Abstract
This report has been prepared as a partial fulfillment of the Orange County Contract No. Y3-819, titled " Monitoring Effectiveness of the Stormwater Treatment Program in Orange County, Florida", which was awarded to Environmental Research and Design, Inc. (ERD) on May 11,1993. One of the primary objectives of this contract is to provide a review of historical water quality information and identification of potential problem areas located within a major watershed area in Orange County. For purposes of this contract, the Little Econlockhatchee (Econ) Drainage Basin was selected for evaluation.
A review of available water quality information for water bodies located within the Little Econ Basin was conducted by ERD. After an initial survey of available water quality information within the study area, it was decided that the continuing water quality monitoring program conducted by the Orange County Environmental Protection Department provided the most extensive and continuous data base available for waterbodies located within the Little Econ Basin.
All available water quality information for major lake systems within the Little Econ Basin was obtained from the Orange County Environmental Protection Department and entered into a statistical database. Descriptive statistics were generated for each available data set, with trend analyses conducted for each major waterbody. This information is used to evaluate current water quality trends in major lake systems and to recommend lake systems with declining water quality where further investigation or retrofit activities may be necessary.
A detailed evaluation was conducted to estimate the stormwater pollutant loadings of nutrients, BOD and suspended solids discharging from sub-basin areas in Orange County portions of the Little Econ to the Little Econ River. This evaluation was performed in four distinct steps. First, land use within each of the 139 sub-basin areas discharging to the Little Econ was digitized based upon available land use maps. Next, estimates of pollutant loadings generated in each sub-basin as a result of stormwater runoff were prepared upon typical pollutant loading rates for land use categories within each sub-basin area. Third, generated pollutant loadings were adjusted to account for pollutant attenuation in stormwater management facilities located within each drainage basin. Finally, additional pollutant attenuation was included for discharges from each drainage basin to account for pollutant uptake and removal which occurs during migration through canals and waterways prior to entering the Little Econ River.
A ranking system for major sub-basin areas in the Little Econ basin is presented based upon estimated annual pollutant loadings of nutrients, BOD and suspended solids from each major sub-basin area. This ranking system is used to identify the top five problem areas, in terms of total annual pollutant loadings and areal pollutant loading rates, within the Little Econ Basin. Selected stormwater management alternatives, including wet detention and alum treatment, are evaluated for each of the top five drainage basin areas. Estimated capital construction costs for recommended alternatives are presented for each of the top five problem areas. In addition, a comparison is also presented of the estimated capital construction costs and annual pollutant removal efficiencies associated with construction of a single regional stormwater treatment facility versus smaller treatment facilities located within each basin area. A summary of recommended treatment alternatives is provided for each of the top five sub-basin areas.
This report is divided into 4 separate sections. Section 1 contains an introduction to the report. Section 2 provides a summary of the evaluation performed of historical water quality characteristics of major waterbodies within the Little Econ Basin. This section includes trend analyses and a ranking of major waterbodies in terms of trophic state characteristics. Areas of problem water quality characteristics are identified.
Section 3 contains an evaluation of pollutant loadings in stormwater runoff within the Little
Econ Basin. A detailed description of current and historical land use characteristics within
the drainage basin is provided, along with estimates of annual loadings from 139 sub-basin areas
discharging into the Little Econ River each year. Section 4 contains an evaluation and
identification of the top five problem areas within the Little Econ Basin. Recommended
stormwater management systems for each basin are provided, along with estimates of capital
construction costs.
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