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Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007

BUTLER CHAIN OF LAKES HYDROLOGIC/NUTRIENT BUDGETS & LAKE MANAGEMENT PLAN

Harvey H. Harper Environmental Research & Design, Inc. (ERD, Inc.) Orlando, Florida Sergio Duarte Orange County-Environmental Protection (EPD) Division Orlando, Florida

The Butler Chain of Lakes consists of 11 interconnected deep waterbodies in southwest Orange County with a combined surface area of over 5000 acres. The lakes in the Chain have historically exhibited oligotrophic characteristics and are renown for excellent water quality and good fishing. In 1987, the Chain was designated as an Outstanding Florida Water by the Florida Legislature. However, rapid residential growth in the basin has increased both the volume of stormwater runoff and mass loadings of nutrients into the Chain-of-Lakes. As a result, the Orange County Environmental Protection Division (EPD) contracted Environmental Research & Design, Inc. to perform a comprehensive loading assessment of the lake system. During 2005- 2006, ERD evaluated historical water quality trends and conducted a 12-month field monitoring program to develop nutrient budgets for each of the 11 lakes. The study included evaluation of hydrologic inputs, nutrients loadings (bulk precipitation, groundwater seepage and stormwater runoff) and sediment interactions to develop hydrologic/nutrient budgets and a watershed/water quality model.

The study concluded that impacts from stormwater and baseflow are less significant than impacts from sources such as groundwater seepage, landscape and fertilization activities, and wetland contributions. Structural nutrient control systems such as retention ponds and alum treatment systems were evaluated for the upstream lakes of the Chain of Lakes. The impact of boating activities on lake water quality was studied and motorized boating restrictions were recommended on water depths of 10 ft. or less to reduce sediment resuspension. The retrofitting of dry detention systems to dry/wet retention was also recommended as a mean of increasing stormwater runoff treatment. Furthermore, changes to existing ordinances were recommended for rear yard berm/swale requirements, shoreline clearings, and sediment/erosion control and landscaping practices, along with requirements for the connection of future developments to the sanitary sewer system.

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NOTES

Session 6B – Page 7

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