1. a) The equation for calculating soil loss due to erosion is as follows:

   

   Where:

   ai	=	long-term average soils loss for the ith day;
   riri	=	erosivity factor;
   ki	=	soil erodibility factor;
   li	=	soil length factor;
   S	=	soil steepness factor;
   ci	=	cover management factor; and
   pi	=	supporting practices factor,
   all on the ith day, except for slop steepness factor (S).

2. b) The average annual soil loss is computed as follows:

   

   Where:

   A	=	average annual soil loss.
   365m	=	number of days per year.
   m	=	number of years in the analysis period. The value for m is 1 for continuous vegetation on range, pasture, and other lands, where conditions are the same year after year, while m = the number of years of cropping management rotations on cropland and the number of years following a disturbance such as construction, logging, grading of a reclaimed surface mine, or closing of a land fill where conditions are changing year to year.

   BOARD NOTE: Soil loss may be calculated using Revised Universal Soil Loss Equation 2 (RUSLE2) software program available at http://fargo.nserl.purdue.edu/rusle2_dataweb/

   RUSLE2_Index.htm. Additional information may be obtained from the United States Department of Agriculture, Agricultural Research Services, 1400 Independence Avenue, S.W., Washington DC 20250, (202) 720-3656.

(Source: Amended at 38 Ill. Reg. 17661, effective August 11, 2014)