When should a flocculent or coagulant aid be used in a sediment basin?

In site situations involving problematic fine-grained soils such as loess or clays, where conventional erosion prevention and sediment control methods either do not or are not expected to satisfactorily achieve the water quality performance criteria of having construction site discharge into receiving streams without an “objectionable color contrast,” design professionals may consider the use of flocculants added to sediment-laden water as it enters the sediment basin. One common and effective flocculant, polyacrlamide (PAM), is sometimes used for increasing the sediment-removal efficiency of a sediment basin. The rate and method of PAM application is critical to its overall performance. Improper introduction of PAM may result in waste, poor performance, or undesirable environmental effects. Design professionals should consult closely with PAM vendors and TDEC officials before specifying its use.  more