A stormwater retention basin under a parking area was recently proposed for the Marriot Hotel in Coatesville.
There is a stormwater infiltration basin under the “Main Street at Exton” mall and Wal-Mart parking lot.
Villanova University also has a parking garage with a stormwater retention basin under it. You can see it from the railroad.
We have intuitions and corporations in Chester County involved with state of the art stormwater management.