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GENERAL41305
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Last modified
8/24/2016 8:08:44 PM
Creation date
11/23/2007 11:08:17 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
General Documents
Doc Date
4/11/1986
Doc Name
Proposed Decision & Findings of Compliance for PR3
From
Permanent Lower Waste Pile
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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-20- <br />the latter massive sandstone produces very little water, as evidenced <br />by the dryness of the Bear Mine and the lack of springs associated with <br />this unit. Coal seams within the Mesa Verde Formation also act as <br />continuous aquifers. The Barren Member of the Mesa Verde Formation <br />contains lenticular channel sandstones, some of which may have <br />sufficient length and thickness to transmit ground water flows <br />regionally. Regional ground water aquifers will be recharged along <br />outcrops and subcrops beneath the alluvium of streams to the southwest <br />of the permit area within the Minnesota Creek Basin. However, due to <br />the steepness of topography in the outcrop areas, (i.e. sandstones are <br />ledge formers), and narrowness of the stream valleys, these regional <br />aquifers receive little recharge. Some recharge to the continuous <br />units and much of the recharge to the more discontinuous, lenticular <br />units will come directly from the percolation of snowmelt and <br />precipitation downward through sands and along fractures. Preliminary <br />pump tests conducted by WECC indicate the transmissivity of the F-Seam <br />to be 16.68 g/d/ft and that of the Barren Member to be 2.46 g/d/ft. A <br />piezometric surface map for the combined F seam and Barren was <br />submitted by WECC. Movement is likely to be very slow on a regional <br />basis and to the north east along dip. <br />Locally, water flow through Fractures probably occurs more rapidly, as <br />suggested by the seasonal fluctuation in discharge rates of some <br />springs in the mine plan area. <br />The direction of migration of water in the F-Seam and larger sands will <br />probably be northeasterly in the direction of dip. Exhibit 2.8.2.A <br />presents a "Composite Barren Member Well Water Level and Spring <br />Elevation Map". This Exhibit generally confirms the northeasterly <br />direction of ground water migration in the shallower units of the <br />Barren Member in the five year permit area. However, based on <br />hydrologic monitoring data, in the Barren Member there appears to be a <br />ground water divide approximately following the topographic divide <br />separating the North Fork from Minnesota Creek. South of this divide, <br />ground water in the Barren Member flows toward Minnesota CreeK. <br />Discharge of ground water occurs through numerous seeps and springs. <br />See Spring Location Map, Exhibit 2.8.1.U. Over 100 springs are located <br />in the life of mine area. Thirty-three of the most significant springs <br />in the permit and adjacent area are tabulated on Table 2.8.1.V. <br />Additional springs are identified on Table 2.8.1.0. Flows from these <br />springs range up to 60 gpm during spring runoff, however, most observed <br />flows are significantly less as depicted on Table 2.8.1.X. <br />Some of these springs appear to be associated with local faulting and <br />fracturing. Others appear associated with landslides or slumps as <br />identified in Exhibit 2.8.1.V. entitled "Spring Locations vs. <br />Topography, Landslides, Rockfalls and Lineaments", and Table 2.8.2. V. <br />entitled "Springs in and Around Five Year Mine Plan, Mt. Gunnison, <br />Colorado". <br />
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