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GENERAL36100
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Last modified
8/24/2016 7:56:47 PM
Creation date
11/23/2007 8:36:15 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981012
IBM Index Class Name
General Documents
Doc Date
12/1/1988
Doc Name
PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN1
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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<br />Major point source mine inflows are related to 2 air shafts and 1 power <br />access bore hole. These sources account for approximately 8 gpm of the <br />total 123 gpm of inflow to the mine. These inflows represent dewatering <br />of perched overburden aquifers, which were intersected during boring <br />operations. <br />The coal seam was observed to be weeping at 3 different mine faces. <br />These weeping faces are contributing 5 gpm. These inflows represent the <br />dewatering of the coal seam aquifer. <br />One channel sandstone was encountered in the 1 P.S. workings which <br />contributes 3 gpm. This channel sand is probably draining ground water <br />from the coal seam. <br />Only one minor inflow was observed issuing from the mine floor. The rate <br />of inflow was estimated to be 1 gpm. This indicates that the New Elk <br />Mine is not significantly impacting the quantity of ground water in <br />underlying aquifers. <br />The major source of mine inflows measured in the New Elk Mine are from <br />weeping seals which close off old mined-out areas. The total quantity of <br />mine inflows from mined-out areas was measured to be 106 gpm. The total <br />area which contributes to these inflows is about 2800 acres. The <br />calculated inflow rate per unit area for the mined-out workings is <br />0.04 gpm/acre. The total inflow rates measured for the mined-out areas <br />would be the sum of the inflows from weeping coal faces, <br />subsidence-induced fractures, any unsealed drill holes in these areas, <br />and vertical leakage through overburden strata. The major source of mine <br />inflows in these areas is probably the weeping coal faces, resulting from <br />dewatering of the coal aquifer. Coal faces on the western edge of the <br />New Elk permit boundary are near the coal seam aquifer recharge area. <br />These workings could quickly capture any recharge waters and channelize <br />flows of water down the dip of the coal seam to the seals, where the <br />inflows were measured. Weeping coal faces were also observed as a major <br />source of inflow in the Golden Eagle. <br />After mining ceases, water will be depleted from the stream/alluvial <br />aquifer systems which will not be returned. This depletion will persist <br />as the mine workings fill with water. Once the mine workings have <br />filled, surface flows and alluvial ground water flows should closely <br />approximate the flows which existed before mining occurred. <br />The water discharged from the New Elk Mine is a sodium bicarbonate type <br />water with an average pH of 7.8 and an average total dissolved solids <br />content of 1138 mq/1 (See Exhibit 10 of renewal application). Under <br />Q7-10 low flow condi ions of 1.6 CFS in the Middle Purgatoire, an average <br />maximum discharge 1 0 gpm from the mi uld increase TDS value in <br />the river by 187 q/1 o a value of 391~m1/1. Based on average values of <br />Na, Ca, and Mg a le for river samp es Station PRS-1 and for mine <br />discharge at Station MONE, an SAR value of 16.7 was computed for the <br />combined waters. The TDS value of 391 mg/1 is less than the drinking <br />water standard of 500 mg/1; the SAR value of 16.7, however, is in excess <br />-23- <br />
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