Sediment Basin and Trap Design Flashcards

A skimmer outlet on a sediment basin is designed to:

Answer: Draw water from the surface of the pool to minimize turbulence and discharge the clearest water

A floating skimmer draws water from just below the surface, discharging the clearest, least turbid water while keeping the turbid bottom water retained for further settling.

What is the purpose of installing an inlet energy dissipater or baffle in a sediment basin?

Answer: To dissipate the energy of incoming flows and prevent short-circuiting

Inlet energy dissipation structures reduce the velocity of incoming runoff to prevent resuspension of settled sediment and reduce the risk of short-circuiting through the basin.

Short-circuiting in a sediment basin means:

Answer: Runoff flowing directly from inlet to outlet without adequate residence time for settling

Short-circuiting occurs when flow channels directly from the inlet to the outlet, bypassing the settling zone and reducing residence time, which dramatically reduces sediment removal efficiency.

The emergency spillway of a sediment basin is designed to:

Answer: Safely pass flows from storms exceeding the design storm without causing basin failure

Emergency spillways safely convey overflows from storms exceeding the design capacity, preventing basin failure and uncontrolled breaching that could release stored sediment.

Which soil property is most important when constructing the embankment of a sediment basin?

Answer: Adequate compaction and low permeability to prevent seepage and embankment failure

Sediment basin embankments must be constructed of properly compacted, low-permeability material to prevent seepage, piping failure, and embankment breaching.

A sediment trap differs from a sediment basin primarily in that:

Answer: Traps are smaller, used for drainage areas under 5 acres, and are simpler in design without a formal outlet structure

Sediment traps are simple, small ponding areas typically used for drainage areas under 5 acres, relying on a rock outlet weir rather than the engineered outlet structures required for larger sediment basins.