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River County Master Stormwater Management Plan (Master Plan), a pollutant loading analysis showed that the three discharge canals of the IRFWCD convey large amounts of suspended solids, nutrients, and floating vegetative debris into the lagoon. Treatment alternatives were investigated in the Master Plan. It was recommended that sediment and floating debris collection systems be used to effect a significant reduction in suspended solids, nutrients, and floatables into the Lagoon. This project is for the construction of a large treatment device on the Main Relief canal that utilizes vortex technology to remove suspended solids and floating debris from a circular flow of canal water within the structure. The proposed location of the treatment structure is west of US Highway 1 and the FEC railroad near the Vero Beach airport. The project will be constructed within the publically owned right-of-way of the Indian River Fanns Water Control District. The vortex unit will be integrated with a self cleaning fixed bar screen and traveling rake to remove large masses of vegetative debris such as hyacinths, water lettuce, duckweed and grasses and floating trash before the water enters the vortex unit. Annual loading of vegetative debris has recently been estimated at 10 million wet pounds. This represents a significant muck and nutrient source to the Indian River Lagoon. Based upon tissue analysis, this loading represents 2,500 lbs. of phosphorus and 20,000 lbs. of nitrogen on a dry weight basis. In addition, the vortex unit itself is designed to remove suspended sediments as well as floating debris. Based on water quality data for the Main Relief Canal and projected removal efficiencies of the vortex unit at a design flow rate of 294 efs, the following annual pollutant load reductions are estimated: TSS — 1,207,989 lbs. TN — 31,234 lbs TP — 7,722. This one project provides a significant opportunity for Indian River County to make great strides in meeting the proposed TMDLs for this basin of the Indian River Lagoon. The bar screen to be constructed is based on a design that has been proven to be effective and has been in continuous operation for over four years at a stormwater treatment area in West Palm Beach as part of the Everglades restoration project. The vortex unit will contain a 2400 -micron stainless steel cylindrical screen, approximately 20 ft. diameter. The shearing effect of the circular flow of water against this screen allows the removal of smaller particles in the 600 -micron range from the stormwater. This vortex unit design has been proven at the higher flow rates similar to the Main Relief Canal, in California and Australia. To ensure the nutrient removal efficiency of this system, maintenance will occur on a daily basis if needed using a frontend loader to remove the solids collected by the screens and a pump installed in the sump of the vortex unit. Indian River County understands that maintenance is the key to pollutant removal efficiency of this type of system. A preliminary engineering report has been completed for this project with unit sizing and site location addressed. Site surveying and final design are ready to begin. Public Outreach: A stormwater education campaign will be initiated in concert with construction to heighten awareness of the canal drainage system and the pollution it carries to the estuary. The St. Johns River Water Management District's 1RL License Plate program has authorized the funding of 100 metal 30" x 34" street signs to be erected at strategic locations throughout the drainage basin. The sign will picture the license plate snook and read: "All Canals Drain To Lagoon - No Trash'". Signs will be placed at intersections near major canals. Newspaper articles and brochures will link the new road signs with the construction of the Main Relief Canal pollution control structure. The County believes that a heightened public awareness through a highway and road signage program will reduce the pollutant loads to our constructed treatment facility for the Indian River lagoon. Effectiveness Monitoring: Project effectiveness monitoring will be conducted to demonstrate the pollutant loading reduction accomplished by the treatment facility. Two types of monitoring will be conducted. 1) to evaluate the effectiveness of the treatment system, composite grab samples will be collected from the stormwater that passes through the treatment facility during seven storm events. Samples will be collected at the influent point to the treatment facility and at the effluent side for comparison. 2) an additional assessment of the pollutant load reduction will be achieved by weighing and quantifying representative samples of the trapped material by the bar screen and the vortex unit. The representative samples of the trapped material will be analyzed for nutrient content on a dry weight basis. A continuously operating flow meter will allow for accurrate estimates of total volume treated. All trapped material removed from the facility will be weighed at the County landfill prior to disposal at the landfill. The County intends to keep daily records of flow and materials DEP Agreement No. G0182, Attachment A, Page 4 of 10