Infiltration design guideline - drawdown time

Warning: The Construction Stormwater permit states: "The Permittee(s) must design the infiltration/filtration system to discharge the water quality volume routed to the system through the soil surface or filter media within 48 hours or less. Additional flows that cannot be infiltrated or filtered within 48 hours must be routed to bypass the system through a stabilized discharge point. The Permittee(s) must design the infiltration system to provide a means to visually verify that the system is discharging through the soil surface or filter media within 48 hours or less."

This schematic defines and demonstrates the concept of bounce and drawdown within an infiltration practice. This figure conceptualizes the water quality volume, the high water level, the proposed drawdown depth, and bounce as they relate to an infiltration practice.