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2007-11-07_HYDROLOGY - M1977300
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2007-11-07_HYDROLOGY - M1977300
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Last modified
8/24/2016 3:18:19 PM
Creation date
12/3/2007 4:13:29 PM
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Template:
DRMS Permit Index
Permit No
M1977300
IBM Index Class Name
HYDROLOGY
Doc Date
11/7/2007
Doc Name
Hydrologic evaluation of mine closure & reclamation
From
Whetstone Associates
To
Cotter Corpoartion
Media Type
D
Archive
No
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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 40 <br />The calculation indicates that an overall bedrock permeability of 2.8x10-' cm/sec would yield the inflows <br />from bedrock observed at the full extent of mining (Table 17). This is higher than bedrock permeabilities <br />measured from underground packer tests, but likely to represent the composite hydraulic conductivity of <br />fractured and unfractured bedrock around the mine. Using this hydraulic conductivity value, the dawdown <br />was calculated to be 14.6 ft below the static water level during the pilot plant pumping test, which indicates <br />that the static water level is about 12 ft below the Steve Level or at an elevation of 6590 ft NAD 27. This <br />simulation suggests that groundwater from deep bedrock will not discharge from the Steve Level adit, since <br />the final static water level will be about 12 ft below the adit. <br />Table 17. Calculation of Final Static Water Level in the Flooded Mine <br />Case I. Fully Mined & Dewatered (1990 -1995) <br />Saturated Thickness (ft) <br />Hydraulic Conductivity (cm/sec) <br />Drawdown (ft) <br />Yield (ft3/day) <br />Yield (gpm) <br />Target yield (gpm) <br />Case II. Refilling, Pilot Plant pumping test (July -Aug <br />2007) <br />Saturated thickness (ft) <br />Static Water Level wrt datum <br />Saturated Thickness (ft) <br />Hydraulic Conductivity (cm/sec) <br />Drawdown below static water level (ft) <br />Yield (ft'/day) <br />Yield (gpm) <br />Target Yield (gpm) <br />2,188 <br />2.8E-07 <br />2188 <br />34,672 <br />180.1 <br />180.1 <br />2,188 <br />0 <br />2,188 <br />2.8E-07 <br />14.6 <br />231 <br />1.2 <br />1.2 <br />This calculated final water level elevation is consistent with the slowing rate of water level rise over time <br />(Figure 22). At the September 2007 rate of water level rise (0.025 ft/day), up to 560 days could be <br />necessary for water level to reach the calculated static. Transient effects, such as infiltration during wet <br />cycles, could accelerate this rise. Conversely, the rate of rise may slow as the water level in the mine <br />approaches equilibrium, and it may take longer than April 2009 to reach this static level. <br />Downward seepage from the upper workings during particularly wet months could temporarily increase <br />water levels in the mine above this calculated static water level. When the mine was fully dewatered at its <br />maximum depth (from 1995 - 1999), the highest monthly infiltration from precipitation was estimated at <br />28 gpm during June, and 8.8 gpm on an annual average. However, now that the mine has substantially <br />filled, the cone of depression in the saturated rock mass has a smaller capture area (Section 0, Figure 20), <br />and infiltration through the upper workings in this area is believed to average less than 1.5 gpm. Flows <br />from individual seeps in the upper workings (measured in 1999) were generally less than 0.25 gpm during a <br />wet spring. Therefore, seasonal conditions are not expected to result in any significant transient head <br />buildup above the static water level. <br />4109B.071116 Whetstone Associates <br />
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