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GENERAL47047
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Last modified
8/24/2016 8:21:44 PM
Creation date
11/23/2007 3:05:36 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1984065
IBM Index Class Name
General Documents
Doc Date
1/1/1985
Doc Name
PROPOSED DECISION and FINDINGS OF COMPLIANCE
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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-25- <br />DESCRIPTION AND HYDROLOGIC IMPACTS <br />OF MINING AT THE EASTSIDE MINE <br />The Eastside Mine is located in Garfield County, approximately 3.5 miles north <br />of the town of Silt. The proposed mine will affect 167 acres of non-federal <br />land during the life-of-mine, with 54 acres being affected during the 5-year <br />permit term. This underground mining operation will result in 12 acres of <br />surface disturbance with the surface facilities and roads. <br />The mine is located adjacent to the perennial-flowing Harvey Gap Drainage. <br />The Harvey Gap Drainage is a deeply incised north-south trending stream <br />valley, which cuts through the resistant sandstone of the Grand Hogback. The <br />nature of this drainage has been altered by construction of canals and a <br />reservoir for irrigation. The Grass Valley Reservoir is located 600 feet <br />upstream of the minesite on Harvey Gap Creek. The water in this reservoir is <br />impounded during high flow seasons from the headwaters of Harvey Gap and from <br />water diverted from the headwaters of East Rifle Creek through the Grass <br />Valley Canal. The impounded water is released from April 15 to October 15 to <br />irrigate almost 6000 acres of land in the Silt and Rifle area. <br />The Eastside Mine will be developed in coals of the Iles and William Fork <br />Formations of the Mesa Verde Group. This 5-year permit is for mining in the <br />E-Seam of the Iles Formation. This seam is approximately 20 feet thick and <br />dips 590 on the average to the south. Coal will be mined by continuous <br />miner or conventional section with approximately 200,000 tons per year <br />projected as maximum production. The life-of-mine plan includes recovery of <br />the Wheeler seams of the Williams Fork Formation, which are separated from the <br />E-Seam by 200 feet of strata characterized as predominately marine shales. <br />The maximum production for the life-of-mine plan is projected at 1,000,000 <br />tons per year. <br />The probable hydrologic consequences of mining at the Eastside Mine have been <br />previously detailed in the Proposed Decision and Findings of Compliance for <br />the Eastside Mine issued December 14, 1984, and on file at the Division. A <br />summary of the projected impacts as detailed in this study follow. <br />Three domestic wells were found to have been completed in the shallow bedrock <br />aquifers of the area of the Eastside Mine. It was projected that mining at <br />the Eastside Mine would not affect these wells because of the extreme dip of <br />bedrock in the area and because of separation of the producing aquifers of <br />these wells from the mined seams at the Eastside Mine by 200 feet or more of <br />shale units. <br />A worst case projected impact to surface water quality was made based upon the <br />following scenarios. The low flow surface water condition was used to predict <br />worst case. These low flow condition occur during periods of non-irrigation <br />from October 15 to April 15, when the Grass Valley Reservoir outlets are <br />closed to store water for the irrigation season. Base flow occurs due to <br />seepage through the reservoir embankment. Base flow is 0.5 cfs at an average <br />TDS of 755 mg/l. <br />
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