2009-12-29_HYDROLOGY - M2002004 (2)

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INTRODUCTION ' Contour Consulting Engineering, LLC, (Contour) collected groundwater samples at the GCC Rio Grande, Pueblo Cement Plant, on October 20, 2009. The samples were collected to satisfy monitoring permit requirements, as stipulated by the Colorado Division of Mining Reclamation and Safety (DRMS). Sampling, beginning in second half, 2008, has gone from quarterly monitoring to semi-annual monitoring. The October 2009 sampling event was the second semi-annual event for 2009. ' WORK PERFORMED ' Contour collected groundwater samples from three shallow alluvial monitoring wells (MW002, MW003, and MW004) in the vicinity of the St. Charles River. The alluvial wells represent downgradient conditions with respect to the Cement Plant operations. Recently ' installed well MWOOIA is completed in the Codell Sandstone. This well was determined to be dry during the first quarter 2008. Approximately 4 feet of water was measured in this well during the second quarter 2008. One full bailer of very clear water was removed from ' the well, and then the well went dry. Similar conditions were encountered during the second half 2008 event, and in both 2009 events, though the depth of water in the well has decreased to 1.2 feet in the most recent event. It is likely that the water produced in this well was a result of formation condensation. The well is 100 feet deep. Samples were not collected from well MW001 A. During the second quarter 2008, GCC installed an additional shallow groundwater monitoring well (MW005) at a location between the mine plant operations and the St. Charles River (shown in Figure 1). The new well location was selected with input from the DRMS. Groundwater was not encountered in the shallow aquifer at the time the well was installed, and no sample was collected. The well was sounded during the second half 2008 ' monitoring event, and was found to be dry, and no sample was collected. The well was also sounded during both 2009 sampling events. Approximately 1 inch of water was measured in well MW005 during the October 2009 event. This water is also likely representative of ' condensation in the well. No sample was collected at MW005. Depth-to-groundwater measurements were performed at each alluvial well prior to sampling. Wells were also sounded to determine total depth. The volume of standing water in each well was determined. Each of the alluvial wells were purged using a new disposable poly bailer. A minimum of three casing volumes was purged from each well ' prior to sampling. Field parameters pH, conductivity, and temperature were recorded as each well volume was removed. Groundwater was purged until these parameters were stabilized and reproducible (typically after three or four measurement sets). 1