2010-12-08_PERMIT FILE - C1981008A ‎(9)‎

• Permit No: C1981008A
• IBM Index Class Name: Permit File
• Doc Date: 12/8/2010
• Doc Name: Protection of the Hydrologic Balance
• Section_Exhibit Name: Section 2.05.6‎(3)‎ Protection of the Hydrologic Balance
• Media Type: D
• Archive: Yes

The total affected area is roughly 768 acres. The volume of the reclaim spoil to be recharged below
the 5580 spoil spring elevation equals 2,778 ac.ft. as determined from D.T.M. modeling of the spoil
area and the pit bottom. Spoil porosity of 15% is determined for the overburden. This yields a pore
volume of (0.15)(2778 ac.ft.) = 416 ac.ft.
Worst Case Discharge
With a pore volume of 416 ac.ft. and assuming a total recharge of 16" per year from all sources
over the 768 acres of spoil, annual recharge equals (16/12)(768) = 1024 ac.ft. per year after full
irrigation in 2013. It should be noted that a portion of the reclaimed area will be restored to dry land
pasture and will therefore will not contribute irrigation recharge, however, other areas will have a
greater recharge than 16" total, therefore, the average of 16" over the reclaimed area is
reasonable. From the year 2003 to 2013, the expected recharge should only be 10% of this
amount, since irrigation will not be used on the majority of the area and the fresh - placed spoil will
be relatively dry.
Spoil spring discharge = (Spoil Spring Recharge) — (Seepage into tow Wall)
Seepage into Low Wall = (10 ft. thick permeable sandstone bed in lowwall)(8500 ft. wide seepage
area)(0.10 ft. per day seepage velocity)(1 /43,560 cu. ft. to ac. ft.)(365 days per year) = 72 ac.ft.
Spoil Spring Discharge = (1024 ac.ft. recharge) — (72 ac.ft. seepage into low wall) = 952 ac.ft. In
the year 2000, the NPDES 001 discharge at the New Horizon #1 Mine showed an average flow of
271,000 gallons per day or 320 acre -feet per year. The NPDES 001 discharge is for practical
purposes composed entirely of spoil water. The New Horizon #2 spoil area is much bigger,
therefore the predicted flow of 1024 acre -feet per year for this area is a reasonable maximum flow
when compared to what is being observed at the #1 Mine.
Worst case time to spring discharge = (Pore Volume) /(Recharge Volume)
= (416 ac.ft.) / (952 ac.ft.) = 0.4 years to actual spring flow after full irrigation is resumed on the
reclaimed land in 2013. This is in the worst case scenario with the maximum amount of spoil
exposed to irrigation water.
Revised August 2010 (PR06) 2.05.6(3) -23