DEQ/OSU Soil Classification Manual
This 40 page bulletin provides information for identifying key soil characteristics
for design and sizing of individual and small public on-site sewage treatment systems,
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The soil is both an anaerobic and aerobic biological community of organisms that decompose organic debris into simple organic material and eventually to humus, CO2 and H2 O. Depending on the flow of water through a soil, the soil can be thought of as either 1) aerobic, 2) anaerobic, or 3) various degree of each. Since soil organisms decompose organic material (mostly depending on concentration) the soil is considered as a dynamic living filter. Inorganic materials are also absorbed and modified by biogeochemical and geochemical soil processes. Toxic elements are sequestrated within recalcitrant humus complexes. Soil as a basis for land-use management and planning Soils are a complex layered system. Soils are classified and identified by the number and characteristics of these layers (also called horizons) (Figure 2). Most people think of the soil as only the surface layer (since other layers require excavation to observe). However individuals who observe road cuts and view excavations realize that soils are a layered system. The characteristics of soil layers and the unique sequence of layers termed a soil type is considered a basic natural resource. The exchange of energy and mass between soil layers is the major determinant of soil potential. Thus, soil as a natural resource is used directly for land-use management and planning.