What’s the plan?

The Four Mile Run Stormwater Improvement Project will allow for PWSA to incrementally redirect stormwater from the surrounding neighborhoods to the new stream system instead of entering the combined sewer system. PWSA is working to control flooding and improve water quality throughout the M29 sewershed.

How is this being designed?

In our region, the clay soil and steep terrain makes it hard for most rainwater to seep into the water table. Because of that, there are two major approaches to managing stormwater. You can move or CONVEY stormwater through gutters, pipes, and streams. And you can hold or DETAIN the water in a bioswale, tank, or pond until a major storm passes and slowly release it.

At the neighborhood scale, this becomes a conveyance network and the form of that network is different depending on the type of neighborhood. The three forms of CONVEYANCE and DETENTION networks are:

Big Conveyance: Manage stormwater by building a giant pipe to convey it further downstream. Big Detention: Manage stormwater at a confluence point by detaining it and releasing at a lower flow rate. Distributed Detention and Conveyance: Manage stormwater local to where it falls with small scale scattered detention sites and curbside roadway conveyance.