GENERAL54873 - Laserfiche WebLink

Home Browse Search

11 in the region are the Rollins Sandstone and the massive sandstone separating the Upper and Lower Coal Members of the A7esa Verda Formation. However, the Later massive sandstone produces very little water, as evidenced by the dryness of the Bear Mine ari5 the lack of springs associated withthis unit. Coal Seams within the Mesa Verda Formation also act as continuous aquifers. The Barren Member of the Mesa Verda Formation contains leuticular channel sandstones, some of which may have suffient length and thickness to transmit ground water flows regionally. Regional ground water aquifers will be recharged along outcrops and subcrops beneath the alluvium of streams to the southwest of the-permit area within the Minnesota Creek Basin. However, due to the steepness of topography in the outcrop areas, (i.e, sandstones are Ledge formers), and narrowness of the stream valleys, these regional aquifers receive Little recharge. Some recharge to the continuous units and much of the recharge to the more discontinuous, lenticular units will come directly from the percolation of snowmelt and precipitation downward through sands and along fractures. Preliminary Dump tests conducted by RRCO indicate the transmissivity of the F seam to be 16.68 g/d/ft and that Of the Barren Member to be 2.A6 g/d/ft. No piezometric surface data for the F seam or for individual continuous sands in the Barren Member are available, so no specific estimates of ground water flow rates can be developed. However, movement is likely to be very slow on a regional basis. Locally, water flow through fractures probably occurs more rapidly, as suggested by the seasonal fuxvation in discharge rates of some springs in the mine plan area. The direction of migration of water in the F-seam and larger sands will probably be northeasterly, down the dip of the beds, although this has not been confirmed b_y test drilling. Exhibit 2.8.2.A presents a "Composite Barren Pfember Well Water Level and Spring Elevation Map." This exhibit generally confirms the northeasterly direction of ground water migration in the shallower units of the Barren Member on the 5-year permit area. However, in the Barren Members there appears to be a ground water divide approximately following the topographic divide separating the North Fork from Minnesota Creek. South of this divide, ground water in the Barren Member flows toward Minnesota Creek. ~"~~' Discharge of ground water occurs through numerous seeps and springs. See Spring location Map Exhibit 2.8.I.U. Over 100 springs are located in%:the mine plan area. Thirty-three of the most significant springs in the permit and adjacent area are tabulated on Table 2.8.Z.V. Additional springs are identified on Table 2.8.1. Q. Flows from these springs range up to 60 gpm; however, most observed flows are significantly less as depicted on Table 2.8.1.X. Some of these springs appear to be associated with local faulting and fracturing. Others appear associated with landslides or slumps. Rs identified in Exhibit 2.8.Z.V. entitled "Spring Locations vs. Topography, Landslides, Rockfalls and Lineaments," and Table 2.8.1. V. entitled "Springs in and Rround 5-Year Mine .Plane, Mt. Gunnison, Colorado."