2010-12-08_PERMIT FILE - C1981008A ‎(2)‎

• Permit No: C1981008A
• IBM Index Class Name: Permit File
• Doc Date: 12/8/2010
• Doc Name: Pond 011 Engineering and Hydrologic Design
• Section_Exhibit Name: Section 2.05.3‎(3)‎ Attachment 2.05.3‎(3)‎-22
• Media Type: D
• Archive: Yes

Post Mine Drainage
• 166.1 acre drainage area
• During mining, the maximum pit pumping rate will be 600 gpm from the active mine pit
pump system into Pond 11.
• Pit pump water will need a retention time of approximate 1 day so the PH of the water
will stabilize and pass the WET toxicity test.
• Therefore, add: [(600gpm x 60mph x 24hpd x 1 days)/7.5 gal per cu- ft] /43560sq -ft per
ac =2.6 ac -ft
Runoff Curve Number and Runoff (SurvCAD)
Project: Pond 011
Location: New Horizon #2
Developed
By: B Langenfeld Date: 09/01/09
Checked: Date:
1. Runoff Curve Number (CN)
Cover description CN
Mined Land, Disturbed (Poor) 87
Herbaceous mixture (Good) 74
Pasture Grassland Range (Good) 80
CN (weighted): 78.9
Total Area: 166.074 Acre
2. Runoff
Return Period:
10 -Year
Rainfall, P:
2.00 in
Runoff, Q:
0.5174 in
Runoff Volume:
7.1608 Acre -Ft
Soil Type Area(Acre)
C 14.700
C 48.430
D 102.944
The pond volume below the emergency spillway will be comprised of three design needs:
1) 10 year storm inflow of 7.2 acre -ft, as described above
2) 3 year sediment delivery of 0.1 acre -ft, as based on the calculations shown below.
3) 2.6 acre -ft of pit pump water.
Revised February 2010 (PR06) Attachment 2.05.3(3) -22 -7