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The revised 2002 SWIM Plan reiterates these strategies and names the IRFWCD sub-basin as a priority non-point source project in the IRL Basin. This project is the first regional effort to reduce pollutant loads and freshwater discharges to the Indian River Lagoon from the IRFWCD . An interim goal of 50% reduction of nutrient and suspended solids has been adopted by all involved parties (Indian River County, IRL Program ( SJRWMD) , IRFWCD, City of Vero Beach) until Total Maximum Daily Loads (TMDLs) or Pollutant Load Reduction Goals (PLRGs) are formally established (FSD-3 ) . This project will implement a new BMP for stormwater management (FSD-4) and this treatment system is an agricultural BMP . As part of the East Indian River County Master Storinwater Management Plan (Master Plan), this project will help complete a comprehensive drainage basin map of the IRL (FSD-5 ) . The environmental education element will inform residents of Indian River County and particularly the citrus growers, about managed stormwater treatment systems, and the potential for pollutant removal in the IRFWCD basin (FSD- 11 ) . Since the IRFWCD is a Florida Statutes Section 298 drainage district, this project will assist in reducing discharges from this large-scale drainage system to the IRL (FSD- 12) . Indian River County will fund operation of this system. (FSD- 14) . Additionally, as part of the master planning process, verification of existing pollutant loads and new loading calculations will be completed (IRL- 1 - 104-D) . Monitoring of the water quality in the canals has already been completed to some extent by IRFWCD and additional monitoring is planned in this project (IRL- 1 - 101 -D) . This project will identify and quantify the nonpoint source problem in this area of the IRFWCD , and provide control (IRL-3 - 107-D) . ESTIMATED POLLUTANT LOAD REDUCTION : The typical challenge in estimating pollutant load reductions is first obtaining an accurate estimate of the pollutant loads from the watershed. These loads are influenced by land use distribution and management practices . Models that estimate the pollutant loads apply coefficients for the various land conditions, land practices and their distribution. This can be done for the Indian River County project. However, 46 years of water quality data does exist for the Indian River Farms canal system. This averaged data, coupled with recent specific field monitoring, provides a more accurate representation of the expected pollutant loadings to the project site . Reducing these loadings by well-established BMP treatment efficiencies will provide a relatively accurate estimate of the project' s pollutant load reduction. According to IRLNEP(b) ( 1994), the total discharge from the IRFWCD is 148 cfs on a mean annual basis . This equates to 96 million gallons/day (MGD) . The Main Relief Canal drainage basin contributes approximately 50% of the flow on average (48 MGD) . The proposed Egret Marsh project anticipates a withdrawal from a point below a control structure that regulates flow from the Lateral C Canal that flows into the Main Relief Canal. This 9,000- acre sub-basin contributes half of the Main Canal ' s flow, or 24 MGD . The proposed Egret Marsh treatment system is designed to handle an average flow of 10 MGD . Based on this average daily withdrawal from the Lateral C canal and the average concentrations of selected pollutants, the annual loading rate can be established for this project as follows : Annual Loadings Based on Average Withdrawal of 10 MGD, Average Canal Water Quality at the Lateral C Canal Radial Gate - Based on IRFWCD and County Data Constituent Lateral C Canal Annual Load lbs. TSS 16 . 0 m L 4877056 TN 1 . 59 m L 48 ,401 TP 0 . 52 m L 15 , 829 A treatment-train approach using multiple Best Management Practices (BMP) is recommended for this site . The flow of canal water will pass first through a pre-treatment pond and then through an Algal Turf Scrubber® (ATSTM) system. While some biological activity will occur in the pre-treatment wet pond, the primary purpose of the pond is to capture suspended solids and floatables at the head of the treatment system. A method for determining the removal efficiency of suspended solids in wet ponds presented in Wanielista and Yousef ( 1993) was used to predict the pre-treatment pond performance given different flow rates . A portion of total nitrogen and total phosphorous load, which is associated with suspended solids will also be removed. From Wanielista and DEP Agreement No. G0143, Attachment A, Page 2 of 9