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this study that the actual removal efficiency is likely higher due to the capture of larger particles moving along the bottom which are not measured by normal sampling methods. Based on this information, and considering some minor removal by the floating boom, a TSS removal efficiency of 60-70% is estimated for the combination of the floating boom and CDS unit for preliminary engineering purposes. The actual suspended solids removal under operating conditions may be considerably different (more or less) depending on the actual particle size distribution and the flow patterns of the storm events. Based on observations in the IRFWCD when the canals are flowing, (which is daily, with or without rainfall events) the CDS units will likely capture a large mass and volume of materials that are currently being discharged into the Indian River Lagoon. For the purposes of estimating pollutant load reductions, it is assumed that the floating debris removal system and the vortex unit will remove only the particulate nutrients, and none of the dissolved nutrients will be removed. Based on literature estimates for total nitrogen (TN), the particulate nutrient content makes up 25% with the remaining being in dissolved form. For total phosphorous (TP), the particulate nutrient content makes up 40% with the remaining being in dissolved form. Using these assumptions, the overall treatment efficiencies are shown in Table 2. Table 2 - Main Relief Canal CDS System Pollutant Removal Efficiencies: Design Flow Rate % of Annual Flow Treated TSS Removal TN Removal TP floating debris deflector, off-line flow channel, bar -screen with rake (lbs/year) (lbs/year) Removal 76 cfs 53% 37% 9% 15% 184 cfs 75% 53% 13% 21% 294 cfs 86% 60% 15% 24% 450 cfs 94% 66% 16% 26% The average values for water quality parameters measured at the spillway on the Main Relief Canal are 14.6 mg/L TSS, 1.51 mg/L TN and 0.14 mg/L Ortho -P. It is assumed that Ortho -P makes up 60% of the TP concentration. These average values come from the ten-year monthly sampling program conducted by Carter Associates for the IRFWCD. While these concentrations are not indicative of storm event values they do offer a long term average and are the most extensive testing available for IRFWCD. Based on these concentrations and the average daily flow of the Main Canal over a ten-year period of 69.84 cfs, the annual pollutant removal quantities are presented in Table 3 for the CDS and floating boom system on the Main Relief Canal. Table 3 - Main Relief Canal CDS System Estimated Pollutant Removal Summary: Design Flow Rate % Flow Treated TSS Removed TN Removed TP Removed floating debris deflector, off-line flow channel, bar -screen with rake (lbs/year) (lbs/year) (lbs/year) 76 cfs 53% 744,459 195249 41759 184 cfs 75% 1,0531479 27,239 6,735 294 cfs 86% 11207,989 31,234 75722 450 cfs 94% 1,320360 34,139 8,441 OUTPUTS/DELIVERABLES: Task 1 - Surveying and Modeling. The selected site on the Main Canal will be surveyed with detailed cross sections in preparation for construction plans. Deliverables: N/A - Completed prior to this Agreement. Task 2 - Prepare and Submit Quality Assurance Project Plan. Prepare a Quality Assurance Project Plan (QAPP) for the water quality monitoring task and submit it to FDEP for review. Deliverables: Quality Assurance Project Plan Task 3 - Construction Plans and Permitting. Construction plans and specifications will be developed for the Main Relief Canal pollution control structure that includes: Canal bank stabilization and erosion control, floating debris deflector, off-line flow channel, bar -screen with rake system, vortex treatment unit with materials pump, conveyor and dewatering screen system, and a materials handling area. Necessary construction permits will also be obtained. Deliverables: Construction plans and specifications, copies of all permits obtained by Indian River County. DEP Agreement No. G0182, Attachment A, Page 6 of 10