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C-PIT Hydrogeologic Investigations Technical Revision No. 8 4: Conclusions Mining Permit M-1977-208 • This reach of the Boulder Feeder Canal was constmcted by drilling and blasting, and shotcrete was originally applied to the eastern wall of the canal to limit seepage losses. This shotcrete is now severely degraded and is not providing any barrier to seepage through the shale fracture system. • Although not confirmed by stream gauging techniques, the potential exists for seepage losses out of the section of the Canal cut into bedrock into the mined out area to the east between the Canal and C-Pit. Over time, this water would saturate the deeper portions of the fill and eventually Elow down dip (southeast) along the top of the Carlile Shale and toward C-Pit. • Significant seepage losses out of the Canal to the west of C-Pit may occur where the relocated canal merges into [he original alignment at the north end of the reach west of C-Pit. This location is west of piezometer P-003, and just north of the station where the upstream Canal flow rate was estimated during gauging. Degraded shotcrete is presently visible on the lower portions of the short fill section that makes up the eastern wall at this transition. • Any losses from the Boulder Feeder Canal and the Swede Ditch eventually make their way into the C-Pit basin. • The hydraulic response observed in well CEM-003 during pit filling shows a connection between C-Pit and the well. CEM-003 is completed in the Smokey I-Iill Shale, and the connection is via fractures in the shale unit. • Fracturing in the Smokey Hill Shale east of C-Pit is not consistent, as well CEM-002 to the south of well CEM-003, completed in the same unit to approximately the same depth, has been dry since it was drilled in April. • There is no indication that alluvial groundwater north of C-Pit has been impacted by C-Pit water constituents. Monitoring well CEM-004 is located immediately northeast of C-Pit and retains a geochemical signature distinct from that of C-Pit. ^ The May 22, 2007 sample Exom CEM-005 was not a representative sample from the limestone formation, but rather was residual water left from the drilling process. The depth of water in the nearly 400-foot well has consistently remained at approximately 5-feet. • The Filling of C-Pit has improved the water chemistry by lowering the pH from 12.5 to less than 8.5 (su). Future sampling will confixxn whether or not other contaminants of concern such as selenium have also changed. • The pond presently located southwest of C-Pit (Figure 2) was formed during the reclamation of the posting-mining landscape in this area. It is fed via a 54-inch culvert that routes runoff from the reclaimed B-Pit area as well as seepage from the Boulder Feeder Canal. • The Southwest Pond water elevation has risen significantly during the summer irrigation season due to accumulated Canal seepage losses along the reach constmcted across the Fill to the west of the pond. • Seepage from the pond southwest of C-Pit may be rechazging the pit, as water works its way along the top of the Caxlile Shale unit that is the bottom of C-Pit. The rise in the Southwest pond water elevation due to accumulating Canal seepage losses during the irrigation season would increase the rate of recharge. ^ Past observations of ice accumulation on the northeastern highwall of C-Pit during cold weather months may be an indication of leakage from the A-Pit water line. Plant operations staff have reported that line breaks occurred in the A-Pit line near the northeast corner of the pit in recent years. • Under its air pollution permits, CEMEX is required to use water sprays to control fugitive dust at the C- Pit CKD disposal site. Water trucks and a sprinkler system apply this water. CEMEX estimates that the annual volume of water applied for dust suppression is currently several million gallons per year. During the summer of 2007, the source of this water has been A-Pit. 42 Use of contents on this sheet is Su6lect Io the Ilmhafions specilietl et the end of this document. \1BCDEN021pmjects\Dala\GEN1CemexITR~B\ReponingiCEME% Report OB-31-07.tloc