What component is typically found in the first stages of a stormwater treatment train?

The first stages of a stormwater treatment train typically include systems designed to manage and treat stormwater runoff effectively. Permeable pavement is commonly found at this initial stage. It allows rainwater to infiltrate through the surface into an underlying storage layer, promoting filtration and reducing the volume of runoff. This early interception is crucial as it helps to capture and manage stormwater right at the source, minimizing the peak flow and potential pollution before it enters more complex treatment systems.

While options like a bioretention basin with an underdrain, sedimentation tank, and excess vegetation areas are important components within a stormwater treatment train, they usually come into play after the initial volume reduction and infiltration processes have begun. For example, bioretention areas are effective for treating and storing water but are often used downstream in the treatment chain after permeable surfaces or similar features have reduced the runoff.