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Sediment Demonstration — Mine Site - revised 1/22/2016 w/ 1/8/2016 addendum Page 2 <br />Section 3.03.1 <br />The following is the methodology and assumptions used in this analysis to demonstrate that the <br />reclaimed area does not contribute excess suspended solids to streamflow as compared to a similar <br />non -mined area. <br />METHODOLOGY AND ASSUMPTIONS <br />The sediment yield for both pre and post mine conditions were determined using the Revised <br />Universal Soil Loss Equation (RUSLE): <br />A=RKLSCP <br />Where: A= Average annual soil loss in tons/acre/yr <br />R= Rainfall factor R <br />K= soil erodibility <br />LS= Length/slope factor <br />C= Cover management <br />P= Support practice <br />Rainfall Energy Factor (R) <br />The R factor is a representation of rainfall energy at a particular location. An average annual R factor <br />is needed when computing long-term erosion. The R factor used in this sediment calculation is the <br />same as the R factor used in the approved Southfield permit application, which was determined using <br />the following equation: <br />Ra,r,war = 27P2,62 2 for a Type II storm <br />P2,6 = 2 year, 6 hour precipitation in inches <br />= 1.2 inches <br />R=27x(1.2)'`'=24.7 <br />Soil Erodibilit (K) <br />K factor in RUSLE represents the soil erodibility and is an integration of the impacts of rainfall and <br />runoff on soil loss for a given soil. No adjustment for K in either the pre -mine condition or the <br />post -mine condition for the effects of rock fragments is warranted, as a detailed analysis of soil <br />texture and rock percentage by weight would be necessary. For this analysis, a K value was selected <br />based on the representative soil at the mine site as presented in the permit application. This value i5 <br />also appropriate for glacial till material for loam soils. <br />K = 0.32 (Soil Type-Kim-Cascalo complex) <br />Length Slope Factor (LS) <br />The LS factor accounts for the effects of topography on soil erosion and are determined by the <br />dimensionless factors L (hillslope length) and S (hillslope-gradient), which together account for both <br />rill and interrill erosion impacts. The equation for determining the LS factor is: <br />