ARCHIVED REPORTS_2010 - Laserfiche WebLink

Home Browse Search

• SOIL LOSS ANALYSES Preliminary soil loss analyses were prepared for the Vertical Expansion Final Grading Plan for North County Recycling Center and Sanitary Landfill (NCRCSL) using the U.S, Department of Agriculture's (USDA's) revised universal soil loss equation. The following summarizes the calculations. Annual soil loss, based on the USDA's Revised Universal Soil Loss Equation (RUSLE), can be assessed using: A = RKLSCP, where: LM A = Average annual soil loss in tons per acre per year R = Rainfall/runoff errosivity K = Soil erodibility LS = Hillslope length and steepness C = Cover -management P = Support practice For A, average annual soil loss, the U.S. Environmental Protection Agency (EPA) recommends that landfill final cover slopes be designed for an annual soil loss of 2 tons per acre per year or less. For R, rainfall/runoff errosivity index, values are provided for numerous cities, and site-specific values are available from the Natural Resources Conservation Service. The value for NCRCSL is 20 (Figure 2-3, Page 49, from Handbook 703 [USDA, 1997]). For K, soil erodibility factor, values for fine -textured soils high in clay have low values (about 0.05 to 0.15). Medium -textured soils, such as silt, have moderate values (about 0.25 to 0.45). Coarse-textured and sandy soils have low values (about 0.05 to 0.2). Organic materials influence these values somewhat. Based on assessed percentages of these soils present in the on-site soils anticipated to be excavated and used for the final cover, the attached nomograph, Figure 3-1, Page 92, from USDA, 1997, indicates the K value may range from 21 to 26. For LS, hillslope length and steepness, RUBLE has combined the effects of hillslope length (L) and gradient (S) factors. Values for NCRCSL for the predominantly 5 and 33 percent slopes with established vegetation and values for barren soil at interim construction areas are presented in Tables 4-1 and 4-3, respectively. (Attachments, Pages 122 and 124, from USDA, 1997). For C, cover -management factor, the assumed value is 1.0 for bare soil. This value can be 0.05 after placement of tracked straw mulch or after a cover of annual grasses is well established. g (Pages 5.22 and 5.23, Erosion and Sediment Control Handbook [Goldman, 1986]).