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Last updated: January 15, 2013


Dept of Interior - People, Land and Water
Restoring South Florida's Future
orange divider

U.S. Fish and Wildlife Service Jamie Rappaport Clark, Director

Janet L. Miller, Bureau Editor

Priorities: Invasive Species, Migratory Birds, Ecosystem Management, Refuges

Everglades Construction Project:

Stormwater Treatment Areas Clean Polluted Runoff Naturally

Susan Jewell, U.S. Fish and Wildlife Sevice

STA construction
(Above) The construction of flow-through treatment marshes, known as Stormwater Treatment Areas, in Loxahatchee National Wildlife Refuge will remove excess nutrients from agricultural runoff to help restore the Everglades ecosystem.
Map showing overview of Everglades
construction projects
(Above) Map showing an overview of Everglades construction projects with an example of a Stormwater Treatment Area. (Click on map for full-scale version.)
In the spring of 1997, bulldozers crushed the saw grass at the Arthur R. Marshall Loxahatchee National Wildlife Refuge, sending the herons flitting for safety. But the refuge staff wasn't upset. For once, the 'dozers were there to help the Everglades.

That's when the dirt was turned for one of the first phases the Everglades Construction Project. It was part of the $825 million water quality restoration project that will take six and a half years to build, if all goes well. The problem? Runoff from the Everglades Agricultural Area flows into the Everglades carrying excess nutrients that cause the ecosystem to be thrown off- balance. The solution? Build Stormwater Treatment Areas (STAs), the flow-through filtration marshes that will be operated to augment the natural filtering abilities of marshes. The plan calls for more than 40,000 acres of effective treatment marshes for STAs, a rather sizable chunk of land by anyone's standards.

Many technologies for removing phosphorus, a major runoff pollutant, were analyzed before the five parties settling the 1988 Everglades Water Quality Lawsuit agreed to the STAs. (The parties were Loxahatchee National Wildlife Refuge, Everglades National Park, Army Corps of Engineers, South Florida Water Management District, and Florida Department of Environmental Protection.) The refuge and the park support the concept because it mimics the natural system as much as possible while causing the least disturbance to the environment. Other technologies were eliminated because they created a toxic byproduct, necessitated the construction of large infrastructures, required the addition of chemicals, or removed too much of the necessary components of Everglades water. While many technologies can remove phosphorus, and some even better than Stormwater Treatment Areas, it is critically important to ecologists that the waters discharging from the STAs have the right balance of carbon, silica, calcium, natural bacteria and algae, and a myriad of other components that aquatic invertebrates require - including a little phosphorus. The technology exists to turn raw sewage into distilled water, but the Everglades doesn't need distilled water - it needs marsh water.

Just how much phosphorus in the runoff is too much for the Everglades? It's a $10 million question. That's about how much money is being spent on research and monitoring to determine the answer.

Photo of osprey
The function of STA's is to restore a healthy balance of nutrients in the water that flows off agricultural lands into the Everglades to sustain wildlife such as the osprey at left, which feeds on aquatic life.
The dilemma arose because the state standard for total phosphorus is in a narrative form. It states that "In no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora or fauna." To be enforceable, it must be quantifiable. For the past few decades, farm runoff has measured as much as 200 parts per billion (ppb) of total phosphorus and sometimes more. The evidence from monitoring indicates that pristine levels were less than 10 ppb, sometimes as little as three or four. The question then becomes, Is that the level above which an imbalance occurs, or can the system take more and still be in balance? Three research groups are conducting separate experiments to determine the threshold of phosphorus balance in the Everglades. Florida International University directs the largest scale project, in collaboration with Loxahatchee National Wildlife Refuge, Everglades National Park, and the South Florida Water Management District. The latter also conducts smaller scale projects, as does the Everglades agricultural community.

While these research projects are underway, the Miccosukee Tribe, which lives in the Everglades, has taken a different approach to improving water quality on their land. (See Living in the Everglades: The Native Americans.) The tribe applied to the U.S. Environmental Protection Agency to set the limit for total phosphorus at 10 ppb for water entering their land. After reviewing some 300 scientific papers regarding water quality in the Everglades, the EPA concluded that 10 ppb total phosphorus is scientifically defensible. On May 20, 1999, the EPA approved it, thus providing a strong vertebra in the spine of the final state standards that the Florida Department of Environmental Protection must set by 2003.

Photo of test cells
Test cells for a Stormwater Treatment Area in the Arthur M. Loxahatchee National Wildlife Refuge.
The STAs are being constructed in six locations, primarily on former farmland and partially on state wildlife management land. They are situated downstream of the main agricultural discharge canals. Thus, all the runoff will flow through a STA for the treatment before entering the Everglades. The South Florida Water Management District is building five of them (STAs 1W, 2, 3/4, 5, and 6), and the Corps is building 1E. Funding for the project is cost-shared between the federal and state governments. Florida's share is about $635 million for construction and operation of the STAs; Interior's share is $190 million, primarily for acquiring land.

While the STAs are designed to remove phosphorus down to 50 ppb from the discharge water, scientists hope that other contaminants will also be removed. At the top of the list is mercury, which has shown a somewhat unexplainable but significant presence in the Everglades.
Photo of hydrologist sampling water
Biologist Lori Wenkert (with the South Florida Water Management District) performing water quality sampling in the Everglades.
Preliminary data from the prototype STA indicates that the filtering marshes will reduce the amount of mercury entering the Everglades in surface waters. Though less is known about pesticides, the same hope exists for their removal.

Under the lawsuit settlement and the Everglades Forever Act, landowners in the Everglades Agricultural Area have been required since 1996 to lower the phosphorus in their runoff by 25 percent. These commercial growers have been using a variety of techniques to accomplish this goal, including applying fertilizer efficiently, preventing runoff with dikes, controlling erosion, and altering pumping operations. These efforts have significantly reduced phosphorus loads from the area, exceeding the target requirement and providing relief even before the STAs are built.

The Everglades Construction Project also involves the control of exotic plants and the improvement of hydropatterns - the flow of water over the surface, including the velocity, direction, location, and depth. If only one aspect of a hydropattern is altered, it could significantly affect the ecosystem. Yet all of these aspects, as well as the hydroperiod (duration of inundation), have been altered in the past 50 years in the River of Grass.

U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
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Last updated: 15 January, 2013 @ 12:44 PM (HSH)