2014-03-11_REVISION - M1977208 (2)

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//Ccmcx March 7, 2014 Mr. Michael Cunningham Environmental Protection Specialist Division of Reclamation, Mining, and Safety 1313 Sherman Street, # 215 Denver, Colorado 80203 Via FED Ex TRK# 7981 5593 7710 RE: Lyons Quarry; DRMS File No. M -1977 -208; Technical Revision 12. Dear Mr. Cunningham; RECEIVED MAR 1 ' 2014 Division of Reclamation, Mining & Safety With this letter, CEMEX is submitting Technical Revision 12 to the Lyons Quarry DMRS File No. M- 1977 -208. The purpose of Technical Revision 12 is to: 1. Identify revised triggers for the monitoring goals for chloride and sulfate monitoring. 2. Add truck/vehicle wash water into C -Pit and/or use of truck/vehicle wash water for dust control on the haul roads associated with C -Pit. 3. Placement of sediment combined with coal in C -Pit that has accumulated from the September 2013 flooding event. 4. Increase the height above grade for the CKD stockpile in C -pit. Details of each revision are described in detail below. 1. Revised triggers for chloride and sulfate monitoring CEMEX would like to tailor the trigger levels for chloride and sulfate concentrations in the C- Pit compliance well to focus on identification of the chemical signature from C -Pit, rather than conduct a more arbitrary comparison to drinking water standards. Monitoring well CEM -005 is a compliance well used to identify potential impacts on the groundwater from C -Pit. The current monitoring triggers for chloride and sulfate monitoring in compliance well CEM -005 are 250 mg/l. These triggers are based on the lower of either agricultural or drinking water standards as described in the letter from Michael Cunningham, DRMS to Denise Arthur, CEMEX, regarding Technical Revision 11, dated September 23, 2011. The agricultural or drinking water standards are conservative based on human consumption of groundwater. Because the groundwater downgradient of C -Pit is not used for drinking water, these standards are not directly relevant to the C -Pit monitoring. Instead, CEMEX would like to propose groundwater monitoring trigger concentrations for chloride and sulfate that are specifically designed to monitor for characteristics of C -Pit water. The Stiff Diagram in Figure 1 is a Stiff Plot for C -Pit that is an average of the cation/anion concentrations for samples collected from C -Pit periodically between 2007 and 2013. As documented on several occasions, this Stiff Plot shows that there is a distinctive cation/anion signature associated with the water in C -Pit. Table 1 provides C -Pit water average concentrations of chloride and sulfate in milligrams per liter and the associated anion/cation signature in milliequivalent per liter, for data collect between 2007 - 2013.. Because of this cation/anion signature, groundwater monitoring downgradient from C -Pit would be most vAF- United States Operations v 1 `n P 0 Box 529, Lyons, CO 80540, USA, Phone (303) 823 -2100, Fax (303) 823 -2199