Water Quality systems, as defined in section 1.4.2 of the City of Austin Environmental Criteria Manual (ECM) , are used to
- Minimize the erosion and transport of soil resulting from development activities.
- Prevent sedimentation in streams, creeks, lakes, waterways, storm drains, etc by ensuring no off-site transport of disturbed sediment for the 2-year 24-hour storm during construction and through establishment of permanent controls.
- Protect and improve the quality of surface water in the Austin environment and maintain and improve the quality and quantity of recharge to groundwater supplies, especially the Edwards aquifer.
- Minimize flooding hazards and silt removal cost associated with excessive sediment accumulation in storm drains and waterways.
- Preserve and protect existing vegetation to the greatest extent possible, particularly native plant and wildlife habitats.
Water quality controls can be achieved with Sedimentation/filtration systems, Wet Ponds (Rain Garden), or if the project fits the criteria found in section 1.6.4.B of the ECM, a fee-in-lieu may be paid instead of installing a water quality system.
Water Detention is covered under the Land Development code, and as defined in section 1.2.1 of the Drainage Criteria Manual, is meant to “control post-development runoff from all development such that no development will result in additional adverse flooding impacts in accordance with Chapter 25-7 of the Land Development Code.” Detention measures may be contained on the project site or, in some areas, utilize a large regional detention pond.
A project may need one or both types of water controls depending on multiple factors including, but not limited to, development type, size, and topography, the amount of impervious cover, proximity to waterways and established water quality transition zones.