Pulverized silty loam has a smooth flour- like feel. The moist cast can be handled freely and there is a slight tendency to form ribbons. The rubbed surface of the ribbon may appear rippled. Silty clay loam aggregates are hard to very hard. When moist, this soil will form very firm casts and will ribbon. It may have a greasy feeling and be somewhat sticky. Silty clay will form a long ribbon when moist. SELECTION OF SITE AND SYSTEM Figure 3.5 Ribbon of moist loam. Clay aggregates are hard and clods are difficult to crush. When pulverized, clay may still have a gritty texture due to the many small aggregates that persist. Ribbons of moist clay can be stretched (Fig- ure 3.6) and have a very smooth satiny feeling. Clay has a sticky feeling when wet. Field estimates of soil texture are subject to error. If the soil you are working with defies all attempts to classify it, you may wish to take samples to an expert. Experts can sometimes be identified through the "Engineers-Geotechnical/Soils" entry in the phone book yellow pages, and you could contact the U.S. Soil Conserva- tion Service or the County Extension Service for help. The "experts" will pulverize your samples and run them through screens with different mesh sizes to sort out the soil particle size distribution according to percentages of sand, silt, and clay. The texture triangle (Figure 3.7) shows the various percentages of sand, silt, and clay that comprise these various soil types. For exam- ple, soil with 50% clay, 40% sand, and 10% silt is classified as clay, whereas 20% clay, 40% sand, and 40% silt is classified as loam. ONSITE WASTEWATER DISPOSAL Figure 3.6 Clay ribbon. Soil Color The telltale sign of a fluctuating ground water table is soil mottling. This term refers to spots or streaks of brown, black, grey, yellow, or red soil interspersed in the actual background color. The mottles are formed when the ground water table moves up and down, creating alternating periods of saturated and drained conditions. These con- ditions correspond to a respectiv