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along with runoff from the flume. The filling period of the test stopped when either the
water level in the flume reached 0.35 m or the slurry tank was emptied.
5.1.2 The Soil and Suspended Solids Slurry
Top soil (Austin silty clay) was used to create the simulated runoff. Various
properties of Austin silty clay are presented in Table 5.1 and Table 5.2.
Table 5.1 Soil Characteristics (SCS, 1974)
Parent material
Austin chalk
Hydraulic Conductivity 1.5-5 cm/hr
Available water capacity 0.15-0.18 m/m
pH 7.9-8.4
Shrinkage limit 11.4 %
Plasticity index 36 %
Liquid limit 64 %
Lineal shrinkage 20.9 %
Volume shrinkage 50.5 %
Table 5.2 Mechanical Sieve Analysis (SCS, 1974)
Particle Size, mm Percent Passing
4.7 100
2.0 99
0.42 98
0.074 92
0.05 89
0.005 58
0.002 42
The soil was screened through a # 8 sieve (3 mm) before being mixed with water
to make a slurry. At the outset of this work, we expected all the soil added to the slurry to
become suspended; however, a fraction of the silty clay did not become suspended. This
phenomenon created difficulties in proportioning the soil and water in the slurry. The
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