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2010-10-01_REVISION - C1981008 (11)
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2010-10-01_REVISION - C1981008 (11)
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Last modified
8/24/2016 4:25:04 PM
Creation date
10/5/2010 7:24:05 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981008
IBM Index Class Name
REVISION
Doc Date
10/1/2010
Doc Name
Proposed Decision & Findings of Compliance
From
DRMS
To
Western Fuels-Colorado, LLC
Type & Sequence
PR6
Email Name
MLT
SB1
Media Type
D
Archive
No
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= (416 ac.ft.) / (952 ac.ft.) = 0.4 years to actual spring flow after full irrigation is <br />resumed on the reclaimed land in 2013. This is in the worst case scenario with the <br />maximum amount of spoil exposed to irrigation water. <br />Realistic Discharge <br />Roughly 422 acres of irrigated land will be constructed in reclamation of the New <br />Horizon 92 mine. An analysis of.these areas separately will provide a more <br />realistic calculation of the potential spoil discharge. <br />With a pore volume of 416 ac.ft. and assuming a total recharge of 16" per year <br />from all sources over the 422 acres of spoil, annual recharge equals (16/12)(422) <br />= 563 ac.ft. per year after full irrigation in 2013. It should be noted that a portion <br />of the reclaimed area will be restored to dry land pasture and will therefore will <br />not contribute irrigation recharge, however, other areas will have a greater <br />recharge than 16" total, therefore, the average of 16" over the reclaimed area is <br />reasonable. From the year 2003 to 2013, the expected recharge should only be <br />10% of this amount, since irrigation will not be used on the majority of the area <br />and the fresh-placed spoil will be relatively dry. <br />Spoil spring discharge = (Spoil Spring Recharge) - (Seepage into Low Wall) <br />Seepage into Low Wall = (10 ft. thick permeable sandstone bed in low wall) <br />(8500 ft. wide seepage area)(0.10 ft. per day seepage velocity)(1/43,560 cu. ft. to <br />ac. ft.)(365 days per year) = 72 ac.ft. <br />Spoil Spring Discharge = (563 ac.ft. recharge) - (72 ac.ft. seepage into low wall) <br />= 490 ac.ft. In the year 2000, the NPDES 001 discharge at the New Horizon #1 <br />Mine showed an average flow of 271,000 gallons per day or 320 acre-feet per <br />year. The NPDES 001 discharge is for practical purposes composed entirely of <br />spoil water. The New Horizon #2 irrigated spoil area is bigger, therefore the <br />predicted flow of 490 acre-feet per year for this area is a reasonable maximum <br />flow when compared to what is being observed at the #1 Mine. <br />Realistic case time to spring discharge = (Pore Volume)/(Recharge Volume) <br />= (416 ac.ft.) / (490 ac.ft.) = 0.8 years to actual spring flow after full irrigation is <br />resumed on the reclaimed land in 2013. This is the most realistic case of when the <br />spoil spring will begin to flow. <br />In both the worst case and the more realistic discharge scenario, it may begin to <br />discharge slightly sooner since irrigation may begin on the eastern portion of the <br />reclaimed area sooner than 2013, thus contributing some discharge. Also, <br />recharge from precipitation has not been factored in the spoil prior to 2013. <br />Assuming that the permanent pipe is installed in the year 2003 and has a life of 30 <br />years, the pipe would be replaced by the ditch in the year 2033. At this time <br />recharge would increase slightly since water from the ditch would provide <br />34
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