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58 Groundwater <br />t <br />5.2.7 Pilot dewatering test <br />A long -term, large -scale pumping test was performed in the footprint of the proposed <br />Phase 1 box cut with the following objectives: <br />• determine the large -scale response to pumping in bedrock units in the <br />vicinity of the initial box cut, <br />• determine the transmissivity of the bedrock units from the top of the water <br />table to below the lowermost seam to be mined (Gb seam), <br />• determine effects of vertical jointing, <br />• characterize composite groundwater quality during dewatering, <br />• generate hydraulic data for refinement and calibration of the pit slope <br />depressurization and regional groundwater models, and <br />• evaluate dewatering rates and methods. <br />The protocol used to conduct the test is provided in Appendix 5.H. The layout of the <br />pumping test monitoring network is described in Section 5.2.5 and shown on Figure 5.8 <br />and Plan 5.1. <br />Stress to the water - bearing units was provided by pumping pilot dewatering well <br />C- 04 -16B at a proposed location of the Phase 1 box cut. For the long -term pumping <br />test, a 7.5 horsepower Gould submersible pump was placed at a depth of 650 ft bls in <br />the well gallery. Flow was controlled and measured using a gate valve and a 1 -inch <br />diameter totalizing meter. Discharge from the well was piped 600 ft from the pilot <br />dewatering well to a temporary storage pond in a small drainage tributary to Little Collom <br />Gulch. The small storage pond was constructed to facilitate infiltration as a method of <br />water disposal. <br />To evaluate the effects of long -term pumping, water levels were monitored at numerous <br />locations and depth intervals. In the immediate vicinity of the pumping well, water levels <br />were monitored in the pumping well, the 6 SP piezometers (SP -1 through SP -6), and <br />18 VWPs installed in 6 locations (VWP -1 through VWP -6). These monitoring locations <br />were installed in close proximity (less than 300 ft) to the pilot, dewatering well <br />(Figure 5.8). <br />An additional 11 monitoring wells and piezometers in the vicinity of the pilot dewatering <br />well were monitored. These included four wells installed by Utah International <br />(DHH -3 -1, DHH -3 -2, DHH -4 -1, and DHH -4 -2), six piezometers (PC- 04 -14FG, 20FG, <br />and 201), C- 04 -17VWP (three sensors), and three baseline monitoring wells <br />(MWC- 04 -13FS, 13FG, and 13H). <br />2572 -R2 Colowyo Coal Company <br />Water Management Consultants <br />