When a filtering practice is used as a sediment basin during construction, how should its bottom elevation compare to the sediment trap bottom?

When a filtering practice is used as a sediment basin during construction, how should its bottom elevation compare to the sediment trap bottom?

• A. Lower than the bottom of the sediment trap
• B. Higher than the bottom of the sediment trap
• C. Equal to the bottom of the sediment trap
• D. Not specified relative to the sediment trap

Answer: (A)

When arranging a filtering practice to serve as a sediment basin during construction, water should flow by gravity from the sediment trap into the filtration unit. Placing the bottom of the filtering practice lower than the bottom of the sediment trap creates a continued downward flow path, preserves head for the filtration process, and helps keep settled sediment in the trap rather than in the filter media. If the filter bottom were at the same level or higher, flow into the filtration unit could be hindered, leading to bypass or re-suspension of sediment and requiring pumping or other measures. So, the lower bottom ensures proper sequencing, treatment effectiveness, and reduces the risk of short-circuiting the system.

When arranging a filtering practice to serve as a sediment basin during construction, water should flow by gravity from the sediment trap into the filtration unit. Placing the bottom of the filtering practice lower than the bottom of the sediment trap creates a continued downward flow path, preserves head for the filtration process, and helps keep settled sediment in the trap rather than in the filter media. If the filter bottom were at the same level or higher, flow into the filtration unit could be hindered, leading to bypass or re-suspension of sediment and requiring pumping or other measures. So, the lower bottom ensures proper sequencing, treatment effectiveness, and reduces the risk of short-circuiting the system.