What is the primary purpose of a Sediment Forebay?

• A. Store treated water
• B. Capture and settle out sediment before stormwater enters the main treatment area
• C. Provide additional irrigation water
• D. Support aquatic life

Answer: (B)

A sediment forebay is an upstream pretreatment step that traps sediment and debris before stormwater reaches the main treatment area. By providing a shallow, still basin (often with baffles), it slows flow and allows heavier particles to settle out quickly. This dramatically reduces the sediment load entering the larger treatment basin, protecting downstream processes, lowering clogging and maintenance, and improving overall treatment efficiency. The other options describe uses that aren’t the primary purpose of a forebay—storing treated water happens after treatment, not before; providing irrigation water isn’t its function; and supporting aquatic life isn’t the main reason for its design.