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C-PIT Hydrogeologic Investigations <br />Technical Revision No. 8 <br />2: Site Analysis and Field Activities Mining Permit M-1977-208 <br />Previous tnining of the limestone and backfilling with unknown materials has complicated the lithology of <br />this area. These ptezometers were designed to be completed to the depth of the top of the Carlile Shale that <br />underlies the Fort Hays Limestone, with the goal of monitoring the depth of any water that may accumulate <br />at this zone. Although the field geologist and driller were careful to auger through the backfill to the depth of <br />competent bedrock, it is not certain that all three piezometers (P-001, P-002, and P-003) were completed to <br />the depth of the Carlile Shale. <br />I piezometers P-004 through P-006 axe located immediately east of the Swede Ditch and are completed in the <br />unconsolidated materials overlying the bedrock between the Swede Ditch and the western highwall of C-Pit. <br />These piezometers were sited to assess potential seepage from the Swede Ditch, which, unlike the Feeder <br />Canal to the west, is believed to be constructed in the surficial, unconsolidated sediments overlying the <br />Smokey Hill Shale that makes up the exposed western highwall of C-Pit. <br />Each piezometer was drilled by Dakota Drilling using 4.25-inch diameter solid stem augers. The piezometers <br />were completed using ten feet of one-inch diameter 0.0]0-inch machine slotted PVC screen in P-001 and P- <br />003 and five feet of the same screen in P-002, P-004, P-005, and P-006. A blank, one-inch PVC riser was <br />used to complete each piezometer above the ground surface. A 10/20 mesh sand filter pack was placed from <br />the bottom depth to approximately 2.5 feet above the screened interval. A hydrated bentonite seal was then <br />placed in the remainder of the hole up to the ground surface. Surface completions consist of a three-foot <br />square concrete pad with protective steel casing around the PVC stick-up. Steel bollards filled with cement <br />were placed around the pads of piezometers P-001, P-002, and P-003 to provide protection from possible <br />vehicular damage. Completion data for the piezometers is summarized in Table 1. <br />Monitoring wells CEM-002, CEM-003, and CEM-004 were installed to the east of the Site during April 2007 <br />' to supplement existing well CEM-001. Wells CEM-002 and CEM-003 are completed in the Smokey Hill <br />Shale umt to the east of C-Pit, at a depth above the top of the Fort Hays Limestone and well below the water <br />surface in C-Pit. These wells are intended to help evaluate the occurrence of water, iE any, to the Smokey Hill <br />Shale in this area, and whether or not it may be coming from C-Pit. <br />Monitoring well CEM-004 is located north of C-Pit and is completed in the St Vrain alluvium. This location <br />' is intended to help evaluate whether C-Pit water is migrating northward to the St. Vxain alluvial system. <br />Each monitoring well was drilled by Dakota Drilling using an air rotary drilling rig. The wells were completed <br />using ten feet of two-inch diameter 0.010-inch machine slotted PVC screen in CEM-004 and 40 feet of the <br />same screen in CEM-002 and CEM-003. Blank two-inch PVC riser was used to complete each well above <br />' the ground surface. A 10/20 mesh sand Filter pack was placed from the bottom depth to approximately two <br />to four feet above the screened interval. A hydrated bentonite seal was then placed in the remainder of the <br />hole until reaching the ground surface. Surface completions consist of athree-foot square concrete pad with <br />' protective steel casing around the PVC stick-up. Steel bollards filled with cement were placed around the <br />pads of the wells to provide protection from possible vehicular damage. <br />Monitoring wells CEM-003 and CEM-004 were developed using atwo-stage pump to surge the water column <br />in each well. Well CEM-003 was pumped dry after removing approximately 20 gallons of water (one well <br />volume). After waiting approximately 20 minutes, an additiona10.25 gallons of accumulated water was <br />removed. Twenty minutes later, a fma10.25 gallons of water was removed, at which point the well was <br />I deemed to be fully developed. Well CEM-004 was pumped dry after removing approximately 2.5 gallons of <br />water (one well volume). After waiting 45 minutes, an additiona10.5 gallons was removed from the well, at <br />which time the well was detemtined to be developed. <br />CEM-002 and the piezometers were not developed due to either being dry or having insufficient water Eor <br />development. <br />2-e <br />Use of contents on this sheet is subject to the Ilm taboos specfhed at the end of ihls document <br />UBCDEN021pmjecislDala\GEN1CemexffR-B~ReponinglCEMEX Repad OB-31-07 tloc <br />