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II 1 C-PIT HYDROGEOLOGIC INVESTIGATIONS ' TECHNICAL REVISION N0. 8 MINING PERMIT M-1977-208 3. OBSERVATIONS AND RESULTS 3.1 Logging of C-Pit and CEM-001 During Pit Filling 3.1.1 Hydraulic Head Data Analysis of concurrent data collected by the In-Situ Multiparameter Troll 9500 data logger units installed in C-Pit and monitoring well CEM-001 indicates that a hydraulic connection exists between C-Pit and the well. As expected, the elevation of the water in C-Pit rose during the filling process due to displacement, as the exposed water surface was reduced to less than one acre from March to May, 2007. Figure 6 shows the tune series plot of the C-Pit water level and the CEM-001 potentiometric head elevation data collected during this period. The elevation of C-Pit water rose from 5195 amsl to over 5213 amsl while C-Pit was filled. The response in CEM-001 is evident, where the potentiometric surface elevation lagged that of C-Pit by approximately two to three feet (Note that the discontinuity in head data collected for CEM-001 from May 3 to May 16th was due to a battery failure of the data logger unit.) The exact nature of the hydraulic connection between C-Pit and CEM-001 is unclear. Geophysical logging of CEM-001 indicated that the reported 40-foot well screen straddles the 15-foot thick Fort Hays Limestone, as well as the underlying and overlying shale units. The hydraulic connection may be from fracturing in the shale units, fractures in the limestone, along the bedding planes between units, or some combination of these possible routes. The plot of C-Pit water elevation shown on Figure 6 indicates that once the filling process was terminated around May 9, 2007, the water level stabilized between 5212-5213 amsl as the system equilibrated. The figure also shows that the head in CEM-001 mirrored the trend in C-Pit water elevation, but offset approximately 1.75 feet lower. Figure 6 also summarizes the head data collected at well CEM-003 (initially taken as individual measurements and then from a hydraulic head data logger installed on May 16, 2007), located to the north of CEM-001 (see Figure 2). CEM-003 is completed in the Smokey Hill Shale above the limestone unit. These data show there is a hydraulic connection between CEM-003 and the water in C-Pit. Well CEM-002, which is located to the south of CEM-001, is also completed in the Smokey Hill Shale at approximately the same depth as CEM-003. Unlike CEM-003, however, CEM-002 has not yielded water thus Ear during this investigation. To aid in interpreting the potential impacts of any seepage losses from the Boulder Feeder Canal on C-Pit, the average daily flow rate in the Feeder Canal was also plotted on Figure 6. These data were obtained from NCWCD (http://www.ncwcd.org/), and indicate that while C-Pit was being Filled during the March to May 2007 period, flows in the canal were minimal. Feeder Canal flows ramped up to over 80 CFS in late June and remain there to this day. Unfoxmnately, there is a gap in the C-Pit water level data during this period of rising flow in the canal, due to the logger being disturbed during the installation of the netting over the north end of C-Pit during mid June. Note, however, that individual (manual) measurements of the head in CEM-001 taken during this period indicate a rising trend starting at June 19th (these data are plotted as red squares on Figure 6). Assuming that this trend mirrors what was taking place in C-Pit during this period, it may be 3-1 Use of contents on this sheet is subject to the limnalions specitiyd et the end of Ihls tlocument. \1BCDEN02~profects\Data~GENlCemex\TR-8'~RepotlmglCEMEX Report 0831~O7.doc