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Electrical Conductivity (EC)-San Miguel Area, Colorado, Parts of Dolores, Montrose, and San Miguel Counties ' J-Bird Mine Site Electrical Conductivity (EC) Electrical Conductivity (EC}- Summary by Map Unit - San Miguel Area, Colorado, Parts of Dolores, Montrose, and San Miguel Counties Map unit symbol Map unit name Rating (millimhos per centimeter) Acres in AOI Percent of AOI 108 Wrayha stony clay loam, 1.0 7.3 100.0% 3 to 40 percent slopes Totals for Area of Interest 7.3 100.0% Description Electrical conductivity (EC) is the electrolytic conductivity of an extract from saturated soil paste, expressed as millimhos per centimeter at 25 degrees C. Electrical conductivity is a measure of the concentration of water-soluble salts in soils. It is used to indicate saline soils. High concentrations of neutral salts, such as sodium chloride and sodium sulfate, may interfere with the absorption of water by plants because the osmotic pressure in the soil solution is nearly as high as or higher than that in the plant cells. For each soil layer, this attribute is actually recorded as three separate values in the database. A low value and a high value indicate the range of this attribute for the soil component. A "representative" value indicates the expected value of this attribute for the component. For this soil property, only the representative value is used. Rating Options Units of Measure: millimhos per centimeter Aggregation Method. Dominant Component Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole. A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not. For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods. USDA Natural Resources Web Soil Survey 2.1 12/24/2008 Niiiiiiii Conservation Service National Cooperative Soil Survey Page 3 of 4