Certified Storm Water Operator Practice Exam

What is the minimum length to width ratio for sediment basins?

1. Two times

2. Three times

3. Four times

4. Five times

The correct answer is: Four times

The minimum length to width ratio for sediment basins is four times the width. This standard helps ensure that sediment basins effectively capture and retain sediment-laden stormwater runoff. A longer basin allows for a greater surface area, which promotes sedimentation as the water flows more slowly and provides adequate time for particles to settle out of suspension. When the ratio is adequate, it also helps to reduce the resuspension of settled sediments, minimizing the amount of pollution that can re-enter the water column. Inadequate length to width ratios could lead to less effective sediment trapping, increased maintenance issues, and potential impacts on water quality downstream. Choosing this ratio reflects best management practices in stormwater management design.