St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District
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Water bodies, watersheds and storm water

Lake Apopka North Shore

Bird

Historically, more than 85 percent of the phosphorus going into Lake Apopka was from farms on the lake’s north shore. To reduce discharges of excessive nutrients to the lake, the St. Johns River Water Management District and the U.S. Department of Agriculture (USDA) purchased almost all of the farms for restoration between 1988 and 2001.

The 1996 Lake Apopka Surface Water Improvement and Management Act authorized the district to set a phosphorus concentration target. Subsequently, the district established a restoration phosphorus-loading target for Lake Apopka of 15.9 metric tons of phosphorus per year. This represents an 88 percent reduction from 1989–1994 farming discharges. The target was later adopted as a total maximum daily load (TMDL) for the lake, with a goal of attaining an in-lake total phosphorus concentration of 55 parts per billion.

Restoration of wetlands on the north shore property can reduce stormwater discharges to Lake Apopka and related nutrient loading, accelerating the recovery of the lake. The innovative restoration and remediation plan for the north shore property focuses on infrastructure improvements, soil inversion and soil amendment work needed to prepare the system for wetland restoration. The soil inversion process was developed as a remediation method to address the high levels of organochlorine pesticides (OCPs) found in organic surface soils (the top 30 centimeters of soil). The pesticides remained in the organic soils from years of farm pesticide applications. The inversion process used modified farm equipment to plow up to one meter deep and essentially flip the soil, bringing up uncontaminated soil from the depths and covering the contaminated surface layer of soil. The work was completed in May 2009 and it helped minimize the accumulation of OCPs into the food chain. The inversion process, on about 4,000 acres, reduced contaminants in the biologically active soil layer to safe levels in the north shore property.

Soils in the north shore property also contained excess nutrients such as phosphorus due to many years of agricultural production. Applying a “soil amendment,” which is an alum by-product from treatment of drinking water, helps to minimize the release of phosphorus from the soil to overlying water when the area is reflooded. The soil amendment was applied to about 7,000 acres in the north shore property and was completed in 2010.

A tractor pulls a special plow that places potentially contaminated soil deep below the surface as part of a soil inversion project.

A tractor pulls a special plow that places potentially contaminated soil deep below the surface as part of a soil inversion project.

As infrastructure is completed for each phase, a biological assessment is prepared for review and submitted to the U.S. Fish and Wildlife Service (USFWS). With USFWS concurrence, saturation and restoration flooding begins. The infrastructure is designed to help establish full wetland habitat with a wide range of water levels. The infrastructure also allows water transfer among different areas within the north shore property to minimize the need to discharge waters to the lake.

As each new phase is flooded and naturally populated with wildlife, fish samples are routinely collected and analyzed to ensure that pesticide levels in their tissues are below established safe levels for fish-eating birds. Newly flooded phases are carefully monitored for at least one year to ensure that any accumulation of pesticides through the aquatic food web does not present a risk to water birds. In addition, weekly bird surveys are conducted to monitor usage and to ensure that problems are detected quickly. As of December 2014, approximately 15,335 acres of former farm land is in various stages of inundation. This represents 100 percent of the areas planned for wetland restoration.

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St. Johns River Water Management District
4049 Reid Street, Palatka, FL 32177
(800) 725-5922