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Colorado Division of Reclamation Mining and Safety January 6, 2011 Mr. Eric Scott 2 103-81640 Limestone mining operations ceased in August 2002. Reclamation and monitoring activities have been occurring onsite since the plant closure in 2002 (Holnam 2002, Holcim 2004, 2005, 2006, 2007, and 2009). Cement kiln dust (CKD) was generated onsite during the production of cement. Disposal of CKD in mined out portions of the Boettcher Quarry began in 1980. Figure 1 shows the approximate locations of CKD disposal in the A-band (Fort Hayes limestone) mining cut. As per the approval of Technical Revision No. 3 (TR-003) to Permit No. M-77-348 by the Division of Minerals and Geology (DMG) on October 15, 1999 (DMG 1999), future CKD disposal would be limited to the areas A2 and A2-A. At that time, these areas contained some ponded precipitation. runoff. The Dry Fill CKD area shown on Figure 1 was filled prior to TR-003. Approximately 140,000 cubic yards (yd3) was placed in area A2 by August 2002, when the plant closed. There are four monitoring wells (MW-1, MW-2, MW-3, and MW-4) that have been used to monitor groundwater near CKD disposal area A2 as an additional condition of TR-003. Three of the monitoring wells (MW-1, MW-2, and MW-3) were installed in June 1998. The fourth monitoring well, MW-4, was installed in April 1999. These wells are shown on Figure 2 relative to CKD disposal area A2. Groundwater was sampled from the four monitoring wells for water quality analysis beginning in April 1999 through July 2000. During this period, a total of eight groundwater samples were collected from each well. A summary of the water quality results for the eight historical groundwater events from each monitoring well is provided in Tables A.1 through A.4 of Attachment A. 2.0 SUMMARY OF FIELD ACTIVITIES Field activities described in this report were conducted by or under the supervision of Golder between July 30 and September 27, 2010. These activities included: ¦ A video survey of monitoring well MW-4; ¦ Pumping of all four wells in advance of the monitoring event; ¦ Hydraulic conductivity testing of monitoring well MW-4; ¦ Purging and sample collection at all four wells. These field activities are summarized below. 2.1 MW-4 Video Survey A video survey of monitoring well MW-4 was performed by Hydro Physics of Denver, Colorado on July 30, 2010. This work was observed by Golder and a representative of Holcim. The purpose of the video inspection was to determine the total depth and screened interval of the well in the absence of other well construction documentation (well construction log). This work was performed in response to a comment by DRMS in their May 20, 2010 letter (DRMS 2010b) and follow-on discussions on June 11, 2010. The video inspection consisted of running a miniature camera attached to a flexible cable into the well and observing the condition of the well casing on a video monitor as the camera is lowered to the bottom of the well. The video was also recorded digitally on a computer along with the depth of the camera below the top of the well casing. Prior to the video inspection, the water level was measured in the well using an electronic water level indicator. The water level indicator, and video camera and cable were all decontaminated prior to use with an AlconoxTM solution followed by a rinse with distilled water. The video inspection identified the total well depth at 188.25 feet below the top of the polyvinyl chloride (PVC) well casing. The well screened interval was observed from approximately 168 to 188 feet below the top of the PVC. These well construction details are also provided in Table 1. During this site visit, Golder also observed the condition, replaced the locks, and measured water levels and total depths in all of the monitoring wells. All four monitoring wells were determined to be in satisfactory condition for sampling. Measured total well depths are also summarized in Table 1. I iA10\81640\0400\gwrep_fn1 _06jan11\10381640 holcim gwrep_fnl-Ilr 06jan11.docx ?? -Golder Associates