Austin General Design Standards for Stormwater Management

In addition to a variety of other specific requirements, the standards provide that the “primary control strategy for water quality basins is to capture a minimum volume of stormwater runoff for treatment, and to release the treated volume in forty-eight (48) hours or as specified. The minimum volume is the first one-half (0.5) inch of runoff plus an additional one-tenth (0.1) inch for each ten (10) percent increase of impervious cover over twenty (20) percent within the drainage area to the control.”