Expected performance benefits for various dewatering practices.
Link to this table

Dewatering Best Management Practices
Sedimentation/ Settling Only (Sediment Traps/ Basins)
Filtration Only (Silt Fence, Dewatering Bag, Geotextile, etc.)
Pretreatment1 + Chemical Flocculants + Settling/Filtration2
Water quantity
Flow attenuation
Secondary benefit
Little or no benefit
Little or no benefit
Runoff volume reduction
Secondary benefit
Little or no benefit
Little or no benefit
Water quality
Soil erosion
Little or no benefit
Little or no benefit
Little or no benefit
Sediment control
Good results
Better results
Best results
Nutrient loading2
Good results
Better results
Best results
Pollutant removal
Total suspended solids
Good results
Better results
Best results
Total phosphorus2
Good results
Better results
Best results
Heavy metals
Good results
Better results
Best results
Floatables
Little or no benefit3
Good results
Good results3
Oil and grease
Little or no benefit3
Some benefit
Some benefit3

1 Pretreatment via settling and/or filtration.
2 For soil-borne nutrients; i.e., not dissolved forms.
3 Benefit can be significantly improved with the use of a floating skimmer for discharge