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C-PIT Hydrogeologic Investigations Technical Revision No. 8 2: Site Analysis and Field Activities Mining Permit M-1977-208 ' Monitoring wells CEM-001 (previously installed by others), CEM-002, and CEM-003 were geophysicapy logged using induced gamma-ray and formation resistivity after completion of the wells. Copies of the logs are in Appendix D. ' Figures 3, 4 and 5 depict three cross sections taken through the C-Pit area, oriented as indicated on Figure 2. These sections display the geology m and around the C-Pit site, based upon interpreting the information obtained during the drilling program, aerial photography and the mining Mstory of the site. As shown on 1 Figure 5 (Section C-C~, two additional bore holes were made at the haul road intersection immediately northeast of C-Pit to determine the depth to bedrock in this area. The drilling indicated that a block of residual bedrock (Smokey Hill Shale) separates the water in C-Pit from the St. Vrain Creek alluvial system to the north. 2.5 Compliance Well CEM-005 Compliance Well CEM-005 was located after consultation with DRMS at a February 22, 2007 meeting at the CEMEX Plant CEM-005 was designed to monitor the Fort Hays Limestone unit approximately 2,700 feet southeast (down-dip) of monitoring well CEM-001. Figure 2 shows the location of CEM-005 relative to C-Pit and the monitoring well network established around C-Pit. CEM-005 is a 4-inch well with PVC casing, drilled to a total depth of 401 feet below ground surface (bgs) on May 14 and 15, 2007. Prior to setting the screen and casing, the open borehole was geophysically logged using induced gamma-ray and formation resistivity to determine the elevations of the contacts between the Fort Hays Limestone, the Smoky Hill Shale above the Fort Hays, and the Carlile Shale unit below. The 10-foot screen was set from 388 to 398 feet bgs and sand packed with 10-20 washed silica sand to 378 feet bgs. The annulus above the sand pack was grouted with bentonite grout from 378 feet bgs to the ground surface. Together, the screen and sand pack monitor the Fort Hays Limestone at the approximate elevations 4836 to 4816 feet amsl (378 to 398 feet bgs) at this location. Figure 9 shows the well construction details and lithology of CEM-005. CEM-005 was first sampled on May 22, 2007, after the well had been completed, grouted, and developed five days previously. Prior to obtaining the sample, the water in the well was removed by the driller through bailing with a 4-inch bailer, from an initial level at approximately 20 feet bgs down to 390 feet bgs, at which time the water level was allowed to recover to 389.75 feet bgs over the course of one hour. Prior to sampling, the well was bailed again and was allowed to recover for another hour before collecting a final baier volume for the sample. The analytical results are summarized on Table 2. CEMEX personnel gauged the depth to water at CEM-005 on June 19, 2007 and determined the water level was 394.85 feet below the top of casing (btoc), ox elevation 4822.38 amsl, confirming that very little recharge had occurred since the initial sampling of May 22, 2007. The water elevation in C-Pit and potentiometric head elevation at well CEM-001 on June 15, 2007 were approximately 5211 and 5213 amsl, respectively. On July 3, 2007, Brown and Caldwell personnel returned to CEM-005 and determined the water level was 394.32 feet btoc, or elevation 4822.91 amsl. The water level was lowered to 395.99 feet btoc by hand bailing, and after approximately three hours only 0.03 feet of recovery in the water level was noted. On July 1Q 2007, ' Brown and Caldwell personnel returned and measured the depth to water in CEM-005 to be 395.69 feet below the top of casing, or elevation 4821.54 amsl. 1 2.9 Use of contains on tMS sheet is suhlect to the hmrtanons speeded althe entl of this document. \\BCDEN02\prolects\DataWENlGemex\TR-8\Reporting~CEMEX Report OB-31-07.dw