For practices with the underdrain perforated pipe installed on the bottom of the storage reservoir and connected to a riser (e.g., standpipe and 90 degree coupling), the active storage component is the storage reservoir depth between the inverts of the reservoir bottom and riser outlet (i.e invert elevation of the 90 degree coupling) and is calculated the same way as above.<br> | For practices with the underdrain perforated pipe installed on the bottom of the storage reservoir and connected to a riser (e.g., standpipe and 90 degree coupling), the active storage component is the storage reservoir depth between the inverts of the reservoir bottom and riser outlet (i.e invert elevation of the 90 degree coupling) and is calculated the same way as above.<br> |