The Design of Temporary Sediment Controls with Special Reference to Water Quality

About the report:

The laboratory and field trapping efficiencies of several types of flow barriers were ascertained. The materials used to fabricate the barriers were various types of hay straw crushed stone and crushed stone/straw mixes. Field checks of systems of battlers have indicated that flow barriers placed by the contractor have a near zero average efficiency. Experimentally modified flow barriers designed by the Soil Loss Equation have an average efficiency approaching that found in the laboratory tests. Sizeable reduction (77%) in the downstream bottom-dwelling organism was observed with the currently used flow barriers, while for the experimental barriers a smaller reduction was noted. Field observations appear to indicate that for relatively short-term, non-point sediment sources, such as highway construction, the bedload may have a more important effect on stream ecology than the suspended load. A method for the estimation of the time required for stream rehabilitation was developed and used in the study. For the area studied, rehabilitation appears to be on the order of two to three months after construction stops and vegetation is established. The rehabilitation time appears to be dependent upon stream flow and upstream colonization factors.

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