An Evaluation of the Use and Effectiveness
of Temporary Sediment Controls
By Michael E. Barrett, M.S., Project Manager John Edmund Kearney,
M.S. Terry Glen McCoy, M.S.
ABSTRACT
An inventory of temporary runoff controls installed on TxDOT construction
sites indicated that rock berms and silt fences were the most commonly
used erosion and sediment controls on construction sites. Sediment ponds
were the most inexpensive control on a cost per area basis and were
used more frequently in the earlier stages of construction. Erosion
control blankets were the most expensive controls and tended to be used
in the later phases of construction.
A field evaluation of the efficiency of silt fences in removing sediment
carried in runoff from highway construction sites showed that sediment
was removed by settling rather than filtration. Geotextile silt fences
proved to be ineffective in reducing turbidity. Monitoring of a single
rock berm showed negligible suspended solids removal.
High sediment removal efficiencies were achieved with silt fences in
flume studies. Mean sediment removal efficiency in the flume was highly
correlated with the detention time of the runoff. The flow rates of
sediment-laden runoff through the control sections were two orders of
magnitude less than those typically specified by transportation agencies.
The flow rate of a sediment slurry through geotextile fences was a function
of apparent opening size as well as permittivity.
Flow rates through rock berms greatly exceeded the rates typically
recommended in guidelines promulgated by regulatory agencies. The short
detention times and large pore size of the berms resulted in only a
slight reduction in the suspended solids load.
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