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C-PIT HYDROGEOLOGIC INVESTIGATIONS TECHNICAL REVISION NO. 8 MINING PERMIT M-1977-208 1. INTRODUCTION This report on C-Pit Hydrogeologic Investigations has been prepared on behalf of the CEMEX cement and quarry complex located in Lyons, Colorado, in fulfillment of the requirements of Technical Revision No. 8 (TR-8) to Mining Permit No. M-1977-208. TR-8 was proposed by CEMEX to the Department of Natural Resources' Division of Reclamation, Mining and Safety (DAMS) by a letter proposal dated March 30, 2007, and was further refined in the CEMEX May 8, 2007 response to the adequacy review outlined by the DAMS letter of Apri123, 2007. The scope of TR-8 evolved from a meeting between CEMEX and DRbIS on February 9, 2007, and with subsequent discussions on the technical and regulatory issues arising from the accumulation of water in CEMEX's permitted disposal site for cement kiln dust (CKD), C-Pit (the Site). The quality of C-Pit water has degraded sufficiently to raise concems for potential waterfowl exposure. Figure 1 is the vicinity map for the Site. At the February 9, 2007 meeting, CEMEX indicated that: • Due to various operational reasons and air permitting considerations, pumping C-Pit water to the plant for cooling was not a viable option to efficiently eliminate the exposed water surface in C-Pit. • CEMEX planned to take a sufficient volume of Fill from available stockpiles to fill in C-Pit and elirr~iuate any exposed surface water by the DAMS deadline of May 17, 2007. ^ Once the exposed water surface in C-Pit was eliminated, CEMEX would continue to use C-Pit as its permitted disposal site for CKD. In responding to CEMEX, DBMS raised concems regarding the potential for adversely impacting usable groundwater in the area around the Site. Specifically, DAMS requested that CEMEX consider the following issues: • What are the sources of water entering C-Pit? • What is the potential for raising the level of groundwater in the area of C-Pit during the filling process, and would mounding of that water result in discharge to the ground surface between C-Pit and A-Pit? • CEMEX was required to submit a plan to characterize and address groundwater at the Site. This report addresses these issues and summarizes the results of the hydrogeologic investigations conducted during the spring and early summer of 2007 at the C-Pit site. 1.7 Project Objectives The primary objective of the TR-8 Hydrogeologic Investigations is to characterize the hydrogeology of the Site sufficiently to determine the source(s) of water into the pit and to design along-term monitoring program fox submittal to DAMS as Techtucal Revision No. 9. The investigation addresses the issues raised by DAMS at the February 9, 2007 meeting, as well as subsequent discussions regarding the need for a compliance well to be completed in the Fort Hays Limestone unit at the eastern extent of the CEMEX property. 1-1 Use 01 contends on IhiS Sheei is suh~eC~ 10 ChB Imlleiion5 SpECi(Btl al the end 01 lhis tlOGUm¢n~ 11BCDEN09pro~eclslDatalGENlGemex:TR-e',Reponmg~CEME% Report 08~3t,07.tloc