2010-12-17_REVISION - C1981019 (153)

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Groundwater 45 C 0 5.2.1 Historic Information Historic hydrogeologic and water quality data in the vicinity of the Collom site were generated by Utah International, Inc. (1984), and BD GeoEnvironmental Services (BDGE) (2001). Locations of all wells discussed in the following section are shown on Plan 5.1. Utah International performed a baseline groundwater assessment in the late 1970s which was limited to three wells — DH -76 -8, DHSS -78 -1, and DH -78 -2. Between 1978 and 1982, water levels and water quality samples were collected annually from these wells. In 1980, Utah International installed four wells (DHSS 80 -1C, DHSS 80 -4, DHSS 80 -5 and DHSS 80 -6) and performed a 19 -hour pumping test. In 1983, 12 additional wells were installed in five clusters to collect groundwater data (water levels and transmissivity) from the Williams Fork Formation. These included: DHH -1 -1, DHH -1 -2, DHH -2 -1A, DHH -2 -2, DHH -3 -1, DHH -3 -2, DHH -4 -1, DHH -4 -2, DHH -4 -3, DHH -5 -1, DHH -5 -2, and DHH -5 -3. Four constant -head aquifer tests were performed. In 1996, BDGE installed and tested six valley fill wells (MJ- 95 -01, MJ- 95 -02, MJ- 95 -03, MT- 95 -01, MT- 95 -02, MW -95 -01 and MW- 95 -03), three wells screened in the Fab seam (UL- 95 -01, UL- 94 -40, and W- 95 -11), and three wells screened in the Trout Creek Sandstone (W- 95 -15, UL -95 -15 and W- 95 -02) (BDGE, 2001). Not every well installed in the vicinity of the proposed mine was used during the pre- feasibility study. Some were outside the study area, others could not be located, and several were unusable. Table 5.1 lists all the preexisting wells, well construction details, and how the well was used during the pre - feasibility study. 5.2.2 Data collected during exploration program Information collected during drilling of exploratory borings was integrated into the site hydrogeologic evaluation. This information included core samples, geophysical logs, and various observations made during drilling. Where feasible, drillers and geologists noted water production rates and water levels. However, most holes were cored using water to improve core recovery and quality, and hydrologic observations therefore could not be made. 5.2.3 Baseline monitoring wells Information on groundwater quality, hydrologic characteristics and groundwater flow at the Collom study area was developed via the installation and testing of 13 bedrock and five valley fill monitoring wells. The new baseline bedrock monitoring wells are listed in Table 5.2, while the new valley fill monitoring wells are listed in Table 5.3 Locations of the baseline monitoring wells are shown on Figure 5.6 and Plan 5.1. The purpose of the monitoring wells was to characterize baseline groundwater quality and water levels in the valley fill and specific units of the Williams Fork Formation (F sandstone down to the I sandstone). • 2572 -R2 Colowyo Coal Company Water Management Consultants