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Vantage to Pomona Heights Chapter 3
<br />230 kV Transmission Line Project FEIS Affected Environment
<br /> PAGE 3-294
<br />• Soils found on alluvial fans;
<br />• Soils found on uplands, hillslopes, ridgetops and benches; and
<br />• Soils found on terraces, floodplains, escarpments, and channeled scablands.
<br />The parent materials for alluvial fan soils primarily consist of loess and alluvium. These soils are well
<br />drained and their slopes range from 0 to 30 percent. The main land uses that overlay this soil group are
<br />military training and grazing. Limitations to the use of these soils include hard pan, salt accumulation, and
<br />the potential for water erosion.
<br />The parent materials for upland, hillslope, ridgetop, and bench soils primarily consist of loess, alluvium,
<br />residuum derived from basalt, colluvium derived from basalt, and loess derived from basalt. These soils
<br />are well drained to somewhat excessively drained and they are generally steeper than alluvial fan soils,
<br />with slopes ranging from 0 to 60 percent. The main uses that overlay this soil group are military training
<br />and grazing. Limitations to the use of these soils include slope, depth to bedrock, rock fragments, and the
<br />potential for water erosion.
<br />The parent materials for terrace, floodplain, escarpment, and Channeled Scabland soils primarily consist
<br />of alluvium, loess, eolian sands, lake sediments, and old alluvium. These soils are well drained to
<br />excessively drained and they are also generally steeper than alluvial fan soils, with slopes ranging from 0
<br />to 60 percent. The main uses that overlay this soil group are military training and grazing. Limitations to
<br />the use of these soils include salt accumulation, depth to bedrock and slope.
<br />Ground disturbance, changes in grade, and changes in soil stability from construction activities can
<br />significantly impact soils susceptible to wind and water erosion. The NRCS considers slope and soil
<br />properties such as cohesion, drainage, and organic content in determining soil erosion potential of soils.
<br />The NRCS data classifies water erosion potential (K factor without rock fragments) on a scale from 0.10
<br />to 0.64, with 0.10 having the lowest water erosion potential and 0.64 having the highest water erosion
<br />potential. In this analysis, water erosion potential from 0.10 to 0.28 is classified as low, water erosion
<br />potential from 0.29 to 0.46 is classified as moderate, and water erosion potential from 0.47 to 0.64 is
<br />classified as high. Water erosion potential for each route segment is discussed in Section 3.15.4. Water
<br />erosion potential for the Project area is presented on the Soil Erosion Potential by Water Map in
<br />Appendix A.
<br />The NRCS data provided classifies wind erosion potential (i.e., Wind Erodibility Index) on a scale from 0
<br />to 250, with 0 having the lowest wind erosion potential and 250 having the highest wind erosion potential.
<br />In this analysis, wind erosion potential from 0 to 50 is classified as low, wind erosion potential from 51 to
<br />100 is classified as moderate, and wind erosion potential from 101 to 250 is classified as high. Wind
<br />erosion potential for each route segment is discussed in Section 3.15.4. Wind erosion potential for the
<br />Project area is presented on the Soil Erosion Potential by Wind Map in Appendix A.
<br />Soils with the ability to recover from degradation will have the best potential for revegetation and
<br />restoration once a construction project has been completed. Soil resilience is dependent upon adequate
<br />stores of organic matter, good soil structure, low salt and sodium levels, adequate nutrient levels,
<br />microbial biomass and diversity, adequate precipitation for recovery, and other soil properties. The NRCS
<br />provides soil restoration potential ratings for each soil type, from low to high restoration potential. Soil
<br />restoration potential for each route segment is discussed in Section 3.15.4. Soil restoration potential for
<br />the Project area is shown on both the Soil Erosion Potential by Water and Soil Erosion Potential by Wind
<br />Maps in Appendix A.
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