summary of values obtained from
more than 1,500 soil tests performed between 1960
and 1982 in the engineering laboratories of the Bureau
of Reclamation in Denver, Colorado. The data,
which were obtained from reports for which laboratory
soil classifications were available, are arranged
according to the USCS groups. The soils are
from the 17 Western States in which the Bureau
operates. Although the sampling area of the soils
tested is limited, it is believed that the USCS is
relatively insensitive to geographical distribution.
The procedure for determining which of the many
submitted samples should be tested was conducive
to obtaining a representative range of values because
samples were selected from the coarsest, the
finest, and the average soil from each source.
For each soil property listed, the average, the
standard deviation, the number of tests performed,
the minimum test value, and the maximum test
value are listed in table 5-l. Because all laboratory
tests, except large-sized permeability tests, were
made on compacted specimens of the minus No. 4
fraction of the soil, data on average values for the
gravels were not available for most properties. The
averages shown are subject to uncertainties that
may arise from sampling fluctuations, and tend to
vary widely from the true averages when the number
of tests is small.