2016-01-13_REVISION - C1981014

• Permit No: C1981014
• IBM Index Class Name: Revision
• Doc Date: 1/13/2016
• Doc Name: Adequacy Response
• From: Kent Gorham
• To: DRMS
• Type & Sequence: SL3
• Email Name: RDZ
• Email Name: JRS
• Media Type: D
• Archive: No

Sediment Demonstration — Mine Site - revised 1/13/2016 w/ addendum Page 2
Section 3.03.1
R= 27 x (1.2)2'2 = 24.7
Soil Erodibility_(!!,:,)
K factor in RUSLE represents the soil erodibility and is an integration of the impacts of rainfall and
runoff on soil loss for a given soil. No adjustment for K in either the pre -mine condition or the
post -mine condition for the effects of rock fragments is warranted, as a detailed analysis of soil
texture and rock percentage by weight would be necessary. For this analysis, a K value was selected
based on the representative soil at the mine site as presented in the permit application. This value is
also appropriate for glacial till material for loam soils.
K = 0.32 (Soil Type-Kim-Cascajo complex)
Length Slope Factor (LS)
The LS factor accounts for the effects of topography on soil erosion and are determined by the
dimensionless factors L (hillslope length) and S (hillslope-gradient), which together account for both
rill and interrill erosion impacts. The equation for determining the LS factor is:
For slopes < 9%
LS = (L/72.6)' x (10.8 x sin(S) + 0.03)
For slopes > 9%
LS=(L/72.6)m x (16.8 x sin(S) — 0.5)
Where: L = Slope length
S = Slope angle
m = 0.3 for slopes< 3%
0.4 for slopes = 4%
0.5 for slopes > 5% and < 10%
0.6 for slopes> 10%
The slope length and slope angles for the non -mined, adjacent land condition and the reclaimed
condition were determined from the Map 33. The LS factor for each slope length and angle were
determined and then averaged.
Length ft
Sloe %
LS Factor
220
11%
2.60
270
3%
.52
400
13%
4.64
160
3%
.45
The average LS is 2.05.
Cover Management Factor (C)
The cover management factor represents the effects of cover above the ground, ground cover (litter),
root mass, incorporated residue, surface roughness, and soil moisture on soil erosion. No
adjustments were made for root mass, incorporated residue, surface roughness, or soil moisture. The
C factors for the non -mined and reclaimed conditions were determined using information from the