Most bioretention cells have overflow pipes that are in the top of the gravel layer or somewhere else in the interior. This changes the amount of the storage volume filled until there is flow out from the cell. Using the site in Exercise 1, modify the equations to incorporate this additional outflow option and show a sketch of the new box model.

You are going to pave a parking lot on 0.5 acre of land. You are required to maintain a minimum of 10 percent of the area as landscaped or green space. You decide to incorporate bioretention cells into three landscape areas in the parking lot.

A. Sketch an example parking lot and show the stormwater mass balances around the parking lot.

B. Sketch one of the bioretention cells and make a box model around it showing the overall water mass balance. Define each variable and incorporate them into Eqs. (10.2.3) and (10.2.4). Assume that there is no overflow pipe in the bioretention cell.