Tons of Pollutants Removed Annually from Stormwater Runoff by Watershed Protection Stormwater Controls
Structural Water Quality Controls remove pollutants from urban stormwater in drainage areas, such as ponds or rain gardens. Total Suspended Solids (TSS) is the pollutant indicator the Watershed Protection Department uses to predict the performance of the control. The amount of pollution removed is directly related to the structural water quality control and the size (acreage) of the contributing drainage area.
The calculation method is performed by using a computer model to predict the amount of pollution entering a structural control. This model then calculates the amount of pollution trapped by the control, and the amount that is released to downstream waterways. The algorithms used in this model were taken from leading scientific publications and were verified by using monitored data collected by Water Quality Management staff. This is a non-cumulative measure that captures the tons of pollutants removed for that year only.
FY 2015-16 Results
The FY 2015-16 target for this measure was 790 tons of TSS removed, and 784 tons of TSS were removed, achieving 99% of the goal.
Assessment of Results
Over time, each water quality control pond built has increased the amount of pollution trapped by the structural controls. High year-to-year increases of pollutants removed indicate that larger controls with larger drainage areas have been built. Small increases indicate focus on small water quality controls, such as rain gardens. The results show that annual goals have not been met since FY 2012-13, although the Department has managed to come close to the goal in these last three fiscal years. During FY 2015-16, construction was completed on three projects that should remove 7.2 tons of suspended pollutants from Austin waterways per year in the future. Two additional projects, which are expected to remove an additional 6.3 tons of pollutants per year, experienced design delays and were rescheduled to be completed in FY 2016-17.
This measure provides information on the functionality of stormwater controls, so the Department will continue to work to achieve the yearly goals. Furthermore, the Department is developing supplementary performance measures for the Stormwater Treatment activity to capture additional information on projects constructed each fiscal year and to identify additional data to report to the public.
For more information contact Eric Loucks, Supervising Engineer, (512) 974-2534.