these wells are indicated on Figures 3 thru 7, Appendix B. Ground Water Samnlin The wells were purged prior to sampling. Prior to purging, the static water level was measured in each ' well. We1]s MW-7 and MW-9 were purged with an electric submersible pump. Wells MW-8 and MW-10 were purged with a bailer due to the depth of the ground water (i.e., 52 and t07 feet, respectively). Due to the low hydraulic conductivity of the aquifer, the wells could not be purged of ' Ground Water Monitoring 2 Copgright 2001 August 6, 2001 KS & Compsny, Inc.