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2010-01-25_PERMIT FILE - C1981044A (4)
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2010-01-25_PERMIT FILE - C1981044A (4)
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Last modified
8/24/2016 3:58:55 PM
Creation date
2/23/2010 10:58:25 AM
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Template:
DRMS Permit Index
Permit No
C1981044A
IBM Index Class Name
Permit File
Doc Date
1/25/2010
Section_Exhibit Name
2.05 Operation and Reclamation Plans
Media Type
D
Archive
Yes
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uality Effects of Post-Minine seeoaee on Williams Fork Alluvial Water <br />After the mines refill, water may move out of the coal subcrop into the William Fork Alluvium. While there is no <br />indication that the flooded mine workings will be under high heads in the subcrap areas, significant heads might <br />occur. Recent excavation of the E Seam area near the SA portal indicates that this area of the mine is not naturally <br />under any hydrostatic head. Therefore, it is expected that the maximum possible head on the No. 5 and No. 6 <br />Mines in the subcrop areas will be approximately 100 feet above ground surface. <br />Possible seepage rates from the seams into the subcrop area were calculated assuming that the water flowed updip <br />from the nearest mine working in each mine to the appropriate subcrop area. The nearest workings for the No. 5 Mine <br />area are 800 feet from the subcrop and for the No. 6 Mine area 1,200 feet away. Using Darcy's Law, a permeability <br />of 2.5 feet per day, aquifer thickness of 12 feet and subcrop width of 1,000 feet produced seepage rates for the E and F <br />Seam subcrops of 19.5 gpm (0.043 cfs) and 13.0 gpm (0.044 cfs), respectively. <br />The potential seepage from the coal seams would affect the water quality in the alluvium downstream of the subcrop <br />area. There is approximately 5.5 million square feet of alluvium in that area. Using a recharge rate of three-(3) inches <br />per year, approximately 0.044 cfs of fresh water (assumed to be the same quality as the existing alluvial water) is <br />added on an annual basis. This value is based upon a lysimeter study performed at the Seneca Mine (Bob Williams, <br />USGS, pers. Communication). In addition, the William Fork River water recharges the alluvium in the spring. There <br />is an average water level rise in the alluvium each year of approximately two (2) feet. Assuming a specific yield of 10 <br />percent, this converts to approximately 0,035 cfs of water on an annualized basis. <br />The net impact of seepages can be estimated using [he mass balance technique, as shown in this permit. The <br />estimated net effect will be an increase in the SAR from 3.6 to 9.4. This is a worstcase calculation and will only <br />occur after the mine is refilled. Since the bottom areas in the vicinity of the mine that are used for agricultural <br />purposed are flood irrigated, the fields would be irrigated with low SAR water. <br />Since the alluvial water is naturally higher in metals and dissolved solids than the mine discharge water, no other <br />impacts on the water quality are expected. Development mining beneath Big Bottom is not anticipated to impact <br />the AVF as there is not subsidence predicted and water inflow discharge will be handled utilizing the existing <br />system and outfalls. <br />Post Minine Discharee - No. 9 Mine <br />The "P" seam was mined from the No. 9 Mine from March 1978 to August 1981. The mine was driven northward <br />in a downdip direction. The approximate elevation of the bottom of the No. 9 mine portal was 6,305 ft., and <br />present ground surface is approximately 6,350 ft. No significant full-extraction mining was performed in the mine. <br />The water level in the Twentymile Sandstone is estimated to be approximately 6,260 ft. at the point which has the <br />highest piezometric level in the Twentymile Sandstone anywhere it underlies the No. 9 Mine. This estimation is <br />based upon the water level contour map for water levels measured in November 1995 (1995 Annual Hydrology <br />Report, Permit C-81-044, Figure 12). The Twentymile Sandstone underlies the "P" seam by approximately 350 ft. <br />The historic water levels in the Twentymile Sandstone have apparently not been effected by the mining in [he area <br />as they have been constant since 1981 (ibid., Figure 10) indicating that there is not a good connection between the <br />aquifer and the mine. Also, the mine was driven in adown-gradient direction so all of the workings are in lower <br />head areas than the portal. <br />The maximum piezometric level of the White Sandstone is estimated to be approximately 6,300 feet where it overlies <br />a location in the No. 9 Mine where measurable flow was encountered. This is based on the mine inflow study (Eagle <br />No. 9 Mine Inflow Study, Map N-11a, 5/8/83) and the December 1985 water level measurements (1985 Annual <br />Hydrology Report, Permit C-81-044, Figure 17). In addition, the maximum projected piezometric level of the White <br />Sandstone where it overlies any portion of No. 9 Mine is less than 6,320 feet, however, this is at the White <br />Permit Renewal No 4 2.05-46 Revised 3/5/03 <br />
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