Ecosystems in the south Florida Everglades have been impacted from anthropogenic activities that include draining of vast areas of wetlands and nutrient input from agricultural runoff. As part of an effort to restore the Everglades, large-scale Stormwater Treatment Areas (STAs) have been constructed and are operated to remove excess phosphorus (P) from agricultural and urban runoff before discharging into the Everglades Protection Area. There are currently five STAs providing a total of approximately 57,000 of effective treatment area.
Over their combined operational histories, the STAs have treated approximately 16 million acre-feet of water, retained over 75% of inflow TP load, and reduced the annual flow-weighted mean TP concentration from 134 to 33 µg/L. Through years of operational and treatment wetland management experience, the District has gained expertise on how to reduce concentrations to approximately 20-30 µg/L. Current regulatory permits and consent orders require outflow concentrations of 13 parts per billion or less. To further improve the STAs’ P reduction performance, additional features are being added, including construction of flow equalization basins and expansion of existing treatment areas. In addition, a robust science plan has been developed to further understand the mechanisms and processes in the STAs that could lead to science-based management strategies and lower outflow concentration levels. The presentation will provide an overview of the STAs’ performance over their operational history, benefits to the downstream marsh, and the continuing efforts to further improve the STAs’ P reduction performance and meet the regulatory limits.