Question

A pervious concrete parking lot is to be used to store storm water. Find the depth needed to handle a 2
hour storm delivering 2.55 in of precipitation. An equivalent amount of runoff must also be handled
from a contributing area around the parking lot (an active system). The concrete is 4” with porosity = 0.15.
The subbase must be at least 4” deep and will have porosity = 0.20. The controlling infiltration rate of the
system is 0.5 in/hr.

1) What volume must be stored in the sub base?

2) What is the depth of the sub base?

Answer 1