hat defines soil type. A determination of the soil type is a necessary step in site evaluation, for it provides a check on the hit-or-miss percolation test described later. The following characteristics will help estimate the soil type: Sand is a type which doesn't require a soil sieve or microscope in order to be identified. Even very fine sand feels gritty. Rub some soil between your fingers or across your front teeth. If there is any grittiness, sand is present. If you squeeze dry sand, it will not main- SELECTION OF SITE AND SYSTEM Table 3.1 Soil Classification Particle Diameter Stone greater than 10 in. Cobble 3 to 10 in. Gravel 2 mm to 3 in. 0.05 mm to 2 mm very coarse 1 mm to 2 mm coarse 0.5 mm to 1 mm medium 0.25 mm to 0.5 mm 0.1 mm to 0.25 mm very fine 0.05 mm to 0.1 mm 0.002 mm to 0.05 mm less than 0.002 mm Source: U.S. Department of Agriculture. tain any structure when the pressure is released. The cast formed when you squeeze wet sand will fall apart when touched. Figure 3.3 shows a moist sand cast. Loamy sand feels gritty, but when dry and rubbed in the palm there will be a stain on the skin from the fine particles. The cast from squeezing moist loamy sand will crumble when touched. Figure 3.3 Moist sand cast. ONSITE WASTEWATER DISPOSAL Figure 3.4 Dry loam cast. Sandy loam aggregates are easily crushed and when rubbed between the fingers, a faint velvety feeling soon gives way to the grittiness of the sand. A cast of moist sandy loam will bear careful handling, but ribbons will not form when it is pressed between the thumb and forefinger. Loam aggregates are crushed under moderate pressure and clods can be quite firm. When pulverized by a shoe sole, loam has a velvety feel that becomes gritty with continued rubbing. Casts can be formed with dry loam (Figure 3.4), and wet casts are fairly stable to the point that fragile ribbons can be formed (Figure 3.5). Finally, the rubbed surface is rough and slightly gritty. Silty loam aggregates may be crushed under moderate pressure and clods are firm to hard. 