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iii iiiiiiiiiiiiiiii <br />999 <br />• <br />• <br />• <br />2.7.5.4 Ground Water Use <br />Doc Date:12/11/2001 <br />Prior to submittal of Trapper's initial permit application, an inventory of water wells within one mile <br />of the proposed permit area was conducted. Design information for these wells is provided in <br />Tables 2.7-22b and 2.7-22c. This inventory indicates a number of water wells are present in the <br />area. Map M-31 shows the locations and permit numbers of wells. Only wells completed in the <br />Third White Sandstone of the Upper Williams Fork formation and situated south of the Big Bottom <br />Syncline are believed to have any potential to be affected by the mine. Wells 93848 and 80998 fit <br />this criteria (refer to Map M-31). In addition, two springs (Lux Springs) with flows of 0.4 and 0.7 <br />cfs are present in the southeast quarter of Section 29, T6N, R91 W. <br />Well 93848 will likely not be impacted by mining operations that occurred in the Browning and Colt <br />pits. The strike and dip of the coal seam and overlying strata in the vicinity of this well make <br />contact with the backfill aquifers in these pits unlikely. Well 80998 appears to have at least some <br />minor potential to be influenced by mining operations in the Flume drainage. This well is <br />approximately 3,500 feet from the edge of the Trapper permit boundary. Water levels and yields <br />from this well are not expected to be measurably affected by mining upgradient of this Third White <br />sandstone well. Mining upgradient in the Third White Sandstone has been shown not to affect <br />water levels downgradient of the mining zone due to the generally quick recovery of water levels <br />at the northern boundary of the mine pits. Higher permeability backfill materials drain water to the <br />northern edge of the pits and allow the backfill aquifers in these areas to recover quickly. No <br />water-level effects were observed in the Third White Sandstone well, P8, approximately 1,000 feet <br />downgradient of mined areas. Monitoring of Third White Sandstone wells GC-2 and GP-9 will <br />define whether any potential water level or water yield impacts can be expected further <br />downgradient in the vicinity of well 80998. No impacts are evident to date. <br />Backfll aquifers at Trapper can be characterized by higher major constituent concentrations such <br />as TDS in some areas. These higher TDS wncentrations might persist for an extended period of <br />time. The higher concentrations from the backfill aquifers may recharge the Third White <br />Sandstone and, therefore, eventually increase major constituent levels in this aquifer as well. <br />Wells completed in this aquifer could potentially be affected. The increase in TDS concentration <br />might be offset somewhat by the influence of higher quality underburden inflows. Continued <br />monitoring at wells GC-2 and GP-9 will better define the potential for water quality influences at <br />Third White Sandstone well 80998. No impacts are evident to date. <br />Well CA-2259 provides water to the two MacNamara Ditches (Map M-31). The well was <br />adjudicated for irrigation, stock water and domestic water use. <br />Periodically, Trapper reviews the filings for Water Division 6, District 44, and updates Map M-31. <br />Revised Map M-31 illustrates all filings within one mile of Trapper's permit boundary. The aquifers <br />to which the adjudicated wells are completed to are as follows: <br />Aquifers <br />First White Sandstone <br />Second White Sandstone <br />Adjudicated Permit Number <br />W-1406-78 <br />020532E-020536F, 84649, 74957, 79350, <br />W840-75, 8577-5A. <br />2-524 <br />Revision: rte' -67 <br />Approved: MA_ K ~~u <br />