Which of the following is NOT typically considered a permanent post-construction BMP?

• A. Detention basins.
• B. Infiltration practices.
• C. Vegetated swales/bioretention areas.
• D. Silt fence.

Answer: (D)

Permanent post-construction BMPs are features designed to stay in place after construction to manage stormwater over the long term, providing ongoing detention, treatment, or infiltration. Detention basins fit this, since they’re built to hold and gradually release runoff long after project completion. Infiltration practices, such as infiltration basins or trenches, are designed to soak runoff into the ground on a lasting basis, continuing to work year after year. Vegetated swales and bioretention areas are landscape-based treatment systems that remain with the site and treat runoff as part of normal operation. A silt fence, by contrast, is a temporary erosion-control device used during construction to keep sediment from leaving the site. It’s not intended as a long-term post-construction solution and is usually removed or replaced with permanent measures once stabilization is achieved.