Conducting Subsurface Environmental Investigations in Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 145

Sand

Silt

Clay

FIGURE 4.16
Relative size difference between a sand, silt, and clay particle. (From United States Department of Agriculture,
From the surface down. An introduction to soil surveys for agronomic use, Washington, DC, http://ftp-fc.egov.
usda.gov/NSSC/Educational_Resources/surdown.pdf (accessed July 4, 2010), 2010a.)

Soil textural triangle

100

90

80

70

Clay

60

50

Silty
clay

Sandy
clay 40

Silty
clay loam

Clay loam

30

Sandy clay loam

20

Loam

Silt loam

Sandy loam

10

Loamy
sand

Silt

Sand

Sand separate, %

FIGURE 4.17
Soil textural chart. (From United States Department of Agriculture, Guide to texture by feel, http://soils.gov/
education/resources/lessons/texture (accessed July 4, 2010), 2010b.)

describe soils on a consistent basis (USDA 2010b). Figure 4.18 is a useful guide when using
the textural chart shown in Figure 4.17, and Figure 4.19 contains the guidelines used to
describe many properties of soil (Virginia Department of Transportation 2003).
Consistency refers to the relative ease a sediment can be deformed. There are various
methods for determining consistency, but in the field, consistency can be estimated using