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4-85 <br />• <br /> <br /> <br />Toxic materials such as boron get into the food chain and <br />are toxic to animals that eat the vegetation (USDA, 1978). <br />All the soils of the site are rated good for boron; no <br />values exceed 1.0 ppm. <br />Excessively high or low pH causes problems in establishing <br />vegetation and as a result influence erosion and stability <br />of the surface (USDA, 1978). Most soils have good or fair <br />pH values throughout. The Rivra variant has strongly alkaline <br />pH values below 14 inches. <br />The available water capacity also is important in establishing <br />vegetation. Soils with low available water capacity may <br />require irrigation for extablishment of vegetation (USDA, <br />1978). AWHC was estimated based on field texture, saturation <br />percentage, and percent coarse fragments (USDA, 1974). Most <br />of the soils are rated good throughout for AWHC. The disturbed <br />land material is rated good or fair. Some subsoils have <br />fair ratings. The Alluvial lands soil is rated fair through- <br />out. The Rivra variant is droughty below 14 inches and is <br />rated poor. <br />The stability of the soil depends upon its erodibility by <br />water and wind and its strength. Water erodibility is indi- <br />cated by the K factor; wind erodibility is rated according <br />to the wind erodibility group. K values for soils of <br />the permit area are calculated from soil erodibility nomograph <br />