_PERMIT FILE - C1981008A ‎(13)‎

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Name: Sedimentation Pond 004
• Section_Exhibit Name: Tab 13 Attachment D
• Media Type: D
• Archive: Yes

In some instances, the mining will cause the drainage area to change
during the life of the sediment structure. When the pit moves into the
watershed, runoff is intercepted by the pit and diverted away from the
structure. In these cases, ' a conservative procedure was used; the
structure was analyzed for the largest anticipated drainage area that
will contribute runoff to the structure. This condition usually occurs
at the start of mining and again during the reclamation period.
Following is a summary of the SEDIMOT II input values used in the Design
Report and the As-Built Report (see the Design Report for the derivation
of the input values) :
10-Year, 24-Hour = 1.60 inches
25-Year, 24-Hour = 1.80 inches
100-Year, 24-Hour = 2.40 inches
SCS Type II Storm
CN = 81
k = 0.25
Disturbed Hydrograph (No. 1)
tc = 0.064 hr.
(1) MUSLE = 0.035 ac-ft. or 65.46 tons
Specific Gravity = 2.5
Submerged Bulk S.G. = 1.25
LS = 4.10
CP = 1.0
The particle size distribution for this sediment pond was taken from
Simons, Li and Associates (Design of Sediment Control Measures for Small
Areas in Surface Coal Mining) . This distribution is representative of a
sandy loam soil similar to those described in Tab 9 of the current Nucla
Mine Plan.
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