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GENERAL35475
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Last modified
8/24/2016 7:56:26 PM
Creation date
11/23/2007 8:20:54 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981021
IBM Index Class Name
General Documents
Doc Date
3/1/1983
Doc Name
PROPOSED DECISION AND FINDINGS OF COMPLIANCE
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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-21- <br />Probable Hvdrolooic Consequences of Mining on Surface Water <br />The Bourg Kline will directly impacts01 acres (0.47 square miles) and will <br />indirectly impact 1,267 acres (1.98 square miles) of Mann Draw. This would <br />result in; 1) directly impacting 14% of the flow in Hann Draw and 0.00014% of <br />the flow in the Canadian River near Brownlee, Colorado; and 2) indirectly <br />impacting the water quality of 0.00099% of the flow in the Canadian River. <br />Under the proposed mining plan, 4.23 acre-feet of water will be lost through <br />pond detention. This amounts to 6% of the annual yield in Mann Draw at the <br />mine site and 4% of the total Mann Draw watershed yield. This effect will <br />occur for the life-of-mine until the sediment ponds are removed. However, <br />this impact will be alleviated somewhat by an increase in total runoff from <br />the mine. The prediction of increased runoff is consistent with what other <br />mines in this area have predicted (see Kerr Coal application - Marr Strip), <br />but the amount of increase and its duration are not quantifiable. <br />The effects of mining in the Coalmont Formation on water quantity in Mann Draw <br />should not be significant. The applicant states that, althougn the Coalmont <br />may have some hydraulic connection with the alluvium, most of the recharge to <br />the alluvium occurs throuyh surface runoff recharge. <br />Considering the above, it appears that the operation will have an <br />insignificant impact on the quantity of water in fdann Draw and the effects <br />will be short-term. <br />Probable Hydrologic Consequences of hlining on Ground Water <br />During mining, the pit of the Bourg Mine may lower the ground water levels <br />within the Sudduth coal seam, the overburden, and the underburden. A <br />conservative estimate of the stored water in the Coalmont Formation which will <br />be affected by mining is 2 acre-feet (using a specific yield of 10%). The <br />water table map (Plate 1) indicates that lowering the water levels in the <br />Coalmont Formation will not affect the quantity of ground water in the <br />alluviwn of Mann Uraw, since this formation does not discharge ground water to <br />the alluvium and is not recharged by the alluvium. <br />The Bourg Mine will affect 0.5% of the total recharge area of the Coalmont <br />Formation in the region (16U acres of 40,000 acres total). The quantity of <br />water recharing the Sudduth coal seam is expected to decrease and the ground <br />water quality within this seam is expected to be degraded following mining. <br />Infiltration studies within reclaimed areas of adjacent mines have shown that <br />the infiltration rate will be decreased. This decreased infiltration will <br />reduce the recharge to the spoil aquifer and the strata affected by mining. <br />The ground water quality within the spoil aquifer and disturbed strata will <br />become degraded through the leaching of soluble salts from broken-up <br />overburden materials. There will oe an increase in total dissolved solids <br />(TUS) and a shift from a sodium bicarbonate to a sodium sulfate type of <br />water. The decreased recharge of the reclaimed area will not affect water use <br />on- or off-site since no wells are completed in, and no springs emanate from, <br />these affected strata in the permit and adjacent areas. The degraded spoil <br />water quality will not affect water use or surface water quality within the <br />
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