Laserfiche WebLink
Custom Soil Resource Report <br />Soil Physical Properties <br />This folder contains a collection of tabular reports that present soil physical properties. <br />The reports (tables) include all selected map units and components for each map unit. <br />Soil physical properties are measured or inferred from direct observations in the field <br />or laboratory. Examples of soil physical properties include percent clay, organic <br />matter, saturated hydraulic conductivity, available water capacity, and bulk density. <br />Engineering Properties (Yuma County - Moser Pit) <br />This table gives the engineering classifications and the range of engineering <br />properties for the layers of each soil in the survey area. <br />Depth to the upper and lower boundaries of each layer is indicated. <br />Texture is given in the standard terms used by the U.S. Department of Agriculture. <br />These terms are defined according to percentages of sand, silt, and clay in the fraction <br />of the soil that is less than 2 millimeters in diameter. "Loam," for example, is soil that <br />is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand. If the <br />content of particles coarser than sand is 15 percent or more, an appropriate modifier <br />is added, for example, "gravelly." <br />Classification of the soils is determined according to the Unified soil classification <br />system (ASTM, 2005) and the system adopted by the American Association of State <br />Highway and Transportation Officials (AASHTO, 2004). <br />The Unified system classifies soils according to properties that affect their use as <br />construction material. Soils are classified according to particle-size distribution of the <br />fraction less than 3 inches in diameter and according to plasticity index, liquid limit, <br />and organic matter content. Sandy and gravelly soils are identified as GW, GP, GM, <br />GC, SW, SP, SM, and SC; silty and clayey soils as ML, CL, OL, MH, CH, and OH; <br />and highly organic soils as PT. Soils exhibiting engineering properties of two groups <br />can have a dual classification, for example, CL-ML. <br />The AASHTO system classifies soils according to those properties that affect roadway <br />construction and maintenance. In this system, the fraction of a mineral soil that is less <br />than 3 inches in diameter is classified in one of seven groups from A-1 through A-7 <br />on the basis of particle-size distribution, liquid limit, and plasticity index. Soils in group <br />A-1 are coarse grained and low in content of fines (silt and clay). At the other extreme, <br />soils in group A-7 are fine grained. Highly organic soils are classified in group A-8 on <br />the basis of visual inspection. <br />If laboratory data are available, the A-1, A-2, and A-7 groups are further classified as <br />A-1-a, A-1-b, A-24, A-2-5, A-2-6, A-2-7, A-7-5, or A-7-6. As an additional refinement, <br />the suitability of a soil as subgrade material can be indicated by a group index number. <br />Group index numbers range from 0 for the best subgrade material to 20 or higher for <br />the poorest. <br />Rock fragments larger than 10 inches in diameter and 3 to 10 inches in diameter are <br />indicated as a percentage of the total soil on a dry-weight basis. The percentages are <br />estimates determined mainly by converting volume percentage in the field to weight <br />percentage. <br />20