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<br />. <br /> <br />Sustaining plant and artimallife. Soil is the foundation for the diversity and productivity of life. <br /> <br />. <br /> <br />Filtering potential pollutants. Minerals and microbes in soil are responsible for filtering, <br />buffering, degrading, immobilizing, and detoxifying organic and inorganic materials, including <br />industrial and municipal by-products and atmospheric deposits. <br /> <br />. <br /> <br />Cycling nutrients. Soil stores, transforms, and cycles carbon, nitrogen, phosphorus, and many <br />other nutrients. <br /> <br />. <br /> <br />Supporting structures. Stable soil provides support for buildings and for archaeological <br />treasures associated with human habitation. <br /> <br />Farmland Soil <br />Congress established specific technical criteria to identify prime farmland soil. In general, the criteria <br />reflect adequate natural moisture content; specific soil temperature range; a pH (measure of acidity or <br />alkalinity) between 4.5 and 8.4 in the rooting zone; low susceptibility to flooding; low risk to wind and <br />water erosion; minimum permeability rates; and low rock fragment content. The United States <br />Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) determines <br />whether soil meets the physical and chemical criteria for Prime Farmland or Farmland of Statewide <br />Importance. Farmlands are further discussed under Agriculture and Grazing, below. <br /> <br />Soil Types for Groundwater Recharge <br />The majority of groundwater recharge derives from stream recharge through gravelly streambeds <br />across the valley floor. Zone 7 recharges groundwater by releasing water into streambeds with high <br />percolation rates and in Lake I of the Chain of Lake with its gravelly western shore. <br /> <br />Soil Supports Structures <br />Buildings need stable soils for support. During seismic activity, some soil types are not as capable of <br />supporting structures as other soil types. <br /> <br />Ground motions during earthquakes are related mainly to local soil conditions. Local soil conditions <br /> <br /> <br />and subsurface geologic characteristics are two of the six major components - including magnitude <br /> <br />and distance - related to structural damage from an earthquake. In addition, where loose granular <br /> <br />sands are present, soils tend to compact resulting in soil liquefaction and settlement. 10 <br /> <br />Landslides and soil erosion are also related to surface and subsurface soil characteristics. Soil type is <br /> <br />just one of numerous factors that contribute to landslides including slope steepness, aspect,1I rainfall, <br /> <br />1U Seed. H. Bolton, Departmenr of Civil Engineering, University of California. Berkdey and I.M. Idriss, Woodward-Clyde <br />Consultants, Ground Motions and Soil L..iqueftction During Earthquakes, Earthquake Engineering Instin.lte. Berkeley, <br />California, 1982. <br /> <br />II Aspect of a slope is exposure to a particular direction. <br /> <br />Con OS Element, CC 082906, clean <br /> <br />VIl-9 <br /> <br />Ciry Council 8/29/2006 <br />